Bug Summary

File:llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
Warning:line 2876, column 21
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name SimpleLoopUnswitch.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/build-llvm/lib/Transforms/Scalar -resource-dir /usr/lib/llvm-13/lib/clang/13.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/build-llvm/include -I /build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-13/lib/clang/13.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/build-llvm/lib/Transforms/Scalar -fdebug-prefix-map=/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b=. -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2021-07-25-235704-44570-1 -x c++ /build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp

/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp

1///===- SimpleLoopUnswitch.cpp - Hoist loop-invariant control flow ---------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h"
10#include "llvm/ADT/DenseMap.h"
11#include "llvm/ADT/STLExtras.h"
12#include "llvm/ADT/Sequence.h"
13#include "llvm/ADT/SetVector.h"
14#include "llvm/ADT/SmallPtrSet.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/ADT/Statistic.h"
17#include "llvm/ADT/Twine.h"
18#include "llvm/Analysis/AssumptionCache.h"
19#include "llvm/Analysis/CFG.h"
20#include "llvm/Analysis/CodeMetrics.h"
21#include "llvm/Analysis/GuardUtils.h"
22#include "llvm/Analysis/InstructionSimplify.h"
23#include "llvm/Analysis/LoopAnalysisManager.h"
24#include "llvm/Analysis/LoopInfo.h"
25#include "llvm/Analysis/LoopIterator.h"
26#include "llvm/Analysis/LoopPass.h"
27#include "llvm/Analysis/MemorySSA.h"
28#include "llvm/Analysis/MemorySSAUpdater.h"
29#include "llvm/Analysis/MustExecute.h"
30#include "llvm/Analysis/ScalarEvolution.h"
31#include "llvm/IR/BasicBlock.h"
32#include "llvm/IR/Constant.h"
33#include "llvm/IR/Constants.h"
34#include "llvm/IR/Dominators.h"
35#include "llvm/IR/Function.h"
36#include "llvm/IR/IRBuilder.h"
37#include "llvm/IR/InstrTypes.h"
38#include "llvm/IR/Instruction.h"
39#include "llvm/IR/Instructions.h"
40#include "llvm/IR/IntrinsicInst.h"
41#include "llvm/IR/PatternMatch.h"
42#include "llvm/IR/Use.h"
43#include "llvm/IR/Value.h"
44#include "llvm/InitializePasses.h"
45#include "llvm/Pass.h"
46#include "llvm/Support/Casting.h"
47#include "llvm/Support/CommandLine.h"
48#include "llvm/Support/Debug.h"
49#include "llvm/Support/ErrorHandling.h"
50#include "llvm/Support/GenericDomTree.h"
51#include "llvm/Support/raw_ostream.h"
52#include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h"
53#include "llvm/Transforms/Utils/BasicBlockUtils.h"
54#include "llvm/Transforms/Utils/Cloning.h"
55#include "llvm/Transforms/Utils/Local.h"
56#include "llvm/Transforms/Utils/LoopUtils.h"
57#include "llvm/Transforms/Utils/ValueMapper.h"
58#include <algorithm>
59#include <cassert>
60#include <iterator>
61#include <numeric>
62#include <utility>
63
64#define DEBUG_TYPE"simple-loop-unswitch" "simple-loop-unswitch"
65
66using namespace llvm;
67using namespace llvm::PatternMatch;
68
69STATISTIC(NumBranches, "Number of branches unswitched")static llvm::Statistic NumBranches = {"simple-loop-unswitch",
"NumBranches", "Number of branches unswitched"}
;
70STATISTIC(NumSwitches, "Number of switches unswitched")static llvm::Statistic NumSwitches = {"simple-loop-unswitch",
"NumSwitches", "Number of switches unswitched"}
;
71STATISTIC(NumGuards, "Number of guards turned into branches for unswitching")static llvm::Statistic NumGuards = {"simple-loop-unswitch", "NumGuards"
, "Number of guards turned into branches for unswitching"}
;
72STATISTIC(NumTrivial, "Number of unswitches that are trivial")static llvm::Statistic NumTrivial = {"simple-loop-unswitch", "NumTrivial"
, "Number of unswitches that are trivial"}
;
73STATISTIC(static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch"
, "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped"
}
74 NumCostMultiplierSkipped,static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch"
, "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped"
}
75 "Number of unswitch candidates that had their cost multiplier skipped")static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch"
, "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped"
}
;
76
77static cl::opt<bool> EnableNonTrivialUnswitch(
78 "enable-nontrivial-unswitch", cl::init(false), cl::Hidden,
79 cl::desc("Forcibly enables non-trivial loop unswitching rather than "
80 "following the configuration passed into the pass."));
81
82static cl::opt<int>
83 UnswitchThreshold("unswitch-threshold", cl::init(50), cl::Hidden,
84 cl::desc("The cost threshold for unswitching a loop."));
85
86static cl::opt<bool> EnableUnswitchCostMultiplier(
87 "enable-unswitch-cost-multiplier", cl::init(true), cl::Hidden,
88 cl::desc("Enable unswitch cost multiplier that prohibits exponential "
89 "explosion in nontrivial unswitch."));
90static cl::opt<int> UnswitchSiblingsToplevelDiv(
91 "unswitch-siblings-toplevel-div", cl::init(2), cl::Hidden,
92 cl::desc("Toplevel siblings divisor for cost multiplier."));
93static cl::opt<int> UnswitchNumInitialUnscaledCandidates(
94 "unswitch-num-initial-unscaled-candidates", cl::init(8), cl::Hidden,
95 cl::desc("Number of unswitch candidates that are ignored when calculating "
96 "cost multiplier."));
97static cl::opt<bool> UnswitchGuards(
98 "simple-loop-unswitch-guards", cl::init(true), cl::Hidden,
99 cl::desc("If enabled, simple loop unswitching will also consider "
100 "llvm.experimental.guard intrinsics as unswitch candidates."));
101static cl::opt<bool> DropNonTrivialImplicitNullChecks(
102 "simple-loop-unswitch-drop-non-trivial-implicit-null-checks",
103 cl::init(false), cl::Hidden,
104 cl::desc("If enabled, drop make.implicit metadata in unswitched implicit "
105 "null checks to save time analyzing if we can keep it."));
106static cl::opt<unsigned>
107 MSSAThreshold("simple-loop-unswitch-memoryssa-threshold",
108 cl::desc("Max number of memory uses to explore during "
109 "partial unswitching analysis"),
110 cl::init(100), cl::Hidden);
111
112/// Collect all of the loop invariant input values transitively used by the
113/// homogeneous instruction graph from a given root.
114///
115/// This essentially walks from a root recursively through loop variant operands
116/// which have the exact same opcode and finds all inputs which are loop
117/// invariant. For some operations these can be re-associated and unswitched out
118/// of the loop entirely.
119static TinyPtrVector<Value *>
120collectHomogenousInstGraphLoopInvariants(Loop &L, Instruction &Root,
121 LoopInfo &LI) {
122 assert(!L.isLoopInvariant(&Root) &&(static_cast <bool> (!L.isLoopInvariant(&Root) &&
"Only need to walk the graph if root itself is not invariant."
) ? void (0) : __assert_fail ("!L.isLoopInvariant(&Root) && \"Only need to walk the graph if root itself is not invariant.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 123, __extension__ __PRETTY_FUNCTION__))
123 "Only need to walk the graph if root itself is not invariant.")(static_cast <bool> (!L.isLoopInvariant(&Root) &&
"Only need to walk the graph if root itself is not invariant."
) ? void (0) : __assert_fail ("!L.isLoopInvariant(&Root) && \"Only need to walk the graph if root itself is not invariant.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 123, __extension__ __PRETTY_FUNCTION__))
;
124 TinyPtrVector<Value *> Invariants;
125
126 bool IsRootAnd = match(&Root, m_LogicalAnd());
127 bool IsRootOr = match(&Root, m_LogicalOr());
128
129 // Build a worklist and recurse through operators collecting invariants.
130 SmallVector<Instruction *, 4> Worklist;
131 SmallPtrSet<Instruction *, 8> Visited;
132 Worklist.push_back(&Root);
133 Visited.insert(&Root);
134 do {
135 Instruction &I = *Worklist.pop_back_val();
136 for (Value *OpV : I.operand_values()) {
137 // Skip constants as unswitching isn't interesting for them.
138 if (isa<Constant>(OpV))
139 continue;
140
141 // Add it to our result if loop invariant.
142 if (L.isLoopInvariant(OpV)) {
143 Invariants.push_back(OpV);
144 continue;
145 }
146
147 // If not an instruction with the same opcode, nothing we can do.
148 Instruction *OpI = dyn_cast<Instruction>(OpV);
149
150 if (OpI && ((IsRootAnd && match(OpI, m_LogicalAnd())) ||
151 (IsRootOr && match(OpI, m_LogicalOr())))) {
152 // Visit this operand.
153 if (Visited.insert(OpI).second)
154 Worklist.push_back(OpI);
155 }
156 }
157 } while (!Worklist.empty());
158
159 return Invariants;
160}
161
162static void replaceLoopInvariantUses(Loop &L, Value *Invariant,
163 Constant &Replacement) {
164 assert(!isa<Constant>(Invariant) && "Why are we unswitching on a constant?")(static_cast <bool> (!isa<Constant>(Invariant) &&
"Why are we unswitching on a constant?") ? void (0) : __assert_fail
("!isa<Constant>(Invariant) && \"Why are we unswitching on a constant?\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 164, __extension__ __PRETTY_FUNCTION__))
;
165
166 // Replace uses of LIC in the loop with the given constant.
167 // We use make_early_inc_range as set invalidates the iterator.
168 for (Use &U : llvm::make_early_inc_range(Invariant->uses())) {
169 Instruction *UserI = dyn_cast<Instruction>(U.getUser());
170
171 // Replace this use within the loop body.
172 if (UserI && L.contains(UserI))
173 U.set(&Replacement);
174 }
175}
176
177/// Check that all the LCSSA PHI nodes in the loop exit block have trivial
178/// incoming values along this edge.
179static bool areLoopExitPHIsLoopInvariant(Loop &L, BasicBlock &ExitingBB,
180 BasicBlock &ExitBB) {
181 for (Instruction &I : ExitBB) {
182 auto *PN = dyn_cast<PHINode>(&I);
183 if (!PN)
184 // No more PHIs to check.
185 return true;
186
187 // If the incoming value for this edge isn't loop invariant the unswitch
188 // won't be trivial.
189 if (!L.isLoopInvariant(PN->getIncomingValueForBlock(&ExitingBB)))
190 return false;
191 }
192 llvm_unreachable("Basic blocks should never be empty!")::llvm::llvm_unreachable_internal("Basic blocks should never be empty!"
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 192)
;
193}
194
195/// Copy a set of loop invariant values \p ToDuplicate and insert them at the
196/// end of \p BB and conditionally branch on the copied condition. We only
197/// branch on a single value.
198static void buildPartialUnswitchConditionalBranch(BasicBlock &BB,
199 ArrayRef<Value *> Invariants,
200 bool Direction,
201 BasicBlock &UnswitchedSucc,
202 BasicBlock &NormalSucc) {
203 IRBuilder<> IRB(&BB);
204
205 Value *Cond = Direction ? IRB.CreateOr(Invariants) :
206 IRB.CreateAnd(Invariants);
207 IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc,
208 Direction ? &NormalSucc : &UnswitchedSucc);
209}
210
211/// Copy a set of loop invariant values, and conditionally branch on them.
212static void buildPartialInvariantUnswitchConditionalBranch(
213 BasicBlock &BB, ArrayRef<Value *> ToDuplicate, bool Direction,
214 BasicBlock &UnswitchedSucc, BasicBlock &NormalSucc, Loop &L,
215 MemorySSAUpdater *MSSAU) {
216 ValueToValueMapTy VMap;
217 for (auto *Val : reverse(ToDuplicate)) {
218 Instruction *Inst = cast<Instruction>(Val);
219 Instruction *NewInst = Inst->clone();
220 BB.getInstList().insert(BB.end(), NewInst);
221 RemapInstruction(NewInst, VMap,
222 RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
223 VMap[Val] = NewInst;
224
225 if (!MSSAU)
226 continue;
227
228 MemorySSA *MSSA = MSSAU->getMemorySSA();
229 if (auto *MemUse =
230 dyn_cast_or_null<MemoryUse>(MSSA->getMemoryAccess(Inst))) {
231 auto *DefiningAccess = MemUse->getDefiningAccess();
232 // Get the first defining access before the loop.
233 while (L.contains(DefiningAccess->getBlock())) {
234 // If the defining access is a MemoryPhi, get the incoming
235 // value for the pre-header as defining access.
236 if (auto *MemPhi = dyn_cast<MemoryPhi>(DefiningAccess))
237 DefiningAccess =
238 MemPhi->getIncomingValueForBlock(L.getLoopPreheader());
239 else
240 DefiningAccess = cast<MemoryDef>(DefiningAccess)->getDefiningAccess();
241 }
242 MSSAU->createMemoryAccessInBB(NewInst, DefiningAccess,
243 NewInst->getParent(),
244 MemorySSA::BeforeTerminator);
245 }
246 }
247
248 IRBuilder<> IRB(&BB);
249 Value *Cond = VMap[ToDuplicate[0]];
250 IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc,
251 Direction ? &NormalSucc : &UnswitchedSucc);
252}
253
254/// Rewrite the PHI nodes in an unswitched loop exit basic block.
255///
256/// Requires that the loop exit and unswitched basic block are the same, and
257/// that the exiting block was a unique predecessor of that block. Rewrites the
258/// PHI nodes in that block such that what were LCSSA PHI nodes become trivial
259/// PHI nodes from the old preheader that now contains the unswitched
260/// terminator.
261static void rewritePHINodesForUnswitchedExitBlock(BasicBlock &UnswitchedBB,
262 BasicBlock &OldExitingBB,
263 BasicBlock &OldPH) {
264 for (PHINode &PN : UnswitchedBB.phis()) {
265 // When the loop exit is directly unswitched we just need to update the
266 // incoming basic block. We loop to handle weird cases with repeated
267 // incoming blocks, but expect to typically only have one operand here.
268 for (auto i : seq<int>(0, PN.getNumOperands())) {
269 assert(PN.getIncomingBlock(i) == &OldExitingBB &&(static_cast <bool> (PN.getIncomingBlock(i) == &OldExitingBB
&& "Found incoming block different from unique predecessor!"
) ? void (0) : __assert_fail ("PN.getIncomingBlock(i) == &OldExitingBB && \"Found incoming block different from unique predecessor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 270, __extension__ __PRETTY_FUNCTION__))
270 "Found incoming block different from unique predecessor!")(static_cast <bool> (PN.getIncomingBlock(i) == &OldExitingBB
&& "Found incoming block different from unique predecessor!"
) ? void (0) : __assert_fail ("PN.getIncomingBlock(i) == &OldExitingBB && \"Found incoming block different from unique predecessor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 270, __extension__ __PRETTY_FUNCTION__))
;
271 PN.setIncomingBlock(i, &OldPH);
272 }
273 }
274}
275
276/// Rewrite the PHI nodes in the loop exit basic block and the split off
277/// unswitched block.
278///
279/// Because the exit block remains an exit from the loop, this rewrites the
280/// LCSSA PHI nodes in it to remove the unswitched edge and introduces PHI
281/// nodes into the unswitched basic block to select between the value in the
282/// old preheader and the loop exit.
283static void rewritePHINodesForExitAndUnswitchedBlocks(BasicBlock &ExitBB,
284 BasicBlock &UnswitchedBB,
285 BasicBlock &OldExitingBB,
286 BasicBlock &OldPH,
287 bool FullUnswitch) {
288 assert(&ExitBB != &UnswitchedBB &&(static_cast <bool> (&ExitBB != &UnswitchedBB &&
"Must have different loop exit and unswitched blocks!") ? void
(0) : __assert_fail ("&ExitBB != &UnswitchedBB && \"Must have different loop exit and unswitched blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 289, __extension__ __PRETTY_FUNCTION__))
289 "Must have different loop exit and unswitched blocks!")(static_cast <bool> (&ExitBB != &UnswitchedBB &&
"Must have different loop exit and unswitched blocks!") ? void
(0) : __assert_fail ("&ExitBB != &UnswitchedBB && \"Must have different loop exit and unswitched blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 289, __extension__ __PRETTY_FUNCTION__))
;
290 Instruction *InsertPt = &*UnswitchedBB.begin();
291 for (PHINode &PN : ExitBB.phis()) {
292 auto *NewPN = PHINode::Create(PN.getType(), /*NumReservedValues*/ 2,
293 PN.getName() + ".split", InsertPt);
294
295 // Walk backwards over the old PHI node's inputs to minimize the cost of
296 // removing each one. We have to do this weird loop manually so that we
297 // create the same number of new incoming edges in the new PHI as we expect
298 // each case-based edge to be included in the unswitched switch in some
299 // cases.
300 // FIXME: This is really, really gross. It would be much cleaner if LLVM
301 // allowed us to create a single entry for a predecessor block without
302 // having separate entries for each "edge" even though these edges are
303 // required to produce identical results.
304 for (int i = PN.getNumIncomingValues() - 1; i >= 0; --i) {
305 if (PN.getIncomingBlock(i) != &OldExitingBB)
306 continue;
307
308 Value *Incoming = PN.getIncomingValue(i);
309 if (FullUnswitch)
310 // No more edge from the old exiting block to the exit block.
311 PN.removeIncomingValue(i);
312
313 NewPN->addIncoming(Incoming, &OldPH);
314 }
315
316 // Now replace the old PHI with the new one and wire the old one in as an
317 // input to the new one.
318 PN.replaceAllUsesWith(NewPN);
319 NewPN->addIncoming(&PN, &ExitBB);
320 }
321}
322
323/// Hoist the current loop up to the innermost loop containing a remaining exit.
324///
325/// Because we've removed an exit from the loop, we may have changed the set of
326/// loops reachable and need to move the current loop up the loop nest or even
327/// to an entirely separate nest.
328static void hoistLoopToNewParent(Loop &L, BasicBlock &Preheader,
329 DominatorTree &DT, LoopInfo &LI,
330 MemorySSAUpdater *MSSAU, ScalarEvolution *SE) {
331 // If the loop is already at the top level, we can't hoist it anywhere.
332 Loop *OldParentL = L.getParentLoop();
333 if (!OldParentL)
334 return;
335
336 SmallVector<BasicBlock *, 4> Exits;
337 L.getExitBlocks(Exits);
338 Loop *NewParentL = nullptr;
339 for (auto *ExitBB : Exits)
340 if (Loop *ExitL = LI.getLoopFor(ExitBB))
341 if (!NewParentL || NewParentL->contains(ExitL))
342 NewParentL = ExitL;
343
344 if (NewParentL == OldParentL)
345 return;
346
347 // The new parent loop (if different) should always contain the old one.
348 if (NewParentL)
349 assert(NewParentL->contains(OldParentL) &&(static_cast <bool> (NewParentL->contains(OldParentL
) && "Can only hoist this loop up the nest!") ? void (
0) : __assert_fail ("NewParentL->contains(OldParentL) && \"Can only hoist this loop up the nest!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 350, __extension__ __PRETTY_FUNCTION__))
350 "Can only hoist this loop up the nest!")(static_cast <bool> (NewParentL->contains(OldParentL
) && "Can only hoist this loop up the nest!") ? void (
0) : __assert_fail ("NewParentL->contains(OldParentL) && \"Can only hoist this loop up the nest!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 350, __extension__ __PRETTY_FUNCTION__))
;
351
352 // The preheader will need to move with the body of this loop. However,
353 // because it isn't in this loop we also need to update the primary loop map.
354 assert(OldParentL == LI.getLoopFor(&Preheader) &&(static_cast <bool> (OldParentL == LI.getLoopFor(&Preheader
) && "Parent loop of this loop should contain this loop's preheader!"
) ? void (0) : __assert_fail ("OldParentL == LI.getLoopFor(&Preheader) && \"Parent loop of this loop should contain this loop's preheader!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 355, __extension__ __PRETTY_FUNCTION__))
355 "Parent loop of this loop should contain this loop's preheader!")(static_cast <bool> (OldParentL == LI.getLoopFor(&Preheader
) && "Parent loop of this loop should contain this loop's preheader!"
) ? void (0) : __assert_fail ("OldParentL == LI.getLoopFor(&Preheader) && \"Parent loop of this loop should contain this loop's preheader!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 355, __extension__ __PRETTY_FUNCTION__))
;
356 LI.changeLoopFor(&Preheader, NewParentL);
357
358 // Remove this loop from its old parent.
359 OldParentL->removeChildLoop(&L);
360
361 // Add the loop either to the new parent or as a top-level loop.
362 if (NewParentL)
363 NewParentL->addChildLoop(&L);
364 else
365 LI.addTopLevelLoop(&L);
366
367 // Remove this loops blocks from the old parent and every other loop up the
368 // nest until reaching the new parent. Also update all of these
369 // no-longer-containing loops to reflect the nesting change.
370 for (Loop *OldContainingL = OldParentL; OldContainingL != NewParentL;
371 OldContainingL = OldContainingL->getParentLoop()) {
372 llvm::erase_if(OldContainingL->getBlocksVector(),
373 [&](const BasicBlock *BB) {
374 return BB == &Preheader || L.contains(BB);
375 });
376
377 OldContainingL->getBlocksSet().erase(&Preheader);
378 for (BasicBlock *BB : L.blocks())
379 OldContainingL->getBlocksSet().erase(BB);
380
381 // Because we just hoisted a loop out of this one, we have essentially
382 // created new exit paths from it. That means we need to form LCSSA PHI
383 // nodes for values used in the no-longer-nested loop.
384 formLCSSA(*OldContainingL, DT, &LI, SE);
385
386 // We shouldn't need to form dedicated exits because the exit introduced
387 // here is the (just split by unswitching) preheader. However, after trivial
388 // unswitching it is possible to get new non-dedicated exits out of parent
389 // loop so let's conservatively form dedicated exit blocks and figure out
390 // if we can optimize later.
391 formDedicatedExitBlocks(OldContainingL, &DT, &LI, MSSAU,
392 /*PreserveLCSSA*/ true);
393 }
394}
395
396// Return the top-most loop containing ExitBB and having ExitBB as exiting block
397// or the loop containing ExitBB, if there is no parent loop containing ExitBB
398// as exiting block.
399static Loop *getTopMostExitingLoop(BasicBlock *ExitBB, LoopInfo &LI) {
400 Loop *TopMost = LI.getLoopFor(ExitBB);
401 Loop *Current = TopMost;
402 while (Current) {
403 if (Current->isLoopExiting(ExitBB))
404 TopMost = Current;
405 Current = Current->getParentLoop();
406 }
407 return TopMost;
408}
409
410/// Unswitch a trivial branch if the condition is loop invariant.
411///
412/// This routine should only be called when loop code leading to the branch has
413/// been validated as trivial (no side effects). This routine checks if the
414/// condition is invariant and one of the successors is a loop exit. This
415/// allows us to unswitch without duplicating the loop, making it trivial.
416///
417/// If this routine fails to unswitch the branch it returns false.
418///
419/// If the branch can be unswitched, this routine splits the preheader and
420/// hoists the branch above that split. Preserves loop simplified form
421/// (splitting the exit block as necessary). It simplifies the branch within
422/// the loop to an unconditional branch but doesn't remove it entirely. Further
423/// cleanup can be done with some simplifycfg like pass.
424///
425/// If `SE` is not null, it will be updated based on the potential loop SCEVs
426/// invalidated by this.
427static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT,
428 LoopInfo &LI, ScalarEvolution *SE,
429 MemorySSAUpdater *MSSAU) {
430 assert(BI.isConditional() && "Can only unswitch a conditional branch!")(static_cast <bool> (BI.isConditional() && "Can only unswitch a conditional branch!"
) ? void (0) : __assert_fail ("BI.isConditional() && \"Can only unswitch a conditional branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 430, __extension__ __PRETTY_FUNCTION__))
;
431 LLVM_DEBUG(dbgs() << " Trying to unswitch branch: " << BI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Trying to unswitch branch: "
<< BI << "\n"; } } while (false)
;
432
433 // The loop invariant values that we want to unswitch.
434 TinyPtrVector<Value *> Invariants;
435
436 // When true, we're fully unswitching the branch rather than just unswitching
437 // some input conditions to the branch.
438 bool FullUnswitch = false;
439
440 if (L.isLoopInvariant(BI.getCondition())) {
441 Invariants.push_back(BI.getCondition());
442 FullUnswitch = true;
443 } else {
444 if (auto *CondInst = dyn_cast<Instruction>(BI.getCondition()))
445 Invariants = collectHomogenousInstGraphLoopInvariants(L, *CondInst, LI);
446 if (Invariants.empty()) {
447 LLVM_DEBUG(dbgs() << " Couldn't find invariant inputs!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Couldn't find invariant inputs!\n"
; } } while (false)
;
448 return false;
449 }
450 }
451
452 // Check that one of the branch's successors exits, and which one.
453 bool ExitDirection = true;
454 int LoopExitSuccIdx = 0;
455 auto *LoopExitBB = BI.getSuccessor(0);
456 if (L.contains(LoopExitBB)) {
457 ExitDirection = false;
458 LoopExitSuccIdx = 1;
459 LoopExitBB = BI.getSuccessor(1);
460 if (L.contains(LoopExitBB)) {
461 LLVM_DEBUG(dbgs() << " Branch doesn't exit the loop!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Branch doesn't exit the loop!\n"
; } } while (false)
;
462 return false;
463 }
464 }
465 auto *ContinueBB = BI.getSuccessor(1 - LoopExitSuccIdx);
466 auto *ParentBB = BI.getParent();
467 if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, *LoopExitBB)) {
468 LLVM_DEBUG(dbgs() << " Loop exit PHI's aren't loop-invariant!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Loop exit PHI's aren't loop-invariant!\n"
; } } while (false)
;
469 return false;
470 }
471
472 // When unswitching only part of the branch's condition, we need the exit
473 // block to be reached directly from the partially unswitched input. This can
474 // be done when the exit block is along the true edge and the branch condition
475 // is a graph of `or` operations, or the exit block is along the false edge
476 // and the condition is a graph of `and` operations.
477 if (!FullUnswitch) {
478 if (ExitDirection ? !match(BI.getCondition(), m_LogicalOr())
479 : !match(BI.getCondition(), m_LogicalAnd())) {
480 LLVM_DEBUG(dbgs() << " Branch condition is in improper form for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Branch condition is in improper form for "
"non-full unswitch!\n"; } } while (false)
481 "non-full unswitch!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Branch condition is in improper form for "
"non-full unswitch!\n"; } } while (false)
;
482 return false;
483 }
484 }
485
486 LLVM_DEBUG({do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
487 dbgs() << " unswitching trivial invariant conditions for: " << BIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
488 << "\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
489 for (Value *Invariant : Invariants) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
490 dbgs() << " " << *Invariant << " == true";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
491 if (Invariant != Invariants.back())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
492 dbgs() << " ||";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
493 dbgs() << "\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
494 }do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
495 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: "
<< BI << "\n"; for (Value *Invariant : Invariants
) { dbgs() << " " << *Invariant << " == true"
; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs
() << "\n"; } }; } } while (false)
;
496
497 // If we have scalar evolutions, we need to invalidate them including this
498 // loop, the loop containing the exit block and the topmost parent loop
499 // exiting via LoopExitBB.
500 if (SE) {
501 if (Loop *ExitL = getTopMostExitingLoop(LoopExitBB, LI))
502 SE->forgetLoop(ExitL);
503 else
504 // Forget the entire nest as this exits the entire nest.
505 SE->forgetTopmostLoop(&L);
506 }
507
508 if (MSSAU && VerifyMemorySSA)
509 MSSAU->getMemorySSA()->verifyMemorySSA();
510
511 // Split the preheader, so that we know that there is a safe place to insert
512 // the conditional branch. We will change the preheader to have a conditional
513 // branch on LoopCond.
514 BasicBlock *OldPH = L.getLoopPreheader();
515 BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI, MSSAU);
516
517 // Now that we have a place to insert the conditional branch, create a place
518 // to branch to: this is the exit block out of the loop that we are
519 // unswitching. We need to split this if there are other loop predecessors.
520 // Because the loop is in simplified form, *any* other predecessor is enough.
521 BasicBlock *UnswitchedBB;
522 if (FullUnswitch && LoopExitBB->getUniquePredecessor()) {
523 assert(LoopExitBB->getUniquePredecessor() == BI.getParent() &&(static_cast <bool> (LoopExitBB->getUniquePredecessor
() == BI.getParent() && "A branch's parent isn't a predecessor!"
) ? void (0) : __assert_fail ("LoopExitBB->getUniquePredecessor() == BI.getParent() && \"A branch's parent isn't a predecessor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 524, __extension__ __PRETTY_FUNCTION__))
524 "A branch's parent isn't a predecessor!")(static_cast <bool> (LoopExitBB->getUniquePredecessor
() == BI.getParent() && "A branch's parent isn't a predecessor!"
) ? void (0) : __assert_fail ("LoopExitBB->getUniquePredecessor() == BI.getParent() && \"A branch's parent isn't a predecessor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 524, __extension__ __PRETTY_FUNCTION__))
;
525 UnswitchedBB = LoopExitBB;
526 } else {
527 UnswitchedBB =
528 SplitBlock(LoopExitBB, &LoopExitBB->front(), &DT, &LI, MSSAU);
529 }
530
531 if (MSSAU && VerifyMemorySSA)
532 MSSAU->getMemorySSA()->verifyMemorySSA();
533
534 // Actually move the invariant uses into the unswitched position. If possible,
535 // we do this by moving the instructions, but when doing partial unswitching
536 // we do it by building a new merge of the values in the unswitched position.
537 OldPH->getTerminator()->eraseFromParent();
538 if (FullUnswitch) {
539 // If fully unswitching, we can use the existing branch instruction.
540 // Splice it into the old PH to gate reaching the new preheader and re-point
541 // its successors.
542 OldPH->getInstList().splice(OldPH->end(), BI.getParent()->getInstList(),
543 BI);
544 if (MSSAU) {
545 // Temporarily clone the terminator, to make MSSA update cheaper by
546 // separating "insert edge" updates from "remove edge" ones.
547 ParentBB->getInstList().push_back(BI.clone());
548 } else {
549 // Create a new unconditional branch that will continue the loop as a new
550 // terminator.
551 BranchInst::Create(ContinueBB, ParentBB);
552 }
553 BI.setSuccessor(LoopExitSuccIdx, UnswitchedBB);
554 BI.setSuccessor(1 - LoopExitSuccIdx, NewPH);
555 } else {
556 // Only unswitching a subset of inputs to the condition, so we will need to
557 // build a new branch that merges the invariant inputs.
558 if (ExitDirection)
559 assert(match(BI.getCondition(), m_LogicalOr()) &&(static_cast <bool> (match(BI.getCondition(), m_LogicalOr
()) && "Must have an `or` of `i1`s or `select i1 X, true, Y`s for the "
"condition!") ? void (0) : __assert_fail ("match(BI.getCondition(), m_LogicalOr()) && \"Must have an `or` of `i1`s or `select i1 X, true, Y`s for the \" \"condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 561, __extension__ __PRETTY_FUNCTION__))
560 "Must have an `or` of `i1`s or `select i1 X, true, Y`s for the "(static_cast <bool> (match(BI.getCondition(), m_LogicalOr
()) && "Must have an `or` of `i1`s or `select i1 X, true, Y`s for the "
"condition!") ? void (0) : __assert_fail ("match(BI.getCondition(), m_LogicalOr()) && \"Must have an `or` of `i1`s or `select i1 X, true, Y`s for the \" \"condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 561, __extension__ __PRETTY_FUNCTION__))
561 "condition!")(static_cast <bool> (match(BI.getCondition(), m_LogicalOr
()) && "Must have an `or` of `i1`s or `select i1 X, true, Y`s for the "
"condition!") ? void (0) : __assert_fail ("match(BI.getCondition(), m_LogicalOr()) && \"Must have an `or` of `i1`s or `select i1 X, true, Y`s for the \" \"condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 561, __extension__ __PRETTY_FUNCTION__))
;
562 else
563 assert(match(BI.getCondition(), m_LogicalAnd()) &&(static_cast <bool> (match(BI.getCondition(), m_LogicalAnd
()) && "Must have an `and` of `i1`s or `select i1 X, Y, false`s for the"
" condition!") ? void (0) : __assert_fail ("match(BI.getCondition(), m_LogicalAnd()) && \"Must have an `and` of `i1`s or `select i1 X, Y, false`s for the\" \" condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 565, __extension__ __PRETTY_FUNCTION__))
564 "Must have an `and` of `i1`s or `select i1 X, Y, false`s for the"(static_cast <bool> (match(BI.getCondition(), m_LogicalAnd
()) && "Must have an `and` of `i1`s or `select i1 X, Y, false`s for the"
" condition!") ? void (0) : __assert_fail ("match(BI.getCondition(), m_LogicalAnd()) && \"Must have an `and` of `i1`s or `select i1 X, Y, false`s for the\" \" condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 565, __extension__ __PRETTY_FUNCTION__))
565 " condition!")(static_cast <bool> (match(BI.getCondition(), m_LogicalAnd
()) && "Must have an `and` of `i1`s or `select i1 X, Y, false`s for the"
" condition!") ? void (0) : __assert_fail ("match(BI.getCondition(), m_LogicalAnd()) && \"Must have an `and` of `i1`s or `select i1 X, Y, false`s for the\" \" condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 565, __extension__ __PRETTY_FUNCTION__))
;
566 buildPartialUnswitchConditionalBranch(*OldPH, Invariants, ExitDirection,
567 *UnswitchedBB, *NewPH);
568 }
569
570 // Update the dominator tree with the added edge.
571 DT.insertEdge(OldPH, UnswitchedBB);
572
573 // After the dominator tree was updated with the added edge, update MemorySSA
574 // if available.
575 if (MSSAU) {
576 SmallVector<CFGUpdate, 1> Updates;
577 Updates.push_back({cfg::UpdateKind::Insert, OldPH, UnswitchedBB});
578 MSSAU->applyInsertUpdates(Updates, DT);
579 }
580
581 // Finish updating dominator tree and memory ssa for full unswitch.
582 if (FullUnswitch) {
583 if (MSSAU) {
584 // Remove the cloned branch instruction.
585 ParentBB->getTerminator()->eraseFromParent();
586 // Create unconditional branch now.
587 BranchInst::Create(ContinueBB, ParentBB);
588 MSSAU->removeEdge(ParentBB, LoopExitBB);
589 }
590 DT.deleteEdge(ParentBB, LoopExitBB);
591 }
592
593 if (MSSAU && VerifyMemorySSA)
594 MSSAU->getMemorySSA()->verifyMemorySSA();
595
596 // Rewrite the relevant PHI nodes.
597 if (UnswitchedBB == LoopExitBB)
598 rewritePHINodesForUnswitchedExitBlock(*UnswitchedBB, *ParentBB, *OldPH);
599 else
600 rewritePHINodesForExitAndUnswitchedBlocks(*LoopExitBB, *UnswitchedBB,
601 *ParentBB, *OldPH, FullUnswitch);
602
603 // The constant we can replace all of our invariants with inside the loop
604 // body. If any of the invariants have a value other than this the loop won't
605 // be entered.
606 ConstantInt *Replacement = ExitDirection
607 ? ConstantInt::getFalse(BI.getContext())
608 : ConstantInt::getTrue(BI.getContext());
609
610 // Since this is an i1 condition we can also trivially replace uses of it
611 // within the loop with a constant.
612 for (Value *Invariant : Invariants)
613 replaceLoopInvariantUses(L, Invariant, *Replacement);
614
615 // If this was full unswitching, we may have changed the nesting relationship
616 // for this loop so hoist it to its correct parent if needed.
617 if (FullUnswitch)
618 hoistLoopToNewParent(L, *NewPH, DT, LI, MSSAU, SE);
619
620 if (MSSAU && VerifyMemorySSA)
621 MSSAU->getMemorySSA()->verifyMemorySSA();
622
623 LLVM_DEBUG(dbgs() << " done: unswitching trivial branch...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " done: unswitching trivial branch...\n"
; } } while (false)
;
624 ++NumTrivial;
625 ++NumBranches;
626 return true;
627}
628
629/// Unswitch a trivial switch if the condition is loop invariant.
630///
631/// This routine should only be called when loop code leading to the switch has
632/// been validated as trivial (no side effects). This routine checks if the
633/// condition is invariant and that at least one of the successors is a loop
634/// exit. This allows us to unswitch without duplicating the loop, making it
635/// trivial.
636///
637/// If this routine fails to unswitch the switch it returns false.
638///
639/// If the switch can be unswitched, this routine splits the preheader and
640/// copies the switch above that split. If the default case is one of the
641/// exiting cases, it copies the non-exiting cases and points them at the new
642/// preheader. If the default case is not exiting, it copies the exiting cases
643/// and points the default at the preheader. It preserves loop simplified form
644/// (splitting the exit blocks as necessary). It simplifies the switch within
645/// the loop by removing now-dead cases. If the default case is one of those
646/// unswitched, it replaces its destination with a new basic block containing
647/// only unreachable. Such basic blocks, while technically loop exits, are not
648/// considered for unswitching so this is a stable transform and the same
649/// switch will not be revisited. If after unswitching there is only a single
650/// in-loop successor, the switch is further simplified to an unconditional
651/// branch. Still more cleanup can be done with some simplifycfg like pass.
652///
653/// If `SE` is not null, it will be updated based on the potential loop SCEVs
654/// invalidated by this.
655static bool unswitchTrivialSwitch(Loop &L, SwitchInst &SI, DominatorTree &DT,
656 LoopInfo &LI, ScalarEvolution *SE,
657 MemorySSAUpdater *MSSAU) {
658 LLVM_DEBUG(dbgs() << " Trying to unswitch switch: " << SI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Trying to unswitch switch: "
<< SI << "\n"; } } while (false)
;
659 Value *LoopCond = SI.getCondition();
660
661 // If this isn't switching on an invariant condition, we can't unswitch it.
662 if (!L.isLoopInvariant(LoopCond))
663 return false;
664
665 auto *ParentBB = SI.getParent();
666
667 // The same check must be used both for the default and the exit cases. We
668 // should never leave edges from the switch instruction to a basic block that
669 // we are unswitching, hence the condition used to determine the default case
670 // needs to also be used to populate ExitCaseIndices, which is then used to
671 // remove cases from the switch.
672 auto IsTriviallyUnswitchableExitBlock = [&](BasicBlock &BBToCheck) {
673 // BBToCheck is not an exit block if it is inside loop L.
674 if (L.contains(&BBToCheck))
675 return false;
676 // BBToCheck is not trivial to unswitch if its phis aren't loop invariant.
677 if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, BBToCheck))
678 return false;
679 // We do not unswitch a block that only has an unreachable statement, as
680 // it's possible this is a previously unswitched block. Only unswitch if
681 // either the terminator is not unreachable, or, if it is, it's not the only
682 // instruction in the block.
683 auto *TI = BBToCheck.getTerminator();
684 bool isUnreachable = isa<UnreachableInst>(TI);
685 return !isUnreachable ||
686 (isUnreachable && (BBToCheck.getFirstNonPHIOrDbg() != TI));
687 };
688
689 SmallVector<int, 4> ExitCaseIndices;
690 for (auto Case : SI.cases())
691 if (IsTriviallyUnswitchableExitBlock(*Case.getCaseSuccessor()))
692 ExitCaseIndices.push_back(Case.getCaseIndex());
693 BasicBlock *DefaultExitBB = nullptr;
694 SwitchInstProfUpdateWrapper::CaseWeightOpt DefaultCaseWeight =
695 SwitchInstProfUpdateWrapper::getSuccessorWeight(SI, 0);
696 if (IsTriviallyUnswitchableExitBlock(*SI.getDefaultDest())) {
697 DefaultExitBB = SI.getDefaultDest();
698 } else if (ExitCaseIndices.empty())
699 return false;
700
701 LLVM_DEBUG(dbgs() << " unswitching trivial switch...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " unswitching trivial switch...\n"
; } } while (false)
;
702
703 if (MSSAU && VerifyMemorySSA)
704 MSSAU->getMemorySSA()->verifyMemorySSA();
705
706 // We may need to invalidate SCEVs for the outermost loop reached by any of
707 // the exits.
708 Loop *OuterL = &L;
709
710 if (DefaultExitBB) {
711 // Clear out the default destination temporarily to allow accurate
712 // predecessor lists to be examined below.
713 SI.setDefaultDest(nullptr);
714 // Check the loop containing this exit.
715 Loop *ExitL = LI.getLoopFor(DefaultExitBB);
716 if (!ExitL || ExitL->contains(OuterL))
717 OuterL = ExitL;
718 }
719
720 // Store the exit cases into a separate data structure and remove them from
721 // the switch.
722 SmallVector<std::tuple<ConstantInt *, BasicBlock *,
723 SwitchInstProfUpdateWrapper::CaseWeightOpt>,
724 4> ExitCases;
725 ExitCases.reserve(ExitCaseIndices.size());
726 SwitchInstProfUpdateWrapper SIW(SI);
727 // We walk the case indices backwards so that we remove the last case first
728 // and don't disrupt the earlier indices.
729 for (unsigned Index : reverse(ExitCaseIndices)) {
730 auto CaseI = SI.case_begin() + Index;
731 // Compute the outer loop from this exit.
732 Loop *ExitL = LI.getLoopFor(CaseI->getCaseSuccessor());
733 if (!ExitL || ExitL->contains(OuterL))
734 OuterL = ExitL;
735 // Save the value of this case.
736 auto W = SIW.getSuccessorWeight(CaseI->getSuccessorIndex());
737 ExitCases.emplace_back(CaseI->getCaseValue(), CaseI->getCaseSuccessor(), W);
738 // Delete the unswitched cases.
739 SIW.removeCase(CaseI);
740 }
741
742 if (SE) {
743 if (OuterL)
744 SE->forgetLoop(OuterL);
745 else
746 SE->forgetTopmostLoop(&L);
747 }
748
749 // Check if after this all of the remaining cases point at the same
750 // successor.
751 BasicBlock *CommonSuccBB = nullptr;
752 if (SI.getNumCases() > 0 &&
753 all_of(drop_begin(SI.cases()), [&SI](const SwitchInst::CaseHandle &Case) {
754 return Case.getCaseSuccessor() == SI.case_begin()->getCaseSuccessor();
755 }))
756 CommonSuccBB = SI.case_begin()->getCaseSuccessor();
757 if (!DefaultExitBB) {
758 // If we're not unswitching the default, we need it to match any cases to
759 // have a common successor or if we have no cases it is the common
760 // successor.
761 if (SI.getNumCases() == 0)
762 CommonSuccBB = SI.getDefaultDest();
763 else if (SI.getDefaultDest() != CommonSuccBB)
764 CommonSuccBB = nullptr;
765 }
766
767 // Split the preheader, so that we know that there is a safe place to insert
768 // the switch.
769 BasicBlock *OldPH = L.getLoopPreheader();
770 BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI, MSSAU);
771 OldPH->getTerminator()->eraseFromParent();
772
773 // Now add the unswitched switch.
774 auto *NewSI = SwitchInst::Create(LoopCond, NewPH, ExitCases.size(), OldPH);
775 SwitchInstProfUpdateWrapper NewSIW(*NewSI);
776
777 // Rewrite the IR for the unswitched basic blocks. This requires two steps.
778 // First, we split any exit blocks with remaining in-loop predecessors. Then
779 // we update the PHIs in one of two ways depending on if there was a split.
780 // We walk in reverse so that we split in the same order as the cases
781 // appeared. This is purely for convenience of reading the resulting IR, but
782 // it doesn't cost anything really.
783 SmallPtrSet<BasicBlock *, 2> UnswitchedExitBBs;
784 SmallDenseMap<BasicBlock *, BasicBlock *, 2> SplitExitBBMap;
785 // Handle the default exit if necessary.
786 // FIXME: It'd be great if we could merge this with the loop below but LLVM's
787 // ranges aren't quite powerful enough yet.
788 if (DefaultExitBB) {
789 if (pred_empty(DefaultExitBB)) {
790 UnswitchedExitBBs.insert(DefaultExitBB);
791 rewritePHINodesForUnswitchedExitBlock(*DefaultExitBB, *ParentBB, *OldPH);
792 } else {
793 auto *SplitBB =
794 SplitBlock(DefaultExitBB, &DefaultExitBB->front(), &DT, &LI, MSSAU);
795 rewritePHINodesForExitAndUnswitchedBlocks(*DefaultExitBB, *SplitBB,
796 *ParentBB, *OldPH,
797 /*FullUnswitch*/ true);
798 DefaultExitBB = SplitExitBBMap[DefaultExitBB] = SplitBB;
799 }
800 }
801 // Note that we must use a reference in the for loop so that we update the
802 // container.
803 for (auto &ExitCase : reverse(ExitCases)) {
804 // Grab a reference to the exit block in the pair so that we can update it.
805 BasicBlock *ExitBB = std::get<1>(ExitCase);
806
807 // If this case is the last edge into the exit block, we can simply reuse it
808 // as it will no longer be a loop exit. No mapping necessary.
809 if (pred_empty(ExitBB)) {
810 // Only rewrite once.
811 if (UnswitchedExitBBs.insert(ExitBB).second)
812 rewritePHINodesForUnswitchedExitBlock(*ExitBB, *ParentBB, *OldPH);
813 continue;
814 }
815
816 // Otherwise we need to split the exit block so that we retain an exit
817 // block from the loop and a target for the unswitched condition.
818 BasicBlock *&SplitExitBB = SplitExitBBMap[ExitBB];
819 if (!SplitExitBB) {
820 // If this is the first time we see this, do the split and remember it.
821 SplitExitBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI, MSSAU);
822 rewritePHINodesForExitAndUnswitchedBlocks(*ExitBB, *SplitExitBB,
823 *ParentBB, *OldPH,
824 /*FullUnswitch*/ true);
825 }
826 // Update the case pair to point to the split block.
827 std::get<1>(ExitCase) = SplitExitBB;
828 }
829
830 // Now add the unswitched cases. We do this in reverse order as we built them
831 // in reverse order.
832 for (auto &ExitCase : reverse(ExitCases)) {
833 ConstantInt *CaseVal = std::get<0>(ExitCase);
834 BasicBlock *UnswitchedBB = std::get<1>(ExitCase);
835
836 NewSIW.addCase(CaseVal, UnswitchedBB, std::get<2>(ExitCase));
837 }
838
839 // If the default was unswitched, re-point it and add explicit cases for
840 // entering the loop.
841 if (DefaultExitBB) {
842 NewSIW->setDefaultDest(DefaultExitBB);
843 NewSIW.setSuccessorWeight(0, DefaultCaseWeight);
844
845 // We removed all the exit cases, so we just copy the cases to the
846 // unswitched switch.
847 for (const auto &Case : SI.cases())
848 NewSIW.addCase(Case.getCaseValue(), NewPH,
849 SIW.getSuccessorWeight(Case.getSuccessorIndex()));
850 } else if (DefaultCaseWeight) {
851 // We have to set branch weight of the default case.
852 uint64_t SW = *DefaultCaseWeight;
853 for (const auto &Case : SI.cases()) {
854 auto W = SIW.getSuccessorWeight(Case.getSuccessorIndex());
855 assert(W &&(static_cast <bool> (W && "case weight must be defined as default case weight is defined"
) ? void (0) : __assert_fail ("W && \"case weight must be defined as default case weight is defined\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 856, __extension__ __PRETTY_FUNCTION__))
856 "case weight must be defined as default case weight is defined")(static_cast <bool> (W && "case weight must be defined as default case weight is defined"
) ? void (0) : __assert_fail ("W && \"case weight must be defined as default case weight is defined\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 856, __extension__ __PRETTY_FUNCTION__))
;
857 SW += *W;
858 }
859 NewSIW.setSuccessorWeight(0, SW);
860 }
861
862 // If we ended up with a common successor for every path through the switch
863 // after unswitching, rewrite it to an unconditional branch to make it easy
864 // to recognize. Otherwise we potentially have to recognize the default case
865 // pointing at unreachable and other complexity.
866 if (CommonSuccBB) {
867 BasicBlock *BB = SI.getParent();
868 // We may have had multiple edges to this common successor block, so remove
869 // them as predecessors. We skip the first one, either the default or the
870 // actual first case.
871 bool SkippedFirst = DefaultExitBB == nullptr;
872 for (auto Case : SI.cases()) {
873 assert(Case.getCaseSuccessor() == CommonSuccBB &&(static_cast <bool> (Case.getCaseSuccessor() == CommonSuccBB
&& "Non-common successor!") ? void (0) : __assert_fail
("Case.getCaseSuccessor() == CommonSuccBB && \"Non-common successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 874, __extension__ __PRETTY_FUNCTION__))
874 "Non-common successor!")(static_cast <bool> (Case.getCaseSuccessor() == CommonSuccBB
&& "Non-common successor!") ? void (0) : __assert_fail
("Case.getCaseSuccessor() == CommonSuccBB && \"Non-common successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 874, __extension__ __PRETTY_FUNCTION__))
;
875 (void)Case;
876 if (!SkippedFirst) {
877 SkippedFirst = true;
878 continue;
879 }
880 CommonSuccBB->removePredecessor(BB,
881 /*KeepOneInputPHIs*/ true);
882 }
883 // Now nuke the switch and replace it with a direct branch.
884 SIW.eraseFromParent();
885 BranchInst::Create(CommonSuccBB, BB);
886 } else if (DefaultExitBB) {
887 assert(SI.getNumCases() > 0 &&(static_cast <bool> (SI.getNumCases() > 0 &&
"If we had no cases we'd have a common successor!") ? void (
0) : __assert_fail ("SI.getNumCases() > 0 && \"If we had no cases we'd have a common successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 888, __extension__ __PRETTY_FUNCTION__))
888 "If we had no cases we'd have a common successor!")(static_cast <bool> (SI.getNumCases() > 0 &&
"If we had no cases we'd have a common successor!") ? void (
0) : __assert_fail ("SI.getNumCases() > 0 && \"If we had no cases we'd have a common successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 888, __extension__ __PRETTY_FUNCTION__))
;
889 // Move the last case to the default successor. This is valid as if the
890 // default got unswitched it cannot be reached. This has the advantage of
891 // being simple and keeping the number of edges from this switch to
892 // successors the same, and avoiding any PHI update complexity.
893 auto LastCaseI = std::prev(SI.case_end());
894
895 SI.setDefaultDest(LastCaseI->getCaseSuccessor());
896 SIW.setSuccessorWeight(
897 0, SIW.getSuccessorWeight(LastCaseI->getSuccessorIndex()));
898 SIW.removeCase(LastCaseI);
899 }
900
901 // Walk the unswitched exit blocks and the unswitched split blocks and update
902 // the dominator tree based on the CFG edits. While we are walking unordered
903 // containers here, the API for applyUpdates takes an unordered list of
904 // updates and requires them to not contain duplicates.
905 SmallVector<DominatorTree::UpdateType, 4> DTUpdates;
906 for (auto *UnswitchedExitBB : UnswitchedExitBBs) {
907 DTUpdates.push_back({DT.Delete, ParentBB, UnswitchedExitBB});
908 DTUpdates.push_back({DT.Insert, OldPH, UnswitchedExitBB});
909 }
910 for (auto SplitUnswitchedPair : SplitExitBBMap) {
911 DTUpdates.push_back({DT.Delete, ParentBB, SplitUnswitchedPair.first});
912 DTUpdates.push_back({DT.Insert, OldPH, SplitUnswitchedPair.second});
913 }
914
915 if (MSSAU) {
916 MSSAU->applyUpdates(DTUpdates, DT, /*UpdateDT=*/true);
917 if (VerifyMemorySSA)
918 MSSAU->getMemorySSA()->verifyMemorySSA();
919 } else {
920 DT.applyUpdates(DTUpdates);
921 }
922
923 assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel
::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)"
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 923, __extension__ __PRETTY_FUNCTION__))
;
924
925 // We may have changed the nesting relationship for this loop so hoist it to
926 // its correct parent if needed.
927 hoistLoopToNewParent(L, *NewPH, DT, LI, MSSAU, SE);
928
929 if (MSSAU && VerifyMemorySSA)
930 MSSAU->getMemorySSA()->verifyMemorySSA();
931
932 ++NumTrivial;
933 ++NumSwitches;
934 LLVM_DEBUG(dbgs() << " done: unswitching trivial switch...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " done: unswitching trivial switch...\n"
; } } while (false)
;
935 return true;
936}
937
938/// This routine scans the loop to find a branch or switch which occurs before
939/// any side effects occur. These can potentially be unswitched without
940/// duplicating the loop. If a branch or switch is successfully unswitched the
941/// scanning continues to see if subsequent branches or switches have become
942/// trivial. Once all trivial candidates have been unswitched, this routine
943/// returns.
944///
945/// The return value indicates whether anything was unswitched (and therefore
946/// changed).
947///
948/// If `SE` is not null, it will be updated based on the potential loop SCEVs
949/// invalidated by this.
950static bool unswitchAllTrivialConditions(Loop &L, DominatorTree &DT,
951 LoopInfo &LI, ScalarEvolution *SE,
952 MemorySSAUpdater *MSSAU) {
953 bool Changed = false;
954
955 // If loop header has only one reachable successor we should keep looking for
956 // trivial condition candidates in the successor as well. An alternative is
957 // to constant fold conditions and merge successors into loop header (then we
958 // only need to check header's terminator). The reason for not doing this in
959 // LoopUnswitch pass is that it could potentially break LoopPassManager's
960 // invariants. Folding dead branches could either eliminate the current loop
961 // or make other loops unreachable. LCSSA form might also not be preserved
962 // after deleting branches. The following code keeps traversing loop header's
963 // successors until it finds the trivial condition candidate (condition that
964 // is not a constant). Since unswitching generates branches with constant
965 // conditions, this scenario could be very common in practice.
966 BasicBlock *CurrentBB = L.getHeader();
967 SmallPtrSet<BasicBlock *, 8> Visited;
968 Visited.insert(CurrentBB);
969 do {
970 // Check if there are any side-effecting instructions (e.g. stores, calls,
971 // volatile loads) in the part of the loop that the code *would* execute
972 // without unswitching.
973 if (MSSAU) // Possible early exit with MSSA
974 if (auto *Defs = MSSAU->getMemorySSA()->getBlockDefs(CurrentBB))
975 if (!isa<MemoryPhi>(*Defs->begin()) || (++Defs->begin() != Defs->end()))
976 return Changed;
977 if (llvm::any_of(*CurrentBB,
978 [](Instruction &I) { return I.mayHaveSideEffects(); }))
979 return Changed;
980
981 Instruction *CurrentTerm = CurrentBB->getTerminator();
982
983 if (auto *SI = dyn_cast<SwitchInst>(CurrentTerm)) {
984 // Don't bother trying to unswitch past a switch with a constant
985 // condition. This should be removed prior to running this pass by
986 // simplifycfg.
987 if (isa<Constant>(SI->getCondition()))
988 return Changed;
989
990 if (!unswitchTrivialSwitch(L, *SI, DT, LI, SE, MSSAU))
991 // Couldn't unswitch this one so we're done.
992 return Changed;
993
994 // Mark that we managed to unswitch something.
995 Changed = true;
996
997 // If unswitching turned the terminator into an unconditional branch then
998 // we can continue. The unswitching logic specifically works to fold any
999 // cases it can into an unconditional branch to make it easier to
1000 // recognize here.
1001 auto *BI = dyn_cast<BranchInst>(CurrentBB->getTerminator());
1002 if (!BI || BI->isConditional())
1003 return Changed;
1004
1005 CurrentBB = BI->getSuccessor(0);
1006 continue;
1007 }
1008
1009 auto *BI = dyn_cast<BranchInst>(CurrentTerm);
1010 if (!BI)
1011 // We do not understand other terminator instructions.
1012 return Changed;
1013
1014 // Don't bother trying to unswitch past an unconditional branch or a branch
1015 // with a constant value. These should be removed by simplifycfg prior to
1016 // running this pass.
1017 if (!BI->isConditional() || isa<Constant>(BI->getCondition()))
1018 return Changed;
1019
1020 // Found a trivial condition candidate: non-foldable conditional branch. If
1021 // we fail to unswitch this, we can't do anything else that is trivial.
1022 if (!unswitchTrivialBranch(L, *BI, DT, LI, SE, MSSAU))
1023 return Changed;
1024
1025 // Mark that we managed to unswitch something.
1026 Changed = true;
1027
1028 // If we only unswitched some of the conditions feeding the branch, we won't
1029 // have collapsed it to a single successor.
1030 BI = cast<BranchInst>(CurrentBB->getTerminator());
1031 if (BI->isConditional())
1032 return Changed;
1033
1034 // Follow the newly unconditional branch into its successor.
1035 CurrentBB = BI->getSuccessor(0);
1036
1037 // When continuing, if we exit the loop or reach a previous visited block,
1038 // then we can not reach any trivial condition candidates (unfoldable
1039 // branch instructions or switch instructions) and no unswitch can happen.
1040 } while (L.contains(CurrentBB) && Visited.insert(CurrentBB).second);
1041
1042 return Changed;
1043}
1044
1045/// Build the cloned blocks for an unswitched copy of the given loop.
1046///
1047/// The cloned blocks are inserted before the loop preheader (`LoopPH`) and
1048/// after the split block (`SplitBB`) that will be used to select between the
1049/// cloned and original loop.
1050///
1051/// This routine handles cloning all of the necessary loop blocks and exit
1052/// blocks including rewriting their instructions and the relevant PHI nodes.
1053/// Any loop blocks or exit blocks which are dominated by a different successor
1054/// than the one for this clone of the loop blocks can be trivially skipped. We
1055/// use the `DominatingSucc` map to determine whether a block satisfies that
1056/// property with a simple map lookup.
1057///
1058/// It also correctly creates the unconditional branch in the cloned
1059/// unswitched parent block to only point at the unswitched successor.
1060///
1061/// This does not handle most of the necessary updates to `LoopInfo`. Only exit
1062/// block splitting is correctly reflected in `LoopInfo`, essentially all of
1063/// the cloned blocks (and their loops) are left without full `LoopInfo`
1064/// updates. This also doesn't fully update `DominatorTree`. It adds the cloned
1065/// blocks to them but doesn't create the cloned `DominatorTree` structure and
1066/// instead the caller must recompute an accurate DT. It *does* correctly
1067/// update the `AssumptionCache` provided in `AC`.
1068static BasicBlock *buildClonedLoopBlocks(
1069 Loop &L, BasicBlock *LoopPH, BasicBlock *SplitBB,
1070 ArrayRef<BasicBlock *> ExitBlocks, BasicBlock *ParentBB,
1071 BasicBlock *UnswitchedSuccBB, BasicBlock *ContinueSuccBB,
1072 const SmallDenseMap<BasicBlock *, BasicBlock *, 16> &DominatingSucc,
1073 ValueToValueMapTy &VMap,
1074 SmallVectorImpl<DominatorTree::UpdateType> &DTUpdates, AssumptionCache &AC,
1075 DominatorTree &DT, LoopInfo &LI, MemorySSAUpdater *MSSAU) {
1076 SmallVector<BasicBlock *, 4> NewBlocks;
1077 NewBlocks.reserve(L.getNumBlocks() + ExitBlocks.size());
1078
1079 // We will need to clone a bunch of blocks, wrap up the clone operation in
1080 // a helper.
1081 auto CloneBlock = [&](BasicBlock *OldBB) {
1082 // Clone the basic block and insert it before the new preheader.
1083 BasicBlock *NewBB = CloneBasicBlock(OldBB, VMap, ".us", OldBB->getParent());
1084 NewBB->moveBefore(LoopPH);
1085
1086 // Record this block and the mapping.
1087 NewBlocks.push_back(NewBB);
1088 VMap[OldBB] = NewBB;
1089
1090 return NewBB;
1091 };
1092
1093 // We skip cloning blocks when they have a dominating succ that is not the
1094 // succ we are cloning for.
1095 auto SkipBlock = [&](BasicBlock *BB) {
1096 auto It = DominatingSucc.find(BB);
1097 return It != DominatingSucc.end() && It->second != UnswitchedSuccBB;
1098 };
1099
1100 // First, clone the preheader.
1101 auto *ClonedPH = CloneBlock(LoopPH);
1102
1103 // Then clone all the loop blocks, skipping the ones that aren't necessary.
1104 for (auto *LoopBB : L.blocks())
1105 if (!SkipBlock(LoopBB))
1106 CloneBlock(LoopBB);
1107
1108 // Split all the loop exit edges so that when we clone the exit blocks, if
1109 // any of the exit blocks are *also* a preheader for some other loop, we
1110 // don't create multiple predecessors entering the loop header.
1111 for (auto *ExitBB : ExitBlocks) {
1112 if (SkipBlock(ExitBB))
1113 continue;
1114
1115 // When we are going to clone an exit, we don't need to clone all the
1116 // instructions in the exit block and we want to ensure we have an easy
1117 // place to merge the CFG, so split the exit first. This is always safe to
1118 // do because there cannot be any non-loop predecessors of a loop exit in
1119 // loop simplified form.
1120 auto *MergeBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI, MSSAU);
1121
1122 // Rearrange the names to make it easier to write test cases by having the
1123 // exit block carry the suffix rather than the merge block carrying the
1124 // suffix.
1125 MergeBB->takeName(ExitBB);
1126 ExitBB->setName(Twine(MergeBB->getName()) + ".split");
1127
1128 // Now clone the original exit block.
1129 auto *ClonedExitBB = CloneBlock(ExitBB);
1130 assert(ClonedExitBB->getTerminator()->getNumSuccessors() == 1 &&(static_cast <bool> (ClonedExitBB->getTerminator()->
getNumSuccessors() == 1 && "Exit block should have been split to have one successor!"
) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getNumSuccessors() == 1 && \"Exit block should have been split to have one successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1131, __extension__ __PRETTY_FUNCTION__))
1131 "Exit block should have been split to have one successor!")(static_cast <bool> (ClonedExitBB->getTerminator()->
getNumSuccessors() == 1 && "Exit block should have been split to have one successor!"
) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getNumSuccessors() == 1 && \"Exit block should have been split to have one successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1131, __extension__ __PRETTY_FUNCTION__))
;
1132 assert(ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB &&(static_cast <bool> (ClonedExitBB->getTerminator()->
getSuccessor(0) == MergeBB && "Cloned exit block has the wrong successor!"
) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB && \"Cloned exit block has the wrong successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1133, __extension__ __PRETTY_FUNCTION__))
1133 "Cloned exit block has the wrong successor!")(static_cast <bool> (ClonedExitBB->getTerminator()->
getSuccessor(0) == MergeBB && "Cloned exit block has the wrong successor!"
) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB && \"Cloned exit block has the wrong successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1133, __extension__ __PRETTY_FUNCTION__))
;
1134
1135 // Remap any cloned instructions and create a merge phi node for them.
1136 for (auto ZippedInsts : llvm::zip_first(
1137 llvm::make_range(ExitBB->begin(), std::prev(ExitBB->end())),
1138 llvm::make_range(ClonedExitBB->begin(),
1139 std::prev(ClonedExitBB->end())))) {
1140 Instruction &I = std::get<0>(ZippedInsts);
1141 Instruction &ClonedI = std::get<1>(ZippedInsts);
1142
1143 // The only instructions in the exit block should be PHI nodes and
1144 // potentially a landing pad.
1145 assert((static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst
>(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!"
) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1147, __extension__ __PRETTY_FUNCTION__))
1146 (isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) &&(static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst
>(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!"
) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1147, __extension__ __PRETTY_FUNCTION__))
1147 "Bad instruction in exit block!")(static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst
>(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!"
) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1147, __extension__ __PRETTY_FUNCTION__))
;
1148 // We should have a value map between the instruction and its clone.
1149 assert(VMap.lookup(&I) == &ClonedI && "Mismatch in the value map!")(static_cast <bool> (VMap.lookup(&I) == &ClonedI
&& "Mismatch in the value map!") ? void (0) : __assert_fail
("VMap.lookup(&I) == &ClonedI && \"Mismatch in the value map!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1149, __extension__ __PRETTY_FUNCTION__))
;
1150
1151 auto *MergePN =
1152 PHINode::Create(I.getType(), /*NumReservedValues*/ 2, ".us-phi",
1153 &*MergeBB->getFirstInsertionPt());
1154 I.replaceAllUsesWith(MergePN);
1155 MergePN->addIncoming(&I, ExitBB);
1156 MergePN->addIncoming(&ClonedI, ClonedExitBB);
1157 }
1158 }
1159
1160 // Rewrite the instructions in the cloned blocks to refer to the instructions
1161 // in the cloned blocks. We have to do this as a second pass so that we have
1162 // everything available. Also, we have inserted new instructions which may
1163 // include assume intrinsics, so we update the assumption cache while
1164 // processing this.
1165 for (auto *ClonedBB : NewBlocks)
1166 for (Instruction &I : *ClonedBB) {
1167 RemapInstruction(&I, VMap,
1168 RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
1169 if (auto *II = dyn_cast<AssumeInst>(&I))
1170 AC.registerAssumption(II);
1171 }
1172
1173 // Update any PHI nodes in the cloned successors of the skipped blocks to not
1174 // have spurious incoming values.
1175 for (auto *LoopBB : L.blocks())
1176 if (SkipBlock(LoopBB))
1177 for (auto *SuccBB : successors(LoopBB))
1178 if (auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB)))
1179 for (PHINode &PN : ClonedSuccBB->phis())
1180 PN.removeIncomingValue(LoopBB, /*DeletePHIIfEmpty*/ false);
1181
1182 // Remove the cloned parent as a predecessor of any successor we ended up
1183 // cloning other than the unswitched one.
1184 auto *ClonedParentBB = cast<BasicBlock>(VMap.lookup(ParentBB));
1185 for (auto *SuccBB : successors(ParentBB)) {
1186 if (SuccBB == UnswitchedSuccBB)
1187 continue;
1188
1189 auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB));
1190 if (!ClonedSuccBB)
1191 continue;
1192
1193 ClonedSuccBB->removePredecessor(ClonedParentBB,
1194 /*KeepOneInputPHIs*/ true);
1195 }
1196
1197 // Replace the cloned branch with an unconditional branch to the cloned
1198 // unswitched successor.
1199 auto *ClonedSuccBB = cast<BasicBlock>(VMap.lookup(UnswitchedSuccBB));
1200 Instruction *ClonedTerminator = ClonedParentBB->getTerminator();
1201 // Trivial Simplification. If Terminator is a conditional branch and
1202 // condition becomes dead - erase it.
1203 Value *ClonedConditionToErase = nullptr;
1204 if (auto *BI = dyn_cast<BranchInst>(ClonedTerminator))
1205 ClonedConditionToErase = BI->getCondition();
1206 else if (auto *SI = dyn_cast<SwitchInst>(ClonedTerminator))
1207 ClonedConditionToErase = SI->getCondition();
1208
1209 ClonedTerminator->eraseFromParent();
1210 BranchInst::Create(ClonedSuccBB, ClonedParentBB);
1211
1212 if (ClonedConditionToErase)
1213 RecursivelyDeleteTriviallyDeadInstructions(ClonedConditionToErase, nullptr,
1214 MSSAU);
1215
1216 // If there are duplicate entries in the PHI nodes because of multiple edges
1217 // to the unswitched successor, we need to nuke all but one as we replaced it
1218 // with a direct branch.
1219 for (PHINode &PN : ClonedSuccBB->phis()) {
1220 bool Found = false;
1221 // Loop over the incoming operands backwards so we can easily delete as we
1222 // go without invalidating the index.
1223 for (int i = PN.getNumOperands() - 1; i >= 0; --i) {
1224 if (PN.getIncomingBlock(i) != ClonedParentBB)
1225 continue;
1226 if (!Found) {
1227 Found = true;
1228 continue;
1229 }
1230 PN.removeIncomingValue(i, /*DeletePHIIfEmpty*/ false);
1231 }
1232 }
1233
1234 // Record the domtree updates for the new blocks.
1235 SmallPtrSet<BasicBlock *, 4> SuccSet;
1236 for (auto *ClonedBB : NewBlocks) {
1237 for (auto *SuccBB : successors(ClonedBB))
1238 if (SuccSet.insert(SuccBB).second)
1239 DTUpdates.push_back({DominatorTree::Insert, ClonedBB, SuccBB});
1240 SuccSet.clear();
1241 }
1242
1243 return ClonedPH;
1244}
1245
1246/// Recursively clone the specified loop and all of its children.
1247///
1248/// The target parent loop for the clone should be provided, or can be null if
1249/// the clone is a top-level loop. While cloning, all the blocks are mapped
1250/// with the provided value map. The entire original loop must be present in
1251/// the value map. The cloned loop is returned.
1252static Loop *cloneLoopNest(Loop &OrigRootL, Loop *RootParentL,
1253 const ValueToValueMapTy &VMap, LoopInfo &LI) {
1254 auto AddClonedBlocksToLoop = [&](Loop &OrigL, Loop &ClonedL) {
1255 assert(ClonedL.getBlocks().empty() && "Must start with an empty loop!")(static_cast <bool> (ClonedL.getBlocks().empty() &&
"Must start with an empty loop!") ? void (0) : __assert_fail
("ClonedL.getBlocks().empty() && \"Must start with an empty loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1255, __extension__ __PRETTY_FUNCTION__))
;
1256 ClonedL.reserveBlocks(OrigL.getNumBlocks());
1257 for (auto *BB : OrigL.blocks()) {
1258 auto *ClonedBB = cast<BasicBlock>(VMap.lookup(BB));
1259 ClonedL.addBlockEntry(ClonedBB);
1260 if (LI.getLoopFor(BB) == &OrigL)
1261 LI.changeLoopFor(ClonedBB, &ClonedL);
1262 }
1263 };
1264
1265 // We specially handle the first loop because it may get cloned into
1266 // a different parent and because we most commonly are cloning leaf loops.
1267 Loop *ClonedRootL = LI.AllocateLoop();
1268 if (RootParentL)
1269 RootParentL->addChildLoop(ClonedRootL);
1270 else
1271 LI.addTopLevelLoop(ClonedRootL);
1272 AddClonedBlocksToLoop(OrigRootL, *ClonedRootL);
1273
1274 if (OrigRootL.isInnermost())
1275 return ClonedRootL;
1276
1277 // If we have a nest, we can quickly clone the entire loop nest using an
1278 // iterative approach because it is a tree. We keep the cloned parent in the
1279 // data structure to avoid repeatedly querying through a map to find it.
1280 SmallVector<std::pair<Loop *, Loop *>, 16> LoopsToClone;
1281 // Build up the loops to clone in reverse order as we'll clone them from the
1282 // back.
1283 for (Loop *ChildL : llvm::reverse(OrigRootL))
1284 LoopsToClone.push_back({ClonedRootL, ChildL});
1285 do {
1286 Loop *ClonedParentL, *L;
1287 std::tie(ClonedParentL, L) = LoopsToClone.pop_back_val();
1288 Loop *ClonedL = LI.AllocateLoop();
1289 ClonedParentL->addChildLoop(ClonedL);
1290 AddClonedBlocksToLoop(*L, *ClonedL);
1291 for (Loop *ChildL : llvm::reverse(*L))
1292 LoopsToClone.push_back({ClonedL, ChildL});
1293 } while (!LoopsToClone.empty());
1294
1295 return ClonedRootL;
1296}
1297
1298/// Build the cloned loops of an original loop from unswitching.
1299///
1300/// Because unswitching simplifies the CFG of the loop, this isn't a trivial
1301/// operation. We need to re-verify that there even is a loop (as the backedge
1302/// may not have been cloned), and even if there are remaining backedges the
1303/// backedge set may be different. However, we know that each child loop is
1304/// undisturbed, we only need to find where to place each child loop within
1305/// either any parent loop or within a cloned version of the original loop.
1306///
1307/// Because child loops may end up cloned outside of any cloned version of the
1308/// original loop, multiple cloned sibling loops may be created. All of them
1309/// are returned so that the newly introduced loop nest roots can be
1310/// identified.
1311static void buildClonedLoops(Loop &OrigL, ArrayRef<BasicBlock *> ExitBlocks,
1312 const ValueToValueMapTy &VMap, LoopInfo &LI,
1313 SmallVectorImpl<Loop *> &NonChildClonedLoops) {
1314 Loop *ClonedL = nullptr;
1315
1316 auto *OrigPH = OrigL.getLoopPreheader();
1317 auto *OrigHeader = OrigL.getHeader();
1318
1319 auto *ClonedPH = cast<BasicBlock>(VMap.lookup(OrigPH));
1320 auto *ClonedHeader = cast<BasicBlock>(VMap.lookup(OrigHeader));
1321
1322 // We need to know the loops of the cloned exit blocks to even compute the
1323 // accurate parent loop. If we only clone exits to some parent of the
1324 // original parent, we want to clone into that outer loop. We also keep track
1325 // of the loops that our cloned exit blocks participate in.
1326 Loop *ParentL = nullptr;
1327 SmallVector<BasicBlock *, 4> ClonedExitsInLoops;
1328 SmallDenseMap<BasicBlock *, Loop *, 16> ExitLoopMap;
1329 ClonedExitsInLoops.reserve(ExitBlocks.size());
1330 for (auto *ExitBB : ExitBlocks)
1331 if (auto *ClonedExitBB = cast_or_null<BasicBlock>(VMap.lookup(ExitBB)))
1332 if (Loop *ExitL = LI.getLoopFor(ExitBB)) {
1333 ExitLoopMap[ClonedExitBB] = ExitL;
1334 ClonedExitsInLoops.push_back(ClonedExitBB);
1335 if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL)))
1336 ParentL = ExitL;
1337 }
1338 assert((!ParentL || ParentL == OrigL.getParentLoop() ||(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop
() || ParentL->contains(OrigL.getParentLoop())) &&
"The computed parent loop should always contain (or be) the parent of "
"the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1341, __extension__ __PRETTY_FUNCTION__))
1339 ParentL->contains(OrigL.getParentLoop())) &&(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop
() || ParentL->contains(OrigL.getParentLoop())) &&
"The computed parent loop should always contain (or be) the parent of "
"the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1341, __extension__ __PRETTY_FUNCTION__))
1340 "The computed parent loop should always contain (or be) the parent of "(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop
() || ParentL->contains(OrigL.getParentLoop())) &&
"The computed parent loop should always contain (or be) the parent of "
"the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1341, __extension__ __PRETTY_FUNCTION__))
1341 "the original loop.")(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop
() || ParentL->contains(OrigL.getParentLoop())) &&
"The computed parent loop should always contain (or be) the parent of "
"the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1341, __extension__ __PRETTY_FUNCTION__))
;
1342
1343 // We build the set of blocks dominated by the cloned header from the set of
1344 // cloned blocks out of the original loop. While not all of these will
1345 // necessarily be in the cloned loop, it is enough to establish that they
1346 // aren't in unreachable cycles, etc.
1347 SmallSetVector<BasicBlock *, 16> ClonedLoopBlocks;
1348 for (auto *BB : OrigL.blocks())
1349 if (auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB)))
1350 ClonedLoopBlocks.insert(ClonedBB);
1351
1352 // Rebuild the set of blocks that will end up in the cloned loop. We may have
1353 // skipped cloning some region of this loop which can in turn skip some of
1354 // the backedges so we have to rebuild the blocks in the loop based on the
1355 // backedges that remain after cloning.
1356 SmallVector<BasicBlock *, 16> Worklist;
1357 SmallPtrSet<BasicBlock *, 16> BlocksInClonedLoop;
1358 for (auto *Pred : predecessors(ClonedHeader)) {
1359 // The only possible non-loop header predecessor is the preheader because
1360 // we know we cloned the loop in simplified form.
1361 if (Pred == ClonedPH)
1362 continue;
1363
1364 // Because the loop was in simplified form, the only non-loop predecessor
1365 // should be the preheader.
1366 assert(ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop "(static_cast <bool> (ClonedLoopBlocks.count(Pred) &&
"Found a predecessor of the loop " "header other than the preheader "
"that is not part of the loop!") ? void (0) : __assert_fail (
"ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1368, __extension__ __PRETTY_FUNCTION__))
1367 "header other than the preheader "(static_cast <bool> (ClonedLoopBlocks.count(Pred) &&
"Found a predecessor of the loop " "header other than the preheader "
"that is not part of the loop!") ? void (0) : __assert_fail (
"ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1368, __extension__ __PRETTY_FUNCTION__))
1368 "that is not part of the loop!")(static_cast <bool> (ClonedLoopBlocks.count(Pred) &&
"Found a predecessor of the loop " "header other than the preheader "
"that is not part of the loop!") ? void (0) : __assert_fail (
"ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1368, __extension__ __PRETTY_FUNCTION__))
;
1369
1370 // Insert this block into the loop set and on the first visit (and if it
1371 // isn't the header we're currently walking) put it into the worklist to
1372 // recurse through.
1373 if (BlocksInClonedLoop.insert(Pred).second && Pred != ClonedHeader)
1374 Worklist.push_back(Pred);
1375 }
1376
1377 // If we had any backedges then there *is* a cloned loop. Put the header into
1378 // the loop set and then walk the worklist backwards to find all the blocks
1379 // that remain within the loop after cloning.
1380 if (!BlocksInClonedLoop.empty()) {
1381 BlocksInClonedLoop.insert(ClonedHeader);
1382
1383 while (!Worklist.empty()) {
1384 BasicBlock *BB = Worklist.pop_back_val();
1385 assert(BlocksInClonedLoop.count(BB) &&(static_cast <bool> (BlocksInClonedLoop.count(BB) &&
"Didn't put block into the loop set!") ? void (0) : __assert_fail
("BlocksInClonedLoop.count(BB) && \"Didn't put block into the loop set!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1386, __extension__ __PRETTY_FUNCTION__))
1386 "Didn't put block into the loop set!")(static_cast <bool> (BlocksInClonedLoop.count(BB) &&
"Didn't put block into the loop set!") ? void (0) : __assert_fail
("BlocksInClonedLoop.count(BB) && \"Didn't put block into the loop set!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1386, __extension__ __PRETTY_FUNCTION__))
;
1387
1388 // Insert any predecessors that are in the possible set into the cloned
1389 // set, and if the insert is successful, add them to the worklist. Note
1390 // that we filter on the blocks that are definitely reachable via the
1391 // backedge to the loop header so we may prune out dead code within the
1392 // cloned loop.
1393 for (auto *Pred : predecessors(BB))
1394 if (ClonedLoopBlocks.count(Pred) &&
1395 BlocksInClonedLoop.insert(Pred).second)
1396 Worklist.push_back(Pred);
1397 }
1398
1399 ClonedL = LI.AllocateLoop();
1400 if (ParentL) {
1401 ParentL->addBasicBlockToLoop(ClonedPH, LI);
1402 ParentL->addChildLoop(ClonedL);
1403 } else {
1404 LI.addTopLevelLoop(ClonedL);
1405 }
1406 NonChildClonedLoops.push_back(ClonedL);
1407
1408 ClonedL->reserveBlocks(BlocksInClonedLoop.size());
1409 // We don't want to just add the cloned loop blocks based on how we
1410 // discovered them. The original order of blocks was carefully built in
1411 // a way that doesn't rely on predecessor ordering. Rather than re-invent
1412 // that logic, we just re-walk the original blocks (and those of the child
1413 // loops) and filter them as we add them into the cloned loop.
1414 for (auto *BB : OrigL.blocks()) {
1415 auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB));
1416 if (!ClonedBB || !BlocksInClonedLoop.count(ClonedBB))
1417 continue;
1418
1419 // Directly add the blocks that are only in this loop.
1420 if (LI.getLoopFor(BB) == &OrigL) {
1421 ClonedL->addBasicBlockToLoop(ClonedBB, LI);
1422 continue;
1423 }
1424
1425 // We want to manually add it to this loop and parents.
1426 // Registering it with LoopInfo will happen when we clone the top
1427 // loop for this block.
1428 for (Loop *PL = ClonedL; PL; PL = PL->getParentLoop())
1429 PL->addBlockEntry(ClonedBB);
1430 }
1431
1432 // Now add each child loop whose header remains within the cloned loop. All
1433 // of the blocks within the loop must satisfy the same constraints as the
1434 // header so once we pass the header checks we can just clone the entire
1435 // child loop nest.
1436 for (Loop *ChildL : OrigL) {
1437 auto *ClonedChildHeader =
1438 cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader()));
1439 if (!ClonedChildHeader || !BlocksInClonedLoop.count(ClonedChildHeader))
1440 continue;
1441
1442#ifndef NDEBUG
1443 // We should never have a cloned child loop header but fail to have
1444 // all of the blocks for that child loop.
1445 for (auto *ChildLoopBB : ChildL->blocks())
1446 assert(BlocksInClonedLoop.count((static_cast <bool> (BlocksInClonedLoop.count( cast<
BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer "
"loop but not all of its blocks!") ? void (0) : __assert_fail
("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1449, __extension__ __PRETTY_FUNCTION__))
1447 cast<BasicBlock>(VMap.lookup(ChildLoopBB))) &&(static_cast <bool> (BlocksInClonedLoop.count( cast<
BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer "
"loop but not all of its blocks!") ? void (0) : __assert_fail
("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1449, __extension__ __PRETTY_FUNCTION__))
1448 "Child cloned loop has a header within the cloned outer "(static_cast <bool> (BlocksInClonedLoop.count( cast<
BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer "
"loop but not all of its blocks!") ? void (0) : __assert_fail
("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1449, __extension__ __PRETTY_FUNCTION__))
1449 "loop but not all of its blocks!")(static_cast <bool> (BlocksInClonedLoop.count( cast<
BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer "
"loop but not all of its blocks!") ? void (0) : __assert_fail
("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1449, __extension__ __PRETTY_FUNCTION__))
;
1450#endif
1451
1452 cloneLoopNest(*ChildL, ClonedL, VMap, LI);
1453 }
1454 }
1455
1456 // Now that we've handled all the components of the original loop that were
1457 // cloned into a new loop, we still need to handle anything from the original
1458 // loop that wasn't in a cloned loop.
1459
1460 // Figure out what blocks are left to place within any loop nest containing
1461 // the unswitched loop. If we never formed a loop, the cloned PH is one of
1462 // them.
1463 SmallPtrSet<BasicBlock *, 16> UnloopedBlockSet;
1464 if (BlocksInClonedLoop.empty())
1465 UnloopedBlockSet.insert(ClonedPH);
1466 for (auto *ClonedBB : ClonedLoopBlocks)
1467 if (!BlocksInClonedLoop.count(ClonedBB))
1468 UnloopedBlockSet.insert(ClonedBB);
1469
1470 // Copy the cloned exits and sort them in ascending loop depth, we'll work
1471 // backwards across these to process them inside out. The order shouldn't
1472 // matter as we're just trying to build up the map from inside-out; we use
1473 // the map in a more stably ordered way below.
1474 auto OrderedClonedExitsInLoops = ClonedExitsInLoops;
1475 llvm::sort(OrderedClonedExitsInLoops, [&](BasicBlock *LHS, BasicBlock *RHS) {
1476 return ExitLoopMap.lookup(LHS)->getLoopDepth() <
1477 ExitLoopMap.lookup(RHS)->getLoopDepth();
1478 });
1479
1480 // Populate the existing ExitLoopMap with everything reachable from each
1481 // exit, starting from the inner most exit.
1482 while (!UnloopedBlockSet.empty() && !OrderedClonedExitsInLoops.empty()) {
1483 assert(Worklist.empty() && "Didn't clear worklist!")(static_cast <bool> (Worklist.empty() && "Didn't clear worklist!"
) ? void (0) : __assert_fail ("Worklist.empty() && \"Didn't clear worklist!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1483, __extension__ __PRETTY_FUNCTION__))
;
1484
1485 BasicBlock *ExitBB = OrderedClonedExitsInLoops.pop_back_val();
1486 Loop *ExitL = ExitLoopMap.lookup(ExitBB);
1487
1488 // Walk the CFG back until we hit the cloned PH adding everything reachable
1489 // and in the unlooped set to this exit block's loop.
1490 Worklist.push_back(ExitBB);
1491 do {
1492 BasicBlock *BB = Worklist.pop_back_val();
1493 // We can stop recursing at the cloned preheader (if we get there).
1494 if (BB == ClonedPH)
1495 continue;
1496
1497 for (BasicBlock *PredBB : predecessors(BB)) {
1498 // If this pred has already been moved to our set or is part of some
1499 // (inner) loop, no update needed.
1500 if (!UnloopedBlockSet.erase(PredBB)) {
1501 assert((static_cast <bool> ((BlocksInClonedLoop.count(PredBB) ||
ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!"
) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1503, __extension__ __PRETTY_FUNCTION__))
1502 (BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) &&(static_cast <bool> ((BlocksInClonedLoop.count(PredBB) ||
ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!"
) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1503, __extension__ __PRETTY_FUNCTION__))
1503 "Predecessor not mapped to a loop!")(static_cast <bool> ((BlocksInClonedLoop.count(PredBB) ||
ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!"
) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1503, __extension__ __PRETTY_FUNCTION__))
;
1504 continue;
1505 }
1506
1507 // We just insert into the loop set here. We'll add these blocks to the
1508 // exit loop after we build up the set in an order that doesn't rely on
1509 // predecessor order (which in turn relies on use list order).
1510 bool Inserted = ExitLoopMap.insert({PredBB, ExitL}).second;
1511 (void)Inserted;
1512 assert(Inserted && "Should only visit an unlooped block once!")(static_cast <bool> (Inserted && "Should only visit an unlooped block once!"
) ? void (0) : __assert_fail ("Inserted && \"Should only visit an unlooped block once!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1512, __extension__ __PRETTY_FUNCTION__))
;
1513
1514 // And recurse through to its predecessors.
1515 Worklist.push_back(PredBB);
1516 }
1517 } while (!Worklist.empty());
1518 }
1519
1520 // Now that the ExitLoopMap gives as mapping for all the non-looping cloned
1521 // blocks to their outer loops, walk the cloned blocks and the cloned exits
1522 // in their original order adding them to the correct loop.
1523
1524 // We need a stable insertion order. We use the order of the original loop
1525 // order and map into the correct parent loop.
1526 for (auto *BB : llvm::concat<BasicBlock *const>(
1527 makeArrayRef(ClonedPH), ClonedLoopBlocks, ClonedExitsInLoops))
1528 if (Loop *OuterL = ExitLoopMap.lookup(BB))
1529 OuterL->addBasicBlockToLoop(BB, LI);
1530
1531#ifndef NDEBUG
1532 for (auto &BBAndL : ExitLoopMap) {
1533 auto *BB = BBAndL.first;
1534 auto *OuterL = BBAndL.second;
1535 assert(LI.getLoopFor(BB) == OuterL &&(static_cast <bool> (LI.getLoopFor(BB) == OuterL &&
"Failed to put all blocks into outer loops!") ? void (0) : __assert_fail
("LI.getLoopFor(BB) == OuterL && \"Failed to put all blocks into outer loops!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1536, __extension__ __PRETTY_FUNCTION__))
1536 "Failed to put all blocks into outer loops!")(static_cast <bool> (LI.getLoopFor(BB) == OuterL &&
"Failed to put all blocks into outer loops!") ? void (0) : __assert_fail
("LI.getLoopFor(BB) == OuterL && \"Failed to put all blocks into outer loops!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1536, __extension__ __PRETTY_FUNCTION__))
;
1537 }
1538#endif
1539
1540 // Now that all the blocks are placed into the correct containing loop in the
1541 // absence of child loops, find all the potentially cloned child loops and
1542 // clone them into whatever outer loop we placed their header into.
1543 for (Loop *ChildL : OrigL) {
1544 auto *ClonedChildHeader =
1545 cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader()));
1546 if (!ClonedChildHeader || BlocksInClonedLoop.count(ClonedChildHeader))
1547 continue;
1548
1549#ifndef NDEBUG
1550 for (auto *ChildLoopBB : ChildL->blocks())
1551 assert(VMap.count(ChildLoopBB) &&(static_cast <bool> (VMap.count(ChildLoopBB) &&
"Cloned a child loop header but not all of that loops blocks!"
) ? void (0) : __assert_fail ("VMap.count(ChildLoopBB) && \"Cloned a child loop header but not all of that loops blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1552, __extension__ __PRETTY_FUNCTION__))
1552 "Cloned a child loop header but not all of that loops blocks!")(static_cast <bool> (VMap.count(ChildLoopBB) &&
"Cloned a child loop header but not all of that loops blocks!"
) ? void (0) : __assert_fail ("VMap.count(ChildLoopBB) && \"Cloned a child loop header but not all of that loops blocks!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1552, __extension__ __PRETTY_FUNCTION__))
;
1553#endif
1554
1555 NonChildClonedLoops.push_back(cloneLoopNest(
1556 *ChildL, ExitLoopMap.lookup(ClonedChildHeader), VMap, LI));
1557 }
1558}
1559
1560static void
1561deleteDeadClonedBlocks(Loop &L, ArrayRef<BasicBlock *> ExitBlocks,
1562 ArrayRef<std::unique_ptr<ValueToValueMapTy>> VMaps,
1563 DominatorTree &DT, MemorySSAUpdater *MSSAU) {
1564 // Find all the dead clones, and remove them from their successors.
1565 SmallVector<BasicBlock *, 16> DeadBlocks;
1566 for (BasicBlock *BB : llvm::concat<BasicBlock *const>(L.blocks(), ExitBlocks))
1567 for (auto &VMap : VMaps)
1568 if (BasicBlock *ClonedBB = cast_or_null<BasicBlock>(VMap->lookup(BB)))
1569 if (!DT.isReachableFromEntry(ClonedBB)) {
1570 for (BasicBlock *SuccBB : successors(ClonedBB))
1571 SuccBB->removePredecessor(ClonedBB);
1572 DeadBlocks.push_back(ClonedBB);
1573 }
1574
1575 // Remove all MemorySSA in the dead blocks
1576 if (MSSAU) {
1577 SmallSetVector<BasicBlock *, 8> DeadBlockSet(DeadBlocks.begin(),
1578 DeadBlocks.end());
1579 MSSAU->removeBlocks(DeadBlockSet);
1580 }
1581
1582 // Drop any remaining references to break cycles.
1583 for (BasicBlock *BB : DeadBlocks)
1584 BB->dropAllReferences();
1585 // Erase them from the IR.
1586 for (BasicBlock *BB : DeadBlocks)
1587 BB->eraseFromParent();
1588}
1589
1590static void deleteDeadBlocksFromLoop(Loop &L,
1591 SmallVectorImpl<BasicBlock *> &ExitBlocks,
1592 DominatorTree &DT, LoopInfo &LI,
1593 MemorySSAUpdater *MSSAU) {
1594 // Find all the dead blocks tied to this loop, and remove them from their
1595 // successors.
1596 SmallSetVector<BasicBlock *, 8> DeadBlockSet;
1597
1598 // Start with loop/exit blocks and get a transitive closure of reachable dead
1599 // blocks.
1600 SmallVector<BasicBlock *, 16> DeathCandidates(ExitBlocks.begin(),
1601 ExitBlocks.end());
1602 DeathCandidates.append(L.blocks().begin(), L.blocks().end());
1603 while (!DeathCandidates.empty()) {
1604 auto *BB = DeathCandidates.pop_back_val();
1605 if (!DeadBlockSet.count(BB) && !DT.isReachableFromEntry(BB)) {
1606 for (BasicBlock *SuccBB : successors(BB)) {
1607 SuccBB->removePredecessor(BB);
1608 DeathCandidates.push_back(SuccBB);
1609 }
1610 DeadBlockSet.insert(BB);
1611 }
1612 }
1613
1614 // Remove all MemorySSA in the dead blocks
1615 if (MSSAU)
1616 MSSAU->removeBlocks(DeadBlockSet);
1617
1618 // Filter out the dead blocks from the exit blocks list so that it can be
1619 // used in the caller.
1620 llvm::erase_if(ExitBlocks,
1621 [&](BasicBlock *BB) { return DeadBlockSet.count(BB); });
1622
1623 // Walk from this loop up through its parents removing all of the dead blocks.
1624 for (Loop *ParentL = &L; ParentL; ParentL = ParentL->getParentLoop()) {
1625 for (auto *BB : DeadBlockSet)
1626 ParentL->getBlocksSet().erase(BB);
1627 llvm::erase_if(ParentL->getBlocksVector(),
1628 [&](BasicBlock *BB) { return DeadBlockSet.count(BB); });
1629 }
1630
1631 // Now delete the dead child loops. This raw delete will clear them
1632 // recursively.
1633 llvm::erase_if(L.getSubLoopsVector(), [&](Loop *ChildL) {
1634 if (!DeadBlockSet.count(ChildL->getHeader()))
1635 return false;
1636
1637 assert(llvm::all_of(ChildL->blocks(),(static_cast <bool> (llvm::all_of(ChildL->blocks(), [
&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB
); }) && "If the child loop header is dead all blocks in the child loop must "
"be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1642, __extension__ __PRETTY_FUNCTION__))
1638 [&](BasicBlock *ChildBB) {(static_cast <bool> (llvm::all_of(ChildL->blocks(), [
&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB
); }) && "If the child loop header is dead all blocks in the child loop must "
"be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1642, __extension__ __PRETTY_FUNCTION__))
1639 return DeadBlockSet.count(ChildBB);(static_cast <bool> (llvm::all_of(ChildL->blocks(), [
&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB
); }) && "If the child loop header is dead all blocks in the child loop must "
"be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1642, __extension__ __PRETTY_FUNCTION__))
1640 }) &&(static_cast <bool> (llvm::all_of(ChildL->blocks(), [
&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB
); }) && "If the child loop header is dead all blocks in the child loop must "
"be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1642, __extension__ __PRETTY_FUNCTION__))
1641 "If the child loop header is dead all blocks in the child loop must "(static_cast <bool> (llvm::all_of(ChildL->blocks(), [
&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB
); }) && "If the child loop header is dead all blocks in the child loop must "
"be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1642, __extension__ __PRETTY_FUNCTION__))
1642 "be dead as well!")(static_cast <bool> (llvm::all_of(ChildL->blocks(), [
&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB
); }) && "If the child loop header is dead all blocks in the child loop must "
"be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1642, __extension__ __PRETTY_FUNCTION__))
;
1643 LI.destroy(ChildL);
1644 return true;
1645 });
1646
1647 // Remove the loop mappings for the dead blocks and drop all the references
1648 // from these blocks to others to handle cyclic references as we start
1649 // deleting the blocks themselves.
1650 for (auto *BB : DeadBlockSet) {
1651 // Check that the dominator tree has already been updated.
1652 assert(!DT.getNode(BB) && "Should already have cleared domtree!")(static_cast <bool> (!DT.getNode(BB) && "Should already have cleared domtree!"
) ? void (0) : __assert_fail ("!DT.getNode(BB) && \"Should already have cleared domtree!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1652, __extension__ __PRETTY_FUNCTION__))
;
1653 LI.changeLoopFor(BB, nullptr);
1654 // Drop all uses of the instructions to make sure we won't have dangling
1655 // uses in other blocks.
1656 for (auto &I : *BB)
1657 if (!I.use_empty())
1658 I.replaceAllUsesWith(UndefValue::get(I.getType()));
1659 BB->dropAllReferences();
1660 }
1661
1662 // Actually delete the blocks now that they've been fully unhooked from the
1663 // IR.
1664 for (auto *BB : DeadBlockSet)
1665 BB->eraseFromParent();
1666}
1667
1668/// Recompute the set of blocks in a loop after unswitching.
1669///
1670/// This walks from the original headers predecessors to rebuild the loop. We
1671/// take advantage of the fact that new blocks can't have been added, and so we
1672/// filter by the original loop's blocks. This also handles potentially
1673/// unreachable code that we don't want to explore but might be found examining
1674/// the predecessors of the header.
1675///
1676/// If the original loop is no longer a loop, this will return an empty set. If
1677/// it remains a loop, all the blocks within it will be added to the set
1678/// (including those blocks in inner loops).
1679static SmallPtrSet<const BasicBlock *, 16> recomputeLoopBlockSet(Loop &L,
1680 LoopInfo &LI) {
1681 SmallPtrSet<const BasicBlock *, 16> LoopBlockSet;
1682
1683 auto *PH = L.getLoopPreheader();
1684 auto *Header = L.getHeader();
1685
1686 // A worklist to use while walking backwards from the header.
1687 SmallVector<BasicBlock *, 16> Worklist;
1688
1689 // First walk the predecessors of the header to find the backedges. This will
1690 // form the basis of our walk.
1691 for (auto *Pred : predecessors(Header)) {
1692 // Skip the preheader.
1693 if (Pred == PH)
1694 continue;
1695
1696 // Because the loop was in simplified form, the only non-loop predecessor
1697 // is the preheader.
1698 assert(L.contains(Pred) && "Found a predecessor of the loop header other "(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other "
"than the preheader that is not part of the " "loop!") ? void
(0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1700, __extension__ __PRETTY_FUNCTION__))
1699 "than the preheader that is not part of the "(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other "
"than the preheader that is not part of the " "loop!") ? void
(0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1700, __extension__ __PRETTY_FUNCTION__))
1700 "loop!")(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other "
"than the preheader that is not part of the " "loop!") ? void
(0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1700, __extension__ __PRETTY_FUNCTION__))
;
1701
1702 // Insert this block into the loop set and on the first visit and, if it
1703 // isn't the header we're currently walking, put it into the worklist to
1704 // recurse through.
1705 if (LoopBlockSet.insert(Pred).second && Pred != Header)
1706 Worklist.push_back(Pred);
1707 }
1708
1709 // If no backedges were found, we're done.
1710 if (LoopBlockSet.empty())
1711 return LoopBlockSet;
1712
1713 // We found backedges, recurse through them to identify the loop blocks.
1714 while (!Worklist.empty()) {
1715 BasicBlock *BB = Worklist.pop_back_val();
1716 assert(LoopBlockSet.count(BB) && "Didn't put block into the loop set!")(static_cast <bool> (LoopBlockSet.count(BB) && "Didn't put block into the loop set!"
) ? void (0) : __assert_fail ("LoopBlockSet.count(BB) && \"Didn't put block into the loop set!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1716, __extension__ __PRETTY_FUNCTION__))
;
1717
1718 // No need to walk past the header.
1719 if (BB == Header)
1720 continue;
1721
1722 // Because we know the inner loop structure remains valid we can use the
1723 // loop structure to jump immediately across the entire nested loop.
1724 // Further, because it is in loop simplified form, we can directly jump
1725 // to its preheader afterward.
1726 if (Loop *InnerL = LI.getLoopFor(BB))
1727 if (InnerL != &L) {
1728 assert(L.contains(InnerL) &&(static_cast <bool> (L.contains(InnerL) && "Should not reach a loop *outside* this loop!"
) ? void (0) : __assert_fail ("L.contains(InnerL) && \"Should not reach a loop *outside* this loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1729, __extension__ __PRETTY_FUNCTION__))
1729 "Should not reach a loop *outside* this loop!")(static_cast <bool> (L.contains(InnerL) && "Should not reach a loop *outside* this loop!"
) ? void (0) : __assert_fail ("L.contains(InnerL) && \"Should not reach a loop *outside* this loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1729, __extension__ __PRETTY_FUNCTION__))
;
1730 // The preheader is the only possible predecessor of the loop so
1731 // insert it into the set and check whether it was already handled.
1732 auto *InnerPH = InnerL->getLoopPreheader();
1733 assert(L.contains(InnerPH) && "Cannot contain an inner loop block "(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block "
"but not contain the inner loop " "preheader!") ? void (0) :
__assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1735, __extension__ __PRETTY_FUNCTION__))
1734 "but not contain the inner loop "(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block "
"but not contain the inner loop " "preheader!") ? void (0) :
__assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1735, __extension__ __PRETTY_FUNCTION__))
1735 "preheader!")(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block "
"but not contain the inner loop " "preheader!") ? void (0) :
__assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1735, __extension__ __PRETTY_FUNCTION__))
;
1736 if (!LoopBlockSet.insert(InnerPH).second)
1737 // The only way to reach the preheader is through the loop body
1738 // itself so if it has been visited the loop is already handled.
1739 continue;
1740
1741 // Insert all of the blocks (other than those already present) into
1742 // the loop set. We expect at least the block that led us to find the
1743 // inner loop to be in the block set, but we may also have other loop
1744 // blocks if they were already enqueued as predecessors of some other
1745 // outer loop block.
1746 for (auto *InnerBB : InnerL->blocks()) {
1747 if (InnerBB == BB) {
1748 assert(LoopBlockSet.count(InnerBB) &&(static_cast <bool> (LoopBlockSet.count(InnerBB) &&
"Block should already be in the set!") ? void (0) : __assert_fail
("LoopBlockSet.count(InnerBB) && \"Block should already be in the set!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1749, __extension__ __PRETTY_FUNCTION__))
1749 "Block should already be in the set!")(static_cast <bool> (LoopBlockSet.count(InnerBB) &&
"Block should already be in the set!") ? void (0) : __assert_fail
("LoopBlockSet.count(InnerBB) && \"Block should already be in the set!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1749, __extension__ __PRETTY_FUNCTION__))
;
1750 continue;
1751 }
1752
1753 LoopBlockSet.insert(InnerBB);
1754 }
1755
1756 // Add the preheader to the worklist so we will continue past the
1757 // loop body.
1758 Worklist.push_back(InnerPH);
1759 continue;
1760 }
1761
1762 // Insert any predecessors that were in the original loop into the new
1763 // set, and if the insert is successful, add them to the worklist.
1764 for (auto *Pred : predecessors(BB))
1765 if (L.contains(Pred) && LoopBlockSet.insert(Pred).second)
1766 Worklist.push_back(Pred);
1767 }
1768
1769 assert(LoopBlockSet.count(Header) && "Cannot fail to add the header!")(static_cast <bool> (LoopBlockSet.count(Header) &&
"Cannot fail to add the header!") ? void (0) : __assert_fail
("LoopBlockSet.count(Header) && \"Cannot fail to add the header!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1769, __extension__ __PRETTY_FUNCTION__))
;
1770
1771 // We've found all the blocks participating in the loop, return our completed
1772 // set.
1773 return LoopBlockSet;
1774}
1775
1776/// Rebuild a loop after unswitching removes some subset of blocks and edges.
1777///
1778/// The removal may have removed some child loops entirely but cannot have
1779/// disturbed any remaining child loops. However, they may need to be hoisted
1780/// to the parent loop (or to be top-level loops). The original loop may be
1781/// completely removed.
1782///
1783/// The sibling loops resulting from this update are returned. If the original
1784/// loop remains a valid loop, it will be the first entry in this list with all
1785/// of the newly sibling loops following it.
1786///
1787/// Returns true if the loop remains a loop after unswitching, and false if it
1788/// is no longer a loop after unswitching (and should not continue to be
1789/// referenced).
1790static bool rebuildLoopAfterUnswitch(Loop &L, ArrayRef<BasicBlock *> ExitBlocks,
1791 LoopInfo &LI,
1792 SmallVectorImpl<Loop *> &HoistedLoops) {
1793 auto *PH = L.getLoopPreheader();
1794
1795 // Compute the actual parent loop from the exit blocks. Because we may have
1796 // pruned some exits the loop may be different from the original parent.
1797 Loop *ParentL = nullptr;
1798 SmallVector<Loop *, 4> ExitLoops;
1799 SmallVector<BasicBlock *, 4> ExitsInLoops;
1800 ExitsInLoops.reserve(ExitBlocks.size());
1801 for (auto *ExitBB : ExitBlocks)
1802 if (Loop *ExitL = LI.getLoopFor(ExitBB)) {
1803 ExitLoops.push_back(ExitL);
1804 ExitsInLoops.push_back(ExitBB);
1805 if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL)))
1806 ParentL = ExitL;
1807 }
1808
1809 // Recompute the blocks participating in this loop. This may be empty if it
1810 // is no longer a loop.
1811 auto LoopBlockSet = recomputeLoopBlockSet(L, LI);
1812
1813 // If we still have a loop, we need to re-set the loop's parent as the exit
1814 // block set changing may have moved it within the loop nest. Note that this
1815 // can only happen when this loop has a parent as it can only hoist the loop
1816 // *up* the nest.
1817 if (!LoopBlockSet.empty() && L.getParentLoop() != ParentL) {
1818 // Remove this loop's (original) blocks from all of the intervening loops.
1819 for (Loop *IL = L.getParentLoop(); IL != ParentL;
1820 IL = IL->getParentLoop()) {
1821 IL->getBlocksSet().erase(PH);
1822 for (auto *BB : L.blocks())
1823 IL->getBlocksSet().erase(BB);
1824 llvm::erase_if(IL->getBlocksVector(), [&](BasicBlock *BB) {
1825 return BB == PH || L.contains(BB);
1826 });
1827 }
1828
1829 LI.changeLoopFor(PH, ParentL);
1830 L.getParentLoop()->removeChildLoop(&L);
1831 if (ParentL)
1832 ParentL->addChildLoop(&L);
1833 else
1834 LI.addTopLevelLoop(&L);
1835 }
1836
1837 // Now we update all the blocks which are no longer within the loop.
1838 auto &Blocks = L.getBlocksVector();
1839 auto BlocksSplitI =
1840 LoopBlockSet.empty()
1841 ? Blocks.begin()
1842 : std::stable_partition(
1843 Blocks.begin(), Blocks.end(),
1844 [&](BasicBlock *BB) { return LoopBlockSet.count(BB); });
1845
1846 // Before we erase the list of unlooped blocks, build a set of them.
1847 SmallPtrSet<BasicBlock *, 16> UnloopedBlocks(BlocksSplitI, Blocks.end());
1848 if (LoopBlockSet.empty())
1849 UnloopedBlocks.insert(PH);
1850
1851 // Now erase these blocks from the loop.
1852 for (auto *BB : make_range(BlocksSplitI, Blocks.end()))
1853 L.getBlocksSet().erase(BB);
1854 Blocks.erase(BlocksSplitI, Blocks.end());
1855
1856 // Sort the exits in ascending loop depth, we'll work backwards across these
1857 // to process them inside out.
1858 llvm::stable_sort(ExitsInLoops, [&](BasicBlock *LHS, BasicBlock *RHS) {
1859 return LI.getLoopDepth(LHS) < LI.getLoopDepth(RHS);
1860 });
1861
1862 // We'll build up a set for each exit loop.
1863 SmallPtrSet<BasicBlock *, 16> NewExitLoopBlocks;
1864 Loop *PrevExitL = L.getParentLoop(); // The deepest possible exit loop.
1865
1866 auto RemoveUnloopedBlocksFromLoop =
1867 [](Loop &L, SmallPtrSetImpl<BasicBlock *> &UnloopedBlocks) {
1868 for (auto *BB : UnloopedBlocks)
1869 L.getBlocksSet().erase(BB);
1870 llvm::erase_if(L.getBlocksVector(), [&](BasicBlock *BB) {
1871 return UnloopedBlocks.count(BB);
1872 });
1873 };
1874
1875 SmallVector<BasicBlock *, 16> Worklist;
1876 while (!UnloopedBlocks.empty() && !ExitsInLoops.empty()) {
1877 assert(Worklist.empty() && "Didn't clear worklist!")(static_cast <bool> (Worklist.empty() && "Didn't clear worklist!"
) ? void (0) : __assert_fail ("Worklist.empty() && \"Didn't clear worklist!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1877, __extension__ __PRETTY_FUNCTION__))
;
1878 assert(NewExitLoopBlocks.empty() && "Didn't clear loop set!")(static_cast <bool> (NewExitLoopBlocks.empty() &&
"Didn't clear loop set!") ? void (0) : __assert_fail ("NewExitLoopBlocks.empty() && \"Didn't clear loop set!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1878, __extension__ __PRETTY_FUNCTION__))
;
1879
1880 // Grab the next exit block, in decreasing loop depth order.
1881 BasicBlock *ExitBB = ExitsInLoops.pop_back_val();
1882 Loop &ExitL = *LI.getLoopFor(ExitBB);
1883 assert(ExitL.contains(&L) && "Exit loop must contain the inner loop!")(static_cast <bool> (ExitL.contains(&L) && "Exit loop must contain the inner loop!"
) ? void (0) : __assert_fail ("ExitL.contains(&L) && \"Exit loop must contain the inner loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1883, __extension__ __PRETTY_FUNCTION__))
;
1884
1885 // Erase all of the unlooped blocks from the loops between the previous
1886 // exit loop and this exit loop. This works because the ExitInLoops list is
1887 // sorted in increasing order of loop depth and thus we visit loops in
1888 // decreasing order of loop depth.
1889 for (; PrevExitL != &ExitL; PrevExitL = PrevExitL->getParentLoop())
1890 RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks);
1891
1892 // Walk the CFG back until we hit the cloned PH adding everything reachable
1893 // and in the unlooped set to this exit block's loop.
1894 Worklist.push_back(ExitBB);
1895 do {
1896 BasicBlock *BB = Worklist.pop_back_val();
1897 // We can stop recursing at the cloned preheader (if we get there).
1898 if (BB == PH)
1899 continue;
1900
1901 for (BasicBlock *PredBB : predecessors(BB)) {
1902 // If this pred has already been moved to our set or is part of some
1903 // (inner) loop, no update needed.
1904 if (!UnloopedBlocks.erase(PredBB)) {
1905 assert((NewExitLoopBlocks.count(PredBB) ||(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) ||
ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!"
) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1907, __extension__ __PRETTY_FUNCTION__))
1906 ExitL.contains(LI.getLoopFor(PredBB))) &&(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) ||
ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!"
) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1907, __extension__ __PRETTY_FUNCTION__))
1907 "Predecessor not in a nested loop (or already visited)!")(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) ||
ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!"
) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1907, __extension__ __PRETTY_FUNCTION__))
;
1908 continue;
1909 }
1910
1911 // We just insert into the loop set here. We'll add these blocks to the
1912 // exit loop after we build up the set in a deterministic order rather
1913 // than the predecessor-influenced visit order.
1914 bool Inserted = NewExitLoopBlocks.insert(PredBB).second;
1915 (void)Inserted;
1916 assert(Inserted && "Should only visit an unlooped block once!")(static_cast <bool> (Inserted && "Should only visit an unlooped block once!"
) ? void (0) : __assert_fail ("Inserted && \"Should only visit an unlooped block once!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1916, __extension__ __PRETTY_FUNCTION__))
;
1917
1918 // And recurse through to its predecessors.
1919 Worklist.push_back(PredBB);
1920 }
1921 } while (!Worklist.empty());
1922
1923 // If blocks in this exit loop were directly part of the original loop (as
1924 // opposed to a child loop) update the map to point to this exit loop. This
1925 // just updates a map and so the fact that the order is unstable is fine.
1926 for (auto *BB : NewExitLoopBlocks)
1927 if (Loop *BBL = LI.getLoopFor(BB))
1928 if (BBL == &L || !L.contains(BBL))
1929 LI.changeLoopFor(BB, &ExitL);
1930
1931 // We will remove the remaining unlooped blocks from this loop in the next
1932 // iteration or below.
1933 NewExitLoopBlocks.clear();
1934 }
1935
1936 // Any remaining unlooped blocks are no longer part of any loop unless they
1937 // are part of some child loop.
1938 for (; PrevExitL; PrevExitL = PrevExitL->getParentLoop())
1939 RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks);
1940 for (auto *BB : UnloopedBlocks)
1941 if (Loop *BBL = LI.getLoopFor(BB))
1942 if (BBL == &L || !L.contains(BBL))
1943 LI.changeLoopFor(BB, nullptr);
1944
1945 // Sink all the child loops whose headers are no longer in the loop set to
1946 // the parent (or to be top level loops). We reach into the loop and directly
1947 // update its subloop vector to make this batch update efficient.
1948 auto &SubLoops = L.getSubLoopsVector();
1949 auto SubLoopsSplitI =
1950 LoopBlockSet.empty()
1951 ? SubLoops.begin()
1952 : std::stable_partition(
1953 SubLoops.begin(), SubLoops.end(), [&](Loop *SubL) {
1954 return LoopBlockSet.count(SubL->getHeader());
1955 });
1956 for (auto *HoistedL : make_range(SubLoopsSplitI, SubLoops.end())) {
1957 HoistedLoops.push_back(HoistedL);
1958 HoistedL->setParentLoop(nullptr);
1959
1960 // To compute the new parent of this hoisted loop we look at where we
1961 // placed the preheader above. We can't lookup the header itself because we
1962 // retained the mapping from the header to the hoisted loop. But the
1963 // preheader and header should have the exact same new parent computed
1964 // based on the set of exit blocks from the original loop as the preheader
1965 // is a predecessor of the header and so reached in the reverse walk. And
1966 // because the loops were all in simplified form the preheader of the
1967 // hoisted loop can't be part of some *other* loop.
1968 if (auto *NewParentL = LI.getLoopFor(HoistedL->getLoopPreheader()))
1969 NewParentL->addChildLoop(HoistedL);
1970 else
1971 LI.addTopLevelLoop(HoistedL);
1972 }
1973 SubLoops.erase(SubLoopsSplitI, SubLoops.end());
1974
1975 // Actually delete the loop if nothing remained within it.
1976 if (Blocks.empty()) {
1977 assert(SubLoops.empty() &&(static_cast <bool> (SubLoops.empty() && "Failed to remove all subloops from the original loop!"
) ? void (0) : __assert_fail ("SubLoops.empty() && \"Failed to remove all subloops from the original loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1978, __extension__ __PRETTY_FUNCTION__))
1978 "Failed to remove all subloops from the original loop!")(static_cast <bool> (SubLoops.empty() && "Failed to remove all subloops from the original loop!"
) ? void (0) : __assert_fail ("SubLoops.empty() && \"Failed to remove all subloops from the original loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 1978, __extension__ __PRETTY_FUNCTION__))
;
1979 if (Loop *ParentL = L.getParentLoop())
1980 ParentL->removeChildLoop(llvm::find(*ParentL, &L));
1981 else
1982 LI.removeLoop(llvm::find(LI, &L));
1983 LI.destroy(&L);
1984 return false;
1985 }
1986
1987 return true;
1988}
1989
1990/// Helper to visit a dominator subtree, invoking a callable on each node.
1991///
1992/// Returning false at any point will stop walking past that node of the tree.
1993template <typename CallableT>
1994void visitDomSubTree(DominatorTree &DT, BasicBlock *BB, CallableT Callable) {
1995 SmallVector<DomTreeNode *, 4> DomWorklist;
1996 DomWorklist.push_back(DT[BB]);
1997#ifndef NDEBUG
1998 SmallPtrSet<DomTreeNode *, 4> Visited;
1999 Visited.insert(DT[BB]);
2000#endif
2001 do {
2002 DomTreeNode *N = DomWorklist.pop_back_val();
2003
2004 // Visit this node.
2005 if (!Callable(N->getBlock()))
2006 continue;
2007
2008 // Accumulate the child nodes.
2009 for (DomTreeNode *ChildN : *N) {
2010 assert(Visited.insert(ChildN).second &&(static_cast <bool> (Visited.insert(ChildN).second &&
"Cannot visit a node twice when walking a tree!") ? void (0)
: __assert_fail ("Visited.insert(ChildN).second && \"Cannot visit a node twice when walking a tree!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2011, __extension__ __PRETTY_FUNCTION__))
2011 "Cannot visit a node twice when walking a tree!")(static_cast <bool> (Visited.insert(ChildN).second &&
"Cannot visit a node twice when walking a tree!") ? void (0)
: __assert_fail ("Visited.insert(ChildN).second && \"Cannot visit a node twice when walking a tree!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2011, __extension__ __PRETTY_FUNCTION__))
;
2012 DomWorklist.push_back(ChildN);
2013 }
2014 } while (!DomWorklist.empty());
2015}
2016
2017static void unswitchNontrivialInvariants(
2018 Loop &L, Instruction &TI, ArrayRef<Value *> Invariants,
2019 SmallVectorImpl<BasicBlock *> &ExitBlocks, IVConditionInfo &PartialIVInfo,
2020 DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC,
2021 function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB,
2022 ScalarEvolution *SE, MemorySSAUpdater *MSSAU) {
2023 auto *ParentBB = TI.getParent();
2024 BranchInst *BI = dyn_cast<BranchInst>(&TI);
2025 SwitchInst *SI = BI ? nullptr : cast<SwitchInst>(&TI);
2026
2027 // We can only unswitch switches, conditional branches with an invariant
2028 // condition, or combining invariant conditions with an instruction or
2029 // partially invariant instructions.
2030 assert((SI || (BI && BI->isConditional())) &&(static_cast <bool> ((SI || (BI && BI->isConditional
())) && "Can only unswitch switches and conditional branch!"
) ? void (0) : __assert_fail ("(SI || (BI && BI->isConditional())) && \"Can only unswitch switches and conditional branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2031, __extension__ __PRETTY_FUNCTION__))
2031 "Can only unswitch switches and conditional branch!")(static_cast <bool> ((SI || (BI && BI->isConditional
())) && "Can only unswitch switches and conditional branch!"
) ? void (0) : __assert_fail ("(SI || (BI && BI->isConditional())) && \"Can only unswitch switches and conditional branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2031, __extension__ __PRETTY_FUNCTION__))
;
2032 bool PartiallyInvariant = !PartialIVInfo.InstToDuplicate.empty();
2033 bool FullUnswitch =
2034 SI || (BI->getCondition() == Invariants[0] && !PartiallyInvariant);
2035 if (FullUnswitch)
2036 assert(Invariants.size() == 1 &&(static_cast <bool> (Invariants.size() == 1 && "Cannot have other invariants with full unswitching!"
) ? void (0) : __assert_fail ("Invariants.size() == 1 && \"Cannot have other invariants with full unswitching!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2037, __extension__ __PRETTY_FUNCTION__))
2037 "Cannot have other invariants with full unswitching!")(static_cast <bool> (Invariants.size() == 1 && "Cannot have other invariants with full unswitching!"
) ? void (0) : __assert_fail ("Invariants.size() == 1 && \"Cannot have other invariants with full unswitching!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2037, __extension__ __PRETTY_FUNCTION__))
;
2038 else
2039 assert(isa<Instruction>(BI->getCondition()) &&(static_cast <bool> (isa<Instruction>(BI->getCondition
()) && "Partial unswitching requires an instruction as the condition!"
) ? void (0) : __assert_fail ("isa<Instruction>(BI->getCondition()) && \"Partial unswitching requires an instruction as the condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2040, __extension__ __PRETTY_FUNCTION__))
2040 "Partial unswitching requires an instruction as the condition!")(static_cast <bool> (isa<Instruction>(BI->getCondition
()) && "Partial unswitching requires an instruction as the condition!"
) ? void (0) : __assert_fail ("isa<Instruction>(BI->getCondition()) && \"Partial unswitching requires an instruction as the condition!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2040, __extension__ __PRETTY_FUNCTION__))
;
2041
2042 if (MSSAU && VerifyMemorySSA)
2043 MSSAU->getMemorySSA()->verifyMemorySSA();
2044
2045 // Constant and BBs tracking the cloned and continuing successor. When we are
2046 // unswitching the entire condition, this can just be trivially chosen to
2047 // unswitch towards `true`. However, when we are unswitching a set of
2048 // invariants combined with `and` or `or` or partially invariant instructions,
2049 // the combining operation determines the best direction to unswitch: we want
2050 // to unswitch the direction that will collapse the branch.
2051 bool Direction = true;
2052 int ClonedSucc = 0;
2053 if (!FullUnswitch) {
2054 Value *Cond = BI->getCondition();
2055 (void)Cond;
2056 assert(((match(Cond, m_LogicalAnd()) ^ match(Cond, m_LogicalOr())) ||(static_cast <bool> (((match(Cond, m_LogicalAnd()) ^ match
(Cond, m_LogicalOr())) || PartiallyInvariant) && "Only `or`, `and`, an `select`, partially invariant instructions "
"can combine invariants being unswitched.") ? void (0) : __assert_fail
("((match(Cond, m_LogicalAnd()) ^ match(Cond, m_LogicalOr())) || PartiallyInvariant) && \"Only `or`, `and`, an `select`, partially invariant instructions \" \"can combine invariants being unswitched.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2059, __extension__ __PRETTY_FUNCTION__))
2057 PartiallyInvariant) &&(static_cast <bool> (((match(Cond, m_LogicalAnd()) ^ match
(Cond, m_LogicalOr())) || PartiallyInvariant) && "Only `or`, `and`, an `select`, partially invariant instructions "
"can combine invariants being unswitched.") ? void (0) : __assert_fail
("((match(Cond, m_LogicalAnd()) ^ match(Cond, m_LogicalOr())) || PartiallyInvariant) && \"Only `or`, `and`, an `select`, partially invariant instructions \" \"can combine invariants being unswitched.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2059, __extension__ __PRETTY_FUNCTION__))
2058 "Only `or`, `and`, an `select`, partially invariant instructions "(static_cast <bool> (((match(Cond, m_LogicalAnd()) ^ match
(Cond, m_LogicalOr())) || PartiallyInvariant) && "Only `or`, `and`, an `select`, partially invariant instructions "
"can combine invariants being unswitched.") ? void (0) : __assert_fail
("((match(Cond, m_LogicalAnd()) ^ match(Cond, m_LogicalOr())) || PartiallyInvariant) && \"Only `or`, `and`, an `select`, partially invariant instructions \" \"can combine invariants being unswitched.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2059, __extension__ __PRETTY_FUNCTION__))
2059 "can combine invariants being unswitched.")(static_cast <bool> (((match(Cond, m_LogicalAnd()) ^ match
(Cond, m_LogicalOr())) || PartiallyInvariant) && "Only `or`, `and`, an `select`, partially invariant instructions "
"can combine invariants being unswitched.") ? void (0) : __assert_fail
("((match(Cond, m_LogicalAnd()) ^ match(Cond, m_LogicalOr())) || PartiallyInvariant) && \"Only `or`, `and`, an `select`, partially invariant instructions \" \"can combine invariants being unswitched.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2059, __extension__ __PRETTY_FUNCTION__))
;
2060 if (!match(BI->getCondition(), m_LogicalOr())) {
2061 if (match(BI->getCondition(), m_LogicalAnd()) ||
2062 (PartiallyInvariant && !PartialIVInfo.KnownValue->isOneValue())) {
2063 Direction = false;
2064 ClonedSucc = 1;
2065 }
2066 }
2067 }
2068
2069 BasicBlock *RetainedSuccBB =
2070 BI ? BI->getSuccessor(1 - ClonedSucc) : SI->getDefaultDest();
2071 SmallSetVector<BasicBlock *, 4> UnswitchedSuccBBs;
2072 if (BI)
2073 UnswitchedSuccBBs.insert(BI->getSuccessor(ClonedSucc));
2074 else
2075 for (auto Case : SI->cases())
2076 if (Case.getCaseSuccessor() != RetainedSuccBB)
2077 UnswitchedSuccBBs.insert(Case.getCaseSuccessor());
2078
2079 assert(!UnswitchedSuccBBs.count(RetainedSuccBB) &&(static_cast <bool> (!UnswitchedSuccBBs.count(RetainedSuccBB
) && "Should not unswitch the same successor we are retaining!"
) ? void (0) : __assert_fail ("!UnswitchedSuccBBs.count(RetainedSuccBB) && \"Should not unswitch the same successor we are retaining!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2080, __extension__ __PRETTY_FUNCTION__))
2080 "Should not unswitch the same successor we are retaining!")(static_cast <bool> (!UnswitchedSuccBBs.count(RetainedSuccBB
) && "Should not unswitch the same successor we are retaining!"
) ? void (0) : __assert_fail ("!UnswitchedSuccBBs.count(RetainedSuccBB) && \"Should not unswitch the same successor we are retaining!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2080, __extension__ __PRETTY_FUNCTION__))
;
2081
2082 // The branch should be in this exact loop. Any inner loop's invariant branch
2083 // should be handled by unswitching that inner loop. The caller of this
2084 // routine should filter out any candidates that remain (but were skipped for
2085 // whatever reason).
2086 assert(LI.getLoopFor(ParentBB) == &L && "Branch in an inner loop!")(static_cast <bool> (LI.getLoopFor(ParentBB) == &L &&
"Branch in an inner loop!") ? void (0) : __assert_fail ("LI.getLoopFor(ParentBB) == &L && \"Branch in an inner loop!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2086, __extension__ __PRETTY_FUNCTION__))
;
2087
2088 // Compute the parent loop now before we start hacking on things.
2089 Loop *ParentL = L.getParentLoop();
2090 // Get blocks in RPO order for MSSA update, before changing the CFG.
2091 LoopBlocksRPO LBRPO(&L);
2092 if (MSSAU)
2093 LBRPO.perform(&LI);
2094
2095 // Compute the outer-most loop containing one of our exit blocks. This is the
2096 // furthest up our loopnest which can be mutated, which we will use below to
2097 // update things.
2098 Loop *OuterExitL = &L;
2099 for (auto *ExitBB : ExitBlocks) {
2100 Loop *NewOuterExitL = LI.getLoopFor(ExitBB);
2101 if (!NewOuterExitL) {
2102 // We exited the entire nest with this block, so we're done.
2103 OuterExitL = nullptr;
2104 break;
2105 }
2106 if (NewOuterExitL != OuterExitL && NewOuterExitL->contains(OuterExitL))
2107 OuterExitL = NewOuterExitL;
2108 }
2109
2110 // At this point, we're definitely going to unswitch something so invalidate
2111 // any cached information in ScalarEvolution for the outer most loop
2112 // containing an exit block and all nested loops.
2113 if (SE) {
2114 if (OuterExitL)
2115 SE->forgetLoop(OuterExitL);
2116 else
2117 SE->forgetTopmostLoop(&L);
2118 }
2119
2120 // If the edge from this terminator to a successor dominates that successor,
2121 // store a map from each block in its dominator subtree to it. This lets us
2122 // tell when cloning for a particular successor if a block is dominated by
2123 // some *other* successor with a single data structure. We use this to
2124 // significantly reduce cloning.
2125 SmallDenseMap<BasicBlock *, BasicBlock *, 16> DominatingSucc;
2126 for (auto *SuccBB : llvm::concat<BasicBlock *const>(
2127 makeArrayRef(RetainedSuccBB), UnswitchedSuccBBs))
2128 if (SuccBB->getUniquePredecessor() ||
2129 llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) {
2130 return PredBB == ParentBB || DT.dominates(SuccBB, PredBB);
2131 }))
2132 visitDomSubTree(DT, SuccBB, [&](BasicBlock *BB) {
2133 DominatingSucc[BB] = SuccBB;
2134 return true;
2135 });
2136
2137 // Split the preheader, so that we know that there is a safe place to insert
2138 // the conditional branch. We will change the preheader to have a conditional
2139 // branch on LoopCond. The original preheader will become the split point
2140 // between the unswitched versions, and we will have a new preheader for the
2141 // original loop.
2142 BasicBlock *SplitBB = L.getLoopPreheader();
2143 BasicBlock *LoopPH = SplitEdge(SplitBB, L.getHeader(), &DT, &LI, MSSAU);
2144
2145 // Keep track of the dominator tree updates needed.
2146 SmallVector<DominatorTree::UpdateType, 4> DTUpdates;
2147
2148 // Clone the loop for each unswitched successor.
2149 SmallVector<std::unique_ptr<ValueToValueMapTy>, 4> VMaps;
2150 VMaps.reserve(UnswitchedSuccBBs.size());
2151 SmallDenseMap<BasicBlock *, BasicBlock *, 4> ClonedPHs;
2152 for (auto *SuccBB : UnswitchedSuccBBs) {
2153 VMaps.emplace_back(new ValueToValueMapTy());
2154 ClonedPHs[SuccBB] = buildClonedLoopBlocks(
2155 L, LoopPH, SplitBB, ExitBlocks, ParentBB, SuccBB, RetainedSuccBB,
2156 DominatingSucc, *VMaps.back(), DTUpdates, AC, DT, LI, MSSAU);
2157 }
2158
2159 // Drop metadata if we may break its semantics by moving this instr into the
2160 // split block.
2161 if (TI.getMetadata(LLVMContext::MD_make_implicit)) {
2162 if (DropNonTrivialImplicitNullChecks)
2163 // Do not spend time trying to understand if we can keep it, just drop it
2164 // to save compile time.
2165 TI.setMetadata(LLVMContext::MD_make_implicit, nullptr);
2166 else {
2167 // It is only legal to preserve make.implicit metadata if we are
2168 // guaranteed no reach implicit null check after following this branch.
2169 ICFLoopSafetyInfo SafetyInfo;
2170 SafetyInfo.computeLoopSafetyInfo(&L);
2171 if (!SafetyInfo.isGuaranteedToExecute(TI, &DT, &L))
2172 TI.setMetadata(LLVMContext::MD_make_implicit, nullptr);
2173 }
2174 }
2175
2176 // The stitching of the branched code back together depends on whether we're
2177 // doing full unswitching or not with the exception that we always want to
2178 // nuke the initial terminator placed in the split block.
2179 SplitBB->getTerminator()->eraseFromParent();
2180 if (FullUnswitch) {
2181 // Splice the terminator from the original loop and rewrite its
2182 // successors.
2183 SplitBB->getInstList().splice(SplitBB->end(), ParentBB->getInstList(), TI);
2184
2185 // Keep a clone of the terminator for MSSA updates.
2186 Instruction *NewTI = TI.clone();
2187 ParentBB->getInstList().push_back(NewTI);
2188
2189 // First wire up the moved terminator to the preheaders.
2190 if (BI) {
2191 BasicBlock *ClonedPH = ClonedPHs.begin()->second;
2192 BI->setSuccessor(ClonedSucc, ClonedPH);
2193 BI->setSuccessor(1 - ClonedSucc, LoopPH);
2194 DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH});
2195 } else {
2196 assert(SI && "Must either be a branch or switch!")(static_cast <bool> (SI && "Must either be a branch or switch!"
) ? void (0) : __assert_fail ("SI && \"Must either be a branch or switch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2196, __extension__ __PRETTY_FUNCTION__))
;
2197
2198 // Walk the cases and directly update their successors.
2199 assert(SI->getDefaultDest() == RetainedSuccBB &&(static_cast <bool> (SI->getDefaultDest() == RetainedSuccBB
&& "Not retaining default successor!") ? void (0) : __assert_fail
("SI->getDefaultDest() == RetainedSuccBB && \"Not retaining default successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2200, __extension__ __PRETTY_FUNCTION__))
2200 "Not retaining default successor!")(static_cast <bool> (SI->getDefaultDest() == RetainedSuccBB
&& "Not retaining default successor!") ? void (0) : __assert_fail
("SI->getDefaultDest() == RetainedSuccBB && \"Not retaining default successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2200, __extension__ __PRETTY_FUNCTION__))
;
2201 SI->setDefaultDest(LoopPH);
2202 for (auto &Case : SI->cases())
2203 if (Case.getCaseSuccessor() == RetainedSuccBB)
2204 Case.setSuccessor(LoopPH);
2205 else
2206 Case.setSuccessor(ClonedPHs.find(Case.getCaseSuccessor())->second);
2207
2208 // We need to use the set to populate domtree updates as even when there
2209 // are multiple cases pointing at the same successor we only want to
2210 // remove and insert one edge in the domtree.
2211 for (BasicBlock *SuccBB : UnswitchedSuccBBs)
2212 DTUpdates.push_back(
2213 {DominatorTree::Insert, SplitBB, ClonedPHs.find(SuccBB)->second});
2214 }
2215
2216 if (MSSAU) {
2217 DT.applyUpdates(DTUpdates);
2218 DTUpdates.clear();
2219
2220 // Remove all but one edge to the retained block and all unswitched
2221 // blocks. This is to avoid having duplicate entries in the cloned Phis,
2222 // when we know we only keep a single edge for each case.
2223 MSSAU->removeDuplicatePhiEdgesBetween(ParentBB, RetainedSuccBB);
2224 for (BasicBlock *SuccBB : UnswitchedSuccBBs)
2225 MSSAU->removeDuplicatePhiEdgesBetween(ParentBB, SuccBB);
2226
2227 for (auto &VMap : VMaps)
2228 MSSAU->updateForClonedLoop(LBRPO, ExitBlocks, *VMap,
2229 /*IgnoreIncomingWithNoClones=*/true);
2230 MSSAU->updateExitBlocksForClonedLoop(ExitBlocks, VMaps, DT);
2231
2232 // Remove all edges to unswitched blocks.
2233 for (BasicBlock *SuccBB : UnswitchedSuccBBs)
2234 MSSAU->removeEdge(ParentBB, SuccBB);
2235 }
2236
2237 // Now unhook the successor relationship as we'll be replacing
2238 // the terminator with a direct branch. This is much simpler for branches
2239 // than switches so we handle those first.
2240 if (BI) {
2241 // Remove the parent as a predecessor of the unswitched successor.
2242 assert(UnswitchedSuccBBs.size() == 1 &&(static_cast <bool> (UnswitchedSuccBBs.size() == 1 &&
"Only one possible unswitched block for a branch!") ? void (
0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2243, __extension__ __PRETTY_FUNCTION__))
2243 "Only one possible unswitched block for a branch!")(static_cast <bool> (UnswitchedSuccBBs.size() == 1 &&
"Only one possible unswitched block for a branch!") ? void (
0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2243, __extension__ __PRETTY_FUNCTION__))
;
2244 BasicBlock *UnswitchedSuccBB = *UnswitchedSuccBBs.begin();
2245 UnswitchedSuccBB->removePredecessor(ParentBB,
2246 /*KeepOneInputPHIs*/ true);
2247 DTUpdates.push_back({DominatorTree::Delete, ParentBB, UnswitchedSuccBB});
2248 } else {
2249 // Note that we actually want to remove the parent block as a predecessor
2250 // of *every* case successor. The case successor is either unswitched,
2251 // completely eliminating an edge from the parent to that successor, or it
2252 // is a duplicate edge to the retained successor as the retained successor
2253 // is always the default successor and as we'll replace this with a direct
2254 // branch we no longer need the duplicate entries in the PHI nodes.
2255 SwitchInst *NewSI = cast<SwitchInst>(NewTI);
2256 assert(NewSI->getDefaultDest() == RetainedSuccBB &&(static_cast <bool> (NewSI->getDefaultDest() == RetainedSuccBB
&& "Not retaining default successor!") ? void (0) : __assert_fail
("NewSI->getDefaultDest() == RetainedSuccBB && \"Not retaining default successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2257, __extension__ __PRETTY_FUNCTION__))
2257 "Not retaining default successor!")(static_cast <bool> (NewSI->getDefaultDest() == RetainedSuccBB
&& "Not retaining default successor!") ? void (0) : __assert_fail
("NewSI->getDefaultDest() == RetainedSuccBB && \"Not retaining default successor!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2257, __extension__ __PRETTY_FUNCTION__))
;
2258 for (auto &Case : NewSI->cases())
2259 Case.getCaseSuccessor()->removePredecessor(
2260 ParentBB,
2261 /*KeepOneInputPHIs*/ true);
2262
2263 // We need to use the set to populate domtree updates as even when there
2264 // are multiple cases pointing at the same successor we only want to
2265 // remove and insert one edge in the domtree.
2266 for (BasicBlock *SuccBB : UnswitchedSuccBBs)
2267 DTUpdates.push_back({DominatorTree::Delete, ParentBB, SuccBB});
2268 }
2269
2270 // After MSSAU update, remove the cloned terminator instruction NewTI.
2271 ParentBB->getTerminator()->eraseFromParent();
2272
2273 // Create a new unconditional branch to the continuing block (as opposed to
2274 // the one cloned).
2275 BranchInst::Create(RetainedSuccBB, ParentBB);
2276 } else {
2277 assert(BI && "Only branches have partial unswitching.")(static_cast <bool> (BI && "Only branches have partial unswitching."
) ? void (0) : __assert_fail ("BI && \"Only branches have partial unswitching.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2277, __extension__ __PRETTY_FUNCTION__))
;
2278 assert(UnswitchedSuccBBs.size() == 1 &&(static_cast <bool> (UnswitchedSuccBBs.size() == 1 &&
"Only one possible unswitched block for a branch!") ? void (
0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2279, __extension__ __PRETTY_FUNCTION__))
2279 "Only one possible unswitched block for a branch!")(static_cast <bool> (UnswitchedSuccBBs.size() == 1 &&
"Only one possible unswitched block for a branch!") ? void (
0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2279, __extension__ __PRETTY_FUNCTION__))
;
2280 BasicBlock *ClonedPH = ClonedPHs.begin()->second;
2281 // When doing a partial unswitch, we have to do a bit more work to build up
2282 // the branch in the split block.
2283 if (PartiallyInvariant)
2284 buildPartialInvariantUnswitchConditionalBranch(
2285 *SplitBB, Invariants, Direction, *ClonedPH, *LoopPH, L, MSSAU);
2286 else
2287 buildPartialUnswitchConditionalBranch(*SplitBB, Invariants, Direction,
2288 *ClonedPH, *LoopPH);
2289 DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH});
2290
2291 if (MSSAU) {
2292 DT.applyUpdates(DTUpdates);
2293 DTUpdates.clear();
2294
2295 // Perform MSSA cloning updates.
2296 for (auto &VMap : VMaps)
2297 MSSAU->updateForClonedLoop(LBRPO, ExitBlocks, *VMap,
2298 /*IgnoreIncomingWithNoClones=*/true);
2299 MSSAU->updateExitBlocksForClonedLoop(ExitBlocks, VMaps, DT);
2300 }
2301 }
2302
2303 // Apply the updates accumulated above to get an up-to-date dominator tree.
2304 DT.applyUpdates(DTUpdates);
2305
2306 // Now that we have an accurate dominator tree, first delete the dead cloned
2307 // blocks so that we can accurately build any cloned loops. It is important to
2308 // not delete the blocks from the original loop yet because we still want to
2309 // reference the original loop to understand the cloned loop's structure.
2310 deleteDeadClonedBlocks(L, ExitBlocks, VMaps, DT, MSSAU);
2311
2312 // Build the cloned loop structure itself. This may be substantially
2313 // different from the original structure due to the simplified CFG. This also
2314 // handles inserting all the cloned blocks into the correct loops.
2315 SmallVector<Loop *, 4> NonChildClonedLoops;
2316 for (std::unique_ptr<ValueToValueMapTy> &VMap : VMaps)
2317 buildClonedLoops(L, ExitBlocks, *VMap, LI, NonChildClonedLoops);
2318
2319 // Now that our cloned loops have been built, we can update the original loop.
2320 // First we delete the dead blocks from it and then we rebuild the loop
2321 // structure taking these deletions into account.
2322 deleteDeadBlocksFromLoop(L, ExitBlocks, DT, LI, MSSAU);
2323
2324 if (MSSAU && VerifyMemorySSA)
2325 MSSAU->getMemorySSA()->verifyMemorySSA();
2326
2327 SmallVector<Loop *, 4> HoistedLoops;
2328 bool IsStillLoop = rebuildLoopAfterUnswitch(L, ExitBlocks, LI, HoistedLoops);
2329
2330 if (MSSAU && VerifyMemorySSA)
2331 MSSAU->getMemorySSA()->verifyMemorySSA();
2332
2333 // This transformation has a high risk of corrupting the dominator tree, and
2334 // the below steps to rebuild loop structures will result in hard to debug
2335 // errors in that case so verify that the dominator tree is sane first.
2336 // FIXME: Remove this when the bugs stop showing up and rely on existing
2337 // verification steps.
2338 assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel
::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)"
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2338, __extension__ __PRETTY_FUNCTION__))
;
2339
2340 if (BI && !PartiallyInvariant) {
2341 // If we unswitched a branch which collapses the condition to a known
2342 // constant we want to replace all the uses of the invariants within both
2343 // the original and cloned blocks. We do this here so that we can use the
2344 // now updated dominator tree to identify which side the users are on.
2345 assert(UnswitchedSuccBBs.size() == 1 &&(static_cast <bool> (UnswitchedSuccBBs.size() == 1 &&
"Only one possible unswitched block for a branch!") ? void (
0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2346, __extension__ __PRETTY_FUNCTION__))
2346 "Only one possible unswitched block for a branch!")(static_cast <bool> (UnswitchedSuccBBs.size() == 1 &&
"Only one possible unswitched block for a branch!") ? void (
0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2346, __extension__ __PRETTY_FUNCTION__))
;
2347 BasicBlock *ClonedPH = ClonedPHs.begin()->second;
2348
2349 // When considering multiple partially-unswitched invariants
2350 // we cant just go replace them with constants in both branches.
2351 //
2352 // For 'AND' we infer that true branch ("continue") means true
2353 // for each invariant operand.
2354 // For 'OR' we can infer that false branch ("continue") means false
2355 // for each invariant operand.
2356 // So it happens that for multiple-partial case we dont replace
2357 // in the unswitched branch.
2358 bool ReplaceUnswitched =
2359 FullUnswitch || (Invariants.size() == 1) || PartiallyInvariant;
2360
2361 ConstantInt *UnswitchedReplacement =
2362 Direction ? ConstantInt::getTrue(BI->getContext())
2363 : ConstantInt::getFalse(BI->getContext());
2364 ConstantInt *ContinueReplacement =
2365 Direction ? ConstantInt::getFalse(BI->getContext())
2366 : ConstantInt::getTrue(BI->getContext());
2367 for (Value *Invariant : Invariants)
2368 // Use make_early_inc_range here as set invalidates the iterator.
2369 for (Use &U : llvm::make_early_inc_range(Invariant->uses())) {
2370 Instruction *UserI = dyn_cast<Instruction>(U.getUser());
2371 if (!UserI)
2372 continue;
2373
2374 // Replace it with the 'continue' side if in the main loop body, and the
2375 // unswitched if in the cloned blocks.
2376 if (DT.dominates(LoopPH, UserI->getParent()))
2377 U.set(ContinueReplacement);
2378 else if (ReplaceUnswitched &&
2379 DT.dominates(ClonedPH, UserI->getParent()))
2380 U.set(UnswitchedReplacement);
2381 }
2382 }
2383
2384 // We can change which blocks are exit blocks of all the cloned sibling
2385 // loops, the current loop, and any parent loops which shared exit blocks
2386 // with the current loop. As a consequence, we need to re-form LCSSA for
2387 // them. But we shouldn't need to re-form LCSSA for any child loops.
2388 // FIXME: This could be made more efficient by tracking which exit blocks are
2389 // new, and focusing on them, but that isn't likely to be necessary.
2390 //
2391 // In order to reasonably rebuild LCSSA we need to walk inside-out across the
2392 // loop nest and update every loop that could have had its exits changed. We
2393 // also need to cover any intervening loops. We add all of these loops to
2394 // a list and sort them by loop depth to achieve this without updating
2395 // unnecessary loops.
2396 auto UpdateLoop = [&](Loop &UpdateL) {
2397#ifndef NDEBUG
2398 UpdateL.verifyLoop();
2399 for (Loop *ChildL : UpdateL) {
2400 ChildL->verifyLoop();
2401 assert(ChildL->isRecursivelyLCSSAForm(DT, LI) &&(static_cast <bool> (ChildL->isRecursivelyLCSSAForm(
DT, LI) && "Perturbed a child loop's LCSSA form!") ? void
(0) : __assert_fail ("ChildL->isRecursivelyLCSSAForm(DT, LI) && \"Perturbed a child loop's LCSSA form!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2402, __extension__ __PRETTY_FUNCTION__))
2402 "Perturbed a child loop's LCSSA form!")(static_cast <bool> (ChildL->isRecursivelyLCSSAForm(
DT, LI) && "Perturbed a child loop's LCSSA form!") ? void
(0) : __assert_fail ("ChildL->isRecursivelyLCSSAForm(DT, LI) && \"Perturbed a child loop's LCSSA form!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2402, __extension__ __PRETTY_FUNCTION__))
;
2403 }
2404#endif
2405 // First build LCSSA for this loop so that we can preserve it when
2406 // forming dedicated exits. We don't want to perturb some other loop's
2407 // LCSSA while doing that CFG edit.
2408 formLCSSA(UpdateL, DT, &LI, SE);
2409
2410 // For loops reached by this loop's original exit blocks we may
2411 // introduced new, non-dedicated exits. At least try to re-form dedicated
2412 // exits for these loops. This may fail if they couldn't have dedicated
2413 // exits to start with.
2414 formDedicatedExitBlocks(&UpdateL, &DT, &LI, MSSAU, /*PreserveLCSSA*/ true);
2415 };
2416
2417 // For non-child cloned loops and hoisted loops, we just need to update LCSSA
2418 // and we can do it in any order as they don't nest relative to each other.
2419 //
2420 // Also check if any of the loops we have updated have become top-level loops
2421 // as that will necessitate widening the outer loop scope.
2422 for (Loop *UpdatedL :
2423 llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) {
2424 UpdateLoop(*UpdatedL);
2425 if (UpdatedL->isOutermost())
2426 OuterExitL = nullptr;
2427 }
2428 if (IsStillLoop) {
2429 UpdateLoop(L);
2430 if (L.isOutermost())
2431 OuterExitL = nullptr;
2432 }
2433
2434 // If the original loop had exit blocks, walk up through the outer most loop
2435 // of those exit blocks to update LCSSA and form updated dedicated exits.
2436 if (OuterExitL != &L)
2437 for (Loop *OuterL = ParentL; OuterL != OuterExitL;
2438 OuterL = OuterL->getParentLoop())
2439 UpdateLoop(*OuterL);
2440
2441#ifndef NDEBUG
2442 // Verify the entire loop structure to catch any incorrect updates before we
2443 // progress in the pass pipeline.
2444 LI.verify(DT);
2445#endif
2446
2447 // Now that we've unswitched something, make callbacks to report the changes.
2448 // For that we need to merge together the updated loops and the cloned loops
2449 // and check whether the original loop survived.
2450 SmallVector<Loop *, 4> SibLoops;
2451 for (Loop *UpdatedL : llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops))
2452 if (UpdatedL->getParentLoop() == ParentL)
2453 SibLoops.push_back(UpdatedL);
2454 UnswitchCB(IsStillLoop, PartiallyInvariant, SibLoops);
2455
2456 if (MSSAU && VerifyMemorySSA)
2457 MSSAU->getMemorySSA()->verifyMemorySSA();
2458
2459 if (BI)
2460 ++NumBranches;
2461 else
2462 ++NumSwitches;
2463}
2464
2465/// Recursively compute the cost of a dominator subtree based on the per-block
2466/// cost map provided.
2467///
2468/// The recursive computation is memozied into the provided DT-indexed cost map
2469/// to allow querying it for most nodes in the domtree without it becoming
2470/// quadratic.
2471static InstructionCost computeDomSubtreeCost(
2472 DomTreeNode &N,
2473 const SmallDenseMap<BasicBlock *, InstructionCost, 4> &BBCostMap,
2474 SmallDenseMap<DomTreeNode *, InstructionCost, 4> &DTCostMap) {
2475 // Don't accumulate cost (or recurse through) blocks not in our block cost
2476 // map and thus not part of the duplication cost being considered.
2477 auto BBCostIt = BBCostMap.find(N.getBlock());
2478 if (BBCostIt == BBCostMap.end())
2479 return 0;
2480
2481 // Lookup this node to see if we already computed its cost.
2482 auto DTCostIt = DTCostMap.find(&N);
2483 if (DTCostIt != DTCostMap.end())
2484 return DTCostIt->second;
2485
2486 // If not, we have to compute it. We can't use insert above and update
2487 // because computing the cost may insert more things into the map.
2488 InstructionCost Cost = std::accumulate(
2489 N.begin(), N.end(), BBCostIt->second,
2490 [&](InstructionCost Sum, DomTreeNode *ChildN) -> InstructionCost {
2491 return Sum + computeDomSubtreeCost(*ChildN, BBCostMap, DTCostMap);
2492 });
2493 bool Inserted = DTCostMap.insert({&N, Cost}).second;
2494 (void)Inserted;
2495 assert(Inserted && "Should not insert a node while visiting children!")(static_cast <bool> (Inserted && "Should not insert a node while visiting children!"
) ? void (0) : __assert_fail ("Inserted && \"Should not insert a node while visiting children!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2495, __extension__ __PRETTY_FUNCTION__))
;
2496 return Cost;
2497}
2498
2499/// Turns a llvm.experimental.guard intrinsic into implicit control flow branch,
2500/// making the following replacement:
2501///
2502/// --code before guard--
2503/// call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
2504/// --code after guard--
2505///
2506/// into
2507///
2508/// --code before guard--
2509/// br i1 %cond, label %guarded, label %deopt
2510///
2511/// guarded:
2512/// --code after guard--
2513///
2514/// deopt:
2515/// call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
2516/// unreachable
2517///
2518/// It also makes all relevant DT and LI updates, so that all structures are in
2519/// valid state after this transform.
2520static BranchInst *
2521turnGuardIntoBranch(IntrinsicInst *GI, Loop &L,
2522 SmallVectorImpl<BasicBlock *> &ExitBlocks,
2523 DominatorTree &DT, LoopInfo &LI, MemorySSAUpdater *MSSAU) {
2524 SmallVector<DominatorTree::UpdateType, 4> DTUpdates;
2525 LLVM_DEBUG(dbgs() << "Turning " << *GI << " into a branch.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Turning " <<
*GI << " into a branch.\n"; } } while (false)
;
2526 BasicBlock *CheckBB = GI->getParent();
2527
2528 if (MSSAU && VerifyMemorySSA)
2529 MSSAU->getMemorySSA()->verifyMemorySSA();
2530
2531 // Remove all CheckBB's successors from DomTree. A block can be seen among
2532 // successors more than once, but for DomTree it should be added only once.
2533 SmallPtrSet<BasicBlock *, 4> Successors;
2534 for (auto *Succ : successors(CheckBB))
2535 if (Successors.insert(Succ).second)
2536 DTUpdates.push_back({DominatorTree::Delete, CheckBB, Succ});
2537
2538 Instruction *DeoptBlockTerm =
2539 SplitBlockAndInsertIfThen(GI->getArgOperand(0), GI, true);
2540 BranchInst *CheckBI = cast<BranchInst>(CheckBB->getTerminator());
2541 // SplitBlockAndInsertIfThen inserts control flow that branches to
2542 // DeoptBlockTerm if the condition is true. We want the opposite.
2543 CheckBI->swapSuccessors();
2544
2545 BasicBlock *GuardedBlock = CheckBI->getSuccessor(0);
2546 GuardedBlock->setName("guarded");
2547 CheckBI->getSuccessor(1)->setName("deopt");
2548 BasicBlock *DeoptBlock = CheckBI->getSuccessor(1);
2549
2550 // We now have a new exit block.
2551 ExitBlocks.push_back(CheckBI->getSuccessor(1));
2552
2553 if (MSSAU)
2554 MSSAU->moveAllAfterSpliceBlocks(CheckBB, GuardedBlock, GI);
2555
2556 GI->moveBefore(DeoptBlockTerm);
2557 GI->setArgOperand(0, ConstantInt::getFalse(GI->getContext()));
2558
2559 // Add new successors of CheckBB into DomTree.
2560 for (auto *Succ : successors(CheckBB))
2561 DTUpdates.push_back({DominatorTree::Insert, CheckBB, Succ});
2562
2563 // Now the blocks that used to be CheckBB's successors are GuardedBlock's
2564 // successors.
2565 for (auto *Succ : Successors)
2566 DTUpdates.push_back({DominatorTree::Insert, GuardedBlock, Succ});
2567
2568 // Make proper changes to DT.
2569 DT.applyUpdates(DTUpdates);
2570 // Inform LI of a new loop block.
2571 L.addBasicBlockToLoop(GuardedBlock, LI);
2572
2573 if (MSSAU) {
2574 MemoryDef *MD = cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(GI));
2575 MSSAU->moveToPlace(MD, DeoptBlock, MemorySSA::BeforeTerminator);
2576 if (VerifyMemorySSA)
2577 MSSAU->getMemorySSA()->verifyMemorySSA();
2578 }
2579
2580 ++NumGuards;
2581 return CheckBI;
2582}
2583
2584/// Cost multiplier is a way to limit potentially exponential behavior
2585/// of loop-unswitch. Cost is multipied in proportion of 2^number of unswitch
2586/// candidates available. Also accounting for the number of "sibling" loops with
2587/// the idea to account for previous unswitches that already happened on this
2588/// cluster of loops. There was an attempt to keep this formula simple,
2589/// just enough to limit the worst case behavior. Even if it is not that simple
2590/// now it is still not an attempt to provide a detailed heuristic size
2591/// prediction.
2592///
2593/// TODO: Make a proper accounting of "explosion" effect for all kinds of
2594/// unswitch candidates, making adequate predictions instead of wild guesses.
2595/// That requires knowing not just the number of "remaining" candidates but
2596/// also costs of unswitching for each of these candidates.
2597static int CalculateUnswitchCostMultiplier(
2598 Instruction &TI, Loop &L, LoopInfo &LI, DominatorTree &DT,
2599 ArrayRef<std::pair<Instruction *, TinyPtrVector<Value *>>>
2600 UnswitchCandidates) {
2601
2602 // Guards and other exiting conditions do not contribute to exponential
2603 // explosion as soon as they dominate the latch (otherwise there might be
2604 // another path to the latch remaining that does not allow to eliminate the
2605 // loop copy on unswitch).
2606 BasicBlock *Latch = L.getLoopLatch();
2607 BasicBlock *CondBlock = TI.getParent();
2608 if (DT.dominates(CondBlock, Latch) &&
2609 (isGuard(&TI) ||
2610 llvm::count_if(successors(&TI), [&L](BasicBlock *SuccBB) {
2611 return L.contains(SuccBB);
2612 }) <= 1)) {
2613 NumCostMultiplierSkipped++;
2614 return 1;
2615 }
2616
2617 auto *ParentL = L.getParentLoop();
2618 int SiblingsCount = (ParentL ? ParentL->getSubLoopsVector().size()
2619 : std::distance(LI.begin(), LI.end()));
2620 // Count amount of clones that all the candidates might cause during
2621 // unswitching. Branch/guard counts as 1, switch counts as log2 of its cases.
2622 int UnswitchedClones = 0;
2623 for (auto Candidate : UnswitchCandidates) {
2624 Instruction *CI = Candidate.first;
2625 BasicBlock *CondBlock = CI->getParent();
2626 bool SkipExitingSuccessors = DT.dominates(CondBlock, Latch);
2627 if (isGuard(CI)) {
2628 if (!SkipExitingSuccessors)
2629 UnswitchedClones++;
2630 continue;
2631 }
2632 int NonExitingSuccessors = llvm::count_if(
2633 successors(CondBlock), [SkipExitingSuccessors, &L](BasicBlock *SuccBB) {
2634 return !SkipExitingSuccessors || L.contains(SuccBB);
2635 });
2636 UnswitchedClones += Log2_32(NonExitingSuccessors);
2637 }
2638
2639 // Ignore up to the "unscaled candidates" number of unswitch candidates
2640 // when calculating the power-of-two scaling of the cost. The main idea
2641 // with this control is to allow a small number of unswitches to happen
2642 // and rely more on siblings multiplier (see below) when the number
2643 // of candidates is small.
2644 unsigned ClonesPower =
2645 std::max(UnswitchedClones - (int)UnswitchNumInitialUnscaledCandidates, 0);
2646
2647 // Allowing top-level loops to spread a bit more than nested ones.
2648 int SiblingsMultiplier =
2649 std::max((ParentL ? SiblingsCount
2650 : SiblingsCount / (int)UnswitchSiblingsToplevelDiv),
2651 1);
2652 // Compute the cost multiplier in a way that won't overflow by saturating
2653 // at an upper bound.
2654 int CostMultiplier;
2655 if (ClonesPower > Log2_32(UnswitchThreshold) ||
2656 SiblingsMultiplier > UnswitchThreshold)
2657 CostMultiplier = UnswitchThreshold;
2658 else
2659 CostMultiplier = std::min(SiblingsMultiplier * (1 << ClonesPower),
2660 (int)UnswitchThreshold);
2661
2662 LLVM_DEBUG(dbgs() << " Computed multiplier " << CostMultiplierdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed multiplier "
<< CostMultiplier << " (siblings " << SiblingsMultiplier
<< " * clones " << (1 << ClonesPower) <<
")" << " for unswitch candidate: " << TI <<
"\n"; } } while (false)
2663 << " (siblings " << SiblingsMultiplier << " * clones "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed multiplier "
<< CostMultiplier << " (siblings " << SiblingsMultiplier
<< " * clones " << (1 << ClonesPower) <<
")" << " for unswitch candidate: " << TI <<
"\n"; } } while (false)
2664 << (1 << ClonesPower) << ")"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed multiplier "
<< CostMultiplier << " (siblings " << SiblingsMultiplier
<< " * clones " << (1 << ClonesPower) <<
")" << " for unswitch candidate: " << TI <<
"\n"; } } while (false)
2665 << " for unswitch candidate: " << TI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed multiplier "
<< CostMultiplier << " (siblings " << SiblingsMultiplier
<< " * clones " << (1 << ClonesPower) <<
")" << " for unswitch candidate: " << TI <<
"\n"; } } while (false)
;
2666 return CostMultiplier;
2667}
2668
2669static bool unswitchBestCondition(
2670 Loop &L, DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC,
2671 AAResults &AA, TargetTransformInfo &TTI,
2672 function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB,
2673 ScalarEvolution *SE, MemorySSAUpdater *MSSAU) {
2674 // Collect all invariant conditions within this loop (as opposed to an inner
2675 // loop which would be handled when visiting that inner loop).
2676 SmallVector<std::pair<Instruction *, TinyPtrVector<Value *>>, 4>
2677 UnswitchCandidates;
2678
2679 // Whether or not we should also collect guards in the loop.
2680 bool CollectGuards = false;
2681 if (UnswitchGuards) {
1
Assuming the condition is false
2
Taking false branch
2682 auto *GuardDecl = L.getHeader()->getParent()->getParent()->getFunction(
2683 Intrinsic::getName(Intrinsic::experimental_guard));
2684 if (GuardDecl && !GuardDecl->use_empty())
2685 CollectGuards = true;
2686 }
2687
2688 IVConditionInfo PartialIVInfo;
3
Calling implicit default constructor for 'IVConditionInfo'
5
Returning from default constructor for 'IVConditionInfo'
2689 for (auto *BB : L.blocks()) {
6
Assuming '__begin1' is equal to '__end1'
2690 if (LI.getLoopFor(BB) != &L)
2691 continue;
2692
2693 if (CollectGuards)
2694 for (auto &I : *BB)
2695 if (isGuard(&I)) {
2696 auto *Cond = cast<IntrinsicInst>(&I)->getArgOperand(0);
2697 // TODO: Support AND, OR conditions and partial unswitching.
2698 if (!isa<Constant>(Cond) && L.isLoopInvariant(Cond))
2699 UnswitchCandidates.push_back({&I, {Cond}});
2700 }
2701
2702 if (auto *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
2703 // We can only consider fully loop-invariant switch conditions as we need
2704 // to completely eliminate the switch after unswitching.
2705 if (!isa<Constant>(SI->getCondition()) &&
2706 L.isLoopInvariant(SI->getCondition()) && !BB->getUniqueSuccessor())
2707 UnswitchCandidates.push_back({SI, {SI->getCondition()}});
2708 continue;
2709 }
2710
2711 auto *BI = dyn_cast<BranchInst>(BB->getTerminator());
2712 if (!BI || !BI->isConditional() || isa<Constant>(BI->getCondition()) ||
2713 BI->getSuccessor(0) == BI->getSuccessor(1))
2714 continue;
2715
2716 // If BI's condition is 'select _, true, false', simplify it to confuse
2717 // matchers
2718 Value *Cond = BI->getCondition(), *CondNext;
2719 while (match(Cond, m_Select(m_Value(CondNext), m_One(), m_Zero())))
2720 Cond = CondNext;
2721 BI->setCondition(Cond);
2722
2723 if (L.isLoopInvariant(BI->getCondition())) {
2724 UnswitchCandidates.push_back({BI, {BI->getCondition()}});
2725 continue;
2726 }
2727
2728 Instruction &CondI = *cast<Instruction>(BI->getCondition());
2729 if (match(&CondI, m_CombineOr(m_LogicalAnd(), m_LogicalOr()))) {
2730 TinyPtrVector<Value *> Invariants =
2731 collectHomogenousInstGraphLoopInvariants(L, CondI, LI);
2732 if (Invariants.empty())
2733 continue;
2734
2735 UnswitchCandidates.push_back({BI, std::move(Invariants)});
2736 continue;
2737 }
2738 }
2739
2740 Instruction *PartialIVCondBranch = nullptr;
2741 if (MSSAU && !findOptionMDForLoop(&L, "llvm.loop.unswitch.partial.disable") &&
7
Assuming 'MSSAU' is null
8
Taking false branch
2742 !any_of(UnswitchCandidates, [&L](auto &TerminatorAndInvariants) {
2743 return TerminatorAndInvariants.first == L.getHeader()->getTerminator();
2744 })) {
2745 MemorySSA *MSSA = MSSAU->getMemorySSA();
2746 if (auto Info = hasPartialIVCondition(L, MSSAThreshold, *MSSA, AA)) {
2747 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "simple-loop-unswitch: Found partially invariant condition "
<< *Info->InstToDuplicate[0] << "\n"; } } while
(false)
2748 dbgs() << "simple-loop-unswitch: Found partially invariant condition "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "simple-loop-unswitch: Found partially invariant condition "
<< *Info->InstToDuplicate[0] << "\n"; } } while
(false)
2749 << *Info->InstToDuplicate[0] << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "simple-loop-unswitch: Found partially invariant condition "
<< *Info->InstToDuplicate[0] << "\n"; } } while
(false)
;
2750 PartialIVInfo = *Info;
2751 PartialIVCondBranch = L.getHeader()->getTerminator();
2752 TinyPtrVector<Value *> ValsToDuplicate;
2753 for (auto *Inst : Info->InstToDuplicate)
2754 ValsToDuplicate.push_back(Inst);
2755 UnswitchCandidates.push_back(
2756 {L.getHeader()->getTerminator(), std::move(ValsToDuplicate)});
2757 }
2758 }
2759
2760 // If we didn't find any candidates, we're done.
2761 if (UnswitchCandidates.empty())
9
Calling 'SmallVectorBase::empty'
12
Returning from 'SmallVectorBase::empty'
13
Taking false branch
2762 return false;
2763
2764 // Check if there are irreducible CFG cycles in this loop. If so, we cannot
2765 // easily unswitch non-trivial edges out of the loop. Doing so might turn the
2766 // irreducible control flow into reducible control flow and introduce new
2767 // loops "out of thin air". If we ever discover important use cases for doing
2768 // this, we can add support to loop unswitch, but it is a lot of complexity
2769 // for what seems little or no real world benefit.
2770 LoopBlocksRPO RPOT(&L);
2771 RPOT.perform(&LI);
2772 if (containsIrreducibleCFG<const BasicBlock *>(RPOT, LI))
14
Calling 'containsIrreducibleCFG<const llvm::BasicBlock *, llvm::LoopBlocksRPO, llvm::LoopInfo, llvm::GraphTraits<const llvm::BasicBlock *>>'
16
Returning from 'containsIrreducibleCFG<const llvm::BasicBlock *, llvm::LoopBlocksRPO, llvm::LoopInfo, llvm::GraphTraits<const llvm::BasicBlock *>>'
17
Taking false branch
2773 return false;
2774
2775 SmallVector<BasicBlock *, 4> ExitBlocks;
2776 L.getUniqueExitBlocks(ExitBlocks);
2777
2778 // We cannot unswitch if exit blocks contain a cleanuppad/catchswitch
2779 // instruction as we don't know how to split those exit blocks.
2780 // FIXME: We should teach SplitBlock to handle this and remove this
2781 // restriction.
2782 for (auto *ExitBB : ExitBlocks) {
18
Assuming '__begin1' is equal to '__end1'
2783 auto *I = ExitBB->getFirstNonPHI();
2784 if (isa<CleanupPadInst>(I) || isa<CatchSwitchInst>(I)) {
2785 LLVM_DEBUG(dbgs() << "Cannot unswitch because of cleanuppad/catchswitch "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Cannot unswitch because of cleanuppad/catchswitch "
"in exit block\n"; } } while (false)
2786 "in exit block\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Cannot unswitch because of cleanuppad/catchswitch "
"in exit block\n"; } } while (false)
;
2787 return false;
2788 }
2789 }
2790
2791 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Considering " <<
UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n"
; } } while (false)
19
Assuming 'DebugFlag' is false
20
Loop condition is false. Exiting loop
2792 dbgs() << "Considering " << UnswitchCandidates.size()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Considering " <<
UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n"
; } } while (false)
2793 << " non-trivial loop invariant conditions for unswitching.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Considering " <<
UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n"
; } } while (false)
;
2794
2795 // Given that unswitching these terminators will require duplicating parts of
2796 // the loop, so we need to be able to model that cost. Compute the ephemeral
2797 // values and set up a data structure to hold per-BB costs. We cache each
2798 // block's cost so that we don't recompute this when considering different
2799 // subsets of the loop for duplication during unswitching.
2800 SmallPtrSet<const Value *, 4> EphValues;
2801 CodeMetrics::collectEphemeralValues(&L, &AC, EphValues);
2802 SmallDenseMap<BasicBlock *, InstructionCost, 4> BBCostMap;
2803
2804 // Compute the cost of each block, as well as the total loop cost. Also, bail
2805 // out if we see instructions which are incompatible with loop unswitching
2806 // (convergent, noduplicate, or cross-basic-block tokens).
2807 // FIXME: We might be able to safely handle some of these in non-duplicated
2808 // regions.
2809 TargetTransformInfo::TargetCostKind CostKind =
2810 L.getHeader()->getParent()->hasMinSize()
21
Assuming the condition is false
22
'?' condition is false
2811 ? TargetTransformInfo::TCK_CodeSize
2812 : TargetTransformInfo::TCK_SizeAndLatency;
2813 InstructionCost LoopCost = 0;
2814 for (auto *BB : L.blocks()) {
23
Assuming '__begin1' is equal to '__end1'
2815 InstructionCost Cost = 0;
2816 for (auto &I : *BB) {
2817 if (EphValues.count(&I))
2818 continue;
2819
2820 if (I.getType()->isTokenTy() && I.isUsedOutsideOfBlock(BB))
2821 return false;
2822 if (auto *CB = dyn_cast<CallBase>(&I))
2823 if (CB->isConvergent() || CB->cannotDuplicate())
2824 return false;
2825
2826 Cost += TTI.getUserCost(&I, CostKind);
2827 }
2828 assert(Cost >= 0 && "Must not have negative costs!")(static_cast <bool> (Cost >= 0 && "Must not have negative costs!"
) ? void (0) : __assert_fail ("Cost >= 0 && \"Must not have negative costs!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2828, __extension__ __PRETTY_FUNCTION__))
;
2829 LoopCost += Cost;
2830 assert(LoopCost >= 0 && "Must not have negative loop costs!")(static_cast <bool> (LoopCost >= 0 && "Must not have negative loop costs!"
) ? void (0) : __assert_fail ("LoopCost >= 0 && \"Must not have negative loop costs!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2830, __extension__ __PRETTY_FUNCTION__))
;
2831 BBCostMap[BB] = Cost;
2832 }
2833 LLVM_DEBUG(dbgs() << " Total loop cost: " << LoopCost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Total loop cost: "
<< LoopCost << "\n"; } } while (false)
;
24
Assuming 'DebugFlag' is false
25
Loop condition is false. Exiting loop
2834
2835 // Now we find the best candidate by searching for the one with the following
2836 // properties in order:
2837 //
2838 // 1) An unswitching cost below the threshold
2839 // 2) The smallest number of duplicated unswitch candidates (to avoid
2840 // creating redundant subsequent unswitching)
2841 // 3) The smallest cost after unswitching.
2842 //
2843 // We prioritize reducing fanout of unswitch candidates provided the cost
2844 // remains below the threshold because this has a multiplicative effect.
2845 //
2846 // This requires memoizing each dominator subtree to avoid redundant work.
2847 //
2848 // FIXME: Need to actually do the number of candidates part above.
2849 SmallDenseMap<DomTreeNode *, InstructionCost, 4> DTCostMap;
2850 // Given a terminator which might be unswitched, computes the non-duplicated
2851 // cost for that terminator.
2852 auto ComputeUnswitchedCost = [&](Instruction &TI,
2853 bool FullUnswitch) -> InstructionCost {
2854 BasicBlock &BB = *TI.getParent();
2855 SmallPtrSet<BasicBlock *, 4> Visited;
2856
2857 InstructionCost Cost = 0;
2858 for (BasicBlock *SuccBB : successors(&BB)) {
2859 // Don't count successors more than once.
2860 if (!Visited.insert(SuccBB).second)
30
Assuming field 'second' is true
31
Taking false branch
2861 continue;
2862
2863 // If this is a partial unswitch candidate, then it must be a conditional
2864 // branch with a condition of either `or`, `and`, their corresponding
2865 // select forms or partially invariant instructions. In that case, one of
2866 // the successors is necessarily duplicated, so don't even try to remove
2867 // its cost.
2868 if (!FullUnswitch
31.1
'FullUnswitch' is false
31.1
'FullUnswitch' is false
31.1
'FullUnswitch' is false
31.1
'FullUnswitch' is false
31.1
'FullUnswitch' is false
) {
32
Taking true branch
2869 auto &BI = cast<BranchInst>(TI);
33
'TI' is a 'BranchInst'
2870 if (match(BI.getCondition(), m_LogicalAnd())) {
34
Calling 'match<llvm::Value, llvm::PatternMatch::LogicalOp_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, 28>>'
41
Returning from 'match<llvm::Value, llvm::PatternMatch::LogicalOp_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, 28>>'
42
Taking false branch
2871 if (SuccBB == BI.getSuccessor(1))
2872 continue;
2873 } else if (match(BI.getCondition(), m_LogicalOr())) {
43
Calling 'match<llvm::Value, llvm::PatternMatch::LogicalOp_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, 29>>'
50
Returning from 'match<llvm::Value, llvm::PatternMatch::LogicalOp_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, 29>>'
51
Taking false branch
2874 if (SuccBB == BI.getSuccessor(0))
2875 continue;
2876 } else if ((PartialIVInfo.KnownValue->isOneValue() &&
52
Called C++ object pointer is null
2877 SuccBB == BI.getSuccessor(0)) ||
2878 (!PartialIVInfo.KnownValue->isOneValue() &&
2879 SuccBB == BI.getSuccessor(1)))
2880 continue;
2881 }
2882
2883 // This successor's domtree will not need to be duplicated after
2884 // unswitching if the edge to the successor dominates it (and thus the
2885 // entire tree). This essentially means there is no other path into this
2886 // subtree and so it will end up live in only one clone of the loop.
2887 if (SuccBB->getUniquePredecessor() ||
2888 llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) {
2889 return PredBB == &BB || DT.dominates(SuccBB, PredBB);
2890 })) {
2891 Cost += computeDomSubtreeCost(*DT[SuccBB], BBCostMap, DTCostMap);
2892 assert(Cost <= LoopCost &&(static_cast <bool> (Cost <= LoopCost && "Non-duplicated cost should never exceed total loop cost!"
) ? void (0) : __assert_fail ("Cost <= LoopCost && \"Non-duplicated cost should never exceed total loop cost!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2893, __extension__ __PRETTY_FUNCTION__))
2893 "Non-duplicated cost should never exceed total loop cost!")(static_cast <bool> (Cost <= LoopCost && "Non-duplicated cost should never exceed total loop cost!"
) ? void (0) : __assert_fail ("Cost <= LoopCost && \"Non-duplicated cost should never exceed total loop cost!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2893, __extension__ __PRETTY_FUNCTION__))
;
2894 }
2895 }
2896
2897 // Now scale the cost by the number of unique successors minus one. We
2898 // subtract one because there is already at least one copy of the entire
2899 // loop. This is computing the new cost of unswitching a condition.
2900 // Note that guards always have 2 unique successors that are implicit and
2901 // will be materialized if we decide to unswitch it.
2902 int SuccessorsCount = isGuard(&TI) ? 2 : Visited.size();
2903 assert(SuccessorsCount > 1 &&(static_cast <bool> (SuccessorsCount > 1 && "Cannot unswitch a condition without multiple distinct successors!"
) ? void (0) : __assert_fail ("SuccessorsCount > 1 && \"Cannot unswitch a condition without multiple distinct successors!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2904, __extension__ __PRETTY_FUNCTION__))
2904 "Cannot unswitch a condition without multiple distinct successors!")(static_cast <bool> (SuccessorsCount > 1 && "Cannot unswitch a condition without multiple distinct successors!"
) ? void (0) : __assert_fail ("SuccessorsCount > 1 && \"Cannot unswitch a condition without multiple distinct successors!\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2904, __extension__ __PRETTY_FUNCTION__))
;
2905 return (LoopCost - Cost) * (SuccessorsCount - 1);
2906 };
2907 Instruction *BestUnswitchTI = nullptr;
2908 InstructionCost BestUnswitchCost = 0;
2909 ArrayRef<Value *> BestUnswitchInvariants;
2910 for (auto &TerminatorAndInvariants : UnswitchCandidates) {
26
Assuming '__begin1' is not equal to '__end1'
2911 Instruction &TI = *TerminatorAndInvariants.first;
2912 ArrayRef<Value *> Invariants = TerminatorAndInvariants.second;
2913 BranchInst *BI = dyn_cast<BranchInst>(&TI);
27
Assuming the object is a 'BranchInst'
2914 InstructionCost CandidateCost = ComputeUnswitchedCost(
29
Calling 'operator()'
2915 TI, /*FullUnswitch*/ !BI
27.1
'BI' is non-null
27.1
'BI' is non-null
27.1
'BI' is non-null
27.1
'BI' is non-null
27.1
'BI' is non-null
|| (Invariants.size() == 1 &&
28
Assuming the condition is false
2916 Invariants[0] == BI->getCondition()));
2917 // Calculate cost multiplier which is a tool to limit potentially
2918 // exponential behavior of loop-unswitch.
2919 if (EnableUnswitchCostMultiplier) {
2920 int CostMultiplier =
2921 CalculateUnswitchCostMultiplier(TI, L, LI, DT, UnswitchCandidates);
2922 assert((static_cast <bool> ((CostMultiplier > 0 && CostMultiplier
<= UnswitchThreshold) && "cost multiplier needs to be in the range of 1..UnswitchThreshold"
) ? void (0) : __assert_fail ("(CostMultiplier > 0 && CostMultiplier <= UnswitchThreshold) && \"cost multiplier needs to be in the range of 1..UnswitchThreshold\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2924, __extension__ __PRETTY_FUNCTION__))
2923 (CostMultiplier > 0 && CostMultiplier <= UnswitchThreshold) &&(static_cast <bool> ((CostMultiplier > 0 && CostMultiplier
<= UnswitchThreshold) && "cost multiplier needs to be in the range of 1..UnswitchThreshold"
) ? void (0) : __assert_fail ("(CostMultiplier > 0 && CostMultiplier <= UnswitchThreshold) && \"cost multiplier needs to be in the range of 1..UnswitchThreshold\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2924, __extension__ __PRETTY_FUNCTION__))
2924 "cost multiplier needs to be in the range of 1..UnswitchThreshold")(static_cast <bool> ((CostMultiplier > 0 && CostMultiplier
<= UnswitchThreshold) && "cost multiplier needs to be in the range of 1..UnswitchThreshold"
) ? void (0) : __assert_fail ("(CostMultiplier > 0 && CostMultiplier <= UnswitchThreshold) && \"cost multiplier needs to be in the range of 1..UnswitchThreshold\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2924, __extension__ __PRETTY_FUNCTION__))
;
2925 CandidateCost *= CostMultiplier;
2926 LLVM_DEBUG(dbgs() << " Computed cost of " << CandidateCostdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed cost of "
<< CandidateCost << " (multiplier: " << CostMultiplier
<< ")" << " for unswitch candidate: " << TI
<< "\n"; } } while (false)
2927 << " (multiplier: " << CostMultiplier << ")"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed cost of "
<< CandidateCost << " (multiplier: " << CostMultiplier
<< ")" << " for unswitch candidate: " << TI
<< "\n"; } } while (false)
2928 << " for unswitch candidate: " << TI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed cost of "
<< CandidateCost << " (multiplier: " << CostMultiplier
<< ")" << " for unswitch candidate: " << TI
<< "\n"; } } while (false)
;
2929 } else {
2930 LLVM_DEBUG(dbgs() << " Computed cost of " << CandidateCostdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed cost of "
<< CandidateCost << " for unswitch candidate: " <<
TI << "\n"; } } while (false)
2931 << " for unswitch candidate: " << TI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Computed cost of "
<< CandidateCost << " for unswitch candidate: " <<
TI << "\n"; } } while (false)
;
2932 }
2933
2934 if (!BestUnswitchTI || CandidateCost < BestUnswitchCost) {
2935 BestUnswitchTI = &TI;
2936 BestUnswitchCost = CandidateCost;
2937 BestUnswitchInvariants = Invariants;
2938 }
2939 }
2940 assert(BestUnswitchTI && "Failed to find loop unswitch candidate")(static_cast <bool> (BestUnswitchTI && "Failed to find loop unswitch candidate"
) ? void (0) : __assert_fail ("BestUnswitchTI && \"Failed to find loop unswitch candidate\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2940, __extension__ __PRETTY_FUNCTION__))
;
2941
2942 if (BestUnswitchCost >= UnswitchThreshold) {
2943 LLVM_DEBUG(dbgs() << "Cannot unswitch, lowest cost found: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Cannot unswitch, lowest cost found: "
<< BestUnswitchCost << "\n"; } } while (false)
2944 << BestUnswitchCost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Cannot unswitch, lowest cost found: "
<< BestUnswitchCost << "\n"; } } while (false)
;
2945 return false;
2946 }
2947
2948 if (BestUnswitchTI != PartialIVCondBranch)
2949 PartialIVInfo.InstToDuplicate.clear();
2950
2951 // If the best candidate is a guard, turn it into a branch.
2952 if (isGuard(BestUnswitchTI))
2953 BestUnswitchTI = turnGuardIntoBranch(cast<IntrinsicInst>(BestUnswitchTI), L,
2954 ExitBlocks, DT, LI, MSSAU);
2955
2956 LLVM_DEBUG(dbgs() << " Unswitching non-trivial (cost = "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Unswitching non-trivial (cost = "
<< BestUnswitchCost << ") terminator: " <<
*BestUnswitchTI << "\n"; } } while (false)
2957 << BestUnswitchCost << ") terminator: " << *BestUnswitchTIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Unswitching non-trivial (cost = "
<< BestUnswitchCost << ") terminator: " <<
*BestUnswitchTI << "\n"; } } while (false)
2958 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << " Unswitching non-trivial (cost = "
<< BestUnswitchCost << ") terminator: " <<
*BestUnswitchTI << "\n"; } } while (false)
;
2959 unswitchNontrivialInvariants(L, *BestUnswitchTI, BestUnswitchInvariants,
2960 ExitBlocks, PartialIVInfo, DT, LI, AC,
2961 UnswitchCB, SE, MSSAU);
2962 return true;
2963}
2964
2965/// Unswitch control flow predicated on loop invariant conditions.
2966///
2967/// This first hoists all branches or switches which are trivial (IE, do not
2968/// require duplicating any part of the loop) out of the loop body. It then
2969/// looks at other loop invariant control flows and tries to unswitch those as
2970/// well by cloning the loop if the result is small enough.
2971///
2972/// The `DT`, `LI`, `AC`, `AA`, `TTI` parameters are required analyses that are
2973/// also updated based on the unswitch. The `MSSA` analysis is also updated if
2974/// valid (i.e. its use is enabled).
2975///
2976/// If either `NonTrivial` is true or the flag `EnableNonTrivialUnswitch` is
2977/// true, we will attempt to do non-trivial unswitching as well as trivial
2978/// unswitching.
2979///
2980/// The `UnswitchCB` callback provided will be run after unswitching is
2981/// complete, with the first parameter set to `true` if the provided loop
2982/// remains a loop, and a list of new sibling loops created.
2983///
2984/// If `SE` is non-null, we will update that analysis based on the unswitching
2985/// done.
2986static bool
2987unswitchLoop(Loop &L, DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC,
2988 AAResults &AA, TargetTransformInfo &TTI, bool Trivial,
2989 bool NonTrivial,
2990 function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB,
2991 ScalarEvolution *SE, MemorySSAUpdater *MSSAU) {
2992 assert(L.isRecursivelyLCSSAForm(DT, LI) &&(static_cast <bool> (L.isRecursivelyLCSSAForm(DT, LI) &&
"Loops must be in LCSSA form before unswitching.") ? void (0
) : __assert_fail ("L.isRecursivelyLCSSAForm(DT, LI) && \"Loops must be in LCSSA form before unswitching.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2993, __extension__ __PRETTY_FUNCTION__))
2993 "Loops must be in LCSSA form before unswitching.")(static_cast <bool> (L.isRecursivelyLCSSAForm(DT, LI) &&
"Loops must be in LCSSA form before unswitching.") ? void (0
) : __assert_fail ("L.isRecursivelyLCSSAForm(DT, LI) && \"Loops must be in LCSSA form before unswitching.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 2993, __extension__ __PRETTY_FUNCTION__))
;
2994
2995 // Must be in loop simplified form: we need a preheader and dedicated exits.
2996 if (!L.isLoopSimplifyForm())
2997 return false;
2998
2999 // Try trivial unswitch first before loop over other basic blocks in the loop.
3000 if (Trivial && unswitchAllTrivialConditions(L, DT, LI, SE, MSSAU)) {
3001 // If we unswitched successfully we will want to clean up the loop before
3002 // processing it further so just mark it as unswitched and return.
3003 UnswitchCB(/*CurrentLoopValid*/ true, false, {});
3004 return true;
3005 }
3006
3007 // Check whether we should continue with non-trivial conditions.
3008 // EnableNonTrivialUnswitch: Global variable that forces non-trivial
3009 // unswitching for testing and debugging.
3010 // NonTrivial: Parameter that enables non-trivial unswitching for this
3011 // invocation of the transform. But this should be allowed only
3012 // for targets without branch divergence.
3013 //
3014 // FIXME: If divergence analysis becomes available to a loop
3015 // transform, we should allow unswitching for non-trivial uniform
3016 // branches even on targets that have divergence.
3017 // https://bugs.llvm.org/show_bug.cgi?id=48819
3018 bool ContinueWithNonTrivial =
3019 EnableNonTrivialUnswitch || (NonTrivial && !TTI.hasBranchDivergence());
3020 if (!ContinueWithNonTrivial)
3021 return false;
3022
3023 // Skip non-trivial unswitching for optsize functions.
3024 if (L.getHeader()->getParent()->hasOptSize())
3025 return false;
3026
3027 // Skip non-trivial unswitching for loops that cannot be cloned.
3028 if (!L.isSafeToClone())
3029 return false;
3030
3031 // For non-trivial unswitching, because it often creates new loops, we rely on
3032 // the pass manager to iterate on the loops rather than trying to immediately
3033 // reach a fixed point. There is no substantial advantage to iterating
3034 // internally, and if any of the new loops are simplified enough to contain
3035 // trivial unswitching we want to prefer those.
3036
3037 // Try to unswitch the best invariant condition. We prefer this full unswitch to
3038 // a partial unswitch when possible below the threshold.
3039 if (unswitchBestCondition(L, DT, LI, AC, AA, TTI, UnswitchCB, SE, MSSAU))
3040 return true;
3041
3042 // No other opportunities to unswitch.
3043 return false;
3044}
3045
3046PreservedAnalyses SimpleLoopUnswitchPass::run(Loop &L, LoopAnalysisManager &AM,
3047 LoopStandardAnalysisResults &AR,
3048 LPMUpdater &U) {
3049 Function &F = *L.getHeader()->getParent();
3050 (void)F;
3051
3052 LLVM_DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << Ldo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Unswitching loop in "
<< F.getName() << ": " << L << "\n";
} } while (false)
3053 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Unswitching loop in "
<< F.getName() << ": " << L << "\n";
} } while (false)
;
3054
3055 // Save the current loop name in a variable so that we can report it even
3056 // after it has been deleted.
3057 std::string LoopName = std::string(L.getName());
3058
3059 auto UnswitchCB = [&L, &U, &LoopName](bool CurrentLoopValid,
3060 bool PartiallyInvariant,
3061 ArrayRef<Loop *> NewLoops) {
3062 // If we did a non-trivial unswitch, we have added new (cloned) loops.
3063 if (!NewLoops.empty())
3064 U.addSiblingLoops(NewLoops);
3065
3066 // If the current loop remains valid, we should revisit it to catch any
3067 // other unswitch opportunities. Otherwise, we need to mark it as deleted.
3068 if (CurrentLoopValid) {
3069 if (PartiallyInvariant) {
3070 // Mark the new loop as partially unswitched, to avoid unswitching on
3071 // the same condition again.
3072 auto &Context = L.getHeader()->getContext();
3073 MDNode *DisableUnswitchMD = MDNode::get(
3074 Context,
3075 MDString::get(Context, "llvm.loop.unswitch.partial.disable"));
3076 MDNode *NewLoopID = makePostTransformationMetadata(
3077 Context, L.getLoopID(), {"llvm.loop.unswitch.partial"},
3078 {DisableUnswitchMD});
3079 L.setLoopID(NewLoopID);
3080 } else
3081 U.revisitCurrentLoop();
3082 } else
3083 U.markLoopAsDeleted(L, LoopName);
3084 };
3085
3086 Optional<MemorySSAUpdater> MSSAU;
3087 if (AR.MSSA) {
3088 MSSAU = MemorySSAUpdater(AR.MSSA);
3089 if (VerifyMemorySSA)
3090 AR.MSSA->verifyMemorySSA();
3091 }
3092 if (!unswitchLoop(L, AR.DT, AR.LI, AR.AC, AR.AA, AR.TTI, Trivial, NonTrivial,
3093 UnswitchCB, &AR.SE,
3094 MSSAU.hasValue() ? MSSAU.getPointer() : nullptr))
3095 return PreservedAnalyses::all();
3096
3097 if (AR.MSSA && VerifyMemorySSA)
3098 AR.MSSA->verifyMemorySSA();
3099
3100 // Historically this pass has had issues with the dominator tree so verify it
3101 // in asserts builds.
3102 assert(AR.DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (AR.DT.verify(DominatorTree::VerificationLevel
::Fast)) ? void (0) : __assert_fail ("AR.DT.verify(DominatorTree::VerificationLevel::Fast)"
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 3102, __extension__ __PRETTY_FUNCTION__))
;
3103
3104 auto PA = getLoopPassPreservedAnalyses();
3105 if (AR.MSSA)
3106 PA.preserve<MemorySSAAnalysis>();
3107 return PA;
3108}
3109
3110namespace {
3111
3112class SimpleLoopUnswitchLegacyPass : public LoopPass {
3113 bool NonTrivial;
3114
3115public:
3116 static char ID; // Pass ID, replacement for typeid
3117
3118 explicit SimpleLoopUnswitchLegacyPass(bool NonTrivial = false)
3119 : LoopPass(ID), NonTrivial(NonTrivial) {
3120 initializeSimpleLoopUnswitchLegacyPassPass(
3121 *PassRegistry::getPassRegistry());
3122 }
3123
3124 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
3125
3126 void getAnalysisUsage(AnalysisUsage &AU) const override {
3127 AU.addRequired<AssumptionCacheTracker>();
3128 AU.addRequired<TargetTransformInfoWrapperPass>();
3129 if (EnableMSSALoopDependency) {
3130 AU.addRequired<MemorySSAWrapperPass>();
3131 AU.addPreserved<MemorySSAWrapperPass>();
3132 }
3133 getLoopAnalysisUsage(AU);
3134 }
3135};
3136
3137} // end anonymous namespace
3138
3139bool SimpleLoopUnswitchLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) {
3140 if (skipLoop(L))
3141 return false;
3142
3143 Function &F = *L->getHeader()->getParent();
3144
3145 LLVM_DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << *Ldo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Unswitching loop in "
<< F.getName() << ": " << *L << "\n"
; } } while (false)
3146 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simple-loop-unswitch")) { dbgs() << "Unswitching loop in "
<< F.getName() << ": " << *L << "\n"
; } } while (false)
;
3147
3148 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
3149 auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
3150 auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
3151 auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
3152 auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
3153 MemorySSA *MSSA = nullptr;
3154 Optional<MemorySSAUpdater> MSSAU;
3155 if (EnableMSSALoopDependency) {
3156 MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA();
3157 MSSAU = MemorySSAUpdater(MSSA);
3158 }
3159
3160 auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
3161 auto *SE = SEWP ? &SEWP->getSE() : nullptr;
3162
3163 auto UnswitchCB = [&L, &LPM](bool CurrentLoopValid, bool PartiallyInvariant,
3164 ArrayRef<Loop *> NewLoops) {
3165 // If we did a non-trivial unswitch, we have added new (cloned) loops.
3166 for (auto *NewL : NewLoops)
3167 LPM.addLoop(*NewL);
3168
3169 // If the current loop remains valid, re-add it to the queue. This is
3170 // a little wasteful as we'll finish processing the current loop as well,
3171 // but it is the best we can do in the old PM.
3172 if (CurrentLoopValid) {
3173 // If the current loop has been unswitched using a partially invariant
3174 // condition, we should not re-add the current loop to avoid unswitching
3175 // on the same condition again.
3176 if (!PartiallyInvariant)
3177 LPM.addLoop(*L);
3178 } else
3179 LPM.markLoopAsDeleted(*L);
3180 };
3181
3182 if (MSSA && VerifyMemorySSA)
3183 MSSA->verifyMemorySSA();
3184
3185 bool Changed =
3186 unswitchLoop(*L, DT, LI, AC, AA, TTI, true, NonTrivial, UnswitchCB, SE,
3187 MSSAU.hasValue() ? MSSAU.getPointer() : nullptr);
3188
3189 if (MSSA && VerifyMemorySSA)
3190 MSSA->verifyMemorySSA();
3191
3192 // Historically this pass has had issues with the dominator tree so verify it
3193 // in asserts builds.
3194 assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel
::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)"
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp"
, 3194, __extension__ __PRETTY_FUNCTION__))
;
3195
3196 return Changed;
3197}
3198
3199char SimpleLoopUnswitchLegacyPass::ID = 0;
3200INITIALIZE_PASS_BEGIN(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry
&Registry) {
3201 "Simple unswitch loops", false, false)static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry
&Registry) {
3202INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry);
3203INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
3204INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry);
3205INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry);
3206INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry);
3207INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
3208INITIALIZE_PASS_END(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch"
, &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false,
false); Registry.registerPass(*PI, true); return PI; } static
llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag
; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry
&Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag
, initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry
)); }
3209 "Simple unswitch loops", false, false)PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch"
, &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false,
false); Registry.registerPass(*PI, true); return PI; } static
llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag
; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry
&Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag
, initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry
)); }
3210
3211Pass *llvm::createSimpleLoopUnswitchLegacyPass(bool NonTrivial) {
3212 return new SimpleLoopUnswitchLegacyPass(NonTrivial);
3213}

/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/Transforms/Utils/LoopUtils.h

1//===- llvm/Transforms/Utils/LoopUtils.h - Loop utilities -------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines some loop transformation utilities.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_TRANSFORMS_UTILS_LOOPUTILS_H
14#define LLVM_TRANSFORMS_UTILS_LOOPUTILS_H
15
16#include "llvm/ADT/StringRef.h"
17#include "llvm/Analysis/IVDescriptors.h"
18#include "llvm/Analysis/TargetTransformInfo.h"
19#include "llvm/Transforms/Utils/ValueMapper.h"
20
21namespace llvm {
22
23template <typename T> class DomTreeNodeBase;
24using DomTreeNode = DomTreeNodeBase<BasicBlock>;
25class AAResults;
26class AliasSet;
27class AliasSetTracker;
28class BasicBlock;
29class BlockFrequencyInfo;
30class ICFLoopSafetyInfo;
31class IRBuilderBase;
32class Loop;
33class LoopInfo;
34class MemoryAccess;
35class MemorySSA;
36class MemorySSAUpdater;
37class OptimizationRemarkEmitter;
38class PredIteratorCache;
39class ScalarEvolution;
40class ScalarEvolutionExpander;
41class SCEV;
42class SCEVExpander;
43class TargetLibraryInfo;
44class LPPassManager;
45class Instruction;
46struct RuntimeCheckingPtrGroup;
47typedef std::pair<const RuntimeCheckingPtrGroup *,
48 const RuntimeCheckingPtrGroup *>
49 RuntimePointerCheck;
50
51template <typename T> class Optional;
52template <typename T, unsigned N> class SmallSetVector;
53template <typename T, unsigned N> class SmallVector;
54template <typename T> class SmallVectorImpl;
55template <typename T, unsigned N> class SmallPriorityWorklist;
56
57BasicBlock *InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo *LI,
58 MemorySSAUpdater *MSSAU, bool PreserveLCSSA);
59
60/// Ensure that all exit blocks of the loop are dedicated exits.
61///
62/// For any loop exit block with non-loop predecessors, we split the loop
63/// predecessors to use a dedicated loop exit block. We update the dominator
64/// tree and loop info if provided, and will preserve LCSSA if requested.
65bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI,
66 MemorySSAUpdater *MSSAU, bool PreserveLCSSA);
67
68/// Ensures LCSSA form for every instruction from the Worklist in the scope of
69/// innermost containing loop.
70///
71/// For the given instruction which have uses outside of the loop, an LCSSA PHI
72/// node is inserted and the uses outside the loop are rewritten to use this
73/// node.
74///
75/// LoopInfo and DominatorTree are required and, since the routine makes no
76/// changes to CFG, preserved.
77///
78/// Returns true if any modifications are made.
79///
80/// This function may introduce unused PHI nodes. If \p PHIsToRemove is not
81/// nullptr, those are added to it (before removing, the caller has to check if
82/// they still do not have any uses). Otherwise the PHIs are directly removed.
83bool formLCSSAForInstructions(
84 SmallVectorImpl<Instruction *> &Worklist, const DominatorTree &DT,
85 const LoopInfo &LI, ScalarEvolution *SE, IRBuilderBase &Builder,
86 SmallVectorImpl<PHINode *> *PHIsToRemove = nullptr);
87
88/// Put loop into LCSSA form.
89///
90/// Looks at all instructions in the loop which have uses outside of the
91/// current loop. For each, an LCSSA PHI node is inserted and the uses outside
92/// the loop are rewritten to use this node. Sub-loops must be in LCSSA form
93/// already.
94///
95/// LoopInfo and DominatorTree are required and preserved.
96///
97/// If ScalarEvolution is passed in, it will be preserved.
98///
99/// Returns true if any modifications are made to the loop.
100bool formLCSSA(Loop &L, const DominatorTree &DT, const LoopInfo *LI,
101 ScalarEvolution *SE);
102
103/// Put a loop nest into LCSSA form.
104///
105/// This recursively forms LCSSA for a loop nest.
106///
107/// LoopInfo and DominatorTree are required and preserved.
108///
109/// If ScalarEvolution is passed in, it will be preserved.
110///
111/// Returns true if any modifications are made to the loop.
112bool formLCSSARecursively(Loop &L, const DominatorTree &DT, const LoopInfo *LI,
113 ScalarEvolution *SE);
114
115/// Flags controlling how much is checked when sinking or hoisting
116/// instructions. The number of memory access in the loop (and whether there
117/// are too many) is determined in the constructors when using MemorySSA.
118class SinkAndHoistLICMFlags {
119public:
120 // Explicitly set limits.
121 SinkAndHoistLICMFlags(unsigned LicmMssaOptCap,
122 unsigned LicmMssaNoAccForPromotionCap, bool IsSink,
123 Loop *L = nullptr, MemorySSA *MSSA = nullptr);
124 // Use default limits.
125 SinkAndHoistLICMFlags(bool IsSink, Loop *L = nullptr,
126 MemorySSA *MSSA = nullptr);
127
128 void setIsSink(bool B) { IsSink = B; }
129 bool getIsSink() { return IsSink; }
130 bool tooManyMemoryAccesses() { return NoOfMemAccTooLarge; }
131 bool tooManyClobberingCalls() { return LicmMssaOptCounter >= LicmMssaOptCap; }
132 void incrementClobberingCalls() { ++LicmMssaOptCounter; }
133
134protected:
135 bool NoOfMemAccTooLarge = false;
136 unsigned LicmMssaOptCounter = 0;
137 unsigned LicmMssaOptCap;
138 unsigned LicmMssaNoAccForPromotionCap;
139 bool IsSink;
140};
141
142/// Walk the specified region of the CFG (defined by all blocks
143/// dominated by the specified block, and that are in the current loop) in
144/// reverse depth first order w.r.t the DominatorTree. This allows us to visit
145/// uses before definitions, allowing us to sink a loop body in one pass without
146/// iteration. Takes DomTreeNode, AAResults, LoopInfo, DominatorTree,
147/// BlockFrequencyInfo, TargetLibraryInfo, Loop, AliasSet information for all
148/// instructions of the loop and loop safety information as
149/// arguments. Diagnostics is emitted via \p ORE. It returns changed status.
150bool sinkRegion(DomTreeNode *, AAResults *, LoopInfo *, DominatorTree *,
151 BlockFrequencyInfo *, TargetLibraryInfo *,
152 TargetTransformInfo *, Loop *, AliasSetTracker *,
153 MemorySSAUpdater *, ICFLoopSafetyInfo *,
154 SinkAndHoistLICMFlags &, OptimizationRemarkEmitter *);
155
156/// Walk the specified region of the CFG (defined by all blocks
157/// dominated by the specified block, and that are in the current loop) in depth
158/// first order w.r.t the DominatorTree. This allows us to visit definitions
159/// before uses, allowing us to hoist a loop body in one pass without iteration.
160/// Takes DomTreeNode, AAResults, LoopInfo, DominatorTree,
161/// BlockFrequencyInfo, TargetLibraryInfo, Loop, AliasSet information for all
162/// instructions of the loop and loop safety information as arguments.
163/// Diagnostics is emitted via \p ORE. It returns changed status.
164bool hoistRegion(DomTreeNode *, AAResults *, LoopInfo *, DominatorTree *,
165 BlockFrequencyInfo *, TargetLibraryInfo *, Loop *,
166 AliasSetTracker *, MemorySSAUpdater *, ScalarEvolution *,
167 ICFLoopSafetyInfo *, SinkAndHoistLICMFlags &,
168 OptimizationRemarkEmitter *, bool);
169
170/// This function deletes dead loops. The caller of this function needs to
171/// guarantee that the loop is infact dead.
172/// The function requires a bunch or prerequisites to be present:
173/// - The loop needs to be in LCSSA form
174/// - The loop needs to have a Preheader
175/// - A unique dedicated exit block must exist
176///
177/// This also updates the relevant analysis information in \p DT, \p SE, \p LI
178/// and \p MSSA if pointers to those are provided.
179/// It also updates the loop PM if an updater struct is provided.
180
181void deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE,
182 LoopInfo *LI, MemorySSA *MSSA = nullptr);
183
184/// Remove the backedge of the specified loop. Handles loop nests and general
185/// loop structures subject to the precondition that the loop has no parent
186/// loop and has a single latch block. Preserves all listed analyses.
187void breakLoopBackedge(Loop *L, DominatorTree &DT, ScalarEvolution &SE,
188 LoopInfo &LI, MemorySSA *MSSA);
189
190/// Try to promote memory values to scalars by sinking stores out of
191/// the loop and moving loads to before the loop. We do this by looping over
192/// the stores in the loop, looking for stores to Must pointers which are
193/// loop invariant. It takes a set of must-alias values, Loop exit blocks
194/// vector, loop exit blocks insertion point vector, PredIteratorCache,
195/// LoopInfo, DominatorTree, Loop, AliasSet information for all instructions
196/// of the loop and loop safety information as arguments.
197/// Diagnostics is emitted via \p ORE. It returns changed status.
198bool promoteLoopAccessesToScalars(
199 const SmallSetVector<Value *, 8> &, SmallVectorImpl<BasicBlock *> &,
200 SmallVectorImpl<Instruction *> &, SmallVectorImpl<MemoryAccess *> &,
201 PredIteratorCache &, LoopInfo *, DominatorTree *, const TargetLibraryInfo *,
202 Loop *, AliasSetTracker *, MemorySSAUpdater *, ICFLoopSafetyInfo *,
203 OptimizationRemarkEmitter *);
204
205/// Does a BFS from a given node to all of its children inside a given loop.
206/// The returned vector of nodes includes the starting point.
207SmallVector<DomTreeNode *, 16> collectChildrenInLoop(DomTreeNode *N,
208 const Loop *CurLoop);
209
210/// Returns the instructions that use values defined in the loop.
211SmallVector<Instruction *, 8> findDefsUsedOutsideOfLoop(Loop *L);
212
213/// Find a combination of metadata ("llvm.loop.vectorize.width" and
214/// "llvm.loop.vectorize.scalable.enable") for a loop and use it to construct a
215/// ElementCount. If the metadata "llvm.loop.vectorize.width" cannot be found
216/// then None is returned.
217Optional<ElementCount>
218getOptionalElementCountLoopAttribute(const Loop *TheLoop);
219
220/// Create a new loop identifier for a loop created from a loop transformation.
221///
222/// @param OrigLoopID The loop ID of the loop before the transformation.
223/// @param FollowupAttrs List of attribute names that contain attributes to be
224/// added to the new loop ID.
225/// @param InheritOptionsAttrsPrefix Selects which attributes should be inherited
226/// from the original loop. The following values
227/// are considered:
228/// nullptr : Inherit all attributes from @p OrigLoopID.
229/// "" : Do not inherit any attribute from @p OrigLoopID; only use
230/// those specified by a followup attribute.
231/// "<prefix>": Inherit all attributes except those which start with
232/// <prefix>; commonly used to remove metadata for the
233/// applied transformation.
234/// @param AlwaysNew If true, do not try to reuse OrigLoopID and never return
235/// None.
236///
237/// @return The loop ID for the after-transformation loop. The following values
238/// can be returned:
239/// None : No followup attribute was found; it is up to the
240/// transformation to choose attributes that make sense.
241/// @p OrigLoopID: The original identifier can be reused.
242/// nullptr : The new loop has no attributes.
243/// MDNode* : A new unique loop identifier.
244Optional<MDNode *>
245makeFollowupLoopID(MDNode *OrigLoopID, ArrayRef<StringRef> FollowupAttrs,
246 const char *InheritOptionsAttrsPrefix = "",
247 bool AlwaysNew = false);
248
249/// Look for the loop attribute that disables all transformation heuristic.
250bool hasDisableAllTransformsHint(const Loop *L);
251
252/// Look for the loop attribute that disables the LICM transformation heuristics.
253bool hasDisableLICMTransformsHint(const Loop *L);
254
255/// The mode sets how eager a transformation should be applied.
256enum TransformationMode {
257 /// The pass can use heuristics to determine whether a transformation should
258 /// be applied.
259 TM_Unspecified,
260
261 /// The transformation should be applied without considering a cost model.
262 TM_Enable,
263
264 /// The transformation should not be applied.
265 TM_Disable,
266
267 /// Force is a flag and should not be used alone.
268 TM_Force = 0x04,
269
270 /// The transformation was directed by the user, e.g. by a #pragma in
271 /// the source code. If the transformation could not be applied, a
272 /// warning should be emitted.
273 TM_ForcedByUser = TM_Enable | TM_Force,
274
275 /// The transformation must not be applied. For instance, `#pragma clang loop
276 /// unroll(disable)` explicitly forbids any unrolling to take place. Unlike
277 /// general loop metadata, it must not be dropped. Most passes should not
278 /// behave differently under TM_Disable and TM_SuppressedByUser.
279 TM_SuppressedByUser = TM_Disable | TM_Force
280};
281
282/// @{
283/// Get the mode for LLVM's supported loop transformations.
284TransformationMode hasUnrollTransformation(const Loop *L);
285TransformationMode hasUnrollAndJamTransformation(const Loop *L);
286TransformationMode hasVectorizeTransformation(const Loop *L);
287TransformationMode hasDistributeTransformation(const Loop *L);
288TransformationMode hasLICMVersioningTransformation(const Loop *L);
289/// @}
290
291/// Set input string into loop metadata by keeping other values intact.
292/// If the string is already in loop metadata update value if it is
293/// different.
294void addStringMetadataToLoop(Loop *TheLoop, const char *MDString,
295 unsigned V = 0);
296
297/// Returns a loop's estimated trip count based on branch weight metadata.
298/// In addition if \p EstimatedLoopInvocationWeight is not null it is
299/// initialized with weight of loop's latch leading to the exit.
300/// Returns 0 when the count is estimated to be 0, or None when a meaningful
301/// estimate can not be made.
302Optional<unsigned>
303getLoopEstimatedTripCount(Loop *L,
304 unsigned *EstimatedLoopInvocationWeight = nullptr);
305
306/// Set a loop's branch weight metadata to reflect that loop has \p
307/// EstimatedTripCount iterations and \p EstimatedLoopInvocationWeight exits
308/// through latch. Returns true if metadata is successfully updated, false
309/// otherwise. Note that loop must have a latch block which controls loop exit
310/// in order to succeed.
311bool setLoopEstimatedTripCount(Loop *L, unsigned EstimatedTripCount,
312 unsigned EstimatedLoopInvocationWeight);
313
314/// Check inner loop (L) backedge count is known to be invariant on all
315/// iterations of its outer loop. If the loop has no parent, this is trivially
316/// true.
317bool hasIterationCountInvariantInParent(Loop *L, ScalarEvolution &SE);
318
319/// Helper to consistently add the set of standard passes to a loop pass's \c
320/// AnalysisUsage.
321///
322/// All loop passes should call this as part of implementing their \c
323/// getAnalysisUsage.
324void getLoopAnalysisUsage(AnalysisUsage &AU);
325
326/// Returns true if is legal to hoist or sink this instruction disregarding the
327/// possible introduction of faults. Reasoning about potential faulting
328/// instructions is the responsibility of the caller since it is challenging to
329/// do efficiently from within this routine.
330/// \p TargetExecutesOncePerLoop is true only when it is guaranteed that the
331/// target executes at most once per execution of the loop body. This is used
332/// to assess the legality of duplicating atomic loads. Generally, this is
333/// true when moving out of loop and not true when moving into loops.
334/// If \p ORE is set use it to emit optimization remarks.
335bool canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
336 Loop *CurLoop, AliasSetTracker *CurAST,
337 MemorySSAUpdater *MSSAU, bool TargetExecutesOncePerLoop,
338 SinkAndHoistLICMFlags *LICMFlags = nullptr,
339 OptimizationRemarkEmitter *ORE = nullptr);
340
341/// Returns a Min/Max operation corresponding to MinMaxRecurrenceKind.
342/// The Builder's fast-math-flags must be set to propagate the expected values.
343Value *createMinMaxOp(IRBuilderBase &Builder, RecurKind RK, Value *Left,
344 Value *Right);
345
346/// Generates an ordered vector reduction using extracts to reduce the value.
347Value *getOrderedReduction(IRBuilderBase &Builder, Value *Acc, Value *Src,
348 unsigned Op, RecurKind MinMaxKind = RecurKind::None,
349 ArrayRef<Value *> RedOps = None);
350
351/// Generates a vector reduction using shufflevectors to reduce the value.
352/// Fast-math-flags are propagated using the IRBuilder's setting.
353Value *getShuffleReduction(IRBuilderBase &Builder, Value *Src, unsigned Op,
354 RecurKind MinMaxKind = RecurKind::None,
355 ArrayRef<Value *> RedOps = None);
356
357/// Create a target reduction of the given vector. The reduction operation
358/// is described by the \p Opcode parameter. min/max reductions require
359/// additional information supplied in \p RdxKind.
360/// The target is queried to determine if intrinsics or shuffle sequences are
361/// required to implement the reduction.
362/// Fast-math-flags are propagated using the IRBuilder's setting.
363Value *createSimpleTargetReduction(IRBuilderBase &B,
364 const TargetTransformInfo *TTI, Value *Src,
365 RecurKind RdxKind,
366 ArrayRef<Value *> RedOps = None);
367
368/// Create a generic target reduction using a recurrence descriptor \p Desc
369/// The target is queried to determine if intrinsics or shuffle sequences are
370/// required to implement the reduction.
371/// Fast-math-flags are propagated using the RecurrenceDescriptor.
372Value *createTargetReduction(IRBuilderBase &B, const TargetTransformInfo *TTI,
373 const RecurrenceDescriptor &Desc, Value *Src);
374
375/// Create an ordered reduction intrinsic using the given recurrence
376/// descriptor \p Desc.
377Value *createOrderedReduction(IRBuilderBase &B,
378 const RecurrenceDescriptor &Desc, Value *Src,
379 Value *Start);
380
381/// Get the intersection (logical and) of all of the potential IR flags
382/// of each scalar operation (VL) that will be converted into a vector (I).
383/// If OpValue is non-null, we only consider operations similar to OpValue
384/// when intersecting.
385/// Flag set: NSW, NUW, exact, and all of fast-math.
386void propagateIRFlags(Value *I, ArrayRef<Value *> VL, Value *OpValue = nullptr);
387
388/// Returns true if we can prove that \p S is defined and always negative in
389/// loop \p L.
390bool isKnownNegativeInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE);
391
392/// Returns true if we can prove that \p S is defined and always non-negative in
393/// loop \p L.
394bool isKnownNonNegativeInLoop(const SCEV *S, const Loop *L,
395 ScalarEvolution &SE);
396
397/// Returns true if \p S is defined and never is equal to signed/unsigned max.
398bool cannotBeMaxInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE,
399 bool Signed);
400
401/// Returns true if \p S is defined and never is equal to signed/unsigned min.
402bool cannotBeMinInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE,
403 bool Signed);
404
405enum ReplaceExitVal { NeverRepl, OnlyCheapRepl, NoHardUse, AlwaysRepl };
406
407/// If the final value of any expressions that are recurrent in the loop can
408/// be computed, substitute the exit values from the loop into any instructions
409/// outside of the loop that use the final values of the current expressions.
410/// Return the number of loop exit values that have been replaced, and the
411/// corresponding phi node will be added to DeadInsts.
412int rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
413 ScalarEvolution *SE, const TargetTransformInfo *TTI,
414 SCEVExpander &Rewriter, DominatorTree *DT,
415 ReplaceExitVal ReplaceExitValue,
416 SmallVector<WeakTrackingVH, 16> &DeadInsts);
417
418/// Set weights for \p UnrolledLoop and \p RemainderLoop based on weights for
419/// \p OrigLoop and the following distribution of \p OrigLoop iteration among \p
420/// UnrolledLoop and \p RemainderLoop. \p UnrolledLoop receives weights that
421/// reflect TC/UF iterations, and \p RemainderLoop receives weights that reflect
422/// the remaining TC%UF iterations.
423///
424/// Note that \p OrigLoop may be equal to either \p UnrolledLoop or \p
425/// RemainderLoop in which case weights for \p OrigLoop are updated accordingly.
426/// Note also behavior is undefined if \p UnrolledLoop and \p RemainderLoop are
427/// equal. \p UF must be greater than zero.
428/// If \p OrigLoop has no profile info associated nothing happens.
429///
430/// This utility may be useful for such optimizations as unroller and
431/// vectorizer as it's typical transformation for them.
432void setProfileInfoAfterUnrolling(Loop *OrigLoop, Loop *UnrolledLoop,
433 Loop *RemainderLoop, uint64_t UF);
434
435/// Utility that implements appending of loops onto a worklist given a range.
436/// We want to process loops in postorder, but the worklist is a LIFO data
437/// structure, so we append to it in *reverse* postorder.
438/// For trees, a preorder traversal is a viable reverse postorder, so we
439/// actually append using a preorder walk algorithm.
440template <typename RangeT>
441void appendLoopsToWorklist(RangeT &&, SmallPriorityWorklist<Loop *, 4> &);
442/// Utility that implements appending of loops onto a worklist given a range.
443/// It has the same behavior as appendLoopsToWorklist, but assumes the range of
444/// loops has already been reversed, so it processes loops in the given order.
445template <typename RangeT>
446void appendReversedLoopsToWorklist(RangeT &&,
447 SmallPriorityWorklist<Loop *, 4> &);
448
449/// Utility that implements appending of loops onto a worklist given LoopInfo.
450/// Calls the templated utility taking a Range of loops, handing it the Loops
451/// in LoopInfo, iterated in reverse. This is because the loops are stored in
452/// RPO w.r.t. the control flow graph in LoopInfo. For the purpose of unrolling,
453/// loop deletion, and LICM, we largely want to work forward across the CFG so
454/// that we visit defs before uses and can propagate simplifications from one
455/// loop nest into the next. Calls appendReversedLoopsToWorklist with the
456/// already reversed loops in LI.
457/// FIXME: Consider changing the order in LoopInfo.
458void appendLoopsToWorklist(LoopInfo &, SmallPriorityWorklist<Loop *, 4> &);
459
460/// Recursively clone the specified loop and all of its children,
461/// mapping the blocks with the specified map.
462Loop *cloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM,
463 LoopInfo *LI, LPPassManager *LPM);
464
465/// Add code that checks at runtime if the accessed arrays in \p PointerChecks
466/// overlap.
467///
468/// Returns a pair of instructions where the first element is the first
469/// instruction generated in possibly a sequence of instructions and the
470/// second value is the final comparator value or NULL if no check is needed.
471std::pair<Instruction *, Instruction *>
472addRuntimeChecks(Instruction *Loc, Loop *TheLoop,
473 const SmallVectorImpl<RuntimePointerCheck> &PointerChecks,
474 SCEVExpander &Expander);
475
476/// Struct to hold information about a partially invariant condition.
477struct IVConditionInfo {
478 /// Instructions that need to be duplicated and checked for the unswitching
479 /// condition.
480 SmallVector<Instruction *> InstToDuplicate;
481
482 /// Constant to indicate for which value the condition is invariant.
483 Constant *KnownValue = nullptr;
4
Null pointer value stored to 'PartialIVInfo.KnownValue'
484
485 /// True if the partially invariant path is no-op (=does not have any
486 /// side-effects and no loop value is used outside the loop).
487 bool PathIsNoop = true;
488
489 /// If the partially invariant path reaches a single exit block, ExitForPath
490 /// is set to that block. Otherwise it is nullptr.
491 BasicBlock *ExitForPath = nullptr;
492};
493
494/// Check if the loop header has a conditional branch that is not
495/// loop-invariant, because it involves load instructions. If all paths from
496/// either the true or false successor to the header or loop exists do not
497/// modify the memory feeding the condition, perform 'partial unswitching'. That
498/// is, duplicate the instructions feeding the condition in the pre-header. Then
499/// unswitch on the duplicated condition. The condition is now known in the
500/// unswitched version for the 'invariant' path through the original loop.
501///
502/// If the branch condition of the header is partially invariant, return a pair
503/// containing the instructions to duplicate and a boolean Constant to update
504/// the condition in the loops created for the true or false successors.
505Optional<IVConditionInfo> hasPartialIVCondition(Loop &L, unsigned MSSAThreshold,
506 MemorySSA &MSSA, AAResults &AA);
507
508} // end namespace llvm
509
510#endif // LLVM_TRANSFORMS_UTILS_LOOPUTILS_H

/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h

1//===- llvm/ADT/SmallVector.h - 'Normally small' vectors --------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the SmallVector class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_ADT_SMALLVECTOR_H
14#define LLVM_ADT_SMALLVECTOR_H
15
16#include "llvm/ADT/iterator_range.h"
17#include "llvm/Support/Compiler.h"
18#include "llvm/Support/ErrorHandling.h"
19#include "llvm/Support/MemAlloc.h"
20#include "llvm/Support/type_traits.h"
21#include <algorithm>
22#include <cassert>
23#include <cstddef>
24#include <cstdlib>
25#include <cstring>
26#include <functional>
27#include <initializer_list>
28#include <iterator>
29#include <limits>
30#include <memory>
31#include <new>
32#include <type_traits>
33#include <utility>
34
35namespace llvm {
36
37/// This is all the stuff common to all SmallVectors.
38///
39/// The template parameter specifies the type which should be used to hold the
40/// Size and Capacity of the SmallVector, so it can be adjusted.
41/// Using 32 bit size is desirable to shrink the size of the SmallVector.
42/// Using 64 bit size is desirable for cases like SmallVector<char>, where a
43/// 32 bit size would limit the vector to ~4GB. SmallVectors are used for
44/// buffering bitcode output - which can exceed 4GB.
45template <class Size_T> class SmallVectorBase {
46protected:
47 void *BeginX;
48 Size_T Size = 0, Capacity;
49
50 /// The maximum value of the Size_T used.
51 static constexpr size_t SizeTypeMax() {
52 return std::numeric_limits<Size_T>::max();
53 }
54
55 SmallVectorBase() = delete;
56 SmallVectorBase(void *FirstEl, size_t TotalCapacity)
57 : BeginX(FirstEl), Capacity(TotalCapacity) {}
58
59 /// This is a helper for \a grow() that's out of line to reduce code
60 /// duplication. This function will report a fatal error if it can't grow at
61 /// least to \p MinSize.
62 void *mallocForGrow(size_t MinSize, size_t TSize, size_t &NewCapacity);
63
64 /// This is an implementation of the grow() method which only works
65 /// on POD-like data types and is out of line to reduce code duplication.
66 /// This function will report a fatal error if it cannot increase capacity.
67 void grow_pod(void *FirstEl, size_t MinSize, size_t TSize);
68
69public:
70 size_t size() const { return Size; }
71 size_t capacity() const { return Capacity; }
72
73 LLVM_NODISCARD[[clang::warn_unused_result]] bool empty() const { return !Size; }
10
Assuming field 'Size' is not equal to 0
11
Returning zero, which participates in a condition later
74
75 /// Set the array size to \p N, which the current array must have enough
76 /// capacity for.
77 ///
78 /// This does not construct or destroy any elements in the vector.
79 ///
80 /// Clients can use this in conjunction with capacity() to write past the end
81 /// of the buffer when they know that more elements are available, and only
82 /// update the size later. This avoids the cost of value initializing elements
83 /// which will only be overwritten.
84 void set_size(size_t N) {
85 assert(N <= capacity())(static_cast <bool> (N <= capacity()) ? void (0) : __assert_fail
("N <= capacity()", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 85, __extension__ __PRETTY_FUNCTION__))
;
86 Size = N;
87 }
88};
89
90template <class T>
91using SmallVectorSizeType =
92 typename std::conditional<sizeof(T) < 4 && sizeof(void *) >= 8, uint64_t,
93 uint32_t>::type;
94
95/// Figure out the offset of the first element.
96template <class T, typename = void> struct SmallVectorAlignmentAndSize {
97 alignas(SmallVectorBase<SmallVectorSizeType<T>>) char Base[sizeof(
98 SmallVectorBase<SmallVectorSizeType<T>>)];
99 alignas(T) char FirstEl[sizeof(T)];
100};
101
102/// This is the part of SmallVectorTemplateBase which does not depend on whether
103/// the type T is a POD. The extra dummy template argument is used by ArrayRef
104/// to avoid unnecessarily requiring T to be complete.
105template <typename T, typename = void>
106class SmallVectorTemplateCommon
107 : public SmallVectorBase<SmallVectorSizeType<T>> {
108 using Base = SmallVectorBase<SmallVectorSizeType<T>>;
109
110 /// Find the address of the first element. For this pointer math to be valid
111 /// with small-size of 0 for T with lots of alignment, it's important that
112 /// SmallVectorStorage is properly-aligned even for small-size of 0.
113 void *getFirstEl() const {
114 return const_cast<void *>(reinterpret_cast<const void *>(
115 reinterpret_cast<const char *>(this) +
116 offsetof(SmallVectorAlignmentAndSize<T>, FirstEl)__builtin_offsetof(SmallVectorAlignmentAndSize<T>, FirstEl
)
));
117 }
118 // Space after 'FirstEl' is clobbered, do not add any instance vars after it.
119
120protected:
121 SmallVectorTemplateCommon(size_t Size) : Base(getFirstEl(), Size) {}
122
123 void grow_pod(size_t MinSize, size_t TSize) {
124 Base::grow_pod(getFirstEl(), MinSize, TSize);
125 }
126
127 /// Return true if this is a smallvector which has not had dynamic
128 /// memory allocated for it.
129 bool isSmall() const { return this->BeginX == getFirstEl(); }
130
131 /// Put this vector in a state of being small.
132 void resetToSmall() {
133 this->BeginX = getFirstEl();
134 this->Size = this->Capacity = 0; // FIXME: Setting Capacity to 0 is suspect.
135 }
136
137 /// Return true if V is an internal reference to the given range.
138 bool isReferenceToRange(const void *V, const void *First, const void *Last) const {
139 // Use std::less to avoid UB.
140 std::less<> LessThan;
141 return !LessThan(V, First) && LessThan(V, Last);
142 }
143
144 /// Return true if V is an internal reference to this vector.
145 bool isReferenceToStorage(const void *V) const {
146 return isReferenceToRange(V, this->begin(), this->end());
147 }
148
149 /// Return true if First and Last form a valid (possibly empty) range in this
150 /// vector's storage.
151 bool isRangeInStorage(const void *First, const void *Last) const {
152 // Use std::less to avoid UB.
153 std::less<> LessThan;
154 return !LessThan(First, this->begin()) && !LessThan(Last, First) &&
155 !LessThan(this->end(), Last);
156 }
157
158 /// Return true unless Elt will be invalidated by resizing the vector to
159 /// NewSize.
160 bool isSafeToReferenceAfterResize(const void *Elt, size_t NewSize) {
161 // Past the end.
162 if (LLVM_LIKELY(!isReferenceToStorage(Elt))__builtin_expect((bool)(!isReferenceToStorage(Elt)), true))
163 return true;
164
165 // Return false if Elt will be destroyed by shrinking.
166 if (NewSize <= this->size())
167 return Elt < this->begin() + NewSize;
168
169 // Return false if we need to grow.
170 return NewSize <= this->capacity();
171 }
172
173 /// Check whether Elt will be invalidated by resizing the vector to NewSize.
174 void assertSafeToReferenceAfterResize(const void *Elt, size_t NewSize) {
175 assert(isSafeToReferenceAfterResize(Elt, NewSize) &&(static_cast <bool> (isSafeToReferenceAfterResize(Elt, NewSize
) && "Attempting to reference an element of the vector in an operation "
"that invalidates it") ? void (0) : __assert_fail ("isSafeToReferenceAfterResize(Elt, NewSize) && \"Attempting to reference an element of the vector in an operation \" \"that invalidates it\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 177, __extension__ __PRETTY_FUNCTION__))
176 "Attempting to reference an element of the vector in an operation "(static_cast <bool> (isSafeToReferenceAfterResize(Elt, NewSize
) && "Attempting to reference an element of the vector in an operation "
"that invalidates it") ? void (0) : __assert_fail ("isSafeToReferenceAfterResize(Elt, NewSize) && \"Attempting to reference an element of the vector in an operation \" \"that invalidates it\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 177, __extension__ __PRETTY_FUNCTION__))
177 "that invalidates it")(static_cast <bool> (isSafeToReferenceAfterResize(Elt, NewSize
) && "Attempting to reference an element of the vector in an operation "
"that invalidates it") ? void (0) : __assert_fail ("isSafeToReferenceAfterResize(Elt, NewSize) && \"Attempting to reference an element of the vector in an operation \" \"that invalidates it\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 177, __extension__ __PRETTY_FUNCTION__))
;
178 }
179
180 /// Check whether Elt will be invalidated by increasing the size of the
181 /// vector by N.
182 void assertSafeToAdd(const void *Elt, size_t N = 1) {
183 this->assertSafeToReferenceAfterResize(Elt, this->size() + N);
184 }
185
186 /// Check whether any part of the range will be invalidated by clearing.
187 void assertSafeToReferenceAfterClear(const T *From, const T *To) {
188 if (From == To)
189 return;
190 this->assertSafeToReferenceAfterResize(From, 0);
191 this->assertSafeToReferenceAfterResize(To - 1, 0);
192 }
193 template <
194 class ItTy,
195 std::enable_if_t<!std::is_same<std::remove_const_t<ItTy>, T *>::value,
196 bool> = false>
197 void assertSafeToReferenceAfterClear(ItTy, ItTy) {}
198
199 /// Check whether any part of the range will be invalidated by growing.
200 void assertSafeToAddRange(const T *From, const T *To) {
201 if (From == To)
202 return;
203 this->assertSafeToAdd(From, To - From);
204 this->assertSafeToAdd(To - 1, To - From);
205 }
206 template <
207 class ItTy,
208 std::enable_if_t<!std::is_same<std::remove_const_t<ItTy>, T *>::value,
209 bool> = false>
210 void assertSafeToAddRange(ItTy, ItTy) {}
211
212 /// Reserve enough space to add one element, and return the updated element
213 /// pointer in case it was a reference to the storage.
214 template <class U>
215 static const T *reserveForParamAndGetAddressImpl(U *This, const T &Elt,
216 size_t N) {
217 size_t NewSize = This->size() + N;
218 if (LLVM_LIKELY(NewSize <= This->capacity())__builtin_expect((bool)(NewSize <= This->capacity()), true
)
)
219 return &Elt;
220
221 bool ReferencesStorage = false;
222 int64_t Index = -1;
223 if (!U::TakesParamByValue) {
224 if (LLVM_UNLIKELY(This->isReferenceToStorage(&Elt))__builtin_expect((bool)(This->isReferenceToStorage(&Elt
)), false)
) {
225 ReferencesStorage = true;
226 Index = &Elt - This->begin();
227 }
228 }
229 This->grow(NewSize);
230 return ReferencesStorage ? This->begin() + Index : &Elt;
231 }
232
233public:
234 using size_type = size_t;
235 using difference_type = ptrdiff_t;
236 using value_type = T;
237 using iterator = T *;
238 using const_iterator = const T *;
239
240 using const_reverse_iterator = std::reverse_iterator<const_iterator>;
241 using reverse_iterator = std::reverse_iterator<iterator>;
242
243 using reference = T &;
244 using const_reference = const T &;
245 using pointer = T *;
246 using const_pointer = const T *;
247
248 using Base::capacity;
249 using Base::empty;
250 using Base::size;
251
252 // forward iterator creation methods.
253 iterator begin() { return (iterator)this->BeginX; }
254 const_iterator begin() const { return (const_iterator)this->BeginX; }
255 iterator end() { return begin() + size(); }
256 const_iterator end() const { return begin() + size(); }
257
258 // reverse iterator creation methods.
259 reverse_iterator rbegin() { return reverse_iterator(end()); }
260 const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
261 reverse_iterator rend() { return reverse_iterator(begin()); }
262 const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
263
264 size_type size_in_bytes() const { return size() * sizeof(T); }
265 size_type max_size() const {
266 return std::min(this->SizeTypeMax(), size_type(-1) / sizeof(T));
267 }
268
269 size_t capacity_in_bytes() const { return capacity() * sizeof(T); }
270
271 /// Return a pointer to the vector's buffer, even if empty().
272 pointer data() { return pointer(begin()); }
273 /// Return a pointer to the vector's buffer, even if empty().
274 const_pointer data() const { return const_pointer(begin()); }
275
276 reference operator[](size_type idx) {
277 assert(idx < size())(static_cast <bool> (idx < size()) ? void (0) : __assert_fail
("idx < size()", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 277, __extension__ __PRETTY_FUNCTION__))
;
278 return begin()[idx];
279 }
280 const_reference operator[](size_type idx) const {
281 assert(idx < size())(static_cast <bool> (idx < size()) ? void (0) : __assert_fail
("idx < size()", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 281, __extension__ __PRETTY_FUNCTION__))
;
282 return begin()[idx];
283 }
284
285 reference front() {
286 assert(!empty())(static_cast <bool> (!empty()) ? void (0) : __assert_fail
("!empty()", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 286, __extension__ __PRETTY_FUNCTION__))
;
287 return begin()[0];
288 }
289 const_reference front() const {
290 assert(!empty())(static_cast <bool> (!empty()) ? void (0) : __assert_fail
("!empty()", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 290, __extension__ __PRETTY_FUNCTION__))
;
291 return begin()[0];
292 }
293
294 reference back() {
295 assert(!empty())(static_cast <bool> (!empty()) ? void (0) : __assert_fail
("!empty()", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 295, __extension__ __PRETTY_FUNCTION__))
;
296 return end()[-1];
297 }
298 const_reference back() const {
299 assert(!empty())(static_cast <bool> (!empty()) ? void (0) : __assert_fail
("!empty()", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 299, __extension__ __PRETTY_FUNCTION__))
;
300 return end()[-1];
301 }
302};
303
304/// SmallVectorTemplateBase<TriviallyCopyable = false> - This is where we put
305/// method implementations that are designed to work with non-trivial T's.
306///
307/// We approximate is_trivially_copyable with trivial move/copy construction and
308/// trivial destruction. While the standard doesn't specify that you're allowed
309/// copy these types with memcpy, there is no way for the type to observe this.
310/// This catches the important case of std::pair<POD, POD>, which is not
311/// trivially assignable.
312template <typename T, bool = (is_trivially_copy_constructible<T>::value) &&
313 (is_trivially_move_constructible<T>::value) &&
314 std::is_trivially_destructible<T>::value>
315class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
316 friend class SmallVectorTemplateCommon<T>;
317
318protected:
319 static constexpr bool TakesParamByValue = false;
320 using ValueParamT = const T &;
321
322 SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
323
324 static void destroy_range(T *S, T *E) {
325 while (S != E) {
326 --E;
327 E->~T();
328 }
329 }
330
331 /// Move the range [I, E) into the uninitialized memory starting with "Dest",
332 /// constructing elements as needed.
333 template<typename It1, typename It2>
334 static void uninitialized_move(It1 I, It1 E, It2 Dest) {
335 std::uninitialized_copy(std::make_move_iterator(I),
336 std::make_move_iterator(E), Dest);
337 }
338
339 /// Copy the range [I, E) onto the uninitialized memory starting with "Dest",
340 /// constructing elements as needed.
341 template<typename It1, typename It2>
342 static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
343 std::uninitialized_copy(I, E, Dest);
344 }
345
346 /// Grow the allocated memory (without initializing new elements), doubling
347 /// the size of the allocated memory. Guarantees space for at least one more
348 /// element, or MinSize more elements if specified.
349 void grow(size_t MinSize = 0);
350
351 /// Create a new allocation big enough for \p MinSize and pass back its size
352 /// in \p NewCapacity. This is the first section of \a grow().
353 T *mallocForGrow(size_t MinSize, size_t &NewCapacity) {
354 return static_cast<T *>(
355 SmallVectorBase<SmallVectorSizeType<T>>::mallocForGrow(
356 MinSize, sizeof(T), NewCapacity));
357 }
358
359 /// Move existing elements over to the new allocation \p NewElts, the middle
360 /// section of \a grow().
361 void moveElementsForGrow(T *NewElts);
362
363 /// Transfer ownership of the allocation, finishing up \a grow().
364 void takeAllocationForGrow(T *NewElts, size_t NewCapacity);
365
366 /// Reserve enough space to add one element, and return the updated element
367 /// pointer in case it was a reference to the storage.
368 const T *reserveForParamAndGetAddress(const T &Elt, size_t N = 1) {
369 return this->reserveForParamAndGetAddressImpl(this, Elt, N);
370 }
371
372 /// Reserve enough space to add one element, and return the updated element
373 /// pointer in case it was a reference to the storage.
374 T *reserveForParamAndGetAddress(T &Elt, size_t N = 1) {
375 return const_cast<T *>(
376 this->reserveForParamAndGetAddressImpl(this, Elt, N));
377 }
378
379 static T &&forward_value_param(T &&V) { return std::move(V); }
380 static const T &forward_value_param(const T &V) { return V; }
381
382 void growAndAssign(size_t NumElts, const T &Elt) {
383 // Grow manually in case Elt is an internal reference.
384 size_t NewCapacity;
385 T *NewElts = mallocForGrow(NumElts, NewCapacity);
386 std::uninitialized_fill_n(NewElts, NumElts, Elt);
387 this->destroy_range(this->begin(), this->end());
388 takeAllocationForGrow(NewElts, NewCapacity);
389 this->set_size(NumElts);
390 }
391
392 template <typename... ArgTypes> T &growAndEmplaceBack(ArgTypes &&... Args) {
393 // Grow manually in case one of Args is an internal reference.
394 size_t NewCapacity;
395 T *NewElts = mallocForGrow(0, NewCapacity);
396 ::new ((void *)(NewElts + this->size())) T(std::forward<ArgTypes>(Args)...);
397 moveElementsForGrow(NewElts);
398 takeAllocationForGrow(NewElts, NewCapacity);
399 this->set_size(this->size() + 1);
400 return this->back();
401 }
402
403public:
404 void push_back(const T &Elt) {
405 const T *EltPtr = reserveForParamAndGetAddress(Elt);
406 ::new ((void *)this->end()) T(*EltPtr);
407 this->set_size(this->size() + 1);
408 }
409
410 void push_back(T &&Elt) {
411 T *EltPtr = reserveForParamAndGetAddress(Elt);
412 ::new ((void *)this->end()) T(::std::move(*EltPtr));
413 this->set_size(this->size() + 1);
414 }
415
416 void pop_back() {
417 this->set_size(this->size() - 1);
418 this->end()->~T();
419 }
420};
421
422// Define this out-of-line to dissuade the C++ compiler from inlining it.
423template <typename T, bool TriviallyCopyable>
424void SmallVectorTemplateBase<T, TriviallyCopyable>::grow(size_t MinSize) {
425 size_t NewCapacity;
426 T *NewElts = mallocForGrow(MinSize, NewCapacity);
427 moveElementsForGrow(NewElts);
428 takeAllocationForGrow(NewElts, NewCapacity);
429}
430
431// Define this out-of-line to dissuade the C++ compiler from inlining it.
432template <typename T, bool TriviallyCopyable>
433void SmallVectorTemplateBase<T, TriviallyCopyable>::moveElementsForGrow(
434 T *NewElts) {
435 // Move the elements over.
436 this->uninitialized_move(this->begin(), this->end(), NewElts);
437
438 // Destroy the original elements.
439 destroy_range(this->begin(), this->end());
440}
441
442// Define this out-of-line to dissuade the C++ compiler from inlining it.
443template <typename T, bool TriviallyCopyable>
444void SmallVectorTemplateBase<T, TriviallyCopyable>::takeAllocationForGrow(
445 T *NewElts, size_t NewCapacity) {
446 // If this wasn't grown from the inline copy, deallocate the old space.
447 if (!this->isSmall())
448 free(this->begin());
449
450 this->BeginX = NewElts;
451 this->Capacity = NewCapacity;
452}
453
454/// SmallVectorTemplateBase<TriviallyCopyable = true> - This is where we put
455/// method implementations that are designed to work with trivially copyable
456/// T's. This allows using memcpy in place of copy/move construction and
457/// skipping destruction.
458template <typename T>
459class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> {
460 friend class SmallVectorTemplateCommon<T>;
461
462protected:
463 /// True if it's cheap enough to take parameters by value. Doing so avoids
464 /// overhead related to mitigations for reference invalidation.
465 static constexpr bool TakesParamByValue = sizeof(T) <= 2 * sizeof(void *);
466
467 /// Either const T& or T, depending on whether it's cheap enough to take
468 /// parameters by value.
469 using ValueParamT =
470 typename std::conditional<TakesParamByValue, T, const T &>::type;
471
472 SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
473
474 // No need to do a destroy loop for POD's.
475 static void destroy_range(T *, T *) {}
476
477 /// Move the range [I, E) onto the uninitialized memory
478 /// starting with "Dest", constructing elements into it as needed.
479 template<typename It1, typename It2>
480 static void uninitialized_move(It1 I, It1 E, It2 Dest) {
481 // Just do a copy.
482 uninitialized_copy(I, E, Dest);
483 }
484
485 /// Copy the range [I, E) onto the uninitialized memory
486 /// starting with "Dest", constructing elements into it as needed.
487 template<typename It1, typename It2>
488 static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
489 // Arbitrary iterator types; just use the basic implementation.
490 std::uninitialized_copy(I, E, Dest);
491 }
492
493 /// Copy the range [I, E) onto the uninitialized memory
494 /// starting with "Dest", constructing elements into it as needed.
495 template <typename T1, typename T2>
496 static void uninitialized_copy(
497 T1 *I, T1 *E, T2 *Dest,
498 std::enable_if_t<std::is_same<typename std::remove_const<T1>::type,
499 T2>::value> * = nullptr) {
500 // Use memcpy for PODs iterated by pointers (which includes SmallVector
501 // iterators): std::uninitialized_copy optimizes to memmove, but we can
502 // use memcpy here. Note that I and E are iterators and thus might be
503 // invalid for memcpy if they are equal.
504 if (I != E)
505 memcpy(reinterpret_cast<void *>(Dest), I, (E - I) * sizeof(T));
506 }
507
508 /// Double the size of the allocated memory, guaranteeing space for at
509 /// least one more element or MinSize if specified.
510 void grow(size_t MinSize = 0) { this->grow_pod(MinSize, sizeof(T)); }
511
512 /// Reserve enough space to add one element, and return the updated element
513 /// pointer in case it was a reference to the storage.
514 const T *reserveForParamAndGetAddress(const T &Elt, size_t N = 1) {
515 return this->reserveForParamAndGetAddressImpl(this, Elt, N);
516 }
517
518 /// Reserve enough space to add one element, and return the updated element
519 /// pointer in case it was a reference to the storage.
520 T *reserveForParamAndGetAddress(T &Elt, size_t N = 1) {
521 return const_cast<T *>(
522 this->reserveForParamAndGetAddressImpl(this, Elt, N));
523 }
524
525 /// Copy \p V or return a reference, depending on \a ValueParamT.
526 static ValueParamT forward_value_param(ValueParamT V) { return V; }
527
528 void growAndAssign(size_t NumElts, T Elt) {
529 // Elt has been copied in case it's an internal reference, side-stepping
530 // reference invalidation problems without losing the realloc optimization.
531 this->set_size(0);
532 this->grow(NumElts);
533 std::uninitialized_fill_n(this->begin(), NumElts, Elt);
534 this->set_size(NumElts);
535 }
536
537 template <typename... ArgTypes> T &growAndEmplaceBack(ArgTypes &&... Args) {
538 // Use push_back with a copy in case Args has an internal reference,
539 // side-stepping reference invalidation problems without losing the realloc
540 // optimization.
541 push_back(T(std::forward<ArgTypes>(Args)...));
542 return this->back();
543 }
544
545public:
546 void push_back(ValueParamT Elt) {
547 const T *EltPtr = reserveForParamAndGetAddress(Elt);
548 memcpy(reinterpret_cast<void *>(this->end()), EltPtr, sizeof(T));
549 this->set_size(this->size() + 1);
550 }
551
552 void pop_back() { this->set_size(this->size() - 1); }
553};
554
555/// This class consists of common code factored out of the SmallVector class to
556/// reduce code duplication based on the SmallVector 'N' template parameter.
557template <typename T>
558class SmallVectorImpl : public SmallVectorTemplateBase<T> {
559 using SuperClass = SmallVectorTemplateBase<T>;
560
561public:
562 using iterator = typename SuperClass::iterator;
563 using const_iterator = typename SuperClass::const_iterator;
564 using reference = typename SuperClass::reference;
565 using size_type = typename SuperClass::size_type;
566
567protected:
568 using SmallVectorTemplateBase<T>::TakesParamByValue;
569 using ValueParamT = typename SuperClass::ValueParamT;
570
571 // Default ctor - Initialize to empty.
572 explicit SmallVectorImpl(unsigned N)
573 : SmallVectorTemplateBase<T>(N) {}
574
575public:
576 SmallVectorImpl(const SmallVectorImpl &) = delete;
577
578 ~SmallVectorImpl() {
579 // Subclass has already destructed this vector's elements.
580 // If this wasn't grown from the inline copy, deallocate the old space.
581 if (!this->isSmall())
582 free(this->begin());
583 }
584
585 void clear() {
586 this->destroy_range(this->begin(), this->end());
587 this->Size = 0;
588 }
589
590private:
591 template <bool ForOverwrite> void resizeImpl(size_type N) {
592 if (N < this->size()) {
593 this->pop_back_n(this->size() - N);
594 } else if (N > this->size()) {
595 this->reserve(N);
596 for (auto I = this->end(), E = this->begin() + N; I != E; ++I)
597 if (ForOverwrite)
598 new (&*I) T;
599 else
600 new (&*I) T();
601 this->set_size(N);
602 }
603 }
604
605public:
606 void resize(size_type N) { resizeImpl<false>(N); }
607
608 /// Like resize, but \ref T is POD, the new values won't be initialized.
609 void resize_for_overwrite(size_type N) { resizeImpl<true>(N); }
610
611 void resize(size_type N, ValueParamT NV) {
612 if (N == this->size())
613 return;
614
615 if (N < this->size()) {
616 this->pop_back_n(this->size() - N);
617 return;
618 }
619
620 // N > this->size(). Defer to append.
621 this->append(N - this->size(), NV);
622 }
623
624 void reserve(size_type N) {
625 if (this->capacity() < N)
626 this->grow(N);
627 }
628
629 void pop_back_n(size_type NumItems) {
630 assert(this->size() >= NumItems)(static_cast <bool> (this->size() >= NumItems) ? void
(0) : __assert_fail ("this->size() >= NumItems", "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 630, __extension__ __PRETTY_FUNCTION__))
;
631 this->destroy_range(this->end() - NumItems, this->end());
632 this->set_size(this->size() - NumItems);
633 }
634
635 LLVM_NODISCARD[[clang::warn_unused_result]] T pop_back_val() {
636 T Result = ::std::move(this->back());
637 this->pop_back();
638 return Result;
639 }
640
641 void swap(SmallVectorImpl &RHS);
642
643 /// Add the specified range to the end of the SmallVector.
644 template <typename in_iter,
645 typename = std::enable_if_t<std::is_convertible<
646 typename std::iterator_traits<in_iter>::iterator_category,
647 std::input_iterator_tag>::value>>
648 void append(in_iter in_start, in_iter in_end) {
649 this->assertSafeToAddRange(in_start, in_end);
650 size_type NumInputs = std::distance(in_start, in_end);
651 this->reserve(this->size() + NumInputs);
652 this->uninitialized_copy(in_start, in_end, this->end());
653 this->set_size(this->size() + NumInputs);
654 }
655
656 /// Append \p NumInputs copies of \p Elt to the end.
657 void append(size_type NumInputs, ValueParamT Elt) {
658 const T *EltPtr = this->reserveForParamAndGetAddress(Elt, NumInputs);
659 std::uninitialized_fill_n(this->end(), NumInputs, *EltPtr);
660 this->set_size(this->size() + NumInputs);
661 }
662
663 void append(std::initializer_list<T> IL) {
664 append(IL.begin(), IL.end());
665 }
666
667 void append(const SmallVectorImpl &RHS) { append(RHS.begin(), RHS.end()); }
668
669 void assign(size_type NumElts, ValueParamT Elt) {
670 // Note that Elt could be an internal reference.
671 if (NumElts > this->capacity()) {
672 this->growAndAssign(NumElts, Elt);
673 return;
674 }
675
676 // Assign over existing elements.
677 std::fill_n(this->begin(), std::min(NumElts, this->size()), Elt);
678 if (NumElts > this->size())
679 std::uninitialized_fill_n(this->end(), NumElts - this->size(), Elt);
680 else if (NumElts < this->size())
681 this->destroy_range(this->begin() + NumElts, this->end());
682 this->set_size(NumElts);
683 }
684
685 // FIXME: Consider assigning over existing elements, rather than clearing &
686 // re-initializing them - for all assign(...) variants.
687
688 template <typename in_iter,
689 typename = std::enable_if_t<std::is_convertible<
690 typename std::iterator_traits<in_iter>::iterator_category,
691 std::input_iterator_tag>::value>>
692 void assign(in_iter in_start, in_iter in_end) {
693 this->assertSafeToReferenceAfterClear(in_start, in_end);
694 clear();
695 append(in_start, in_end);
696 }
697
698 void assign(std::initializer_list<T> IL) {
699 clear();
700 append(IL);
701 }
702
703 void assign(const SmallVectorImpl &RHS) { assign(RHS.begin(), RHS.end()); }
704
705 iterator erase(const_iterator CI) {
706 // Just cast away constness because this is a non-const member function.
707 iterator I = const_cast<iterator>(CI);
708
709 assert(this->isReferenceToStorage(CI) && "Iterator to erase is out of bounds.")(static_cast <bool> (this->isReferenceToStorage(CI) &&
"Iterator to erase is out of bounds.") ? void (0) : __assert_fail
("this->isReferenceToStorage(CI) && \"Iterator to erase is out of bounds.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 709, __extension__ __PRETTY_FUNCTION__))
;
710
711 iterator N = I;
712 // Shift all elts down one.
713 std::move(I+1, this->end(), I);
714 // Drop the last elt.
715 this->pop_back();
716 return(N);
717 }
718
719 iterator erase(const_iterator CS, const_iterator CE) {
720 // Just cast away constness because this is a non-const member function.
721 iterator S = const_cast<iterator>(CS);
722 iterator E = const_cast<iterator>(CE);
723
724 assert(this->isRangeInStorage(S, E) && "Range to erase is out of bounds.")(static_cast <bool> (this->isRangeInStorage(S, E) &&
"Range to erase is out of bounds.") ? void (0) : __assert_fail
("this->isRangeInStorage(S, E) && \"Range to erase is out of bounds.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 724, __extension__ __PRETTY_FUNCTION__))
;
725
726 iterator N = S;
727 // Shift all elts down.
728 iterator I = std::move(E, this->end(), S);
729 // Drop the last elts.
730 this->destroy_range(I, this->end());
731 this->set_size(I - this->begin());
732 return(N);
733 }
734
735private:
736 template <class ArgType> iterator insert_one_impl(iterator I, ArgType &&Elt) {
737 // Callers ensure that ArgType is derived from T.
738 static_assert(
739 std::is_same<std::remove_const_t<std::remove_reference_t<ArgType>>,
740 T>::value,
741 "ArgType must be derived from T!");
742
743 if (I == this->end()) { // Important special case for empty vector.
744 this->push_back(::std::forward<ArgType>(Elt));
745 return this->end()-1;
746 }
747
748 assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.")(static_cast <bool> (this->isReferenceToStorage(I) &&
"Insertion iterator is out of bounds.") ? void (0) : __assert_fail
("this->isReferenceToStorage(I) && \"Insertion iterator is out of bounds.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 748, __extension__ __PRETTY_FUNCTION__))
;
749
750 // Grow if necessary.
751 size_t Index = I - this->begin();
752 std::remove_reference_t<ArgType> *EltPtr =
753 this->reserveForParamAndGetAddress(Elt);
754 I = this->begin() + Index;
755
756 ::new ((void*) this->end()) T(::std::move(this->back()));
757 // Push everything else over.
758 std::move_backward(I, this->end()-1, this->end());
759 this->set_size(this->size() + 1);
760
761 // If we just moved the element we're inserting, be sure to update
762 // the reference (never happens if TakesParamByValue).
763 static_assert(!TakesParamByValue || std::is_same<ArgType, T>::value,
764 "ArgType must be 'T' when taking by value!");
765 if (!TakesParamByValue && this->isReferenceToRange(EltPtr, I, this->end()))
766 ++EltPtr;
767
768 *I = ::std::forward<ArgType>(*EltPtr);
769 return I;
770 }
771
772public:
773 iterator insert(iterator I, T &&Elt) {
774 return insert_one_impl(I, this->forward_value_param(std::move(Elt)));
775 }
776
777 iterator insert(iterator I, const T &Elt) {
778 return insert_one_impl(I, this->forward_value_param(Elt));
779 }
780
781 iterator insert(iterator I, size_type NumToInsert, ValueParamT Elt) {
782 // Convert iterator to elt# to avoid invalidating iterator when we reserve()
783 size_t InsertElt = I - this->begin();
784
785 if (I == this->end()) { // Important special case for empty vector.
786 append(NumToInsert, Elt);
787 return this->begin()+InsertElt;
788 }
789
790 assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.")(static_cast <bool> (this->isReferenceToStorage(I) &&
"Insertion iterator is out of bounds.") ? void (0) : __assert_fail
("this->isReferenceToStorage(I) && \"Insertion iterator is out of bounds.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 790, __extension__ __PRETTY_FUNCTION__))
;
791
792 // Ensure there is enough space, and get the (maybe updated) address of
793 // Elt.
794 const T *EltPtr = this->reserveForParamAndGetAddress(Elt, NumToInsert);
795
796 // Uninvalidate the iterator.
797 I = this->begin()+InsertElt;
798
799 // If there are more elements between the insertion point and the end of the
800 // range than there are being inserted, we can use a simple approach to
801 // insertion. Since we already reserved space, we know that this won't
802 // reallocate the vector.
803 if (size_t(this->end()-I) >= NumToInsert) {
804 T *OldEnd = this->end();
805 append(std::move_iterator<iterator>(this->end() - NumToInsert),
806 std::move_iterator<iterator>(this->end()));
807
808 // Copy the existing elements that get replaced.
809 std::move_backward(I, OldEnd-NumToInsert, OldEnd);
810
811 // If we just moved the element we're inserting, be sure to update
812 // the reference (never happens if TakesParamByValue).
813 if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end())
814 EltPtr += NumToInsert;
815
816 std::fill_n(I, NumToInsert, *EltPtr);
817 return I;
818 }
819
820 // Otherwise, we're inserting more elements than exist already, and we're
821 // not inserting at the end.
822
823 // Move over the elements that we're about to overwrite.
824 T *OldEnd = this->end();
825 this->set_size(this->size() + NumToInsert);
826 size_t NumOverwritten = OldEnd-I;
827 this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten);
828
829 // If we just moved the element we're inserting, be sure to update
830 // the reference (never happens if TakesParamByValue).
831 if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end())
832 EltPtr += NumToInsert;
833
834 // Replace the overwritten part.
835 std::fill_n(I, NumOverwritten, *EltPtr);
836
837 // Insert the non-overwritten middle part.
838 std::uninitialized_fill_n(OldEnd, NumToInsert - NumOverwritten, *EltPtr);
839 return I;
840 }
841
842 template <typename ItTy,
843 typename = std::enable_if_t<std::is_convertible<
844 typename std::iterator_traits<ItTy>::iterator_category,
845 std::input_iterator_tag>::value>>
846 iterator insert(iterator I, ItTy From, ItTy To) {
847 // Convert iterator to elt# to avoid invalidating iterator when we reserve()
848 size_t InsertElt = I - this->begin();
849
850 if (I == this->end()) { // Important special case for empty vector.
851 append(From, To);
852 return this->begin()+InsertElt;
853 }
854
855 assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.")(static_cast <bool> (this->isReferenceToStorage(I) &&
"Insertion iterator is out of bounds.") ? void (0) : __assert_fail
("this->isReferenceToStorage(I) && \"Insertion iterator is out of bounds.\""
, "/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/ADT/SmallVector.h"
, 855, __extension__ __PRETTY_FUNCTION__))
;
856
857 // Check that the reserve that follows doesn't invalidate the iterators.
858 this->assertSafeToAddRange(From, To);
859
860 size_t NumToInsert = std::distance(From, To);
861
862 // Ensure there is enough space.
863 reserve(this->size() + NumToInsert);
864
865 // Uninvalidate the iterator.
866 I = this->begin()+InsertElt;
867
868 // If there are more elements between the insertion point and the end of the
869 // range than there are being inserted, we can use a simple approach to
870 // insertion. Since we already reserved space, we know that this won't
871 // reallocate the vector.
872 if (size_t(this->end()-I) >= NumToInsert) {
873 T *OldEnd = this->end();
874 append(std::move_iterator<iterator>(this->end() - NumToInsert),
875 std::move_iterator<iterator>(this->end()));
876
877 // Copy the existing elements that get replaced.
878 std::move_backward(I, OldEnd-NumToInsert, OldEnd);
879
880 std::copy(From, To, I);
881 return I;
882 }
883
884 // Otherwise, we're inserting more elements than exist already, and we're
885 // not inserting at the end.
886
887 // Move over the elements that we're about to overwrite.
888 T *OldEnd = this->end();
889 this->set_size(this->size() + NumToInsert);
890 size_t NumOverwritten = OldEnd-I;
891 this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten);
892
893 // Replace the overwritten part.
894 for (T *J = I; NumOverwritten > 0; --NumOverwritten) {
895 *J = *From;
896 ++J; ++From;
897 }
898
899 // Insert the non-overwritten middle part.
900 this->uninitialized_copy(From, To, OldEnd);
901 return I;
902 }
903
904 void insert(iterator I, std::initializer_list<T> IL) {
905 insert(I, IL.begin(), IL.end());
906 }
907
908 template <typename... ArgTypes> reference emplace_back(ArgTypes &&... Args) {
909 if (LLVM_UNLIKELY(this->size() >= this->capacity())__builtin_expect((bool)(this->size() >= this->capacity
()), false)
)
910 return this->growAndEmplaceBack(std::forward<ArgTypes>(Args)...);
911
912 ::new ((void *)this->end()) T(std::forward<ArgTypes>(Args)...);
913 this->set_size(this->size() + 1);
914 return this->back();
915 }
916
917 SmallVectorImpl &operator=(const SmallVectorImpl &RHS);
918
919 SmallVectorImpl &operator=(SmallVectorImpl &&RHS);
920
921 bool operator==(const SmallVectorImpl &RHS) const {
922 if (this->size() != RHS.size()) return false;
923 return std::equal(this->begin(), this->end(), RHS.begin());
924 }
925 bool operator!=(const SmallVectorImpl &RHS) const {
926 return !(*this == RHS);
927 }
928
929 bool operator<(const SmallVectorImpl &RHS) const {
930 return std::lexicographical_compare(this->begin(), this->end(),
931 RHS.begin(), RHS.end());
932 }
933};
934
935template <typename T>
936void SmallVectorImpl<T>::swap(SmallVectorImpl<T> &RHS) {
937 if (this == &RHS) return;
938
939 // We can only avoid copying elements if neither vector is small.
940 if (!this->isSmall() && !RHS.isSmall()) {
941 std::swap(this->BeginX, RHS.BeginX);
942 std::swap(this->Size, RHS.Size);
943 std::swap(this->Capacity, RHS.Capacity);
944 return;
945 }
946 this->reserve(RHS.size());
947 RHS.reserve(this->size());
948
949 // Swap the shared elements.
950 size_t NumShared = this->size();
951 if (NumShared > RHS.size()) NumShared = RHS.size();
952 for (size_type i = 0; i != NumShared; ++i)
953 std::swap((*this)[i], RHS[i]);
954
955 // Copy over the extra elts.
956 if (this->size() > RHS.size()) {
957 size_t EltDiff = this->size() - RHS.size();
958 this->uninitialized_copy(this->begin()+NumShared, this->end(), RHS.end());
959 RHS.set_size(RHS.size() + EltDiff);
960 this->destroy_range(this->begin()+NumShared, this->end());
961 this->set_size(NumShared);
962 } else if (RHS.size() > this->size()) {
963 size_t EltDiff = RHS.size() - this->size();
964 this->uninitialized_copy(RHS.begin()+NumShared, RHS.end(), this->end());
965 this->set_size(this->size() + EltDiff);
966 this->destroy_range(RHS.begin()+NumShared, RHS.end());
967 RHS.set_size(NumShared);
968 }
969}
970
971template <typename T>
972SmallVectorImpl<T> &SmallVectorImpl<T>::
973 operator=(const SmallVectorImpl<T> &RHS) {
974 // Avoid self-assignment.
975 if (this == &RHS) return *this;
976
977 // If we already have sufficient space, assign the common elements, then
978 // destroy any excess.
979 size_t RHSSize = RHS.size();
980 size_t CurSize = this->size();
981 if (CurSize >= RHSSize) {
982 // Assign common elements.
983 iterator NewEnd;
984 if (RHSSize)
985 NewEnd = std::copy(RHS.begin(), RHS.begin()+RHSSize, this->begin());
986 else
987 NewEnd = this->begin();
988
989 // Destroy excess elements.
990 this->destroy_range(NewEnd, this->end());
991
992 // Trim.
993 this->set_size(RHSSize);
994 return *this;
995 }
996
997 // If we have to grow to have enough elements, destroy the current elements.
998 // This allows us to avoid copying them during the grow.
999 // FIXME: don't do this if they're efficiently moveable.
1000 if (this->capacity() < RHSSize) {
1001 // Destroy current elements.
1002 this->clear();
1003 CurSize = 0;
1004 this->grow(RHSSize);
1005 } else if (CurSize) {
1006 // Otherwise, use assignment for the already-constructed elements.
1007 std::copy(RHS.begin(), RHS.begin()+CurSize, this->begin());
1008 }
1009
1010 // Copy construct the new elements in place.
1011 this->uninitialized_copy(RHS.begin()+CurSize, RHS.end(),
1012 this->begin()+CurSize);
1013
1014 // Set end.
1015 this->set_size(RHSSize);
1016 return *this;
1017}
1018
1019template <typename T>
1020SmallVectorImpl<T> &SmallVectorImpl<T>::operator=(SmallVectorImpl<T> &&RHS) {
1021 // Avoid self-assignment.
1022 if (this == &RHS) return *this;
1023
1024 // If the RHS isn't small, clear this vector and then steal its buffer.
1025 if (!RHS.isSmall()) {
1026 this->destroy_range(this->begin(), this->end());
1027 if (!this->isSmall()) free(this->begin());
1028 this->BeginX = RHS.BeginX;
1029 this->Size = RHS.Size;
1030 this->Capacity = RHS.Capacity;
1031 RHS.resetToSmall();
1032 return *this;
1033 }
1034
1035 // If we already have sufficient space, assign the common elements, then
1036 // destroy any excess.
1037 size_t RHSSize = RHS.size();
1038 size_t CurSize = this->size();
1039 if (CurSize >= RHSSize) {
1040 // Assign common elements.
1041 iterator NewEnd = this->begin();
1042 if (RHSSize)
1043 NewEnd = std::move(RHS.begin(), RHS.end(), NewEnd);
1044
1045 // Destroy excess elements and trim the bounds.
1046 this->destroy_range(NewEnd, this->end());
1047 this->set_size(RHSSize);
1048
1049 // Clear the RHS.
1050 RHS.clear();
1051
1052 return *this;
1053 }
1054
1055 // If we have to grow to have enough elements, destroy the current elements.
1056 // This allows us to avoid copying them during the grow.
1057 // FIXME: this may not actually make any sense if we can efficiently move
1058 // elements.
1059 if (this->capacity() < RHSSize) {
1060 // Destroy current elements.
1061 this->clear();
1062 CurSize = 0;
1063 this->grow(RHSSize);
1064 } else if (CurSize) {
1065 // Otherwise, use assignment for the already-constructed elements.
1066 std::move(RHS.begin(), RHS.begin()+CurSize, this->begin());
1067 }
1068
1069 // Move-construct the new elements in place.
1070 this->uninitialized_move(RHS.begin()+CurSize, RHS.end(),
1071 this->begin()+CurSize);
1072
1073 // Set end.
1074 this->set_size(RHSSize);
1075
1076 RHS.clear();
1077 return *this;
1078}
1079
1080/// Storage for the SmallVector elements. This is specialized for the N=0 case
1081/// to avoid allocating unnecessary storage.
1082template <typename T, unsigned N>
1083struct SmallVectorStorage {
1084 alignas(T) char InlineElts[N * sizeof(T)];
1085};
1086
1087/// We need the storage to be properly aligned even for small-size of 0 so that
1088/// the pointer math in \a SmallVectorTemplateCommon::getFirstEl() is
1089/// well-defined.
1090template <typename T> struct alignas(T) SmallVectorStorage<T, 0> {};
1091
1092/// Forward declaration of SmallVector so that
1093/// calculateSmallVectorDefaultInlinedElements can reference
1094/// `sizeof(SmallVector<T, 0>)`.
1095template <typename T, unsigned N> class LLVM_GSL_OWNER[[gsl::Owner]] SmallVector;
1096
1097/// Helper class for calculating the default number of inline elements for
1098/// `SmallVector<T>`.
1099///
1100/// This should be migrated to a constexpr function when our minimum
1101/// compiler support is enough for multi-statement constexpr functions.
1102template <typename T> struct CalculateSmallVectorDefaultInlinedElements {
1103 // Parameter controlling the default number of inlined elements
1104 // for `SmallVector<T>`.
1105 //
1106 // The default number of inlined elements ensures that
1107 // 1. There is at least one inlined element.
1108 // 2. `sizeof(SmallVector<T>) <= kPreferredSmallVectorSizeof` unless
1109 // it contradicts 1.
1110 static constexpr size_t kPreferredSmallVectorSizeof = 64;
1111
1112 // static_assert that sizeof(T) is not "too big".
1113 //
1114 // Because our policy guarantees at least one inlined element, it is possible
1115 // for an arbitrarily large inlined element to allocate an arbitrarily large
1116 // amount of inline storage. We generally consider it an antipattern for a
1117 // SmallVector to allocate an excessive amount of inline storage, so we want
1118 // to call attention to these cases and make sure that users are making an
1119 // intentional decision if they request a lot of inline storage.
1120 //
1121 // We want this assertion to trigger in pathological cases, but otherwise
1122 // not be too easy to hit. To accomplish that, the cutoff is actually somewhat
1123 // larger than kPreferredSmallVectorSizeof (otherwise,
1124 // `SmallVector<SmallVector<T>>` would be one easy way to trip it, and that
1125 // pattern seems useful in practice).
1126 //
1127 // One wrinkle is that this assertion is in theory non-portable, since
1128 // sizeof(T) is in general platform-dependent. However, we don't expect this
1129 // to be much of an issue, because most LLVM development happens on 64-bit
1130 // hosts, and therefore sizeof(T) is expected to *decrease* when compiled for
1131 // 32-bit hosts, dodging the issue. The reverse situation, where development
1132 // happens on a 32-bit host and then fails due to sizeof(T) *increasing* on a
1133 // 64-bit host, is expected to be very rare.
1134 static_assert(
1135 sizeof(T) <= 256,
1136 "You are trying to use a default number of inlined elements for "
1137 "`SmallVector<T>` but `sizeof(T)` is really big! Please use an "
1138 "explicit number of inlined elements with `SmallVector<T, N>` to make "
1139 "sure you really want that much inline storage.");
1140
1141 // Discount the size of the header itself when calculating the maximum inline
1142 // bytes.
1143 static constexpr size_t PreferredInlineBytes =
1144 kPreferredSmallVectorSizeof - sizeof(SmallVector<T, 0>);
1145 static constexpr size_t NumElementsThatFit = PreferredInlineBytes / sizeof(T);
1146 static constexpr size_t value =
1147 NumElementsThatFit == 0 ? 1 : NumElementsThatFit;
1148};
1149
1150/// This is a 'vector' (really, a variable-sized array), optimized
1151/// for the case when the array is small. It contains some number of elements
1152/// in-place, which allows it to avoid heap allocation when the actual number of
1153/// elements is below that threshold. This allows normal "small" cases to be
1154/// fast without losing generality for large inputs.
1155///
1156/// \note
1157/// In the absence of a well-motivated choice for the number of inlined
1158/// elements \p N, it is recommended to use \c SmallVector<T> (that is,
1159/// omitting the \p N). This will choose a default number of inlined elements
1160/// reasonable for allocation on the stack (for example, trying to keep \c
1161/// sizeof(SmallVector<T>) around 64 bytes).
1162///
1163/// \warning This does not attempt to be exception safe.
1164///
1165/// \see https://llvm.org/docs/ProgrammersManual.html#llvm-adt-smallvector-h
1166template <typename T,
1167 unsigned N = CalculateSmallVectorDefaultInlinedElements<T>::value>
1168class LLVM_GSL_OWNER[[gsl::Owner]] SmallVector : public SmallVectorImpl<T>,
1169 SmallVectorStorage<T, N> {
1170public:
1171 SmallVector() : SmallVectorImpl<T>(N) {}
1172
1173 ~SmallVector() {
1174 // Destroy the constructed elements in the vector.
1175 this->destroy_range(this->begin(), this->end());
1176 }
1177
1178 explicit SmallVector(size_t Size, const T &Value = T())
1179 : SmallVectorImpl<T>(N) {
1180 this->assign(Size, Value);
1181 }
1182
1183 template <typename ItTy,
1184 typename = std::enable_if_t<std::is_convertible<
1185 typename std::iterator_traits<ItTy>::iterator_category,
1186 std::input_iterator_tag>::value>>
1187 SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(N) {
1188 this->append(S, E);
1189 }
1190
1191 template <typename RangeTy>
1192 explicit SmallVector(const iterator_range<RangeTy> &R)
1193 : SmallVectorImpl<T>(N) {
1194 this->append(R.begin(), R.end());
1195 }
1196
1197 SmallVector(std::initializer_list<T> IL) : SmallVectorImpl<T>(N) {
1198 this->assign(IL);
1199 }
1200
1201 SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(N) {
1202 if (!RHS.empty())
1203 SmallVectorImpl<T>::operator=(RHS);
1204 }
1205
1206 SmallVector &operator=(const SmallVector &RHS) {
1207 SmallVectorImpl<T>::operator=(RHS);
1208 return *this;
1209 }
1210
1211 SmallVector(SmallVector &&RHS) : SmallVectorImpl<T>(N) {
1212 if (!RHS.empty())
1213 SmallVectorImpl<T>::operator=(::std::move(RHS));
1214 }
1215
1216 SmallVector(SmallVectorImpl<T> &&RHS) : SmallVectorImpl<T>(N) {
1217 if (!RHS.empty())
1218 SmallVectorImpl<T>::operator=(::std::move(RHS));
1219 }
1220
1221 SmallVector &operator=(SmallVector &&RHS) {
1222 SmallVectorImpl<T>::operator=(::std::move(RHS));
1223 return *this;
1224 }
1225
1226 SmallVector &operator=(SmallVectorImpl<T> &&RHS) {
1227 SmallVectorImpl<T>::operator=(::std::move(RHS));
1228 return *this;
1229 }
1230
1231 SmallVector &operator=(std::initializer_list<T> IL) {
1232 this->assign(IL);
1233 return *this;
1234 }
1235};
1236
1237template <typename T, unsigned N>
1238inline size_t capacity_in_bytes(const SmallVector<T, N> &X) {
1239 return X.capacity_in_bytes();
1240}
1241
1242/// Given a range of type R, iterate the entire range and return a
1243/// SmallVector with elements of the vector. This is useful, for example,
1244/// when you want to iterate a range and then sort the results.
1245template <unsigned Size, typename R>
1246SmallVector<typename std::remove_const<typename std::remove_reference<
1247 decltype(*std::begin(std::declval<R &>()))>::type>::type,
1248 Size>
1249to_vector(R &&Range) {
1250 return {std::begin(Range), std::end(Range)};
1251}
1252
1253} // end namespace llvm
1254
1255namespace std {
1256
1257 /// Implement std::swap in terms of SmallVector swap.
1258 template<typename T>
1259 inline void
1260 swap(llvm::SmallVectorImpl<T> &LHS, llvm::SmallVectorImpl<T> &RHS) {
1261 LHS.swap(RHS);
1262 }
1263
1264 /// Implement std::swap in terms of SmallVector swap.
1265 template<typename T, unsigned N>
1266 inline void
1267 swap(llvm::SmallVector<T, N> &LHS, llvm::SmallVector<T, N> &RHS) {
1268 LHS.swap(RHS);
1269 }
1270
1271} // end namespace std
1272
1273#endif // LLVM_ADT_SMALLVECTOR_H

/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/Analysis/CFG.h

1//===-- Analysis/CFG.h - BasicBlock Analyses --------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This family of functions performs analyses on basic blocks, and instructions
10// contained within basic blocks.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ANALYSIS_CFG_H
15#define LLVM_ANALYSIS_CFG_H
16
17#include "llvm/ADT/GraphTraits.h"
18#include "llvm/ADT/SmallPtrSet.h"
19#include <utility>
20
21namespace llvm {
22
23class BasicBlock;
24class DominatorTree;
25class Function;
26class Instruction;
27class LoopInfo;
28template <typename T> class SmallVectorImpl;
29
30/// Analyze the specified function to find all of the loop backedges in the
31/// function and return them. This is a relatively cheap (compared to
32/// computing dominators and loop info) analysis.
33///
34/// The output is added to Result, as pairs of <from,to> edge info.
35void FindFunctionBackedges(
36 const Function &F,
37 SmallVectorImpl<std::pair<const BasicBlock *, const BasicBlock *> > &
38 Result);
39
40/// Search for the specified successor of basic block BB and return its position
41/// in the terminator instruction's list of successors. It is an error to call
42/// this with a block that is not a successor.
43unsigned GetSuccessorNumber(const BasicBlock *BB, const BasicBlock *Succ);
44
45/// Return true if the specified edge is a critical edge. Critical edges are
46/// edges from a block with multiple successors to a block with multiple
47/// predecessors.
48///
49bool isCriticalEdge(const Instruction *TI, unsigned SuccNum,
50 bool AllowIdenticalEdges = false);
51bool isCriticalEdge(const Instruction *TI, const BasicBlock *Succ,
52 bool AllowIdenticalEdges = false);
53
54/// Determine whether instruction 'To' is reachable from 'From', without passing
55/// through any blocks in ExclusionSet, returning true if uncertain.
56///
57/// Determine whether there is a path from From to To within a single function.
58/// Returns false only if we can prove that once 'From' has been executed then
59/// 'To' can not be executed. Conservatively returns true.
60///
61/// This function is linear with respect to the number of blocks in the CFG,
62/// walking down successors from From to reach To, with a fixed threshold.
63/// Using DT or LI allows us to answer more quickly. LI reduces the cost of
64/// an entire loop of any number of blocks to be the same as the cost of a
65/// single block. DT reduces the cost by allowing the search to terminate when
66/// we find a block that dominates the block containing 'To'. DT is most useful
67/// on branchy code but not loops, and LI is most useful on code with loops but
68/// does not help on branchy code outside loops.
69bool isPotentiallyReachable(
70 const Instruction *From, const Instruction *To,
71 const SmallPtrSetImpl<BasicBlock *> *ExclusionSet = nullptr,
72 const DominatorTree *DT = nullptr, const LoopInfo *LI = nullptr);
73
74/// Determine whether block 'To' is reachable from 'From', returning
75/// true if uncertain.
76///
77/// Determine whether there is a path from From to To within a single function.
78/// Returns false only if we can prove that once 'From' has been reached then
79/// 'To' can not be executed. Conservatively returns true.
80bool isPotentiallyReachable(
81 const BasicBlock *From, const BasicBlock *To,
82 const SmallPtrSetImpl<BasicBlock *> *ExclusionSet = nullptr,
83 const DominatorTree *DT = nullptr, const LoopInfo *LI = nullptr);
84
85/// Determine whether there is at least one path from a block in
86/// 'Worklist' to 'StopBB' without passing through any blocks in
87/// 'ExclusionSet', returning true if uncertain.
88///
89/// Determine whether there is a path from at least one block in Worklist to
90/// StopBB within a single function without passing through any of the blocks
91/// in 'ExclusionSet'. Returns false only if we can prove that once any block
92/// in 'Worklist' has been reached then 'StopBB' can not be executed.
93/// Conservatively returns true.
94bool isPotentiallyReachableFromMany(
95 SmallVectorImpl<BasicBlock *> &Worklist, BasicBlock *StopBB,
96 const SmallPtrSetImpl<BasicBlock *> *ExclusionSet,
97 const DominatorTree *DT = nullptr, const LoopInfo *LI = nullptr);
98
99/// Return true if the control flow in \p RPOTraversal is irreducible.
100///
101/// This is a generic implementation to detect CFG irreducibility based on loop
102/// info analysis. It can be used for any kind of CFG (Loop, MachineLoop,
103/// Function, MachineFunction, etc.) by providing an RPO traversal (\p
104/// RPOTraversal) and the loop info analysis (\p LI) of the CFG. This utility
105/// function is only recommended when loop info analysis is available. If loop
106/// info analysis isn't available, please, don't compute it explicitly for this
107/// purpose. There are more efficient ways to detect CFG irreducibility that
108/// don't require recomputing loop info analysis (e.g., T1/T2 or Tarjan's
109/// algorithm).
110///
111/// Requirements:
112/// 1) GraphTraits must be implemented for NodeT type. It is used to access
113/// NodeT successors.
114// 2) \p RPOTraversal must be a valid reverse post-order traversal of the
115/// target CFG with begin()/end() iterator interfaces.
116/// 3) \p LI must be a valid LoopInfoBase that contains up-to-date loop
117/// analysis information of the CFG.
118///
119/// This algorithm uses the information about reducible loop back-edges already
120/// computed in \p LI. When a back-edge is found during the RPO traversal, the
121/// algorithm checks whether the back-edge is one of the reducible back-edges in
122/// loop info. If it isn't, the CFG is irreducible. For example, for the CFG
123/// below (canonical irreducible graph) loop info won't contain any loop, so the
124/// algorithm will return that the CFG is irreducible when checking the B <-
125/// -> C back-edge.
126///
127/// (A->B, A->C, B->C, C->B, C->D)
128/// A
129/// / \
130/// B<- ->C
131/// |
132/// D
133///
134template <class NodeT, class RPOTraversalT, class LoopInfoT,
135 class GT = GraphTraits<NodeT>>
136bool containsIrreducibleCFG(RPOTraversalT &RPOTraversal, const LoopInfoT &LI) {
137 /// Check whether the edge (\p Src, \p Dst) is a reducible loop backedge
138 /// according to LI. I.e., check if there exists a loop that contains Src and
139 /// where Dst is the loop header.
140 auto isProperBackedge = [&](NodeT Src, NodeT Dst) {
141 for (const auto *Lp = LI.getLoopFor(Src); Lp; Lp = Lp->getParentLoop()) {
142 if (Lp->getHeader() == Dst)
143 return true;
144 }
145 return false;
146 };
147
148 SmallPtrSet<NodeT, 32> Visited;
149 for (NodeT Node : RPOTraversal) {
150 Visited.insert(Node);
151 for (NodeT Succ : make_range(GT::child_begin(Node), GT::child_end(Node))) {
152 // Succ hasn't been visited yet
153 if (!Visited.count(Succ))
154 continue;
155 // We already visited Succ, thus Node->Succ must be a backedge. Check that
156 // the head matches what we have in the loop information. Otherwise, we
157 // have an irreducible graph.
158 if (!isProperBackedge(Node, Succ))
159 return true;
160 }
161 }
162
163 return false;
15
Returning zero, which participates in a condition later
164}
165} // End llvm namespace
166
167#endif

/build/llvm-toolchain-snapshot-13~++20210725100615+e3251f2ec44b/llvm/include/llvm/IR/PatternMatch.h

1//===- PatternMatch.h - Match on the LLVM IR --------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file provides a simple and efficient mechanism for performing general
10// tree-based pattern matches on the LLVM IR. The power of these routines is
11// that it allows you to write concise patterns that are expressive and easy to
12// understand. The other major advantage of this is that it allows you to
13// trivially capture/bind elements in the pattern to variables. For example,
14// you can do something like this:
15//
16// Value *Exp = ...
17// Value *X, *Y; ConstantInt *C1, *C2; // (X & C1) | (Y & C2)
18// if (match(Exp, m_Or(m_And(m_Value(X), m_ConstantInt(C1)),
19// m_And(m_Value(Y), m_ConstantInt(C2))))) {
20// ... Pattern is matched and variables are bound ...
21// }
22//
23// This is primarily useful to things like the instruction combiner, but can
24// also be useful for static analysis tools or code generators.
25//
26//===----------------------------------------------------------------------===//
27
28#ifndef LLVM_IR_PATTERNMATCH_H
29#define LLVM_IR_PATTERNMATCH_H
30
31#include "llvm/ADT/APFloat.h"
32#include "llvm/ADT/APInt.h"
33#include "llvm/IR/Constant.h"
34#include "llvm/IR/Constants.h"
35#include "llvm/IR/DataLayout.h"
36#include "llvm/IR/InstrTypes.h"
37#include "llvm/IR/Instruction.h"
38#include "llvm/IR/Instructions.h"
39#include "llvm/IR/IntrinsicInst.h"
40#include "llvm/IR/Intrinsics.h"
41#include "llvm/IR/Operator.h"
42#include "llvm/IR/Value.h"
43#include "llvm/Support/Casting.h"
44#include <cstdint>
45
46namespace llvm {
47namespace PatternMatch {
48
49template <typename Val, typename Pattern> bool match(Val *V, const Pattern &P) {
50 return const_cast<Pattern &>(P).match(V);
35
Calling 'LogicalOp_match::match'
39
Returning from 'LogicalOp_match::match'
40
Returning zero, which participates in a condition later
44
Calling 'LogicalOp_match::match'
48
Returning from 'LogicalOp_match::match'
49
Returning zero, which participates in a condition later
51}
52
53template <typename Pattern> bool match(ArrayRef<int> Mask, const Pattern &P) {
54 return const_cast<Pattern &>(P).match(Mask);
55}
56
57template <typename SubPattern_t> struct OneUse_match {
58 SubPattern_t SubPattern;
59
60 OneUse_match(const SubPattern_t &SP) : SubPattern(SP) {}
61
62 template <typename OpTy> bool match(OpTy *V) {
63 return V->hasOneUse() && SubPattern.match(V);
64 }
65};
66
67template <typename T> inline OneUse_match<T> m_OneUse(const T &SubPattern) {
68 return SubPattern;
69}
70
71template <typename Class> struct class_match {
72 template <typename ITy> bool match(ITy *V) { return isa<Class>(V); }
73};
74
75/// Match an arbitrary value and ignore it.
76inline class_match<Value> m_Value() { return class_match<Value>(); }
77
78/// Match an arbitrary unary operation and ignore it.
79inline class_match<UnaryOperator> m_UnOp() {
80 return class_match<UnaryOperator>();
81}
82
83/// Match an arbitrary binary operation and ignore it.
84inline class_match<BinaryOperator> m_BinOp() {
85 return class_match<BinaryOperator>();
86}
87
88/// Matches any compare instruction and ignore it.
89inline class_match<CmpInst> m_Cmp() { return class_match<CmpInst>(); }
90
91struct undef_match {
92 static bool check(const Value *V) {
93 if (isa<UndefValue>(V))
94 return true;
95
96 const auto *CA = dyn_cast<ConstantAggregate>(V);
97 if (!CA)
98 return false;
99
100 SmallPtrSet<const ConstantAggregate *, 8> Seen;
101 SmallVector<const ConstantAggregate *, 8> Worklist;
102
103 // Either UndefValue, PoisonValue, or an aggregate that only contains
104 // these is accepted by matcher.
105 // CheckValue returns false if CA cannot satisfy this constraint.
106 auto CheckValue = [&](const ConstantAggregate *CA) {
107 for (const Value *Op : CA->operand_values()) {
108 if (isa<UndefValue>(Op))
109 continue;
110
111 const auto *CA = dyn_cast<ConstantAggregate>(Op);
112 if (!CA)
113 return false;
114 if (Seen.insert(CA).second)
115 Worklist.emplace_back(CA);
116 }
117
118 return true;
119 };
120
121 if (!CheckValue(CA))
122 return false;
123
124 while (!Worklist.empty()) {
125 if (!CheckValue(Worklist.pop_back_val()))
126 return false;
127 }
128 return true;
129 }
130 template <typename ITy> bool match(ITy *V) { return check(V); }
131};
132
133/// Match an arbitrary undef constant. This matches poison as well.
134/// If this is an aggregate and contains a non-aggregate element that is
135/// neither undef nor poison, the aggregate is not matched.
136inline auto m_Undef() { return undef_match(); }
137
138/// Match an arbitrary poison constant.
139inline class_match<PoisonValue> m_Poison() { return class_match<PoisonValue>(); }
140
141/// Match an arbitrary Constant and ignore it.
142inline class_match<Constant> m_Constant() { return class_match<Constant>(); }
143
144/// Match an arbitrary ConstantInt and ignore it.
145inline class_match<ConstantInt> m_ConstantInt() {
146 return class_match<ConstantInt>();
147}
148
149/// Match an arbitrary ConstantFP and ignore it.
150inline class_match<ConstantFP> m_ConstantFP() {
151 return class_match<ConstantFP>();
152}
153
154/// Match an arbitrary ConstantExpr and ignore it.
155inline class_match<ConstantExpr> m_ConstantExpr() {
156 return class_match<ConstantExpr>();
157}
158
159/// Match an arbitrary basic block value and ignore it.
160inline class_match<BasicBlock> m_BasicBlock() {
161