File: | build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp |
Warning: | line 2913, column 21 Called C++ object pointer is null |
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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/LoopAnalysisManager.h" | ||||
23 | #include "llvm/Analysis/LoopInfo.h" | ||||
24 | #include "llvm/Analysis/LoopIterator.h" | ||||
25 | #include "llvm/Analysis/LoopPass.h" | ||||
26 | #include "llvm/Analysis/MemorySSA.h" | ||||
27 | #include "llvm/Analysis/MemorySSAUpdater.h" | ||||
28 | #include "llvm/Analysis/MustExecute.h" | ||||
29 | #include "llvm/Analysis/ScalarEvolution.h" | ||||
30 | #include "llvm/Analysis/TargetTransformInfo.h" | ||||
31 | #include "llvm/Analysis/ValueTracking.h" | ||||
32 | #include "llvm/IR/BasicBlock.h" | ||||
33 | #include "llvm/IR/Constant.h" | ||||
34 | #include "llvm/IR/Constants.h" | ||||
35 | #include "llvm/IR/Dominators.h" | ||||
36 | #include "llvm/IR/Function.h" | ||||
37 | #include "llvm/IR/IRBuilder.h" | ||||
38 | #include "llvm/IR/InstrTypes.h" | ||||
39 | #include "llvm/IR/Instruction.h" | ||||
40 | #include "llvm/IR/Instructions.h" | ||||
41 | #include "llvm/IR/IntrinsicInst.h" | ||||
42 | #include "llvm/IR/PatternMatch.h" | ||||
43 | #include "llvm/IR/Use.h" | ||||
44 | #include "llvm/IR/Value.h" | ||||
45 | #include "llvm/InitializePasses.h" | ||||
46 | #include "llvm/Pass.h" | ||||
47 | #include "llvm/Support/Casting.h" | ||||
48 | #include "llvm/Support/CommandLine.h" | ||||
49 | #include "llvm/Support/Debug.h" | ||||
50 | #include "llvm/Support/ErrorHandling.h" | ||||
51 | #include "llvm/Support/GenericDomTree.h" | ||||
52 | #include "llvm/Support/InstructionCost.h" | ||||
53 | #include "llvm/Support/raw_ostream.h" | ||||
54 | #include "llvm/Transforms/Scalar/LoopPassManager.h" | ||||
55 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" | ||||
56 | #include "llvm/Transforms/Utils/Cloning.h" | ||||
57 | #include "llvm/Transforms/Utils/Local.h" | ||||
58 | #include "llvm/Transforms/Utils/LoopUtils.h" | ||||
59 | #include "llvm/Transforms/Utils/ValueMapper.h" | ||||
60 | #include <algorithm> | ||||
61 | #include <cassert> | ||||
62 | #include <iterator> | ||||
63 | #include <numeric> | ||||
64 | #include <utility> | ||||
65 | |||||
66 | #define DEBUG_TYPE"simple-loop-unswitch" "simple-loop-unswitch" | ||||
67 | |||||
68 | using namespace llvm; | ||||
69 | using namespace llvm::PatternMatch; | ||||
70 | |||||
71 | STATISTIC(NumBranches, "Number of branches unswitched")static llvm::Statistic NumBranches = {"simple-loop-unswitch", "NumBranches", "Number of branches unswitched"}; | ||||
72 | STATISTIC(NumSwitches, "Number of switches unswitched")static llvm::Statistic NumSwitches = {"simple-loop-unswitch", "NumSwitches", "Number of switches unswitched"}; | ||||
73 | STATISTIC(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"}; | ||||
74 | STATISTIC(NumTrivial, "Number of unswitches that are trivial")static llvm::Statistic NumTrivial = {"simple-loop-unswitch", "NumTrivial" , "Number of unswitches that are trivial"}; | ||||
75 | STATISTIC(static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch" , "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped" } | ||||
76 | NumCostMultiplierSkipped,static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch" , "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped" } | ||||
77 | "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" }; | ||||
78 | |||||
79 | static cl::opt<bool> EnableNonTrivialUnswitch( | ||||
80 | "enable-nontrivial-unswitch", cl::init(false), cl::Hidden, | ||||
81 | cl::desc("Forcibly enables non-trivial loop unswitching rather than " | ||||
82 | "following the configuration passed into the pass.")); | ||||
83 | |||||
84 | static cl::opt<int> | ||||
85 | UnswitchThreshold("unswitch-threshold", cl::init(50), cl::Hidden, | ||||
86 | cl::ZeroOrMore, | ||||
87 | cl::desc("The cost threshold for unswitching a loop.")); | ||||
88 | |||||
89 | static cl::opt<bool> EnableUnswitchCostMultiplier( | ||||
90 | "enable-unswitch-cost-multiplier", cl::init(true), cl::Hidden, | ||||
91 | cl::desc("Enable unswitch cost multiplier that prohibits exponential " | ||||
92 | "explosion in nontrivial unswitch.")); | ||||
93 | static cl::opt<int> UnswitchSiblingsToplevelDiv( | ||||
94 | "unswitch-siblings-toplevel-div", cl::init(2), cl::Hidden, | ||||
95 | cl::desc("Toplevel siblings divisor for cost multiplier.")); | ||||
96 | static cl::opt<int> UnswitchNumInitialUnscaledCandidates( | ||||
97 | "unswitch-num-initial-unscaled-candidates", cl::init(8), cl::Hidden, | ||||
98 | cl::desc("Number of unswitch candidates that are ignored when calculating " | ||||
99 | "cost multiplier.")); | ||||
100 | static cl::opt<bool> UnswitchGuards( | ||||
101 | "simple-loop-unswitch-guards", cl::init(true), cl::Hidden, | ||||
102 | cl::desc("If enabled, simple loop unswitching will also consider " | ||||
103 | "llvm.experimental.guard intrinsics as unswitch candidates.")); | ||||
104 | static cl::opt<bool> DropNonTrivialImplicitNullChecks( | ||||
105 | "simple-loop-unswitch-drop-non-trivial-implicit-null-checks", | ||||
106 | cl::init(false), cl::Hidden, | ||||
107 | cl::desc("If enabled, drop make.implicit metadata in unswitched implicit " | ||||
108 | "null checks to save time analyzing if we can keep it.")); | ||||
109 | static cl::opt<unsigned> | ||||
110 | MSSAThreshold("simple-loop-unswitch-memoryssa-threshold", | ||||
111 | cl::desc("Max number of memory uses to explore during " | ||||
112 | "partial unswitching analysis"), | ||||
113 | cl::init(100), cl::Hidden); | ||||
114 | static cl::opt<bool> FreezeLoopUnswitchCond( | ||||
115 | "freeze-loop-unswitch-cond", cl::init(false), cl::Hidden, | ||||
116 | cl::desc("If enabled, the freeze instruction will be added to condition " | ||||
117 | "of loop unswitch to prevent miscompilation.")); | ||||
118 | |||||
119 | /// Collect all of the loop invariant input values transitively used by the | ||||
120 | /// homogeneous instruction graph from a given root. | ||||
121 | /// | ||||
122 | /// This essentially walks from a root recursively through loop variant operands | ||||
123 | /// which have the exact same opcode and finds all inputs which are loop | ||||
124 | /// invariant. For some operations these can be re-associated and unswitched out | ||||
125 | /// of the loop entirely. | ||||
126 | static TinyPtrVector<Value *> | ||||
127 | collectHomogenousInstGraphLoopInvariants(Loop &L, Instruction &Root, | ||||
128 | LoopInfo &LI) { | ||||
129 | 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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 130, __extension__ __PRETTY_FUNCTION__)) | ||||
130 | "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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 130, __extension__ __PRETTY_FUNCTION__)); | ||||
131 | TinyPtrVector<Value *> Invariants; | ||||
132 | |||||
133 | bool IsRootAnd = match(&Root, m_LogicalAnd()); | ||||
134 | bool IsRootOr = match(&Root, m_LogicalOr()); | ||||
135 | |||||
136 | // Build a worklist and recurse through operators collecting invariants. | ||||
137 | SmallVector<Instruction *, 4> Worklist; | ||||
138 | SmallPtrSet<Instruction *, 8> Visited; | ||||
139 | Worklist.push_back(&Root); | ||||
140 | Visited.insert(&Root); | ||||
141 | do { | ||||
142 | Instruction &I = *Worklist.pop_back_val(); | ||||
143 | for (Value *OpV : I.operand_values()) { | ||||
144 | // Skip constants as unswitching isn't interesting for them. | ||||
145 | if (isa<Constant>(OpV)) | ||||
146 | continue; | ||||
147 | |||||
148 | // Add it to our result if loop invariant. | ||||
149 | if (L.isLoopInvariant(OpV)) { | ||||
150 | Invariants.push_back(OpV); | ||||
151 | continue; | ||||
152 | } | ||||
153 | |||||
154 | // If not an instruction with the same opcode, nothing we can do. | ||||
155 | Instruction *OpI = dyn_cast<Instruction>(OpV); | ||||
156 | |||||
157 | if (OpI && ((IsRootAnd && match(OpI, m_LogicalAnd())) || | ||||
158 | (IsRootOr && match(OpI, m_LogicalOr())))) { | ||||
159 | // Visit this operand. | ||||
160 | if (Visited.insert(OpI).second) | ||||
161 | Worklist.push_back(OpI); | ||||
162 | } | ||||
163 | } | ||||
164 | } while (!Worklist.empty()); | ||||
165 | |||||
166 | return Invariants; | ||||
167 | } | ||||
168 | |||||
169 | static void replaceLoopInvariantUses(Loop &L, Value *Invariant, | ||||
170 | Constant &Replacement) { | ||||
171 | 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?\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 171, __extension__ __PRETTY_FUNCTION__)); | ||||
172 | |||||
173 | // Replace uses of LIC in the loop with the given constant. | ||||
174 | // We use make_early_inc_range as set invalidates the iterator. | ||||
175 | for (Use &U : llvm::make_early_inc_range(Invariant->uses())) { | ||||
176 | Instruction *UserI = dyn_cast<Instruction>(U.getUser()); | ||||
177 | |||||
178 | // Replace this use within the loop body. | ||||
179 | if (UserI && L.contains(UserI)) | ||||
180 | U.set(&Replacement); | ||||
181 | } | ||||
182 | } | ||||
183 | |||||
184 | /// Check that all the LCSSA PHI nodes in the loop exit block have trivial | ||||
185 | /// incoming values along this edge. | ||||
186 | static bool areLoopExitPHIsLoopInvariant(Loop &L, BasicBlock &ExitingBB, | ||||
187 | BasicBlock &ExitBB) { | ||||
188 | for (Instruction &I : ExitBB) { | ||||
189 | auto *PN = dyn_cast<PHINode>(&I); | ||||
190 | if (!PN) | ||||
191 | // No more PHIs to check. | ||||
192 | return true; | ||||
193 | |||||
194 | // If the incoming value for this edge isn't loop invariant the unswitch | ||||
195 | // won't be trivial. | ||||
196 | if (!L.isLoopInvariant(PN->getIncomingValueForBlock(&ExitingBB))) | ||||
197 | return false; | ||||
198 | } | ||||
199 | llvm_unreachable("Basic blocks should never be empty!")::llvm::llvm_unreachable_internal("Basic blocks should never be empty!" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 199); | ||||
200 | } | ||||
201 | |||||
202 | /// Copy a set of loop invariant values \p ToDuplicate and insert them at the | ||||
203 | /// end of \p BB and conditionally branch on the copied condition. We only | ||||
204 | /// branch on a single value. | ||||
205 | static void buildPartialUnswitchConditionalBranch( | ||||
206 | BasicBlock &BB, ArrayRef<Value *> Invariants, bool Direction, | ||||
207 | BasicBlock &UnswitchedSucc, BasicBlock &NormalSucc, bool InsertFreeze) { | ||||
208 | IRBuilder<> IRB(&BB); | ||||
209 | |||||
210 | Value *Cond = Direction ? IRB.CreateOr(Invariants) : | ||||
211 | IRB.CreateAnd(Invariants); | ||||
212 | if (InsertFreeze) | ||||
213 | Cond = IRB.CreateFreeze(Cond, Cond->getName() + ".fr"); | ||||
214 | IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc, | ||||
215 | Direction ? &NormalSucc : &UnswitchedSucc); | ||||
216 | } | ||||
217 | |||||
218 | /// Copy a set of loop invariant values, and conditionally branch on them. | ||||
219 | static void buildPartialInvariantUnswitchConditionalBranch( | ||||
220 | BasicBlock &BB, ArrayRef<Value *> ToDuplicate, bool Direction, | ||||
221 | BasicBlock &UnswitchedSucc, BasicBlock &NormalSucc, Loop &L, | ||||
222 | MemorySSAUpdater *MSSAU) { | ||||
223 | ValueToValueMapTy VMap; | ||||
224 | for (auto *Val : reverse(ToDuplicate)) { | ||||
225 | Instruction *Inst = cast<Instruction>(Val); | ||||
226 | Instruction *NewInst = Inst->clone(); | ||||
227 | BB.getInstList().insert(BB.end(), NewInst); | ||||
228 | RemapInstruction(NewInst, VMap, | ||||
229 | RF_NoModuleLevelChanges | RF_IgnoreMissingLocals); | ||||
230 | VMap[Val] = NewInst; | ||||
231 | |||||
232 | if (!MSSAU) | ||||
233 | continue; | ||||
234 | |||||
235 | MemorySSA *MSSA = MSSAU->getMemorySSA(); | ||||
236 | if (auto *MemUse = | ||||
237 | dyn_cast_or_null<MemoryUse>(MSSA->getMemoryAccess(Inst))) { | ||||
238 | auto *DefiningAccess = MemUse->getDefiningAccess(); | ||||
239 | // Get the first defining access before the loop. | ||||
240 | while (L.contains(DefiningAccess->getBlock())) { | ||||
241 | // If the defining access is a MemoryPhi, get the incoming | ||||
242 | // value for the pre-header as defining access. | ||||
243 | if (auto *MemPhi = dyn_cast<MemoryPhi>(DefiningAccess)) | ||||
244 | DefiningAccess = | ||||
245 | MemPhi->getIncomingValueForBlock(L.getLoopPreheader()); | ||||
246 | else | ||||
247 | DefiningAccess = cast<MemoryDef>(DefiningAccess)->getDefiningAccess(); | ||||
248 | } | ||||
249 | MSSAU->createMemoryAccessInBB(NewInst, DefiningAccess, | ||||
250 | NewInst->getParent(), | ||||
251 | MemorySSA::BeforeTerminator); | ||||
252 | } | ||||
253 | } | ||||
254 | |||||
255 | IRBuilder<> IRB(&BB); | ||||
256 | Value *Cond = VMap[ToDuplicate[0]]; | ||||
257 | IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc, | ||||
258 | Direction ? &NormalSucc : &UnswitchedSucc); | ||||
259 | } | ||||
260 | |||||
261 | /// Rewrite the PHI nodes in an unswitched loop exit basic block. | ||||
262 | /// | ||||
263 | /// Requires that the loop exit and unswitched basic block are the same, and | ||||
264 | /// that the exiting block was a unique predecessor of that block. Rewrites the | ||||
265 | /// PHI nodes in that block such that what were LCSSA PHI nodes become trivial | ||||
266 | /// PHI nodes from the old preheader that now contains the unswitched | ||||
267 | /// terminator. | ||||
268 | static void rewritePHINodesForUnswitchedExitBlock(BasicBlock &UnswitchedBB, | ||||
269 | BasicBlock &OldExitingBB, | ||||
270 | BasicBlock &OldPH) { | ||||
271 | for (PHINode &PN : UnswitchedBB.phis()) { | ||||
272 | // When the loop exit is directly unswitched we just need to update the | ||||
273 | // incoming basic block. We loop to handle weird cases with repeated | ||||
274 | // incoming blocks, but expect to typically only have one operand here. | ||||
275 | for (auto i : seq<int>(0, PN.getNumOperands())) { | ||||
276 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 277, __extension__ __PRETTY_FUNCTION__)) | ||||
277 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 277, __extension__ __PRETTY_FUNCTION__)); | ||||
278 | PN.setIncomingBlock(i, &OldPH); | ||||
279 | } | ||||
280 | } | ||||
281 | } | ||||
282 | |||||
283 | /// Rewrite the PHI nodes in the loop exit basic block and the split off | ||||
284 | /// unswitched block. | ||||
285 | /// | ||||
286 | /// Because the exit block remains an exit from the loop, this rewrites the | ||||
287 | /// LCSSA PHI nodes in it to remove the unswitched edge and introduces PHI | ||||
288 | /// nodes into the unswitched basic block to select between the value in the | ||||
289 | /// old preheader and the loop exit. | ||||
290 | static void rewritePHINodesForExitAndUnswitchedBlocks(BasicBlock &ExitBB, | ||||
291 | BasicBlock &UnswitchedBB, | ||||
292 | BasicBlock &OldExitingBB, | ||||
293 | BasicBlock &OldPH, | ||||
294 | bool FullUnswitch) { | ||||
295 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 296, __extension__ __PRETTY_FUNCTION__)) | ||||
296 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 296, __extension__ __PRETTY_FUNCTION__)); | ||||
297 | Instruction *InsertPt = &*UnswitchedBB.begin(); | ||||
298 | for (PHINode &PN : ExitBB.phis()) { | ||||
299 | auto *NewPN = PHINode::Create(PN.getType(), /*NumReservedValues*/ 2, | ||||
300 | PN.getName() + ".split", InsertPt); | ||||
301 | |||||
302 | // Walk backwards over the old PHI node's inputs to minimize the cost of | ||||
303 | // removing each one. We have to do this weird loop manually so that we | ||||
304 | // create the same number of new incoming edges in the new PHI as we expect | ||||
305 | // each case-based edge to be included in the unswitched switch in some | ||||
306 | // cases. | ||||
307 | // FIXME: This is really, really gross. It would be much cleaner if LLVM | ||||
308 | // allowed us to create a single entry for a predecessor block without | ||||
309 | // having separate entries for each "edge" even though these edges are | ||||
310 | // required to produce identical results. | ||||
311 | for (int i = PN.getNumIncomingValues() - 1; i >= 0; --i) { | ||||
312 | if (PN.getIncomingBlock(i) != &OldExitingBB) | ||||
313 | continue; | ||||
314 | |||||
315 | Value *Incoming = PN.getIncomingValue(i); | ||||
316 | if (FullUnswitch) | ||||
317 | // No more edge from the old exiting block to the exit block. | ||||
318 | PN.removeIncomingValue(i); | ||||
319 | |||||
320 | NewPN->addIncoming(Incoming, &OldPH); | ||||
321 | } | ||||
322 | |||||
323 | // Now replace the old PHI with the new one and wire the old one in as an | ||||
324 | // input to the new one. | ||||
325 | PN.replaceAllUsesWith(NewPN); | ||||
326 | NewPN->addIncoming(&PN, &ExitBB); | ||||
327 | } | ||||
328 | } | ||||
329 | |||||
330 | /// Hoist the current loop up to the innermost loop containing a remaining exit. | ||||
331 | /// | ||||
332 | /// Because we've removed an exit from the loop, we may have changed the set of | ||||
333 | /// loops reachable and need to move the current loop up the loop nest or even | ||||
334 | /// to an entirely separate nest. | ||||
335 | static void hoistLoopToNewParent(Loop &L, BasicBlock &Preheader, | ||||
336 | DominatorTree &DT, LoopInfo &LI, | ||||
337 | MemorySSAUpdater *MSSAU, ScalarEvolution *SE) { | ||||
338 | // If the loop is already at the top level, we can't hoist it anywhere. | ||||
339 | Loop *OldParentL = L.getParentLoop(); | ||||
340 | if (!OldParentL) | ||||
341 | return; | ||||
342 | |||||
343 | SmallVector<BasicBlock *, 4> Exits; | ||||
344 | L.getExitBlocks(Exits); | ||||
345 | Loop *NewParentL = nullptr; | ||||
346 | for (auto *ExitBB : Exits) | ||||
347 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) | ||||
348 | if (!NewParentL || NewParentL->contains(ExitL)) | ||||
349 | NewParentL = ExitL; | ||||
350 | |||||
351 | if (NewParentL == OldParentL) | ||||
352 | return; | ||||
353 | |||||
354 | // The new parent loop (if different) should always contain the old one. | ||||
355 | if (NewParentL) | ||||
356 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 357, __extension__ __PRETTY_FUNCTION__)) | ||||
357 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 357, __extension__ __PRETTY_FUNCTION__)); | ||||
358 | |||||
359 | // The preheader will need to move with the body of this loop. However, | ||||
360 | // because it isn't in this loop we also need to update the primary loop map. | ||||
361 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 362, __extension__ __PRETTY_FUNCTION__)) | ||||
362 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 362, __extension__ __PRETTY_FUNCTION__)); | ||||
363 | LI.changeLoopFor(&Preheader, NewParentL); | ||||
364 | |||||
365 | // Remove this loop from its old parent. | ||||
366 | OldParentL->removeChildLoop(&L); | ||||
367 | |||||
368 | // Add the loop either to the new parent or as a top-level loop. | ||||
369 | if (NewParentL) | ||||
370 | NewParentL->addChildLoop(&L); | ||||
371 | else | ||||
372 | LI.addTopLevelLoop(&L); | ||||
373 | |||||
374 | // Remove this loops blocks from the old parent and every other loop up the | ||||
375 | // nest until reaching the new parent. Also update all of these | ||||
376 | // no-longer-containing loops to reflect the nesting change. | ||||
377 | for (Loop *OldContainingL = OldParentL; OldContainingL != NewParentL; | ||||
378 | OldContainingL = OldContainingL->getParentLoop()) { | ||||
379 | llvm::erase_if(OldContainingL->getBlocksVector(), | ||||
380 | [&](const BasicBlock *BB) { | ||||
381 | return BB == &Preheader || L.contains(BB); | ||||
382 | }); | ||||
383 | |||||
384 | OldContainingL->getBlocksSet().erase(&Preheader); | ||||
385 | for (BasicBlock *BB : L.blocks()) | ||||
386 | OldContainingL->getBlocksSet().erase(BB); | ||||
387 | |||||
388 | // Because we just hoisted a loop out of this one, we have essentially | ||||
389 | // created new exit paths from it. That means we need to form LCSSA PHI | ||||
390 | // nodes for values used in the no-longer-nested loop. | ||||
391 | formLCSSA(*OldContainingL, DT, &LI, SE); | ||||
392 | |||||
393 | // We shouldn't need to form dedicated exits because the exit introduced | ||||
394 | // here is the (just split by unswitching) preheader. However, after trivial | ||||
395 | // unswitching it is possible to get new non-dedicated exits out of parent | ||||
396 | // loop so let's conservatively form dedicated exit blocks and figure out | ||||
397 | // if we can optimize later. | ||||
398 | formDedicatedExitBlocks(OldContainingL, &DT, &LI, MSSAU, | ||||
399 | /*PreserveLCSSA*/ true); | ||||
400 | } | ||||
401 | } | ||||
402 | |||||
403 | // Return the top-most loop containing ExitBB and having ExitBB as exiting block | ||||
404 | // or the loop containing ExitBB, if there is no parent loop containing ExitBB | ||||
405 | // as exiting block. | ||||
406 | static Loop *getTopMostExitingLoop(BasicBlock *ExitBB, LoopInfo &LI) { | ||||
407 | Loop *TopMost = LI.getLoopFor(ExitBB); | ||||
408 | Loop *Current = TopMost; | ||||
409 | while (Current) { | ||||
410 | if (Current->isLoopExiting(ExitBB)) | ||||
411 | TopMost = Current; | ||||
412 | Current = Current->getParentLoop(); | ||||
413 | } | ||||
414 | return TopMost; | ||||
415 | } | ||||
416 | |||||
417 | /// Unswitch a trivial branch if the condition is loop invariant. | ||||
418 | /// | ||||
419 | /// This routine should only be called when loop code leading to the branch has | ||||
420 | /// been validated as trivial (no side effects). This routine checks if the | ||||
421 | /// condition is invariant and one of the successors is a loop exit. This | ||||
422 | /// allows us to unswitch without duplicating the loop, making it trivial. | ||||
423 | /// | ||||
424 | /// If this routine fails to unswitch the branch it returns false. | ||||
425 | /// | ||||
426 | /// If the branch can be unswitched, this routine splits the preheader and | ||||
427 | /// hoists the branch above that split. Preserves loop simplified form | ||||
428 | /// (splitting the exit block as necessary). It simplifies the branch within | ||||
429 | /// the loop to an unconditional branch but doesn't remove it entirely. Further | ||||
430 | /// cleanup can be done with some simplifycfg like pass. | ||||
431 | /// | ||||
432 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | ||||
433 | /// invalidated by this. | ||||
434 | static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT, | ||||
435 | LoopInfo &LI, ScalarEvolution *SE, | ||||
436 | MemorySSAUpdater *MSSAU) { | ||||
437 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 437, __extension__ __PRETTY_FUNCTION__)); | ||||
438 | 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); | ||||
439 | |||||
440 | // The loop invariant values that we want to unswitch. | ||||
441 | TinyPtrVector<Value *> Invariants; | ||||
442 | |||||
443 | // When true, we're fully unswitching the branch rather than just unswitching | ||||
444 | // some input conditions to the branch. | ||||
445 | bool FullUnswitch = false; | ||||
446 | |||||
447 | if (L.isLoopInvariant(BI.getCondition())) { | ||||
448 | Invariants.push_back(BI.getCondition()); | ||||
449 | FullUnswitch = true; | ||||
450 | } else { | ||||
451 | if (auto *CondInst = dyn_cast<Instruction>(BI.getCondition())) | ||||
452 | Invariants = collectHomogenousInstGraphLoopInvariants(L, *CondInst, LI); | ||||
453 | if (Invariants.empty()) { | ||||
454 | 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); | ||||
455 | return false; | ||||
456 | } | ||||
457 | } | ||||
458 | |||||
459 | // Check that one of the branch's successors exits, and which one. | ||||
460 | bool ExitDirection = true; | ||||
461 | int LoopExitSuccIdx = 0; | ||||
462 | auto *LoopExitBB = BI.getSuccessor(0); | ||||
463 | if (L.contains(LoopExitBB)) { | ||||
464 | ExitDirection = false; | ||||
465 | LoopExitSuccIdx = 1; | ||||
466 | LoopExitBB = BI.getSuccessor(1); | ||||
467 | if (L.contains(LoopExitBB)) { | ||||
468 | 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); | ||||
469 | return false; | ||||
470 | } | ||||
471 | } | ||||
472 | auto *ContinueBB = BI.getSuccessor(1 - LoopExitSuccIdx); | ||||
473 | auto *ParentBB = BI.getParent(); | ||||
474 | if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, *LoopExitBB)) { | ||||
475 | 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); | ||||
476 | return false; | ||||
477 | } | ||||
478 | |||||
479 | // When unswitching only part of the branch's condition, we need the exit | ||||
480 | // block to be reached directly from the partially unswitched input. This can | ||||
481 | // be done when the exit block is along the true edge and the branch condition | ||||
482 | // is a graph of `or` operations, or the exit block is along the false edge | ||||
483 | // and the condition is a graph of `and` operations. | ||||
484 | if (!FullUnswitch) { | ||||
485 | if (ExitDirection ? !match(BI.getCondition(), m_LogicalOr()) | ||||
486 | : !match(BI.getCondition(), m_LogicalAnd())) { | ||||
487 | 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) | ||||
488 | "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); | ||||
489 | return false; | ||||
490 | } | ||||
491 | } | ||||
492 | |||||
493 | 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) | ||||
494 | 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) | ||||
495 | << "\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) | ||||
496 | 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) | ||||
497 | 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) | ||||
498 | 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) | ||||
499 | 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) | ||||
500 | 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) | ||||
501 | }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) | ||||
502 | })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); | ||||
503 | |||||
504 | // If we have scalar evolutions, we need to invalidate them including this | ||||
505 | // loop, the loop containing the exit block and the topmost parent loop | ||||
506 | // exiting via LoopExitBB. | ||||
507 | if (SE) { | ||||
508 | if (Loop *ExitL = getTopMostExitingLoop(LoopExitBB, LI)) | ||||
509 | SE->forgetLoop(ExitL); | ||||
510 | else | ||||
511 | // Forget the entire nest as this exits the entire nest. | ||||
512 | SE->forgetTopmostLoop(&L); | ||||
513 | } | ||||
514 | |||||
515 | if (MSSAU && VerifyMemorySSA) | ||||
516 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
517 | |||||
518 | // Split the preheader, so that we know that there is a safe place to insert | ||||
519 | // the conditional branch. We will change the preheader to have a conditional | ||||
520 | // branch on LoopCond. | ||||
521 | BasicBlock *OldPH = L.getLoopPreheader(); | ||||
522 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI, MSSAU); | ||||
523 | |||||
524 | // Now that we have a place to insert the conditional branch, create a place | ||||
525 | // to branch to: this is the exit block out of the loop that we are | ||||
526 | // unswitching. We need to split this if there are other loop predecessors. | ||||
527 | // Because the loop is in simplified form, *any* other predecessor is enough. | ||||
528 | BasicBlock *UnswitchedBB; | ||||
529 | if (FullUnswitch && LoopExitBB->getUniquePredecessor()) { | ||||
530 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 531, __extension__ __PRETTY_FUNCTION__)) | ||||
531 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 531, __extension__ __PRETTY_FUNCTION__)); | ||||
532 | UnswitchedBB = LoopExitBB; | ||||
533 | } else { | ||||
534 | UnswitchedBB = | ||||
535 | SplitBlock(LoopExitBB, &LoopExitBB->front(), &DT, &LI, MSSAU); | ||||
536 | } | ||||
537 | |||||
538 | if (MSSAU && VerifyMemorySSA) | ||||
539 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
540 | |||||
541 | // Actually move the invariant uses into the unswitched position. If possible, | ||||
542 | // we do this by moving the instructions, but when doing partial unswitching | ||||
543 | // we do it by building a new merge of the values in the unswitched position. | ||||
544 | OldPH->getTerminator()->eraseFromParent(); | ||||
545 | if (FullUnswitch) { | ||||
546 | // If fully unswitching, we can use the existing branch instruction. | ||||
547 | // Splice it into the old PH to gate reaching the new preheader and re-point | ||||
548 | // its successors. | ||||
549 | OldPH->getInstList().splice(OldPH->end(), BI.getParent()->getInstList(), | ||||
550 | BI); | ||||
551 | if (MSSAU) { | ||||
552 | // Temporarily clone the terminator, to make MSSA update cheaper by | ||||
553 | // separating "insert edge" updates from "remove edge" ones. | ||||
554 | ParentBB->getInstList().push_back(BI.clone()); | ||||
555 | } else { | ||||
556 | // Create a new unconditional branch that will continue the loop as a new | ||||
557 | // terminator. | ||||
558 | BranchInst::Create(ContinueBB, ParentBB); | ||||
559 | } | ||||
560 | BI.setSuccessor(LoopExitSuccIdx, UnswitchedBB); | ||||
561 | BI.setSuccessor(1 - LoopExitSuccIdx, NewPH); | ||||
562 | } else { | ||||
563 | // Only unswitching a subset of inputs to the condition, so we will need to | ||||
564 | // build a new branch that merges the invariant inputs. | ||||
565 | if (ExitDirection) | ||||
566 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 568, __extension__ __PRETTY_FUNCTION__)) | ||||
567 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 568, __extension__ __PRETTY_FUNCTION__)) | ||||
568 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 568, __extension__ __PRETTY_FUNCTION__)); | ||||
569 | else | ||||
570 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 572, __extension__ __PRETTY_FUNCTION__)) | ||||
571 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 572, __extension__ __PRETTY_FUNCTION__)) | ||||
572 | " 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 572, __extension__ __PRETTY_FUNCTION__)); | ||||
573 | buildPartialUnswitchConditionalBranch(*OldPH, Invariants, ExitDirection, | ||||
574 | *UnswitchedBB, *NewPH, false); | ||||
575 | } | ||||
576 | |||||
577 | // Update the dominator tree with the added edge. | ||||
578 | DT.insertEdge(OldPH, UnswitchedBB); | ||||
579 | |||||
580 | // After the dominator tree was updated with the added edge, update MemorySSA | ||||
581 | // if available. | ||||
582 | if (MSSAU) { | ||||
583 | SmallVector<CFGUpdate, 1> Updates; | ||||
584 | Updates.push_back({cfg::UpdateKind::Insert, OldPH, UnswitchedBB}); | ||||
585 | MSSAU->applyInsertUpdates(Updates, DT); | ||||
586 | } | ||||
587 | |||||
588 | // Finish updating dominator tree and memory ssa for full unswitch. | ||||
589 | if (FullUnswitch) { | ||||
590 | if (MSSAU) { | ||||
591 | // Remove the cloned branch instruction. | ||||
592 | ParentBB->getTerminator()->eraseFromParent(); | ||||
593 | // Create unconditional branch now. | ||||
594 | BranchInst::Create(ContinueBB, ParentBB); | ||||
595 | MSSAU->removeEdge(ParentBB, LoopExitBB); | ||||
596 | } | ||||
597 | DT.deleteEdge(ParentBB, LoopExitBB); | ||||
598 | } | ||||
599 | |||||
600 | if (MSSAU && VerifyMemorySSA) | ||||
601 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
602 | |||||
603 | // Rewrite the relevant PHI nodes. | ||||
604 | if (UnswitchedBB == LoopExitBB) | ||||
605 | rewritePHINodesForUnswitchedExitBlock(*UnswitchedBB, *ParentBB, *OldPH); | ||||
606 | else | ||||
607 | rewritePHINodesForExitAndUnswitchedBlocks(*LoopExitBB, *UnswitchedBB, | ||||
608 | *ParentBB, *OldPH, FullUnswitch); | ||||
609 | |||||
610 | // The constant we can replace all of our invariants with inside the loop | ||||
611 | // body. If any of the invariants have a value other than this the loop won't | ||||
612 | // be entered. | ||||
613 | ConstantInt *Replacement = ExitDirection | ||||
614 | ? ConstantInt::getFalse(BI.getContext()) | ||||
615 | : ConstantInt::getTrue(BI.getContext()); | ||||
616 | |||||
617 | // Since this is an i1 condition we can also trivially replace uses of it | ||||
618 | // within the loop with a constant. | ||||
619 | for (Value *Invariant : Invariants) | ||||
620 | replaceLoopInvariantUses(L, Invariant, *Replacement); | ||||
621 | |||||
622 | // If this was full unswitching, we may have changed the nesting relationship | ||||
623 | // for this loop so hoist it to its correct parent if needed. | ||||
624 | if (FullUnswitch) | ||||
625 | hoistLoopToNewParent(L, *NewPH, DT, LI, MSSAU, SE); | ||||
626 | |||||
627 | if (MSSAU && VerifyMemorySSA) | ||||
628 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
629 | |||||
630 | 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); | ||||
631 | ++NumTrivial; | ||||
632 | ++NumBranches; | ||||
633 | return true; | ||||
634 | } | ||||
635 | |||||
636 | /// Unswitch a trivial switch if the condition is loop invariant. | ||||
637 | /// | ||||
638 | /// This routine should only be called when loop code leading to the switch has | ||||
639 | /// been validated as trivial (no side effects). This routine checks if the | ||||
640 | /// condition is invariant and that at least one of the successors is a loop | ||||
641 | /// exit. This allows us to unswitch without duplicating the loop, making it | ||||
642 | /// trivial. | ||||
643 | /// | ||||
644 | /// If this routine fails to unswitch the switch it returns false. | ||||
645 | /// | ||||
646 | /// If the switch can be unswitched, this routine splits the preheader and | ||||
647 | /// copies the switch above that split. If the default case is one of the | ||||
648 | /// exiting cases, it copies the non-exiting cases and points them at the new | ||||
649 | /// preheader. If the default case is not exiting, it copies the exiting cases | ||||
650 | /// and points the default at the preheader. It preserves loop simplified form | ||||
651 | /// (splitting the exit blocks as necessary). It simplifies the switch within | ||||
652 | /// the loop by removing now-dead cases. If the default case is one of those | ||||
653 | /// unswitched, it replaces its destination with a new basic block containing | ||||
654 | /// only unreachable. Such basic blocks, while technically loop exits, are not | ||||
655 | /// considered for unswitching so this is a stable transform and the same | ||||
656 | /// switch will not be revisited. If after unswitching there is only a single | ||||
657 | /// in-loop successor, the switch is further simplified to an unconditional | ||||
658 | /// branch. Still more cleanup can be done with some simplifycfg like pass. | ||||
659 | /// | ||||
660 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | ||||
661 | /// invalidated by this. | ||||
662 | static bool unswitchTrivialSwitch(Loop &L, SwitchInst &SI, DominatorTree &DT, | ||||
663 | LoopInfo &LI, ScalarEvolution *SE, | ||||
664 | MemorySSAUpdater *MSSAU) { | ||||
665 | 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); | ||||
666 | Value *LoopCond = SI.getCondition(); | ||||
667 | |||||
668 | // If this isn't switching on an invariant condition, we can't unswitch it. | ||||
669 | if (!L.isLoopInvariant(LoopCond)) | ||||
670 | return false; | ||||
671 | |||||
672 | auto *ParentBB = SI.getParent(); | ||||
673 | |||||
674 | // The same check must be used both for the default and the exit cases. We | ||||
675 | // should never leave edges from the switch instruction to a basic block that | ||||
676 | // we are unswitching, hence the condition used to determine the default case | ||||
677 | // needs to also be used to populate ExitCaseIndices, which is then used to | ||||
678 | // remove cases from the switch. | ||||
679 | auto IsTriviallyUnswitchableExitBlock = [&](BasicBlock &BBToCheck) { | ||||
680 | // BBToCheck is not an exit block if it is inside loop L. | ||||
681 | if (L.contains(&BBToCheck)) | ||||
682 | return false; | ||||
683 | // BBToCheck is not trivial to unswitch if its phis aren't loop invariant. | ||||
684 | if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, BBToCheck)) | ||||
685 | return false; | ||||
686 | // We do not unswitch a block that only has an unreachable statement, as | ||||
687 | // it's possible this is a previously unswitched block. Only unswitch if | ||||
688 | // either the terminator is not unreachable, or, if it is, it's not the only | ||||
689 | // instruction in the block. | ||||
690 | auto *TI = BBToCheck.getTerminator(); | ||||
691 | bool isUnreachable = isa<UnreachableInst>(TI); | ||||
692 | return !isUnreachable || | ||||
693 | (isUnreachable && (BBToCheck.getFirstNonPHIOrDbg() != TI)); | ||||
694 | }; | ||||
695 | |||||
696 | SmallVector<int, 4> ExitCaseIndices; | ||||
697 | for (auto Case : SI.cases()) | ||||
698 | if (IsTriviallyUnswitchableExitBlock(*Case.getCaseSuccessor())) | ||||
699 | ExitCaseIndices.push_back(Case.getCaseIndex()); | ||||
700 | BasicBlock *DefaultExitBB = nullptr; | ||||
701 | SwitchInstProfUpdateWrapper::CaseWeightOpt DefaultCaseWeight = | ||||
702 | SwitchInstProfUpdateWrapper::getSuccessorWeight(SI, 0); | ||||
703 | if (IsTriviallyUnswitchableExitBlock(*SI.getDefaultDest())) { | ||||
704 | DefaultExitBB = SI.getDefaultDest(); | ||||
705 | } else if (ExitCaseIndices.empty()) | ||||
706 | return false; | ||||
707 | |||||
708 | LLVM_DEBUG(dbgs() << " unswitching trivial switch...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " unswitching trivial switch...\n" ; } } while (false); | ||||
709 | |||||
710 | if (MSSAU && VerifyMemorySSA) | ||||
711 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
712 | |||||
713 | // We may need to invalidate SCEVs for the outermost loop reached by any of | ||||
714 | // the exits. | ||||
715 | Loop *OuterL = &L; | ||||
716 | |||||
717 | if (DefaultExitBB) { | ||||
718 | // Clear out the default destination temporarily to allow accurate | ||||
719 | // predecessor lists to be examined below. | ||||
720 | SI.setDefaultDest(nullptr); | ||||
721 | // Check the loop containing this exit. | ||||
722 | Loop *ExitL = LI.getLoopFor(DefaultExitBB); | ||||
723 | if (!ExitL || ExitL->contains(OuterL)) | ||||
724 | OuterL = ExitL; | ||||
725 | } | ||||
726 | |||||
727 | // Store the exit cases into a separate data structure and remove them from | ||||
728 | // the switch. | ||||
729 | SmallVector<std::tuple<ConstantInt *, BasicBlock *, | ||||
730 | SwitchInstProfUpdateWrapper::CaseWeightOpt>, | ||||
731 | 4> ExitCases; | ||||
732 | ExitCases.reserve(ExitCaseIndices.size()); | ||||
733 | SwitchInstProfUpdateWrapper SIW(SI); | ||||
734 | // We walk the case indices backwards so that we remove the last case first | ||||
735 | // and don't disrupt the earlier indices. | ||||
736 | for (unsigned Index : reverse(ExitCaseIndices)) { | ||||
737 | auto CaseI = SI.case_begin() + Index; | ||||
738 | // Compute the outer loop from this exit. | ||||
739 | Loop *ExitL = LI.getLoopFor(CaseI->getCaseSuccessor()); | ||||
740 | if (!ExitL || ExitL->contains(OuterL)) | ||||
741 | OuterL = ExitL; | ||||
742 | // Save the value of this case. | ||||
743 | auto W = SIW.getSuccessorWeight(CaseI->getSuccessorIndex()); | ||||
744 | ExitCases.emplace_back(CaseI->getCaseValue(), CaseI->getCaseSuccessor(), W); | ||||
745 | // Delete the unswitched cases. | ||||
746 | SIW.removeCase(CaseI); | ||||
747 | } | ||||
748 | |||||
749 | if (SE) { | ||||
750 | if (OuterL) | ||||
751 | SE->forgetLoop(OuterL); | ||||
752 | else | ||||
753 | SE->forgetTopmostLoop(&L); | ||||
754 | } | ||||
755 | |||||
756 | // Check if after this all of the remaining cases point at the same | ||||
757 | // successor. | ||||
758 | BasicBlock *CommonSuccBB = nullptr; | ||||
759 | if (SI.getNumCases() > 0 && | ||||
760 | all_of(drop_begin(SI.cases()), [&SI](const SwitchInst::CaseHandle &Case) { | ||||
761 | return Case.getCaseSuccessor() == SI.case_begin()->getCaseSuccessor(); | ||||
762 | })) | ||||
763 | CommonSuccBB = SI.case_begin()->getCaseSuccessor(); | ||||
764 | if (!DefaultExitBB) { | ||||
765 | // If we're not unswitching the default, we need it to match any cases to | ||||
766 | // have a common successor or if we have no cases it is the common | ||||
767 | // successor. | ||||
768 | if (SI.getNumCases() == 0) | ||||
769 | CommonSuccBB = SI.getDefaultDest(); | ||||
770 | else if (SI.getDefaultDest() != CommonSuccBB) | ||||
771 | CommonSuccBB = nullptr; | ||||
772 | } | ||||
773 | |||||
774 | // Split the preheader, so that we know that there is a safe place to insert | ||||
775 | // the switch. | ||||
776 | BasicBlock *OldPH = L.getLoopPreheader(); | ||||
777 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI, MSSAU); | ||||
778 | OldPH->getTerminator()->eraseFromParent(); | ||||
779 | |||||
780 | // Now add the unswitched switch. | ||||
781 | auto *NewSI = SwitchInst::Create(LoopCond, NewPH, ExitCases.size(), OldPH); | ||||
782 | SwitchInstProfUpdateWrapper NewSIW(*NewSI); | ||||
783 | |||||
784 | // Rewrite the IR for the unswitched basic blocks. This requires two steps. | ||||
785 | // First, we split any exit blocks with remaining in-loop predecessors. Then | ||||
786 | // we update the PHIs in one of two ways depending on if there was a split. | ||||
787 | // We walk in reverse so that we split in the same order as the cases | ||||
788 | // appeared. This is purely for convenience of reading the resulting IR, but | ||||
789 | // it doesn't cost anything really. | ||||
790 | SmallPtrSet<BasicBlock *, 2> UnswitchedExitBBs; | ||||
791 | SmallDenseMap<BasicBlock *, BasicBlock *, 2> SplitExitBBMap; | ||||
792 | // Handle the default exit if necessary. | ||||
793 | // FIXME: It'd be great if we could merge this with the loop below but LLVM's | ||||
794 | // ranges aren't quite powerful enough yet. | ||||
795 | if (DefaultExitBB) { | ||||
796 | if (pred_empty(DefaultExitBB)) { | ||||
797 | UnswitchedExitBBs.insert(DefaultExitBB); | ||||
798 | rewritePHINodesForUnswitchedExitBlock(*DefaultExitBB, *ParentBB, *OldPH); | ||||
799 | } else { | ||||
800 | auto *SplitBB = | ||||
801 | SplitBlock(DefaultExitBB, &DefaultExitBB->front(), &DT, &LI, MSSAU); | ||||
802 | rewritePHINodesForExitAndUnswitchedBlocks(*DefaultExitBB, *SplitBB, | ||||
803 | *ParentBB, *OldPH, | ||||
804 | /*FullUnswitch*/ true); | ||||
805 | DefaultExitBB = SplitExitBBMap[DefaultExitBB] = SplitBB; | ||||
806 | } | ||||
807 | } | ||||
808 | // Note that we must use a reference in the for loop so that we update the | ||||
809 | // container. | ||||
810 | for (auto &ExitCase : reverse(ExitCases)) { | ||||
811 | // Grab a reference to the exit block in the pair so that we can update it. | ||||
812 | BasicBlock *ExitBB = std::get<1>(ExitCase); | ||||
813 | |||||
814 | // If this case is the last edge into the exit block, we can simply reuse it | ||||
815 | // as it will no longer be a loop exit. No mapping necessary. | ||||
816 | if (pred_empty(ExitBB)) { | ||||
817 | // Only rewrite once. | ||||
818 | if (UnswitchedExitBBs.insert(ExitBB).second) | ||||
819 | rewritePHINodesForUnswitchedExitBlock(*ExitBB, *ParentBB, *OldPH); | ||||
820 | continue; | ||||
821 | } | ||||
822 | |||||
823 | // Otherwise we need to split the exit block so that we retain an exit | ||||
824 | // block from the loop and a target for the unswitched condition. | ||||
825 | BasicBlock *&SplitExitBB = SplitExitBBMap[ExitBB]; | ||||
826 | if (!SplitExitBB) { | ||||
827 | // If this is the first time we see this, do the split and remember it. | ||||
828 | SplitExitBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI, MSSAU); | ||||
829 | rewritePHINodesForExitAndUnswitchedBlocks(*ExitBB, *SplitExitBB, | ||||
830 | *ParentBB, *OldPH, | ||||
831 | /*FullUnswitch*/ true); | ||||
832 | } | ||||
833 | // Update the case pair to point to the split block. | ||||
834 | std::get<1>(ExitCase) = SplitExitBB; | ||||
835 | } | ||||
836 | |||||
837 | // Now add the unswitched cases. We do this in reverse order as we built them | ||||
838 | // in reverse order. | ||||
839 | for (auto &ExitCase : reverse(ExitCases)) { | ||||
840 | ConstantInt *CaseVal = std::get<0>(ExitCase); | ||||
841 | BasicBlock *UnswitchedBB = std::get<1>(ExitCase); | ||||
842 | |||||
843 | NewSIW.addCase(CaseVal, UnswitchedBB, std::get<2>(ExitCase)); | ||||
844 | } | ||||
845 | |||||
846 | // If the default was unswitched, re-point it and add explicit cases for | ||||
847 | // entering the loop. | ||||
848 | if (DefaultExitBB) { | ||||
849 | NewSIW->setDefaultDest(DefaultExitBB); | ||||
850 | NewSIW.setSuccessorWeight(0, DefaultCaseWeight); | ||||
851 | |||||
852 | // We removed all the exit cases, so we just copy the cases to the | ||||
853 | // unswitched switch. | ||||
854 | for (const auto &Case : SI.cases()) | ||||
855 | NewSIW.addCase(Case.getCaseValue(), NewPH, | ||||
856 | SIW.getSuccessorWeight(Case.getSuccessorIndex())); | ||||
857 | } else if (DefaultCaseWeight) { | ||||
858 | // We have to set branch weight of the default case. | ||||
859 | uint64_t SW = *DefaultCaseWeight; | ||||
860 | for (const auto &Case : SI.cases()) { | ||||
861 | auto W = SIW.getSuccessorWeight(Case.getSuccessorIndex()); | ||||
862 | 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\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 863, __extension__ __PRETTY_FUNCTION__)) | ||||
863 | "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\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 863, __extension__ __PRETTY_FUNCTION__)); | ||||
864 | SW += *W; | ||||
865 | } | ||||
866 | NewSIW.setSuccessorWeight(0, SW); | ||||
867 | } | ||||
868 | |||||
869 | // If we ended up with a common successor for every path through the switch | ||||
870 | // after unswitching, rewrite it to an unconditional branch to make it easy | ||||
871 | // to recognize. Otherwise we potentially have to recognize the default case | ||||
872 | // pointing at unreachable and other complexity. | ||||
873 | if (CommonSuccBB) { | ||||
874 | BasicBlock *BB = SI.getParent(); | ||||
875 | // We may have had multiple edges to this common successor block, so remove | ||||
876 | // them as predecessors. We skip the first one, either the default or the | ||||
877 | // actual first case. | ||||
878 | bool SkippedFirst = DefaultExitBB == nullptr; | ||||
879 | for (auto Case : SI.cases()) { | ||||
880 | assert(Case.getCaseSuccessor() == CommonSuccBB &&(static_cast <bool> (Case.getCaseSuccessor() == CommonSuccBB && "Non-common successor!") ? void (0) : __assert_fail ("Case.getCaseSuccessor() == CommonSuccBB && \"Non-common successor!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 881, __extension__ __PRETTY_FUNCTION__)) | ||||
881 | "Non-common successor!")(static_cast <bool> (Case.getCaseSuccessor() == CommonSuccBB && "Non-common successor!") ? void (0) : __assert_fail ("Case.getCaseSuccessor() == CommonSuccBB && \"Non-common successor!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 881, __extension__ __PRETTY_FUNCTION__)); | ||||
882 | (void)Case; | ||||
883 | if (!SkippedFirst) { | ||||
884 | SkippedFirst = true; | ||||
885 | continue; | ||||
886 | } | ||||
887 | CommonSuccBB->removePredecessor(BB, | ||||
888 | /*KeepOneInputPHIs*/ true); | ||||
889 | } | ||||
890 | // Now nuke the switch and replace it with a direct branch. | ||||
891 | SIW.eraseFromParent(); | ||||
892 | BranchInst::Create(CommonSuccBB, BB); | ||||
893 | } else if (DefaultExitBB) { | ||||
894 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 895, __extension__ __PRETTY_FUNCTION__)) | ||||
895 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 895, __extension__ __PRETTY_FUNCTION__)); | ||||
896 | // Move the last case to the default successor. This is valid as if the | ||||
897 | // default got unswitched it cannot be reached. This has the advantage of | ||||
898 | // being simple and keeping the number of edges from this switch to | ||||
899 | // successors the same, and avoiding any PHI update complexity. | ||||
900 | auto LastCaseI = std::prev(SI.case_end()); | ||||
901 | |||||
902 | SI.setDefaultDest(LastCaseI->getCaseSuccessor()); | ||||
903 | SIW.setSuccessorWeight( | ||||
904 | 0, SIW.getSuccessorWeight(LastCaseI->getSuccessorIndex())); | ||||
905 | SIW.removeCase(LastCaseI); | ||||
906 | } | ||||
907 | |||||
908 | // Walk the unswitched exit blocks and the unswitched split blocks and update | ||||
909 | // the dominator tree based on the CFG edits. While we are walking unordered | ||||
910 | // containers here, the API for applyUpdates takes an unordered list of | ||||
911 | // updates and requires them to not contain duplicates. | ||||
912 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | ||||
913 | for (auto *UnswitchedExitBB : UnswitchedExitBBs) { | ||||
914 | DTUpdates.push_back({DT.Delete, ParentBB, UnswitchedExitBB}); | ||||
915 | DTUpdates.push_back({DT.Insert, OldPH, UnswitchedExitBB}); | ||||
916 | } | ||||
917 | for (auto SplitUnswitchedPair : SplitExitBBMap) { | ||||
918 | DTUpdates.push_back({DT.Delete, ParentBB, SplitUnswitchedPair.first}); | ||||
919 | DTUpdates.push_back({DT.Insert, OldPH, SplitUnswitchedPair.second}); | ||||
920 | } | ||||
921 | |||||
922 | if (MSSAU) { | ||||
923 | MSSAU->applyUpdates(DTUpdates, DT, /*UpdateDT=*/true); | ||||
924 | if (VerifyMemorySSA) | ||||
925 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
926 | } else { | ||||
927 | DT.applyUpdates(DTUpdates); | ||||
928 | } | ||||
929 | |||||
930 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 930, __extension__ __PRETTY_FUNCTION__)); | ||||
931 | |||||
932 | // We may have changed the nesting relationship for this loop so hoist it to | ||||
933 | // its correct parent if needed. | ||||
934 | hoistLoopToNewParent(L, *NewPH, DT, LI, MSSAU, SE); | ||||
935 | |||||
936 | if (MSSAU && VerifyMemorySSA) | ||||
937 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
938 | |||||
939 | ++NumTrivial; | ||||
940 | ++NumSwitches; | ||||
941 | 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); | ||||
942 | return true; | ||||
943 | } | ||||
944 | |||||
945 | /// This routine scans the loop to find a branch or switch which occurs before | ||||
946 | /// any side effects occur. These can potentially be unswitched without | ||||
947 | /// duplicating the loop. If a branch or switch is successfully unswitched the | ||||
948 | /// scanning continues to see if subsequent branches or switches have become | ||||
949 | /// trivial. Once all trivial candidates have been unswitched, this routine | ||||
950 | /// returns. | ||||
951 | /// | ||||
952 | /// The return value indicates whether anything was unswitched (and therefore | ||||
953 | /// changed). | ||||
954 | /// | ||||
955 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | ||||
956 | /// invalidated by this. | ||||
957 | static bool unswitchAllTrivialConditions(Loop &L, DominatorTree &DT, | ||||
958 | LoopInfo &LI, ScalarEvolution *SE, | ||||
959 | MemorySSAUpdater *MSSAU) { | ||||
960 | bool Changed = false; | ||||
961 | |||||
962 | // If loop header has only one reachable successor we should keep looking for | ||||
963 | // trivial condition candidates in the successor as well. An alternative is | ||||
964 | // to constant fold conditions and merge successors into loop header (then we | ||||
965 | // only need to check header's terminator). The reason for not doing this in | ||||
966 | // LoopUnswitch pass is that it could potentially break LoopPassManager's | ||||
967 | // invariants. Folding dead branches could either eliminate the current loop | ||||
968 | // or make other loops unreachable. LCSSA form might also not be preserved | ||||
969 | // after deleting branches. The following code keeps traversing loop header's | ||||
970 | // successors until it finds the trivial condition candidate (condition that | ||||
971 | // is not a constant). Since unswitching generates branches with constant | ||||
972 | // conditions, this scenario could be very common in practice. | ||||
973 | BasicBlock *CurrentBB = L.getHeader(); | ||||
974 | SmallPtrSet<BasicBlock *, 8> Visited; | ||||
975 | Visited.insert(CurrentBB); | ||||
976 | do { | ||||
977 | // Check if there are any side-effecting instructions (e.g. stores, calls, | ||||
978 | // volatile loads) in the part of the loop that the code *would* execute | ||||
979 | // without unswitching. | ||||
980 | if (MSSAU) // Possible early exit with MSSA | ||||
981 | if (auto *Defs = MSSAU->getMemorySSA()->getBlockDefs(CurrentBB)) | ||||
982 | if (!isa<MemoryPhi>(*Defs->begin()) || (++Defs->begin() != Defs->end())) | ||||
983 | return Changed; | ||||
984 | if (llvm::any_of(*CurrentBB, | ||||
985 | [](Instruction &I) { return I.mayHaveSideEffects(); })) | ||||
986 | return Changed; | ||||
987 | |||||
988 | Instruction *CurrentTerm = CurrentBB->getTerminator(); | ||||
989 | |||||
990 | if (auto *SI = dyn_cast<SwitchInst>(CurrentTerm)) { | ||||
991 | // Don't bother trying to unswitch past a switch with a constant | ||||
992 | // condition. This should be removed prior to running this pass by | ||||
993 | // simplifycfg. | ||||
994 | if (isa<Constant>(SI->getCondition())) | ||||
995 | return Changed; | ||||
996 | |||||
997 | if (!unswitchTrivialSwitch(L, *SI, DT, LI, SE, MSSAU)) | ||||
998 | // Couldn't unswitch this one so we're done. | ||||
999 | return Changed; | ||||
1000 | |||||
1001 | // Mark that we managed to unswitch something. | ||||
1002 | Changed = true; | ||||
1003 | |||||
1004 | // If unswitching turned the terminator into an unconditional branch then | ||||
1005 | // we can continue. The unswitching logic specifically works to fold any | ||||
1006 | // cases it can into an unconditional branch to make it easier to | ||||
1007 | // recognize here. | ||||
1008 | auto *BI = dyn_cast<BranchInst>(CurrentBB->getTerminator()); | ||||
1009 | if (!BI || BI->isConditional()) | ||||
1010 | return Changed; | ||||
1011 | |||||
1012 | CurrentBB = BI->getSuccessor(0); | ||||
1013 | continue; | ||||
1014 | } | ||||
1015 | |||||
1016 | auto *BI = dyn_cast<BranchInst>(CurrentTerm); | ||||
1017 | if (!BI) | ||||
1018 | // We do not understand other terminator instructions. | ||||
1019 | return Changed; | ||||
1020 | |||||
1021 | // Don't bother trying to unswitch past an unconditional branch or a branch | ||||
1022 | // with a constant value. These should be removed by simplifycfg prior to | ||||
1023 | // running this pass. | ||||
1024 | if (!BI->isConditional() || isa<Constant>(BI->getCondition())) | ||||
1025 | return Changed; | ||||
1026 | |||||
1027 | // Found a trivial condition candidate: non-foldable conditional branch. If | ||||
1028 | // we fail to unswitch this, we can't do anything else that is trivial. | ||||
1029 | if (!unswitchTrivialBranch(L, *BI, DT, LI, SE, MSSAU)) | ||||
1030 | return Changed; | ||||
1031 | |||||
1032 | // Mark that we managed to unswitch something. | ||||
1033 | Changed = true; | ||||
1034 | |||||
1035 | // If we only unswitched some of the conditions feeding the branch, we won't | ||||
1036 | // have collapsed it to a single successor. | ||||
1037 | BI = cast<BranchInst>(CurrentBB->getTerminator()); | ||||
1038 | if (BI->isConditional()) | ||||
1039 | return Changed; | ||||
1040 | |||||
1041 | // Follow the newly unconditional branch into its successor. | ||||
1042 | CurrentBB = BI->getSuccessor(0); | ||||
1043 | |||||
1044 | // When continuing, if we exit the loop or reach a previous visited block, | ||||
1045 | // then we can not reach any trivial condition candidates (unfoldable | ||||
1046 | // branch instructions or switch instructions) and no unswitch can happen. | ||||
1047 | } while (L.contains(CurrentBB) && Visited.insert(CurrentBB).second); | ||||
1048 | |||||
1049 | return Changed; | ||||
1050 | } | ||||
1051 | |||||
1052 | /// Build the cloned blocks for an unswitched copy of the given loop. | ||||
1053 | /// | ||||
1054 | /// The cloned blocks are inserted before the loop preheader (`LoopPH`) and | ||||
1055 | /// after the split block (`SplitBB`) that will be used to select between the | ||||
1056 | /// cloned and original loop. | ||||
1057 | /// | ||||
1058 | /// This routine handles cloning all of the necessary loop blocks and exit | ||||
1059 | /// blocks including rewriting their instructions and the relevant PHI nodes. | ||||
1060 | /// Any loop blocks or exit blocks which are dominated by a different successor | ||||
1061 | /// than the one for this clone of the loop blocks can be trivially skipped. We | ||||
1062 | /// use the `DominatingSucc` map to determine whether a block satisfies that | ||||
1063 | /// property with a simple map lookup. | ||||
1064 | /// | ||||
1065 | /// It also correctly creates the unconditional branch in the cloned | ||||
1066 | /// unswitched parent block to only point at the unswitched successor. | ||||
1067 | /// | ||||
1068 | /// This does not handle most of the necessary updates to `LoopInfo`. Only exit | ||||
1069 | /// block splitting is correctly reflected in `LoopInfo`, essentially all of | ||||
1070 | /// the cloned blocks (and their loops) are left without full `LoopInfo` | ||||
1071 | /// updates. This also doesn't fully update `DominatorTree`. It adds the cloned | ||||
1072 | /// blocks to them but doesn't create the cloned `DominatorTree` structure and | ||||
1073 | /// instead the caller must recompute an accurate DT. It *does* correctly | ||||
1074 | /// update the `AssumptionCache` provided in `AC`. | ||||
1075 | static BasicBlock *buildClonedLoopBlocks( | ||||
1076 | Loop &L, BasicBlock *LoopPH, BasicBlock *SplitBB, | ||||
1077 | ArrayRef<BasicBlock *> ExitBlocks, BasicBlock *ParentBB, | ||||
1078 | BasicBlock *UnswitchedSuccBB, BasicBlock *ContinueSuccBB, | ||||
1079 | const SmallDenseMap<BasicBlock *, BasicBlock *, 16> &DominatingSucc, | ||||
1080 | ValueToValueMapTy &VMap, | ||||
1081 | SmallVectorImpl<DominatorTree::UpdateType> &DTUpdates, AssumptionCache &AC, | ||||
1082 | DominatorTree &DT, LoopInfo &LI, MemorySSAUpdater *MSSAU) { | ||||
1083 | SmallVector<BasicBlock *, 4> NewBlocks; | ||||
1084 | NewBlocks.reserve(L.getNumBlocks() + ExitBlocks.size()); | ||||
1085 | |||||
1086 | // We will need to clone a bunch of blocks, wrap up the clone operation in | ||||
1087 | // a helper. | ||||
1088 | auto CloneBlock = [&](BasicBlock *OldBB) { | ||||
1089 | // Clone the basic block and insert it before the new preheader. | ||||
1090 | BasicBlock *NewBB = CloneBasicBlock(OldBB, VMap, ".us", OldBB->getParent()); | ||||
1091 | NewBB->moveBefore(LoopPH); | ||||
1092 | |||||
1093 | // Record this block and the mapping. | ||||
1094 | NewBlocks.push_back(NewBB); | ||||
1095 | VMap[OldBB] = NewBB; | ||||
1096 | |||||
1097 | return NewBB; | ||||
1098 | }; | ||||
1099 | |||||
1100 | // We skip cloning blocks when they have a dominating succ that is not the | ||||
1101 | // succ we are cloning for. | ||||
1102 | auto SkipBlock = [&](BasicBlock *BB) { | ||||
1103 | auto It = DominatingSucc.find(BB); | ||||
1104 | return It != DominatingSucc.end() && It->second != UnswitchedSuccBB; | ||||
1105 | }; | ||||
1106 | |||||
1107 | // First, clone the preheader. | ||||
1108 | auto *ClonedPH = CloneBlock(LoopPH); | ||||
1109 | |||||
1110 | // Then clone all the loop blocks, skipping the ones that aren't necessary. | ||||
1111 | for (auto *LoopBB : L.blocks()) | ||||
1112 | if (!SkipBlock(LoopBB)) | ||||
1113 | CloneBlock(LoopBB); | ||||
1114 | |||||
1115 | // Split all the loop exit edges so that when we clone the exit blocks, if | ||||
1116 | // any of the exit blocks are *also* a preheader for some other loop, we | ||||
1117 | // don't create multiple predecessors entering the loop header. | ||||
1118 | for (auto *ExitBB : ExitBlocks) { | ||||
1119 | if (SkipBlock(ExitBB)) | ||||
1120 | continue; | ||||
1121 | |||||
1122 | // When we are going to clone an exit, we don't need to clone all the | ||||
1123 | // instructions in the exit block and we want to ensure we have an easy | ||||
1124 | // place to merge the CFG, so split the exit first. This is always safe to | ||||
1125 | // do because there cannot be any non-loop predecessors of a loop exit in | ||||
1126 | // loop simplified form. | ||||
1127 | auto *MergeBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI, MSSAU); | ||||
1128 | |||||
1129 | // Rearrange the names to make it easier to write test cases by having the | ||||
1130 | // exit block carry the suffix rather than the merge block carrying the | ||||
1131 | // suffix. | ||||
1132 | MergeBB->takeName(ExitBB); | ||||
1133 | ExitBB->setName(Twine(MergeBB->getName()) + ".split"); | ||||
1134 | |||||
1135 | // Now clone the original exit block. | ||||
1136 | auto *ClonedExitBB = CloneBlock(ExitBB); | ||||
1137 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1138, __extension__ __PRETTY_FUNCTION__)) | ||||
1138 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1138, __extension__ __PRETTY_FUNCTION__)); | ||||
1139 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1140, __extension__ __PRETTY_FUNCTION__)) | ||||
1140 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1140, __extension__ __PRETTY_FUNCTION__)); | ||||
1141 | |||||
1142 | // Remap any cloned instructions and create a merge phi node for them. | ||||
1143 | for (auto ZippedInsts : llvm::zip_first( | ||||
1144 | llvm::make_range(ExitBB->begin(), std::prev(ExitBB->end())), | ||||
1145 | llvm::make_range(ClonedExitBB->begin(), | ||||
1146 | std::prev(ClonedExitBB->end())))) { | ||||
1147 | Instruction &I = std::get<0>(ZippedInsts); | ||||
1148 | Instruction &ClonedI = std::get<1>(ZippedInsts); | ||||
1149 | |||||
1150 | // The only instructions in the exit block should be PHI nodes and | ||||
1151 | // potentially a landing pad. | ||||
1152 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1154, __extension__ __PRETTY_FUNCTION__)) | ||||
1153 | (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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1154, __extension__ __PRETTY_FUNCTION__)) | ||||
1154 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1154, __extension__ __PRETTY_FUNCTION__)); | ||||
1155 | // We should have a value map between the instruction and its clone. | ||||
1156 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1156, __extension__ __PRETTY_FUNCTION__)); | ||||
1157 | |||||
1158 | auto *MergePN = | ||||
1159 | PHINode::Create(I.getType(), /*NumReservedValues*/ 2, ".us-phi", | ||||
1160 | &*MergeBB->getFirstInsertionPt()); | ||||
1161 | I.replaceAllUsesWith(MergePN); | ||||
1162 | MergePN->addIncoming(&I, ExitBB); | ||||
1163 | MergePN->addIncoming(&ClonedI, ClonedExitBB); | ||||
1164 | } | ||||
1165 | } | ||||
1166 | |||||
1167 | // Rewrite the instructions in the cloned blocks to refer to the instructions | ||||
1168 | // in the cloned blocks. We have to do this as a second pass so that we have | ||||
1169 | // everything available. Also, we have inserted new instructions which may | ||||
1170 | // include assume intrinsics, so we update the assumption cache while | ||||
1171 | // processing this. | ||||
1172 | for (auto *ClonedBB : NewBlocks) | ||||
1173 | for (Instruction &I : *ClonedBB) { | ||||
1174 | RemapInstruction(&I, VMap, | ||||
1175 | RF_NoModuleLevelChanges | RF_IgnoreMissingLocals); | ||||
1176 | if (auto *II = dyn_cast<AssumeInst>(&I)) | ||||
1177 | AC.registerAssumption(II); | ||||
1178 | } | ||||
1179 | |||||
1180 | // Update any PHI nodes in the cloned successors of the skipped blocks to not | ||||
1181 | // have spurious incoming values. | ||||
1182 | for (auto *LoopBB : L.blocks()) | ||||
1183 | if (SkipBlock(LoopBB)) | ||||
1184 | for (auto *SuccBB : successors(LoopBB)) | ||||
1185 | if (auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB))) | ||||
1186 | for (PHINode &PN : ClonedSuccBB->phis()) | ||||
1187 | PN.removeIncomingValue(LoopBB, /*DeletePHIIfEmpty*/ false); | ||||
1188 | |||||
1189 | // Remove the cloned parent as a predecessor of any successor we ended up | ||||
1190 | // cloning other than the unswitched one. | ||||
1191 | auto *ClonedParentBB = cast<BasicBlock>(VMap.lookup(ParentBB)); | ||||
1192 | for (auto *SuccBB : successors(ParentBB)) { | ||||
1193 | if (SuccBB == UnswitchedSuccBB) | ||||
1194 | continue; | ||||
1195 | |||||
1196 | auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB)); | ||||
1197 | if (!ClonedSuccBB) | ||||
1198 | continue; | ||||
1199 | |||||
1200 | ClonedSuccBB->removePredecessor(ClonedParentBB, | ||||
1201 | /*KeepOneInputPHIs*/ true); | ||||
1202 | } | ||||
1203 | |||||
1204 | // Replace the cloned branch with an unconditional branch to the cloned | ||||
1205 | // unswitched successor. | ||||
1206 | auto *ClonedSuccBB = cast<BasicBlock>(VMap.lookup(UnswitchedSuccBB)); | ||||
1207 | Instruction *ClonedTerminator = ClonedParentBB->getTerminator(); | ||||
1208 | // Trivial Simplification. If Terminator is a conditional branch and | ||||
1209 | // condition becomes dead - erase it. | ||||
1210 | Value *ClonedConditionToErase = nullptr; | ||||
1211 | if (auto *BI = dyn_cast<BranchInst>(ClonedTerminator)) | ||||
1212 | ClonedConditionToErase = BI->getCondition(); | ||||
1213 | else if (auto *SI = dyn_cast<SwitchInst>(ClonedTerminator)) | ||||
1214 | ClonedConditionToErase = SI->getCondition(); | ||||
1215 | |||||
1216 | ClonedTerminator->eraseFromParent(); | ||||
1217 | BranchInst::Create(ClonedSuccBB, ClonedParentBB); | ||||
1218 | |||||
1219 | if (ClonedConditionToErase) | ||||
1220 | RecursivelyDeleteTriviallyDeadInstructions(ClonedConditionToErase, nullptr, | ||||
1221 | MSSAU); | ||||
1222 | |||||
1223 | // If there are duplicate entries in the PHI nodes because of multiple edges | ||||
1224 | // to the unswitched successor, we need to nuke all but one as we replaced it | ||||
1225 | // with a direct branch. | ||||
1226 | for (PHINode &PN : ClonedSuccBB->phis()) { | ||||
1227 | bool Found = false; | ||||
1228 | // Loop over the incoming operands backwards so we can easily delete as we | ||||
1229 | // go without invalidating the index. | ||||
1230 | for (int i = PN.getNumOperands() - 1; i >= 0; --i) { | ||||
1231 | if (PN.getIncomingBlock(i) != ClonedParentBB) | ||||
1232 | continue; | ||||
1233 | if (!Found) { | ||||
1234 | Found = true; | ||||
1235 | continue; | ||||
1236 | } | ||||
1237 | PN.removeIncomingValue(i, /*DeletePHIIfEmpty*/ false); | ||||
1238 | } | ||||
1239 | } | ||||
1240 | |||||
1241 | // Record the domtree updates for the new blocks. | ||||
1242 | SmallPtrSet<BasicBlock *, 4> SuccSet; | ||||
1243 | for (auto *ClonedBB : NewBlocks) { | ||||
1244 | for (auto *SuccBB : successors(ClonedBB)) | ||||
1245 | if (SuccSet.insert(SuccBB).second) | ||||
1246 | DTUpdates.push_back({DominatorTree::Insert, ClonedBB, SuccBB}); | ||||
1247 | SuccSet.clear(); | ||||
1248 | } | ||||
1249 | |||||
1250 | return ClonedPH; | ||||
1251 | } | ||||
1252 | |||||
1253 | /// Recursively clone the specified loop and all of its children. | ||||
1254 | /// | ||||
1255 | /// The target parent loop for the clone should be provided, or can be null if | ||||
1256 | /// the clone is a top-level loop. While cloning, all the blocks are mapped | ||||
1257 | /// with the provided value map. The entire original loop must be present in | ||||
1258 | /// the value map. The cloned loop is returned. | ||||
1259 | static Loop *cloneLoopNest(Loop &OrigRootL, Loop *RootParentL, | ||||
1260 | const ValueToValueMapTy &VMap, LoopInfo &LI) { | ||||
1261 | auto AddClonedBlocksToLoop = [&](Loop &OrigL, Loop &ClonedL) { | ||||
1262 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1262, __extension__ __PRETTY_FUNCTION__)); | ||||
1263 | ClonedL.reserveBlocks(OrigL.getNumBlocks()); | ||||
1264 | for (auto *BB : OrigL.blocks()) { | ||||
1265 | auto *ClonedBB = cast<BasicBlock>(VMap.lookup(BB)); | ||||
1266 | ClonedL.addBlockEntry(ClonedBB); | ||||
1267 | if (LI.getLoopFor(BB) == &OrigL) | ||||
1268 | LI.changeLoopFor(ClonedBB, &ClonedL); | ||||
1269 | } | ||||
1270 | }; | ||||
1271 | |||||
1272 | // We specially handle the first loop because it may get cloned into | ||||
1273 | // a different parent and because we most commonly are cloning leaf loops. | ||||
1274 | Loop *ClonedRootL = LI.AllocateLoop(); | ||||
1275 | if (RootParentL) | ||||
1276 | RootParentL->addChildLoop(ClonedRootL); | ||||
1277 | else | ||||
1278 | LI.addTopLevelLoop(ClonedRootL); | ||||
1279 | AddClonedBlocksToLoop(OrigRootL, *ClonedRootL); | ||||
1280 | |||||
1281 | if (OrigRootL.isInnermost()) | ||||
1282 | return ClonedRootL; | ||||
1283 | |||||
1284 | // If we have a nest, we can quickly clone the entire loop nest using an | ||||
1285 | // iterative approach because it is a tree. We keep the cloned parent in the | ||||
1286 | // data structure to avoid repeatedly querying through a map to find it. | ||||
1287 | SmallVector<std::pair<Loop *, Loop *>, 16> LoopsToClone; | ||||
1288 | // Build up the loops to clone in reverse order as we'll clone them from the | ||||
1289 | // back. | ||||
1290 | for (Loop *ChildL : llvm::reverse(OrigRootL)) | ||||
1291 | LoopsToClone.push_back({ClonedRootL, ChildL}); | ||||
1292 | do { | ||||
1293 | Loop *ClonedParentL, *L; | ||||
1294 | std::tie(ClonedParentL, L) = LoopsToClone.pop_back_val(); | ||||
1295 | Loop *ClonedL = LI.AllocateLoop(); | ||||
1296 | ClonedParentL->addChildLoop(ClonedL); | ||||
1297 | AddClonedBlocksToLoop(*L, *ClonedL); | ||||
1298 | for (Loop *ChildL : llvm::reverse(*L)) | ||||
1299 | LoopsToClone.push_back({ClonedL, ChildL}); | ||||
1300 | } while (!LoopsToClone.empty()); | ||||
1301 | |||||
1302 | return ClonedRootL; | ||||
1303 | } | ||||
1304 | |||||
1305 | /// Build the cloned loops of an original loop from unswitching. | ||||
1306 | /// | ||||
1307 | /// Because unswitching simplifies the CFG of the loop, this isn't a trivial | ||||
1308 | /// operation. We need to re-verify that there even is a loop (as the backedge | ||||
1309 | /// may not have been cloned), and even if there are remaining backedges the | ||||
1310 | /// backedge set may be different. However, we know that each child loop is | ||||
1311 | /// undisturbed, we only need to find where to place each child loop within | ||||
1312 | /// either any parent loop or within a cloned version of the original loop. | ||||
1313 | /// | ||||
1314 | /// Because child loops may end up cloned outside of any cloned version of the | ||||
1315 | /// original loop, multiple cloned sibling loops may be created. All of them | ||||
1316 | /// are returned so that the newly introduced loop nest roots can be | ||||
1317 | /// identified. | ||||
1318 | static void buildClonedLoops(Loop &OrigL, ArrayRef<BasicBlock *> ExitBlocks, | ||||
1319 | const ValueToValueMapTy &VMap, LoopInfo &LI, | ||||
1320 | SmallVectorImpl<Loop *> &NonChildClonedLoops) { | ||||
1321 | Loop *ClonedL = nullptr; | ||||
1322 | |||||
1323 | auto *OrigPH = OrigL.getLoopPreheader(); | ||||
1324 | auto *OrigHeader = OrigL.getHeader(); | ||||
1325 | |||||
1326 | auto *ClonedPH = cast<BasicBlock>(VMap.lookup(OrigPH)); | ||||
1327 | auto *ClonedHeader = cast<BasicBlock>(VMap.lookup(OrigHeader)); | ||||
1328 | |||||
1329 | // We need to know the loops of the cloned exit blocks to even compute the | ||||
1330 | // accurate parent loop. If we only clone exits to some parent of the | ||||
1331 | // original parent, we want to clone into that outer loop. We also keep track | ||||
1332 | // of the loops that our cloned exit blocks participate in. | ||||
1333 | Loop *ParentL = nullptr; | ||||
1334 | SmallVector<BasicBlock *, 4> ClonedExitsInLoops; | ||||
1335 | SmallDenseMap<BasicBlock *, Loop *, 16> ExitLoopMap; | ||||
1336 | ClonedExitsInLoops.reserve(ExitBlocks.size()); | ||||
1337 | for (auto *ExitBB : ExitBlocks) | ||||
1338 | if (auto *ClonedExitBB = cast_or_null<BasicBlock>(VMap.lookup(ExitBB))) | ||||
1339 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | ||||
1340 | ExitLoopMap[ClonedExitBB] = ExitL; | ||||
1341 | ClonedExitsInLoops.push_back(ClonedExitBB); | ||||
1342 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | ||||
1343 | ParentL = ExitL; | ||||
1344 | } | ||||
1345 | 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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1348, __extension__ __PRETTY_FUNCTION__)) | ||||
1346 | 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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1348, __extension__ __PRETTY_FUNCTION__)) | ||||
1347 | "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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1348, __extension__ __PRETTY_FUNCTION__)) | ||||
1348 | "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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1348, __extension__ __PRETTY_FUNCTION__)); | ||||
1349 | |||||
1350 | // We build the set of blocks dominated by the cloned header from the set of | ||||
1351 | // cloned blocks out of the original loop. While not all of these will | ||||
1352 | // necessarily be in the cloned loop, it is enough to establish that they | ||||
1353 | // aren't in unreachable cycles, etc. | ||||
1354 | SmallSetVector<BasicBlock *, 16> ClonedLoopBlocks; | ||||
1355 | for (auto *BB : OrigL.blocks()) | ||||
1356 | if (auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB))) | ||||
1357 | ClonedLoopBlocks.insert(ClonedBB); | ||||
1358 | |||||
1359 | // Rebuild the set of blocks that will end up in the cloned loop. We may have | ||||
1360 | // skipped cloning some region of this loop which can in turn skip some of | ||||
1361 | // the backedges so we have to rebuild the blocks in the loop based on the | ||||
1362 | // backedges that remain after cloning. | ||||
1363 | SmallVector<BasicBlock *, 16> Worklist; | ||||
1364 | SmallPtrSet<BasicBlock *, 16> BlocksInClonedLoop; | ||||
1365 | for (auto *Pred : predecessors(ClonedHeader)) { | ||||
1366 | // The only possible non-loop header predecessor is the preheader because | ||||
1367 | // we know we cloned the loop in simplified form. | ||||
1368 | if (Pred == ClonedPH) | ||||
1369 | continue; | ||||
1370 | |||||
1371 | // Because the loop was in simplified form, the only non-loop predecessor | ||||
1372 | // should be the preheader. | ||||
1373 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1375, __extension__ __PRETTY_FUNCTION__)) | ||||
1374 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1375, __extension__ __PRETTY_FUNCTION__)) | ||||
1375 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1375, __extension__ __PRETTY_FUNCTION__)); | ||||
1376 | |||||
1377 | // Insert this block into the loop set and on the first visit (and if it | ||||
1378 | // isn't the header we're currently walking) put it into the worklist to | ||||
1379 | // recurse through. | ||||
1380 | if (BlocksInClonedLoop.insert(Pred).second && Pred != ClonedHeader) | ||||
1381 | Worklist.push_back(Pred); | ||||
1382 | } | ||||
1383 | |||||
1384 | // If we had any backedges then there *is* a cloned loop. Put the header into | ||||
1385 | // the loop set and then walk the worklist backwards to find all the blocks | ||||
1386 | // that remain within the loop after cloning. | ||||
1387 | if (!BlocksInClonedLoop.empty()) { | ||||
1388 | BlocksInClonedLoop.insert(ClonedHeader); | ||||
1389 | |||||
1390 | while (!Worklist.empty()) { | ||||
1391 | BasicBlock *BB = Worklist.pop_back_val(); | ||||
1392 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1393, __extension__ __PRETTY_FUNCTION__)) | ||||
1393 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1393, __extension__ __PRETTY_FUNCTION__)); | ||||
1394 | |||||
1395 | // Insert any predecessors that are in the possible set into the cloned | ||||
1396 | // set, and if the insert is successful, add them to the worklist. Note | ||||
1397 | // that we filter on the blocks that are definitely reachable via the | ||||
1398 | // backedge to the loop header so we may prune out dead code within the | ||||
1399 | // cloned loop. | ||||
1400 | for (auto *Pred : predecessors(BB)) | ||||
1401 | if (ClonedLoopBlocks.count(Pred) && | ||||
1402 | BlocksInClonedLoop.insert(Pred).second) | ||||
1403 | Worklist.push_back(Pred); | ||||
1404 | } | ||||
1405 | |||||
1406 | ClonedL = LI.AllocateLoop(); | ||||
1407 | if (ParentL) { | ||||
1408 | ParentL->addBasicBlockToLoop(ClonedPH, LI); | ||||
1409 | ParentL->addChildLoop(ClonedL); | ||||
1410 | } else { | ||||
1411 | LI.addTopLevelLoop(ClonedL); | ||||
1412 | } | ||||
1413 | NonChildClonedLoops.push_back(ClonedL); | ||||
1414 | |||||
1415 | ClonedL->reserveBlocks(BlocksInClonedLoop.size()); | ||||
1416 | // We don't want to just add the cloned loop blocks based on how we | ||||
1417 | // discovered them. The original order of blocks was carefully built in | ||||
1418 | // a way that doesn't rely on predecessor ordering. Rather than re-invent | ||||
1419 | // that logic, we just re-walk the original blocks (and those of the child | ||||
1420 | // loops) and filter them as we add them into the cloned loop. | ||||
1421 | for (auto *BB : OrigL.blocks()) { | ||||
1422 | auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB)); | ||||
1423 | if (!ClonedBB || !BlocksInClonedLoop.count(ClonedBB)) | ||||
1424 | continue; | ||||
1425 | |||||
1426 | // Directly add the blocks that are only in this loop. | ||||
1427 | if (LI.getLoopFor(BB) == &OrigL) { | ||||
1428 | ClonedL->addBasicBlockToLoop(ClonedBB, LI); | ||||
1429 | continue; | ||||
1430 | } | ||||
1431 | |||||
1432 | // We want to manually add it to this loop and parents. | ||||
1433 | // Registering it with LoopInfo will happen when we clone the top | ||||
1434 | // loop for this block. | ||||
1435 | for (Loop *PL = ClonedL; PL; PL = PL->getParentLoop()) | ||||
1436 | PL->addBlockEntry(ClonedBB); | ||||
1437 | } | ||||
1438 | |||||
1439 | // Now add each child loop whose header remains within the cloned loop. All | ||||
1440 | // of the blocks within the loop must satisfy the same constraints as the | ||||
1441 | // header so once we pass the header checks we can just clone the entire | ||||
1442 | // child loop nest. | ||||
1443 | for (Loop *ChildL : OrigL) { | ||||
1444 | auto *ClonedChildHeader = | ||||
1445 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | ||||
1446 | if (!ClonedChildHeader || !BlocksInClonedLoop.count(ClonedChildHeader)) | ||||
1447 | continue; | ||||
1448 | |||||
1449 | #ifndef NDEBUG | ||||
1450 | // We should never have a cloned child loop header but fail to have | ||||
1451 | // all of the blocks for that child loop. | ||||
1452 | for (auto *ChildLoopBB : ChildL->blocks()) | ||||
1453 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1456, __extension__ __PRETTY_FUNCTION__)) | ||||
1454 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1456, __extension__ __PRETTY_FUNCTION__)) | ||||
1455 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1456, __extension__ __PRETTY_FUNCTION__)) | ||||
1456 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1456, __extension__ __PRETTY_FUNCTION__)); | ||||
1457 | #endif | ||||
1458 | |||||
1459 | cloneLoopNest(*ChildL, ClonedL, VMap, LI); | ||||
1460 | } | ||||
1461 | } | ||||
1462 | |||||
1463 | // Now that we've handled all the components of the original loop that were | ||||
1464 | // cloned into a new loop, we still need to handle anything from the original | ||||
1465 | // loop that wasn't in a cloned loop. | ||||
1466 | |||||
1467 | // Figure out what blocks are left to place within any loop nest containing | ||||
1468 | // the unswitched loop. If we never formed a loop, the cloned PH is one of | ||||
1469 | // them. | ||||
1470 | SmallPtrSet<BasicBlock *, 16> UnloopedBlockSet; | ||||
1471 | if (BlocksInClonedLoop.empty()) | ||||
1472 | UnloopedBlockSet.insert(ClonedPH); | ||||
1473 | for (auto *ClonedBB : ClonedLoopBlocks) | ||||
1474 | if (!BlocksInClonedLoop.count(ClonedBB)) | ||||
1475 | UnloopedBlockSet.insert(ClonedBB); | ||||
1476 | |||||
1477 | // Copy the cloned exits and sort them in ascending loop depth, we'll work | ||||
1478 | // backwards across these to process them inside out. The order shouldn't | ||||
1479 | // matter as we're just trying to build up the map from inside-out; we use | ||||
1480 | // the map in a more stably ordered way below. | ||||
1481 | auto OrderedClonedExitsInLoops = ClonedExitsInLoops; | ||||
1482 | llvm::sort(OrderedClonedExitsInLoops, [&](BasicBlock *LHS, BasicBlock *RHS) { | ||||
1483 | return ExitLoopMap.lookup(LHS)->getLoopDepth() < | ||||
1484 | ExitLoopMap.lookup(RHS)->getLoopDepth(); | ||||
1485 | }); | ||||
1486 | |||||
1487 | // Populate the existing ExitLoopMap with everything reachable from each | ||||
1488 | // exit, starting from the inner most exit. | ||||
1489 | while (!UnloopedBlockSet.empty() && !OrderedClonedExitsInLoops.empty()) { | ||||
1490 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1490, __extension__ __PRETTY_FUNCTION__)); | ||||
1491 | |||||
1492 | BasicBlock *ExitBB = OrderedClonedExitsInLoops.pop_back_val(); | ||||
1493 | Loop *ExitL = ExitLoopMap.lookup(ExitBB); | ||||
1494 | |||||
1495 | // Walk the CFG back until we hit the cloned PH adding everything reachable | ||||
1496 | // and in the unlooped set to this exit block's loop. | ||||
1497 | Worklist.push_back(ExitBB); | ||||
1498 | do { | ||||
1499 | BasicBlock *BB = Worklist.pop_back_val(); | ||||
1500 | // We can stop recursing at the cloned preheader (if we get there). | ||||
1501 | if (BB == ClonedPH) | ||||
1502 | continue; | ||||
1503 | |||||
1504 | for (BasicBlock *PredBB : predecessors(BB)) { | ||||
1505 | // If this pred has already been moved to our set or is part of some | ||||
1506 | // (inner) loop, no update needed. | ||||
1507 | if (!UnloopedBlockSet.erase(PredBB)) { | ||||
1508 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1510, __extension__ __PRETTY_FUNCTION__)) | ||||
1509 | (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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1510, __extension__ __PRETTY_FUNCTION__)) | ||||
1510 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1510, __extension__ __PRETTY_FUNCTION__)); | ||||
1511 | continue; | ||||
1512 | } | ||||
1513 | |||||
1514 | // We just insert into the loop set here. We'll add these blocks to the | ||||
1515 | // exit loop after we build up the set in an order that doesn't rely on | ||||
1516 | // predecessor order (which in turn relies on use list order). | ||||
1517 | bool Inserted = ExitLoopMap.insert({PredBB, ExitL}).second; | ||||
1518 | (void)Inserted; | ||||
1519 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1519, __extension__ __PRETTY_FUNCTION__)); | ||||
1520 | |||||
1521 | // And recurse through to its predecessors. | ||||
1522 | Worklist.push_back(PredBB); | ||||
1523 | } | ||||
1524 | } while (!Worklist.empty()); | ||||
1525 | } | ||||
1526 | |||||
1527 | // Now that the ExitLoopMap gives as mapping for all the non-looping cloned | ||||
1528 | // blocks to their outer loops, walk the cloned blocks and the cloned exits | ||||
1529 | // in their original order adding them to the correct loop. | ||||
1530 | |||||
1531 | // We need a stable insertion order. We use the order of the original loop | ||||
1532 | // order and map into the correct parent loop. | ||||
1533 | for (auto *BB : llvm::concat<BasicBlock *const>( | ||||
1534 | makeArrayRef(ClonedPH), ClonedLoopBlocks, ClonedExitsInLoops)) | ||||
1535 | if (Loop *OuterL = ExitLoopMap.lookup(BB)) | ||||
1536 | OuterL->addBasicBlockToLoop(BB, LI); | ||||
1537 | |||||
1538 | #ifndef NDEBUG | ||||
1539 | for (auto &BBAndL : ExitLoopMap) { | ||||
1540 | auto *BB = BBAndL.first; | ||||
1541 | auto *OuterL = BBAndL.second; | ||||
1542 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1543, __extension__ __PRETTY_FUNCTION__)) | ||||
1543 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1543, __extension__ __PRETTY_FUNCTION__)); | ||||
1544 | } | ||||
1545 | #endif | ||||
1546 | |||||
1547 | // Now that all the blocks are placed into the correct containing loop in the | ||||
1548 | // absence of child loops, find all the potentially cloned child loops and | ||||
1549 | // clone them into whatever outer loop we placed their header into. | ||||
1550 | for (Loop *ChildL : OrigL) { | ||||
1551 | auto *ClonedChildHeader = | ||||
1552 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | ||||
1553 | if (!ClonedChildHeader || BlocksInClonedLoop.count(ClonedChildHeader)) | ||||
1554 | continue; | ||||
1555 | |||||
1556 | #ifndef NDEBUG | ||||
1557 | for (auto *ChildLoopBB : ChildL->blocks()) | ||||
1558 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1559, __extension__ __PRETTY_FUNCTION__)) | ||||
1559 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1559, __extension__ __PRETTY_FUNCTION__)); | ||||
1560 | #endif | ||||
1561 | |||||
1562 | NonChildClonedLoops.push_back(cloneLoopNest( | ||||
1563 | *ChildL, ExitLoopMap.lookup(ClonedChildHeader), VMap, LI)); | ||||
1564 | } | ||||
1565 | } | ||||
1566 | |||||
1567 | static void | ||||
1568 | deleteDeadClonedBlocks(Loop &L, ArrayRef<BasicBlock *> ExitBlocks, | ||||
1569 | ArrayRef<std::unique_ptr<ValueToValueMapTy>> VMaps, | ||||
1570 | DominatorTree &DT, MemorySSAUpdater *MSSAU) { | ||||
1571 | // Find all the dead clones, and remove them from their successors. | ||||
1572 | SmallVector<BasicBlock *, 16> DeadBlocks; | ||||
1573 | for (BasicBlock *BB : llvm::concat<BasicBlock *const>(L.blocks(), ExitBlocks)) | ||||
1574 | for (auto &VMap : VMaps) | ||||
1575 | if (BasicBlock *ClonedBB = cast_or_null<BasicBlock>(VMap->lookup(BB))) | ||||
1576 | if (!DT.isReachableFromEntry(ClonedBB)) { | ||||
1577 | for (BasicBlock *SuccBB : successors(ClonedBB)) | ||||
1578 | SuccBB->removePredecessor(ClonedBB); | ||||
1579 | DeadBlocks.push_back(ClonedBB); | ||||
1580 | } | ||||
1581 | |||||
1582 | // Remove all MemorySSA in the dead blocks | ||||
1583 | if (MSSAU) { | ||||
1584 | SmallSetVector<BasicBlock *, 8> DeadBlockSet(DeadBlocks.begin(), | ||||
1585 | DeadBlocks.end()); | ||||
1586 | MSSAU->removeBlocks(DeadBlockSet); | ||||
1587 | } | ||||
1588 | |||||
1589 | // Drop any remaining references to break cycles. | ||||
1590 | for (BasicBlock *BB : DeadBlocks) | ||||
1591 | BB->dropAllReferences(); | ||||
1592 | // Erase them from the IR. | ||||
1593 | for (BasicBlock *BB : DeadBlocks) | ||||
1594 | BB->eraseFromParent(); | ||||
1595 | } | ||||
1596 | |||||
1597 | static void | ||||
1598 | deleteDeadBlocksFromLoop(Loop &L, | ||||
1599 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | ||||
1600 | DominatorTree &DT, LoopInfo &LI, | ||||
1601 | MemorySSAUpdater *MSSAU, | ||||
1602 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||
1603 | // Find all the dead blocks tied to this loop, and remove them from their | ||||
1604 | // successors. | ||||
1605 | SmallSetVector<BasicBlock *, 8> DeadBlockSet; | ||||
1606 | |||||
1607 | // Start with loop/exit blocks and get a transitive closure of reachable dead | ||||
1608 | // blocks. | ||||
1609 | SmallVector<BasicBlock *, 16> DeathCandidates(ExitBlocks.begin(), | ||||
1610 | ExitBlocks.end()); | ||||
1611 | DeathCandidates.append(L.blocks().begin(), L.blocks().end()); | ||||
1612 | while (!DeathCandidates.empty()) { | ||||
1613 | auto *BB = DeathCandidates.pop_back_val(); | ||||
1614 | if (!DeadBlockSet.count(BB) && !DT.isReachableFromEntry(BB)) { | ||||
1615 | for (BasicBlock *SuccBB : successors(BB)) { | ||||
1616 | SuccBB->removePredecessor(BB); | ||||
1617 | DeathCandidates.push_back(SuccBB); | ||||
1618 | } | ||||
1619 | DeadBlockSet.insert(BB); | ||||
1620 | } | ||||
1621 | } | ||||
1622 | |||||
1623 | // Remove all MemorySSA in the dead blocks | ||||
1624 | if (MSSAU) | ||||
1625 | MSSAU->removeBlocks(DeadBlockSet); | ||||
1626 | |||||
1627 | // Filter out the dead blocks from the exit blocks list so that it can be | ||||
1628 | // used in the caller. | ||||
1629 | llvm::erase_if(ExitBlocks, | ||||
1630 | [&](BasicBlock *BB) { return DeadBlockSet.count(BB); }); | ||||
1631 | |||||
1632 | // Walk from this loop up through its parents removing all of the dead blocks. | ||||
1633 | for (Loop *ParentL = &L; ParentL; ParentL = ParentL->getParentLoop()) { | ||||
1634 | for (auto *BB : DeadBlockSet) | ||||
1635 | ParentL->getBlocksSet().erase(BB); | ||||
1636 | llvm::erase_if(ParentL->getBlocksVector(), | ||||
1637 | [&](BasicBlock *BB) { return DeadBlockSet.count(BB); }); | ||||
1638 | } | ||||
1639 | |||||
1640 | // Now delete the dead child loops. This raw delete will clear them | ||||
1641 | // recursively. | ||||
1642 | llvm::erase_if(L.getSubLoopsVector(), [&](Loop *ChildL) { | ||||
1643 | if (!DeadBlockSet.count(ChildL->getHeader())) | ||||
1644 | return false; | ||||
1645 | |||||
1646 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1651, __extension__ __PRETTY_FUNCTION__)) | ||||
1647 | [&](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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1651, __extension__ __PRETTY_FUNCTION__)) | ||||
1648 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1651, __extension__ __PRETTY_FUNCTION__)) | ||||
1649 | }) &&(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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1651, __extension__ __PRETTY_FUNCTION__)) | ||||
1650 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1651, __extension__ __PRETTY_FUNCTION__)) | ||||
1651 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1651, __extension__ __PRETTY_FUNCTION__)); | ||||
1652 | DestroyLoopCB(*ChildL, ChildL->getName()); | ||||
1653 | LI.destroy(ChildL); | ||||
1654 | return true; | ||||
1655 | }); | ||||
1656 | |||||
1657 | // Remove the loop mappings for the dead blocks and drop all the references | ||||
1658 | // from these blocks to others to handle cyclic references as we start | ||||
1659 | // deleting the blocks themselves. | ||||
1660 | for (auto *BB : DeadBlockSet) { | ||||
1661 | // Check that the dominator tree has already been updated. | ||||
1662 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1662, __extension__ __PRETTY_FUNCTION__)); | ||||
1663 | LI.changeLoopFor(BB, nullptr); | ||||
1664 | // Drop all uses of the instructions to make sure we won't have dangling | ||||
1665 | // uses in other blocks. | ||||
1666 | for (auto &I : *BB) | ||||
1667 | if (!I.use_empty()) | ||||
1668 | I.replaceAllUsesWith(UndefValue::get(I.getType())); | ||||
1669 | BB->dropAllReferences(); | ||||
1670 | } | ||||
1671 | |||||
1672 | // Actually delete the blocks now that they've been fully unhooked from the | ||||
1673 | // IR. | ||||
1674 | for (auto *BB : DeadBlockSet) | ||||
1675 | BB->eraseFromParent(); | ||||
1676 | } | ||||
1677 | |||||
1678 | /// Recompute the set of blocks in a loop after unswitching. | ||||
1679 | /// | ||||
1680 | /// This walks from the original headers predecessors to rebuild the loop. We | ||||
1681 | /// take advantage of the fact that new blocks can't have been added, and so we | ||||
1682 | /// filter by the original loop's blocks. This also handles potentially | ||||
1683 | /// unreachable code that we don't want to explore but might be found examining | ||||
1684 | /// the predecessors of the header. | ||||
1685 | /// | ||||
1686 | /// If the original loop is no longer a loop, this will return an empty set. If | ||||
1687 | /// it remains a loop, all the blocks within it will be added to the set | ||||
1688 | /// (including those blocks in inner loops). | ||||
1689 | static SmallPtrSet<const BasicBlock *, 16> recomputeLoopBlockSet(Loop &L, | ||||
1690 | LoopInfo &LI) { | ||||
1691 | SmallPtrSet<const BasicBlock *, 16> LoopBlockSet; | ||||
1692 | |||||
1693 | auto *PH = L.getLoopPreheader(); | ||||
1694 | auto *Header = L.getHeader(); | ||||
1695 | |||||
1696 | // A worklist to use while walking backwards from the header. | ||||
1697 | SmallVector<BasicBlock *, 16> Worklist; | ||||
1698 | |||||
1699 | // First walk the predecessors of the header to find the backedges. This will | ||||
1700 | // form the basis of our walk. | ||||
1701 | for (auto *Pred : predecessors(Header)) { | ||||
1702 | // Skip the preheader. | ||||
1703 | if (Pred == PH) | ||||
1704 | continue; | ||||
1705 | |||||
1706 | // Because the loop was in simplified form, the only non-loop predecessor | ||||
1707 | // is the preheader. | ||||
1708 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1710, __extension__ __PRETTY_FUNCTION__)) | ||||
1709 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1710, __extension__ __PRETTY_FUNCTION__)) | ||||
1710 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1710, __extension__ __PRETTY_FUNCTION__)); | ||||
1711 | |||||
1712 | // Insert this block into the loop set and on the first visit and, if it | ||||
1713 | // isn't the header we're currently walking, put it into the worklist to | ||||
1714 | // recurse through. | ||||
1715 | if (LoopBlockSet.insert(Pred).second && Pred != Header) | ||||
1716 | Worklist.push_back(Pred); | ||||
1717 | } | ||||
1718 | |||||
1719 | // If no backedges were found, we're done. | ||||
1720 | if (LoopBlockSet.empty()) | ||||
1721 | return LoopBlockSet; | ||||
1722 | |||||
1723 | // We found backedges, recurse through them to identify the loop blocks. | ||||
1724 | while (!Worklist.empty()) { | ||||
1725 | BasicBlock *BB = Worklist.pop_back_val(); | ||||
1726 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1726, __extension__ __PRETTY_FUNCTION__)); | ||||
1727 | |||||
1728 | // No need to walk past the header. | ||||
1729 | if (BB == Header) | ||||
1730 | continue; | ||||
1731 | |||||
1732 | // Because we know the inner loop structure remains valid we can use the | ||||
1733 | // loop structure to jump immediately across the entire nested loop. | ||||
1734 | // Further, because it is in loop simplified form, we can directly jump | ||||
1735 | // to its preheader afterward. | ||||
1736 | if (Loop *InnerL = LI.getLoopFor(BB)) | ||||
1737 | if (InnerL != &L) { | ||||
1738 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1739, __extension__ __PRETTY_FUNCTION__)) | ||||
1739 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1739, __extension__ __PRETTY_FUNCTION__)); | ||||
1740 | // The preheader is the only possible predecessor of the loop so | ||||
1741 | // insert it into the set and check whether it was already handled. | ||||
1742 | auto *InnerPH = InnerL->getLoopPreheader(); | ||||
1743 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1745, __extension__ __PRETTY_FUNCTION__)) | ||||
1744 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1745, __extension__ __PRETTY_FUNCTION__)) | ||||
1745 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1745, __extension__ __PRETTY_FUNCTION__)); | ||||
1746 | if (!LoopBlockSet.insert(InnerPH).second) | ||||
1747 | // The only way to reach the preheader is through the loop body | ||||
1748 | // itself so if it has been visited the loop is already handled. | ||||
1749 | continue; | ||||
1750 | |||||
1751 | // Insert all of the blocks (other than those already present) into | ||||
1752 | // the loop set. We expect at least the block that led us to find the | ||||
1753 | // inner loop to be in the block set, but we may also have other loop | ||||
1754 | // blocks if they were already enqueued as predecessors of some other | ||||
1755 | // outer loop block. | ||||
1756 | for (auto *InnerBB : InnerL->blocks()) { | ||||
1757 | if (InnerBB == BB) { | ||||
1758 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1759, __extension__ __PRETTY_FUNCTION__)) | ||||
1759 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1759, __extension__ __PRETTY_FUNCTION__)); | ||||
1760 | continue; | ||||
1761 | } | ||||
1762 | |||||
1763 | LoopBlockSet.insert(InnerBB); | ||||
1764 | } | ||||
1765 | |||||
1766 | // Add the preheader to the worklist so we will continue past the | ||||
1767 | // loop body. | ||||
1768 | Worklist.push_back(InnerPH); | ||||
1769 | continue; | ||||
1770 | } | ||||
1771 | |||||
1772 | // Insert any predecessors that were in the original loop into the new | ||||
1773 | // set, and if the insert is successful, add them to the worklist. | ||||
1774 | for (auto *Pred : predecessors(BB)) | ||||
1775 | if (L.contains(Pred) && LoopBlockSet.insert(Pred).second) | ||||
1776 | Worklist.push_back(Pred); | ||||
1777 | } | ||||
1778 | |||||
1779 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1779, __extension__ __PRETTY_FUNCTION__)); | ||||
1780 | |||||
1781 | // We've found all the blocks participating in the loop, return our completed | ||||
1782 | // set. | ||||
1783 | return LoopBlockSet; | ||||
1784 | } | ||||
1785 | |||||
1786 | /// Rebuild a loop after unswitching removes some subset of blocks and edges. | ||||
1787 | /// | ||||
1788 | /// The removal may have removed some child loops entirely but cannot have | ||||
1789 | /// disturbed any remaining child loops. However, they may need to be hoisted | ||||
1790 | /// to the parent loop (or to be top-level loops). The original loop may be | ||||
1791 | /// completely removed. | ||||
1792 | /// | ||||
1793 | /// The sibling loops resulting from this update are returned. If the original | ||||
1794 | /// loop remains a valid loop, it will be the first entry in this list with all | ||||
1795 | /// of the newly sibling loops following it. | ||||
1796 | /// | ||||
1797 | /// Returns true if the loop remains a loop after unswitching, and false if it | ||||
1798 | /// is no longer a loop after unswitching (and should not continue to be | ||||
1799 | /// referenced). | ||||
1800 | static bool rebuildLoopAfterUnswitch(Loop &L, ArrayRef<BasicBlock *> ExitBlocks, | ||||
1801 | LoopInfo &LI, | ||||
1802 | SmallVectorImpl<Loop *> &HoistedLoops) { | ||||
1803 | auto *PH = L.getLoopPreheader(); | ||||
1804 | |||||
1805 | // Compute the actual parent loop from the exit blocks. Because we may have | ||||
1806 | // pruned some exits the loop may be different from the original parent. | ||||
1807 | Loop *ParentL = nullptr; | ||||
1808 | SmallVector<Loop *, 4> ExitLoops; | ||||
1809 | SmallVector<BasicBlock *, 4> ExitsInLoops; | ||||
1810 | ExitsInLoops.reserve(ExitBlocks.size()); | ||||
1811 | for (auto *ExitBB : ExitBlocks) | ||||
1812 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | ||||
1813 | ExitLoops.push_back(ExitL); | ||||
1814 | ExitsInLoops.push_back(ExitBB); | ||||
1815 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | ||||
1816 | ParentL = ExitL; | ||||
1817 | } | ||||
1818 | |||||
1819 | // Recompute the blocks participating in this loop. This may be empty if it | ||||
1820 | // is no longer a loop. | ||||
1821 | auto LoopBlockSet = recomputeLoopBlockSet(L, LI); | ||||
1822 | |||||
1823 | // If we still have a loop, we need to re-set the loop's parent as the exit | ||||
1824 | // block set changing may have moved it within the loop nest. Note that this | ||||
1825 | // can only happen when this loop has a parent as it can only hoist the loop | ||||
1826 | // *up* the nest. | ||||
1827 | if (!LoopBlockSet.empty() && L.getParentLoop() != ParentL) { | ||||
1828 | // Remove this loop's (original) blocks from all of the intervening loops. | ||||
1829 | for (Loop *IL = L.getParentLoop(); IL != ParentL; | ||||
1830 | IL = IL->getParentLoop()) { | ||||
1831 | IL->getBlocksSet().erase(PH); | ||||
1832 | for (auto *BB : L.blocks()) | ||||
1833 | IL->getBlocksSet().erase(BB); | ||||
1834 | llvm::erase_if(IL->getBlocksVector(), [&](BasicBlock *BB) { | ||||
1835 | return BB == PH || L.contains(BB); | ||||
1836 | }); | ||||
1837 | } | ||||
1838 | |||||
1839 | LI.changeLoopFor(PH, ParentL); | ||||
1840 | L.getParentLoop()->removeChildLoop(&L); | ||||
1841 | if (ParentL) | ||||
1842 | ParentL->addChildLoop(&L); | ||||
1843 | else | ||||
1844 | LI.addTopLevelLoop(&L); | ||||
1845 | } | ||||
1846 | |||||
1847 | // Now we update all the blocks which are no longer within the loop. | ||||
1848 | auto &Blocks = L.getBlocksVector(); | ||||
1849 | auto BlocksSplitI = | ||||
1850 | LoopBlockSet.empty() | ||||
1851 | ? Blocks.begin() | ||||
1852 | : std::stable_partition( | ||||
1853 | Blocks.begin(), Blocks.end(), | ||||
1854 | [&](BasicBlock *BB) { return LoopBlockSet.count(BB); }); | ||||
1855 | |||||
1856 | // Before we erase the list of unlooped blocks, build a set of them. | ||||
1857 | SmallPtrSet<BasicBlock *, 16> UnloopedBlocks(BlocksSplitI, Blocks.end()); | ||||
1858 | if (LoopBlockSet.empty()) | ||||
1859 | UnloopedBlocks.insert(PH); | ||||
1860 | |||||
1861 | // Now erase these blocks from the loop. | ||||
1862 | for (auto *BB : make_range(BlocksSplitI, Blocks.end())) | ||||
1863 | L.getBlocksSet().erase(BB); | ||||
1864 | Blocks.erase(BlocksSplitI, Blocks.end()); | ||||
1865 | |||||
1866 | // Sort the exits in ascending loop depth, we'll work backwards across these | ||||
1867 | // to process them inside out. | ||||
1868 | llvm::stable_sort(ExitsInLoops, [&](BasicBlock *LHS, BasicBlock *RHS) { | ||||
1869 | return LI.getLoopDepth(LHS) < LI.getLoopDepth(RHS); | ||||
1870 | }); | ||||
1871 | |||||
1872 | // We'll build up a set for each exit loop. | ||||
1873 | SmallPtrSet<BasicBlock *, 16> NewExitLoopBlocks; | ||||
1874 | Loop *PrevExitL = L.getParentLoop(); // The deepest possible exit loop. | ||||
1875 | |||||
1876 | auto RemoveUnloopedBlocksFromLoop = | ||||
1877 | [](Loop &L, SmallPtrSetImpl<BasicBlock *> &UnloopedBlocks) { | ||||
1878 | for (auto *BB : UnloopedBlocks) | ||||
1879 | L.getBlocksSet().erase(BB); | ||||
1880 | llvm::erase_if(L.getBlocksVector(), [&](BasicBlock *BB) { | ||||
1881 | return UnloopedBlocks.count(BB); | ||||
1882 | }); | ||||
1883 | }; | ||||
1884 | |||||
1885 | SmallVector<BasicBlock *, 16> Worklist; | ||||
1886 | while (!UnloopedBlocks.empty() && !ExitsInLoops.empty()) { | ||||
1887 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1887, __extension__ __PRETTY_FUNCTION__)); | ||||
1888 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1888, __extension__ __PRETTY_FUNCTION__)); | ||||
1889 | |||||
1890 | // Grab the next exit block, in decreasing loop depth order. | ||||
1891 | BasicBlock *ExitBB = ExitsInLoops.pop_back_val(); | ||||
1892 | Loop &ExitL = *LI.getLoopFor(ExitBB); | ||||
1893 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1893, __extension__ __PRETTY_FUNCTION__)); | ||||
1894 | |||||
1895 | // Erase all of the unlooped blocks from the loops between the previous | ||||
1896 | // exit loop and this exit loop. This works because the ExitInLoops list is | ||||
1897 | // sorted in increasing order of loop depth and thus we visit loops in | ||||
1898 | // decreasing order of loop depth. | ||||
1899 | for (; PrevExitL != &ExitL; PrevExitL = PrevExitL->getParentLoop()) | ||||
1900 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | ||||
1901 | |||||
1902 | // Walk the CFG back until we hit the cloned PH adding everything reachable | ||||
1903 | // and in the unlooped set to this exit block's loop. | ||||
1904 | Worklist.push_back(ExitBB); | ||||
1905 | do { | ||||
1906 | BasicBlock *BB = Worklist.pop_back_val(); | ||||
1907 | // We can stop recursing at the cloned preheader (if we get there). | ||||
1908 | if (BB == PH) | ||||
1909 | continue; | ||||
1910 | |||||
1911 | for (BasicBlock *PredBB : predecessors(BB)) { | ||||
1912 | // If this pred has already been moved to our set or is part of some | ||||
1913 | // (inner) loop, no update needed. | ||||
1914 | if (!UnloopedBlocks.erase(PredBB)) { | ||||
1915 | 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)!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1917, __extension__ __PRETTY_FUNCTION__)) | ||||
1916 | 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)!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1917, __extension__ __PRETTY_FUNCTION__)) | ||||
1917 | "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)!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1917, __extension__ __PRETTY_FUNCTION__)); | ||||
1918 | continue; | ||||
1919 | } | ||||
1920 | |||||
1921 | // We just insert into the loop set here. We'll add these blocks to the | ||||
1922 | // exit loop after we build up the set in a deterministic order rather | ||||
1923 | // than the predecessor-influenced visit order. | ||||
1924 | bool Inserted = NewExitLoopBlocks.insert(PredBB).second; | ||||
1925 | (void)Inserted; | ||||
1926 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1926, __extension__ __PRETTY_FUNCTION__)); | ||||
1927 | |||||
1928 | // And recurse through to its predecessors. | ||||
1929 | Worklist.push_back(PredBB); | ||||
1930 | } | ||||
1931 | } while (!Worklist.empty()); | ||||
1932 | |||||
1933 | // If blocks in this exit loop were directly part of the original loop (as | ||||
1934 | // opposed to a child loop) update the map to point to this exit loop. This | ||||
1935 | // just updates a map and so the fact that the order is unstable is fine. | ||||
1936 | for (auto *BB : NewExitLoopBlocks) | ||||
1937 | if (Loop *BBL = LI.getLoopFor(BB)) | ||||
1938 | if (BBL == &L || !L.contains(BBL)) | ||||
1939 | LI.changeLoopFor(BB, &ExitL); | ||||
1940 | |||||
1941 | // We will remove the remaining unlooped blocks from this loop in the next | ||||
1942 | // iteration or below. | ||||
1943 | NewExitLoopBlocks.clear(); | ||||
1944 | } | ||||
1945 | |||||
1946 | // Any remaining unlooped blocks are no longer part of any loop unless they | ||||
1947 | // are part of some child loop. | ||||
1948 | for (; PrevExitL; PrevExitL = PrevExitL->getParentLoop()) | ||||
1949 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | ||||
1950 | for (auto *BB : UnloopedBlocks) | ||||
1951 | if (Loop *BBL = LI.getLoopFor(BB)) | ||||
1952 | if (BBL == &L || !L.contains(BBL)) | ||||
1953 | LI.changeLoopFor(BB, nullptr); | ||||
1954 | |||||
1955 | // Sink all the child loops whose headers are no longer in the loop set to | ||||
1956 | // the parent (or to be top level loops). We reach into the loop and directly | ||||
1957 | // update its subloop vector to make this batch update efficient. | ||||
1958 | auto &SubLoops = L.getSubLoopsVector(); | ||||
1959 | auto SubLoopsSplitI = | ||||
1960 | LoopBlockSet.empty() | ||||
1961 | ? SubLoops.begin() | ||||
1962 | : std::stable_partition( | ||||
1963 | SubLoops.begin(), SubLoops.end(), [&](Loop *SubL) { | ||||
1964 | return LoopBlockSet.count(SubL->getHeader()); | ||||
1965 | }); | ||||
1966 | for (auto *HoistedL : make_range(SubLoopsSplitI, SubLoops.end())) { | ||||
1967 | HoistedLoops.push_back(HoistedL); | ||||
1968 | HoistedL->setParentLoop(nullptr); | ||||
1969 | |||||
1970 | // To compute the new parent of this hoisted loop we look at where we | ||||
1971 | // placed the preheader above. We can't lookup the header itself because we | ||||
1972 | // retained the mapping from the header to the hoisted loop. But the | ||||
1973 | // preheader and header should have the exact same new parent computed | ||||
1974 | // based on the set of exit blocks from the original loop as the preheader | ||||
1975 | // is a predecessor of the header and so reached in the reverse walk. And | ||||
1976 | // because the loops were all in simplified form the preheader of the | ||||
1977 | // hoisted loop can't be part of some *other* loop. | ||||
1978 | if (auto *NewParentL = LI.getLoopFor(HoistedL->getLoopPreheader())) | ||||
1979 | NewParentL->addChildLoop(HoistedL); | ||||
1980 | else | ||||
1981 | LI.addTopLevelLoop(HoistedL); | ||||
1982 | } | ||||
1983 | SubLoops.erase(SubLoopsSplitI, SubLoops.end()); | ||||
1984 | |||||
1985 | // Actually delete the loop if nothing remained within it. | ||||
1986 | if (Blocks.empty()) { | ||||
1987 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1988, __extension__ __PRETTY_FUNCTION__)) | ||||
1988 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 1988, __extension__ __PRETTY_FUNCTION__)); | ||||
1989 | if (Loop *ParentL = L.getParentLoop()) | ||||
1990 | ParentL->removeChildLoop(llvm::find(*ParentL, &L)); | ||||
1991 | else | ||||
1992 | LI.removeLoop(llvm::find(LI, &L)); | ||||
1993 | // markLoopAsDeleted for L should be triggered by the caller (it is typically | ||||
1994 | // done by using the UnswitchCB callback). | ||||
1995 | LI.destroy(&L); | ||||
1996 | return false; | ||||
1997 | } | ||||
1998 | |||||
1999 | return true; | ||||
2000 | } | ||||
2001 | |||||
2002 | /// Helper to visit a dominator subtree, invoking a callable on each node. | ||||
2003 | /// | ||||
2004 | /// Returning false at any point will stop walking past that node of the tree. | ||||
2005 | template <typename CallableT> | ||||
2006 | void visitDomSubTree(DominatorTree &DT, BasicBlock *BB, CallableT Callable) { | ||||
2007 | SmallVector<DomTreeNode *, 4> DomWorklist; | ||||
2008 | DomWorklist.push_back(DT[BB]); | ||||
2009 | #ifndef NDEBUG | ||||
2010 | SmallPtrSet<DomTreeNode *, 4> Visited; | ||||
2011 | Visited.insert(DT[BB]); | ||||
2012 | #endif | ||||
2013 | do { | ||||
2014 | DomTreeNode *N = DomWorklist.pop_back_val(); | ||||
2015 | |||||
2016 | // Visit this node. | ||||
2017 | if (!Callable(N->getBlock())) | ||||
2018 | continue; | ||||
2019 | |||||
2020 | // Accumulate the child nodes. | ||||
2021 | for (DomTreeNode *ChildN : *N) { | ||||
2022 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2023, __extension__ __PRETTY_FUNCTION__)) | ||||
2023 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2023, __extension__ __PRETTY_FUNCTION__)); | ||||
2024 | DomWorklist.push_back(ChildN); | ||||
2025 | } | ||||
2026 | } while (!DomWorklist.empty()); | ||||
2027 | } | ||||
2028 | |||||
2029 | static void unswitchNontrivialInvariants( | ||||
2030 | Loop &L, Instruction &TI, ArrayRef<Value *> Invariants, | ||||
2031 | SmallVectorImpl<BasicBlock *> &ExitBlocks, IVConditionInfo &PartialIVInfo, | ||||
2032 | DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | ||||
2033 | function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB, | ||||
2034 | ScalarEvolution *SE, MemorySSAUpdater *MSSAU, | ||||
2035 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||
2036 | auto *ParentBB = TI.getParent(); | ||||
2037 | BranchInst *BI = dyn_cast<BranchInst>(&TI); | ||||
2038 | SwitchInst *SI = BI ? nullptr : cast<SwitchInst>(&TI); | ||||
2039 | |||||
2040 | // We can only unswitch switches, conditional branches with an invariant | ||||
2041 | // condition, or combining invariant conditions with an instruction or | ||||
2042 | // partially invariant instructions. | ||||
2043 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2044, __extension__ __PRETTY_FUNCTION__)) | ||||
2044 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2044, __extension__ __PRETTY_FUNCTION__)); | ||||
2045 | bool PartiallyInvariant = !PartialIVInfo.InstToDuplicate.empty(); | ||||
2046 | bool FullUnswitch = | ||||
2047 | SI || (BI->getCondition() == Invariants[0] && !PartiallyInvariant); | ||||
2048 | if (FullUnswitch) | ||||
2049 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2050, __extension__ __PRETTY_FUNCTION__)) | ||||
2050 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2050, __extension__ __PRETTY_FUNCTION__)); | ||||
2051 | else | ||||
2052 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2053, __extension__ __PRETTY_FUNCTION__)) | ||||
2053 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2053, __extension__ __PRETTY_FUNCTION__)); | ||||
2054 | |||||
2055 | if (MSSAU && VerifyMemorySSA) | ||||
2056 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
2057 | |||||
2058 | // Constant and BBs tracking the cloned and continuing successor. When we are | ||||
2059 | // unswitching the entire condition, this can just be trivially chosen to | ||||
2060 | // unswitch towards `true`. However, when we are unswitching a set of | ||||
2061 | // invariants combined with `and` or `or` or partially invariant instructions, | ||||
2062 | // the combining operation determines the best direction to unswitch: we want | ||||
2063 | // to unswitch the direction that will collapse the branch. | ||||
2064 | bool Direction = true; | ||||
2065 | int ClonedSucc = 0; | ||||
2066 | if (!FullUnswitch) { | ||||
2067 | Value *Cond = BI->getCondition(); | ||||
2068 | (void)Cond; | ||||
2069 | 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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2072, __extension__ __PRETTY_FUNCTION__)) | ||||
2070 | 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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2072, __extension__ __PRETTY_FUNCTION__)) | ||||
2071 | "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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2072, __extension__ __PRETTY_FUNCTION__)) | ||||
2072 | "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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2072, __extension__ __PRETTY_FUNCTION__)); | ||||
2073 | if (!match(BI->getCondition(), m_LogicalOr())) { | ||||
2074 | if (match(BI->getCondition(), m_LogicalAnd()) || | ||||
2075 | (PartiallyInvariant && !PartialIVInfo.KnownValue->isOneValue())) { | ||||
2076 | Direction = false; | ||||
2077 | ClonedSucc = 1; | ||||
2078 | } | ||||
2079 | } | ||||
2080 | } | ||||
2081 | |||||
2082 | BasicBlock *RetainedSuccBB = | ||||
2083 | BI ? BI->getSuccessor(1 - ClonedSucc) : SI->getDefaultDest(); | ||||
2084 | SmallSetVector<BasicBlock *, 4> UnswitchedSuccBBs; | ||||
2085 | if (BI) | ||||
2086 | UnswitchedSuccBBs.insert(BI->getSuccessor(ClonedSucc)); | ||||
2087 | else | ||||
2088 | for (auto Case : SI->cases()) | ||||
2089 | if (Case.getCaseSuccessor() != RetainedSuccBB) | ||||
2090 | UnswitchedSuccBBs.insert(Case.getCaseSuccessor()); | ||||
2091 | |||||
2092 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2093, __extension__ __PRETTY_FUNCTION__)) | ||||
2093 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2093, __extension__ __PRETTY_FUNCTION__)); | ||||
2094 | |||||
2095 | // The branch should be in this exact loop. Any inner loop's invariant branch | ||||
2096 | // should be handled by unswitching that inner loop. The caller of this | ||||
2097 | // routine should filter out any candidates that remain (but were skipped for | ||||
2098 | // whatever reason). | ||||
2099 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2099, __extension__ __PRETTY_FUNCTION__)); | ||||
2100 | |||||
2101 | // Compute the parent loop now before we start hacking on things. | ||||
2102 | Loop *ParentL = L.getParentLoop(); | ||||
2103 | // Get blocks in RPO order for MSSA update, before changing the CFG. | ||||
2104 | LoopBlocksRPO LBRPO(&L); | ||||
2105 | if (MSSAU) | ||||
2106 | LBRPO.perform(&LI); | ||||
2107 | |||||
2108 | // Compute the outer-most loop containing one of our exit blocks. This is the | ||||
2109 | // furthest up our loopnest which can be mutated, which we will use below to | ||||
2110 | // update things. | ||||
2111 | Loop *OuterExitL = &L; | ||||
2112 | for (auto *ExitBB : ExitBlocks) { | ||||
2113 | Loop *NewOuterExitL = LI.getLoopFor(ExitBB); | ||||
2114 | if (!NewOuterExitL) { | ||||
2115 | // We exited the entire nest with this block, so we're done. | ||||
2116 | OuterExitL = nullptr; | ||||
2117 | break; | ||||
2118 | } | ||||
2119 | if (NewOuterExitL != OuterExitL && NewOuterExitL->contains(OuterExitL)) | ||||
2120 | OuterExitL = NewOuterExitL; | ||||
2121 | } | ||||
2122 | |||||
2123 | // At this point, we're definitely going to unswitch something so invalidate | ||||
2124 | // any cached information in ScalarEvolution for the outer most loop | ||||
2125 | // containing an exit block and all nested loops. | ||||
2126 | if (SE) { | ||||
2127 | if (OuterExitL) | ||||
2128 | SE->forgetLoop(OuterExitL); | ||||
2129 | else | ||||
2130 | SE->forgetTopmostLoop(&L); | ||||
2131 | } | ||||
2132 | |||||
2133 | bool InsertFreeze = false; | ||||
2134 | if (FreezeLoopUnswitchCond) { | ||||
2135 | ICFLoopSafetyInfo SafetyInfo; | ||||
2136 | SafetyInfo.computeLoopSafetyInfo(&L); | ||||
2137 | InsertFreeze = !SafetyInfo.isGuaranteedToExecute(TI, &DT, &L); | ||||
2138 | } | ||||
2139 | |||||
2140 | // If the edge from this terminator to a successor dominates that successor, | ||||
2141 | // store a map from each block in its dominator subtree to it. This lets us | ||||
2142 | // tell when cloning for a particular successor if a block is dominated by | ||||
2143 | // some *other* successor with a single data structure. We use this to | ||||
2144 | // significantly reduce cloning. | ||||
2145 | SmallDenseMap<BasicBlock *, BasicBlock *, 16> DominatingSucc; | ||||
2146 | for (auto *SuccBB : llvm::concat<BasicBlock *const>( | ||||
2147 | makeArrayRef(RetainedSuccBB), UnswitchedSuccBBs)) | ||||
2148 | if (SuccBB->getUniquePredecessor() || | ||||
2149 | llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) { | ||||
2150 | return PredBB == ParentBB || DT.dominates(SuccBB, PredBB); | ||||
2151 | })) | ||||
2152 | visitDomSubTree(DT, SuccBB, [&](BasicBlock *BB) { | ||||
2153 | DominatingSucc[BB] = SuccBB; | ||||
2154 | return true; | ||||
2155 | }); | ||||
2156 | |||||
2157 | // Split the preheader, so that we know that there is a safe place to insert | ||||
2158 | // the conditional branch. We will change the preheader to have a conditional | ||||
2159 | // branch on LoopCond. The original preheader will become the split point | ||||
2160 | // between the unswitched versions, and we will have a new preheader for the | ||||
2161 | // original loop. | ||||
2162 | BasicBlock *SplitBB = L.getLoopPreheader(); | ||||
2163 | BasicBlock *LoopPH = SplitEdge(SplitBB, L.getHeader(), &DT, &LI, MSSAU); | ||||
2164 | |||||
2165 | // Keep track of the dominator tree updates needed. | ||||
2166 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | ||||
2167 | |||||
2168 | // Clone the loop for each unswitched successor. | ||||
2169 | SmallVector<std::unique_ptr<ValueToValueMapTy>, 4> VMaps; | ||||
2170 | VMaps.reserve(UnswitchedSuccBBs.size()); | ||||
2171 | SmallDenseMap<BasicBlock *, BasicBlock *, 4> ClonedPHs; | ||||
2172 | for (auto *SuccBB : UnswitchedSuccBBs) { | ||||
2173 | VMaps.emplace_back(new ValueToValueMapTy()); | ||||
2174 | ClonedPHs[SuccBB] = buildClonedLoopBlocks( | ||||
2175 | L, LoopPH, SplitBB, ExitBlocks, ParentBB, SuccBB, RetainedSuccBB, | ||||
2176 | DominatingSucc, *VMaps.back(), DTUpdates, AC, DT, LI, MSSAU); | ||||
2177 | } | ||||
2178 | |||||
2179 | // Drop metadata if we may break its semantics by moving this instr into the | ||||
2180 | // split block. | ||||
2181 | if (TI.getMetadata(LLVMContext::MD_make_implicit)) { | ||||
2182 | if (DropNonTrivialImplicitNullChecks) | ||||
2183 | // Do not spend time trying to understand if we can keep it, just drop it | ||||
2184 | // to save compile time. | ||||
2185 | TI.setMetadata(LLVMContext::MD_make_implicit, nullptr); | ||||
2186 | else { | ||||
2187 | // It is only legal to preserve make.implicit metadata if we are | ||||
2188 | // guaranteed no reach implicit null check after following this branch. | ||||
2189 | ICFLoopSafetyInfo SafetyInfo; | ||||
2190 | SafetyInfo.computeLoopSafetyInfo(&L); | ||||
2191 | if (!SafetyInfo.isGuaranteedToExecute(TI, &DT, &L)) | ||||
2192 | TI.setMetadata(LLVMContext::MD_make_implicit, nullptr); | ||||
2193 | } | ||||
2194 | } | ||||
2195 | |||||
2196 | // The stitching of the branched code back together depends on whether we're | ||||
2197 | // doing full unswitching or not with the exception that we always want to | ||||
2198 | // nuke the initial terminator placed in the split block. | ||||
2199 | SplitBB->getTerminator()->eraseFromParent(); | ||||
2200 | if (FullUnswitch) { | ||||
2201 | // Splice the terminator from the original loop and rewrite its | ||||
2202 | // successors. | ||||
2203 | SplitBB->getInstList().splice(SplitBB->end(), ParentBB->getInstList(), TI); | ||||
2204 | |||||
2205 | // Keep a clone of the terminator for MSSA updates. | ||||
2206 | Instruction *NewTI = TI.clone(); | ||||
2207 | ParentBB->getInstList().push_back(NewTI); | ||||
2208 | |||||
2209 | // First wire up the moved terminator to the preheaders. | ||||
2210 | if (BI) { | ||||
2211 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | ||||
2212 | BI->setSuccessor(ClonedSucc, ClonedPH); | ||||
2213 | BI->setSuccessor(1 - ClonedSucc, LoopPH); | ||||
2214 | if (InsertFreeze) { | ||||
2215 | auto Cond = BI->getCondition(); | ||||
2216 | if (!isGuaranteedNotToBeUndefOrPoison(Cond, &AC, BI, &DT)) | ||||
2217 | BI->setCondition(new FreezeInst(Cond, Cond->getName() + ".fr", BI)); | ||||
2218 | } | ||||
2219 | DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH}); | ||||
2220 | } else { | ||||
2221 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2221, __extension__ __PRETTY_FUNCTION__)); | ||||
2222 | |||||
2223 | // Walk the cases and directly update their successors. | ||||
2224 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2225, __extension__ __PRETTY_FUNCTION__)) | ||||
2225 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2225, __extension__ __PRETTY_FUNCTION__)); | ||||
2226 | SI->setDefaultDest(LoopPH); | ||||
2227 | for (auto &Case : SI->cases()) | ||||
2228 | if (Case.getCaseSuccessor() == RetainedSuccBB) | ||||
2229 | Case.setSuccessor(LoopPH); | ||||
2230 | else | ||||
2231 | Case.setSuccessor(ClonedPHs.find(Case.getCaseSuccessor())->second); | ||||
2232 | |||||
2233 | if (InsertFreeze) { | ||||
2234 | auto Cond = SI->getCondition(); | ||||
2235 | if (!isGuaranteedNotToBeUndefOrPoison(Cond, &AC, SI, &DT)) | ||||
2236 | SI->setCondition(new FreezeInst(Cond, Cond->getName() + ".fr", SI)); | ||||
2237 | } | ||||
2238 | // We need to use the set to populate domtree updates as even when there | ||||
2239 | // are multiple cases pointing at the same successor we only want to | ||||
2240 | // remove and insert one edge in the domtree. | ||||
2241 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||
2242 | DTUpdates.push_back( | ||||
2243 | {DominatorTree::Insert, SplitBB, ClonedPHs.find(SuccBB)->second}); | ||||
2244 | } | ||||
2245 | |||||
2246 | if (MSSAU) { | ||||
2247 | DT.applyUpdates(DTUpdates); | ||||
2248 | DTUpdates.clear(); | ||||
2249 | |||||
2250 | // Remove all but one edge to the retained block and all unswitched | ||||
2251 | // blocks. This is to avoid having duplicate entries in the cloned Phis, | ||||
2252 | // when we know we only keep a single edge for each case. | ||||
2253 | MSSAU->removeDuplicatePhiEdgesBetween(ParentBB, RetainedSuccBB); | ||||
2254 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||
2255 | MSSAU->removeDuplicatePhiEdgesBetween(ParentBB, SuccBB); | ||||
2256 | |||||
2257 | for (auto &VMap : VMaps) | ||||
2258 | MSSAU->updateForClonedLoop(LBRPO, ExitBlocks, *VMap, | ||||
2259 | /*IgnoreIncomingWithNoClones=*/true); | ||||
2260 | MSSAU->updateExitBlocksForClonedLoop(ExitBlocks, VMaps, DT); | ||||
2261 | |||||
2262 | // Remove all edges to unswitched blocks. | ||||
2263 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||
2264 | MSSAU->removeEdge(ParentBB, SuccBB); | ||||
2265 | } | ||||
2266 | |||||
2267 | // Now unhook the successor relationship as we'll be replacing | ||||
2268 | // the terminator with a direct branch. This is much simpler for branches | ||||
2269 | // than switches so we handle those first. | ||||
2270 | if (BI) { | ||||
2271 | // Remove the parent as a predecessor of the unswitched successor. | ||||
2272 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2273, __extension__ __PRETTY_FUNCTION__)) | ||||
2273 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2273, __extension__ __PRETTY_FUNCTION__)); | ||||
2274 | BasicBlock *UnswitchedSuccBB = *UnswitchedSuccBBs.begin(); | ||||
2275 | UnswitchedSuccBB->removePredecessor(ParentBB, | ||||
2276 | /*KeepOneInputPHIs*/ true); | ||||
2277 | DTUpdates.push_back({DominatorTree::Delete, ParentBB, UnswitchedSuccBB}); | ||||
2278 | } else { | ||||
2279 | // Note that we actually want to remove the parent block as a predecessor | ||||
2280 | // of *every* case successor. The case successor is either unswitched, | ||||
2281 | // completely eliminating an edge from the parent to that successor, or it | ||||
2282 | // is a duplicate edge to the retained successor as the retained successor | ||||
2283 | // is always the default successor and as we'll replace this with a direct | ||||
2284 | // branch we no longer need the duplicate entries in the PHI nodes. | ||||
2285 | SwitchInst *NewSI = cast<SwitchInst>(NewTI); | ||||
2286 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2287, __extension__ __PRETTY_FUNCTION__)) | ||||
2287 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2287, __extension__ __PRETTY_FUNCTION__)); | ||||
2288 | for (auto &Case : NewSI->cases()) | ||||
2289 | Case.getCaseSuccessor()->removePredecessor( | ||||
2290 | ParentBB, | ||||
2291 | /*KeepOneInputPHIs*/ true); | ||||
2292 | |||||
2293 | // We need to use the set to populate domtree updates as even when there | ||||
2294 | // are multiple cases pointing at the same successor we only want to | ||||
2295 | // remove and insert one edge in the domtree. | ||||
2296 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||
2297 | DTUpdates.push_back({DominatorTree::Delete, ParentBB, SuccBB}); | ||||
2298 | } | ||||
2299 | |||||
2300 | // After MSSAU update, remove the cloned terminator instruction NewTI. | ||||
2301 | ParentBB->getTerminator()->eraseFromParent(); | ||||
2302 | |||||
2303 | // Create a new unconditional branch to the continuing block (as opposed to | ||||
2304 | // the one cloned). | ||||
2305 | BranchInst::Create(RetainedSuccBB, ParentBB); | ||||
2306 | } else { | ||||
2307 | 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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2307, __extension__ __PRETTY_FUNCTION__)); | ||||
2308 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2309, __extension__ __PRETTY_FUNCTION__)) | ||||
2309 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2309, __extension__ __PRETTY_FUNCTION__)); | ||||
2310 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | ||||
2311 | // When doing a partial unswitch, we have to do a bit more work to build up | ||||
2312 | // the branch in the split block. | ||||
2313 | if (PartiallyInvariant) | ||||
2314 | buildPartialInvariantUnswitchConditionalBranch( | ||||
2315 | *SplitBB, Invariants, Direction, *ClonedPH, *LoopPH, L, MSSAU); | ||||
2316 | else | ||||
2317 | buildPartialUnswitchConditionalBranch(*SplitBB, Invariants, Direction, | ||||
2318 | *ClonedPH, *LoopPH, InsertFreeze); | ||||
2319 | DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH}); | ||||
2320 | |||||
2321 | if (MSSAU) { | ||||
2322 | DT.applyUpdates(DTUpdates); | ||||
2323 | DTUpdates.clear(); | ||||
2324 | |||||
2325 | // Perform MSSA cloning updates. | ||||
2326 | for (auto &VMap : VMaps) | ||||
2327 | MSSAU->updateForClonedLoop(LBRPO, ExitBlocks, *VMap, | ||||
2328 | /*IgnoreIncomingWithNoClones=*/true); | ||||
2329 | MSSAU->updateExitBlocksForClonedLoop(ExitBlocks, VMaps, DT); | ||||
2330 | } | ||||
2331 | } | ||||
2332 | |||||
2333 | // Apply the updates accumulated above to get an up-to-date dominator tree. | ||||
2334 | DT.applyUpdates(DTUpdates); | ||||
2335 | |||||
2336 | // Now that we have an accurate dominator tree, first delete the dead cloned | ||||
2337 | // blocks so that we can accurately build any cloned loops. It is important to | ||||
2338 | // not delete the blocks from the original loop yet because we still want to | ||||
2339 | // reference the original loop to understand the cloned loop's structure. | ||||
2340 | deleteDeadClonedBlocks(L, ExitBlocks, VMaps, DT, MSSAU); | ||||
2341 | |||||
2342 | // Build the cloned loop structure itself. This may be substantially | ||||
2343 | // different from the original structure due to the simplified CFG. This also | ||||
2344 | // handles inserting all the cloned blocks into the correct loops. | ||||
2345 | SmallVector<Loop *, 4> NonChildClonedLoops; | ||||
2346 | for (std::unique_ptr<ValueToValueMapTy> &VMap : VMaps) | ||||
2347 | buildClonedLoops(L, ExitBlocks, *VMap, LI, NonChildClonedLoops); | ||||
2348 | |||||
2349 | // Now that our cloned loops have been built, we can update the original loop. | ||||
2350 | // First we delete the dead blocks from it and then we rebuild the loop | ||||
2351 | // structure taking these deletions into account. | ||||
2352 | deleteDeadBlocksFromLoop(L, ExitBlocks, DT, LI, MSSAU, DestroyLoopCB); | ||||
2353 | |||||
2354 | if (MSSAU && VerifyMemorySSA) | ||||
2355 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
2356 | |||||
2357 | SmallVector<Loop *, 4> HoistedLoops; | ||||
2358 | bool IsStillLoop = rebuildLoopAfterUnswitch(L, ExitBlocks, LI, HoistedLoops); | ||||
2359 | |||||
2360 | if (MSSAU && VerifyMemorySSA) | ||||
2361 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
2362 | |||||
2363 | // This transformation has a high risk of corrupting the dominator tree, and | ||||
2364 | // the below steps to rebuild loop structures will result in hard to debug | ||||
2365 | // errors in that case so verify that the dominator tree is sane first. | ||||
2366 | // FIXME: Remove this when the bugs stop showing up and rely on existing | ||||
2367 | // verification steps. | ||||
2368 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2368, __extension__ __PRETTY_FUNCTION__)); | ||||
2369 | |||||
2370 | if (BI && !PartiallyInvariant) { | ||||
2371 | // If we unswitched a branch which collapses the condition to a known | ||||
2372 | // constant we want to replace all the uses of the invariants within both | ||||
2373 | // the original and cloned blocks. We do this here so that we can use the | ||||
2374 | // now updated dominator tree to identify which side the users are on. | ||||
2375 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2376, __extension__ __PRETTY_FUNCTION__)) | ||||
2376 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2376, __extension__ __PRETTY_FUNCTION__)); | ||||
2377 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | ||||
2378 | |||||
2379 | // When considering multiple partially-unswitched invariants | ||||
2380 | // we cant just go replace them with constants in both branches. | ||||
2381 | // | ||||
2382 | // For 'AND' we infer that true branch ("continue") means true | ||||
2383 | // for each invariant operand. | ||||
2384 | // For 'OR' we can infer that false branch ("continue") means false | ||||
2385 | // for each invariant operand. | ||||
2386 | // So it happens that for multiple-partial case we dont replace | ||||
2387 | // in the unswitched branch. | ||||
2388 | bool ReplaceUnswitched = | ||||
2389 | FullUnswitch || (Invariants.size() == 1) || PartiallyInvariant; | ||||
2390 | |||||
2391 | ConstantInt *UnswitchedReplacement = | ||||
2392 | Direction ? ConstantInt::getTrue(BI->getContext()) | ||||
2393 | : ConstantInt::getFalse(BI->getContext()); | ||||
2394 | ConstantInt *ContinueReplacement = | ||||
2395 | Direction ? ConstantInt::getFalse(BI->getContext()) | ||||
2396 | : ConstantInt::getTrue(BI->getContext()); | ||||
2397 | for (Value *Invariant : Invariants) { | ||||
2398 | assert(!isa<Constant>(Invariant) &&(static_cast <bool> (!isa<Constant>(Invariant) && "Should not be replacing constant values!") ? void (0) : __assert_fail ("!isa<Constant>(Invariant) && \"Should not be replacing constant values!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2399, __extension__ __PRETTY_FUNCTION__)) | ||||
2399 | "Should not be replacing constant values!")(static_cast <bool> (!isa<Constant>(Invariant) && "Should not be replacing constant values!") ? void (0) : __assert_fail ("!isa<Constant>(Invariant) && \"Should not be replacing constant values!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2399, __extension__ __PRETTY_FUNCTION__)); | ||||
2400 | // Use make_early_inc_range here as set invalidates the iterator. | ||||
2401 | for (Use &U : llvm::make_early_inc_range(Invariant->uses())) { | ||||
2402 | Instruction *UserI = dyn_cast<Instruction>(U.getUser()); | ||||
2403 | if (!UserI) | ||||
2404 | continue; | ||||
2405 | |||||
2406 | // Replace it with the 'continue' side if in the main loop body, and the | ||||
2407 | // unswitched if in the cloned blocks. | ||||
2408 | if (DT.dominates(LoopPH, UserI->getParent())) | ||||
2409 | U.set(ContinueReplacement); | ||||
2410 | else if (ReplaceUnswitched && | ||||
2411 | DT.dominates(ClonedPH, UserI->getParent())) | ||||
2412 | U.set(UnswitchedReplacement); | ||||
2413 | } | ||||
2414 | } | ||||
2415 | } | ||||
2416 | |||||
2417 | // We can change which blocks are exit blocks of all the cloned sibling | ||||
2418 | // loops, the current loop, and any parent loops which shared exit blocks | ||||
2419 | // with the current loop. As a consequence, we need to re-form LCSSA for | ||||
2420 | // them. But we shouldn't need to re-form LCSSA for any child loops. | ||||
2421 | // FIXME: This could be made more efficient by tracking which exit blocks are | ||||
2422 | // new, and focusing on them, but that isn't likely to be necessary. | ||||
2423 | // | ||||
2424 | // In order to reasonably rebuild LCSSA we need to walk inside-out across the | ||||
2425 | // loop nest and update every loop that could have had its exits changed. We | ||||
2426 | // also need to cover any intervening loops. We add all of these loops to | ||||
2427 | // a list and sort them by loop depth to achieve this without updating | ||||
2428 | // unnecessary loops. | ||||
2429 | auto UpdateLoop = [&](Loop &UpdateL) { | ||||
2430 | #ifndef NDEBUG | ||||
2431 | UpdateL.verifyLoop(); | ||||
2432 | for (Loop *ChildL : UpdateL) { | ||||
2433 | ChildL->verifyLoop(); | ||||
2434 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2435, __extension__ __PRETTY_FUNCTION__)) | ||||
2435 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2435, __extension__ __PRETTY_FUNCTION__)); | ||||
2436 | } | ||||
2437 | #endif | ||||
2438 | // First build LCSSA for this loop so that we can preserve it when | ||||
2439 | // forming dedicated exits. We don't want to perturb some other loop's | ||||
2440 | // LCSSA while doing that CFG edit. | ||||
2441 | formLCSSA(UpdateL, DT, &LI, SE); | ||||
2442 | |||||
2443 | // For loops reached by this loop's original exit blocks we may | ||||
2444 | // introduced new, non-dedicated exits. At least try to re-form dedicated | ||||
2445 | // exits for these loops. This may fail if they couldn't have dedicated | ||||
2446 | // exits to start with. | ||||
2447 | formDedicatedExitBlocks(&UpdateL, &DT, &LI, MSSAU, /*PreserveLCSSA*/ true); | ||||
2448 | }; | ||||
2449 | |||||
2450 | // For non-child cloned loops and hoisted loops, we just need to update LCSSA | ||||
2451 | // and we can do it in any order as they don't nest relative to each other. | ||||
2452 | // | ||||
2453 | // Also check if any of the loops we have updated have become top-level loops | ||||
2454 | // as that will necessitate widening the outer loop scope. | ||||
2455 | for (Loop *UpdatedL : | ||||
2456 | llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) { | ||||
2457 | UpdateLoop(*UpdatedL); | ||||
2458 | if (UpdatedL->isOutermost()) | ||||
2459 | OuterExitL = nullptr; | ||||
2460 | } | ||||
2461 | if (IsStillLoop) { | ||||
2462 | UpdateLoop(L); | ||||
2463 | if (L.isOutermost()) | ||||
2464 | OuterExitL = nullptr; | ||||
2465 | } | ||||
2466 | |||||
2467 | // If the original loop had exit blocks, walk up through the outer most loop | ||||
2468 | // of those exit blocks to update LCSSA and form updated dedicated exits. | ||||
2469 | if (OuterExitL != &L) | ||||
2470 | for (Loop *OuterL = ParentL; OuterL != OuterExitL; | ||||
2471 | OuterL = OuterL->getParentLoop()) | ||||
2472 | UpdateLoop(*OuterL); | ||||
2473 | |||||
2474 | #ifndef NDEBUG | ||||
2475 | // Verify the entire loop structure to catch any incorrect updates before we | ||||
2476 | // progress in the pass pipeline. | ||||
2477 | LI.verify(DT); | ||||
2478 | #endif | ||||
2479 | |||||
2480 | // Now that we've unswitched something, make callbacks to report the changes. | ||||
2481 | // For that we need to merge together the updated loops and the cloned loops | ||||
2482 | // and check whether the original loop survived. | ||||
2483 | SmallVector<Loop *, 4> SibLoops; | ||||
2484 | for (Loop *UpdatedL : llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) | ||||
2485 | if (UpdatedL->getParentLoop() == ParentL) | ||||
2486 | SibLoops.push_back(UpdatedL); | ||||
2487 | UnswitchCB(IsStillLoop, PartiallyInvariant, SibLoops); | ||||
2488 | |||||
2489 | if (MSSAU && VerifyMemorySSA) | ||||
2490 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
2491 | |||||
2492 | if (BI) | ||||
2493 | ++NumBranches; | ||||
2494 | else | ||||
2495 | ++NumSwitches; | ||||
2496 | } | ||||
2497 | |||||
2498 | /// Recursively compute the cost of a dominator subtree based on the per-block | ||||
2499 | /// cost map provided. | ||||
2500 | /// | ||||
2501 | /// The recursive computation is memozied into the provided DT-indexed cost map | ||||
2502 | /// to allow querying it for most nodes in the domtree without it becoming | ||||
2503 | /// quadratic. | ||||
2504 | static InstructionCost computeDomSubtreeCost( | ||||
2505 | DomTreeNode &N, | ||||
2506 | const SmallDenseMap<BasicBlock *, InstructionCost, 4> &BBCostMap, | ||||
2507 | SmallDenseMap<DomTreeNode *, InstructionCost, 4> &DTCostMap) { | ||||
2508 | // Don't accumulate cost (or recurse through) blocks not in our block cost | ||||
2509 | // map and thus not part of the duplication cost being considered. | ||||
2510 | auto BBCostIt = BBCostMap.find(N.getBlock()); | ||||
2511 | if (BBCostIt == BBCostMap.end()) | ||||
2512 | return 0; | ||||
2513 | |||||
2514 | // Lookup this node to see if we already computed its cost. | ||||
2515 | auto DTCostIt = DTCostMap.find(&N); | ||||
2516 | if (DTCostIt != DTCostMap.end()) | ||||
2517 | return DTCostIt->second; | ||||
2518 | |||||
2519 | // If not, we have to compute it. We can't use insert above and update | ||||
2520 | // because computing the cost may insert more things into the map. | ||||
2521 | InstructionCost Cost = std::accumulate( | ||||
2522 | N.begin(), N.end(), BBCostIt->second, | ||||
2523 | [&](InstructionCost Sum, DomTreeNode *ChildN) -> InstructionCost { | ||||
2524 | return Sum + computeDomSubtreeCost(*ChildN, BBCostMap, DTCostMap); | ||||
2525 | }); | ||||
2526 | bool Inserted = DTCostMap.insert({&N, Cost}).second; | ||||
2527 | (void)Inserted; | ||||
2528 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2528, __extension__ __PRETTY_FUNCTION__)); | ||||
2529 | return Cost; | ||||
2530 | } | ||||
2531 | |||||
2532 | /// Turns a llvm.experimental.guard intrinsic into implicit control flow branch, | ||||
2533 | /// making the following replacement: | ||||
2534 | /// | ||||
2535 | /// --code before guard-- | ||||
2536 | /// call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ] | ||||
2537 | /// --code after guard-- | ||||
2538 | /// | ||||
2539 | /// into | ||||
2540 | /// | ||||
2541 | /// --code before guard-- | ||||
2542 | /// br i1 %cond, label %guarded, label %deopt | ||||
2543 | /// | ||||
2544 | /// guarded: | ||||
2545 | /// --code after guard-- | ||||
2546 | /// | ||||
2547 | /// deopt: | ||||
2548 | /// call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ] | ||||
2549 | /// unreachable | ||||
2550 | /// | ||||
2551 | /// It also makes all relevant DT and LI updates, so that all structures are in | ||||
2552 | /// valid state after this transform. | ||||
2553 | static BranchInst * | ||||
2554 | turnGuardIntoBranch(IntrinsicInst *GI, Loop &L, | ||||
2555 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | ||||
2556 | DominatorTree &DT, LoopInfo &LI, MemorySSAUpdater *MSSAU) { | ||||
2557 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | ||||
2558 | 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); | ||||
2559 | BasicBlock *CheckBB = GI->getParent(); | ||||
2560 | |||||
2561 | if (MSSAU && VerifyMemorySSA) | ||||
2562 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
2563 | |||||
2564 | // Remove all CheckBB's successors from DomTree. A block can be seen among | ||||
2565 | // successors more than once, but for DomTree it should be added only once. | ||||
2566 | SmallPtrSet<BasicBlock *, 4> Successors; | ||||
2567 | for (auto *Succ : successors(CheckBB)) | ||||
2568 | if (Successors.insert(Succ).second) | ||||
2569 | DTUpdates.push_back({DominatorTree::Delete, CheckBB, Succ}); | ||||
2570 | |||||
2571 | Instruction *DeoptBlockTerm = | ||||
2572 | SplitBlockAndInsertIfThen(GI->getArgOperand(0), GI, true); | ||||
2573 | BranchInst *CheckBI = cast<BranchInst>(CheckBB->getTerminator()); | ||||
2574 | // SplitBlockAndInsertIfThen inserts control flow that branches to | ||||
2575 | // DeoptBlockTerm if the condition is true. We want the opposite. | ||||
2576 | CheckBI->swapSuccessors(); | ||||
2577 | |||||
2578 | BasicBlock *GuardedBlock = CheckBI->getSuccessor(0); | ||||
2579 | GuardedBlock->setName("guarded"); | ||||
2580 | CheckBI->getSuccessor(1)->setName("deopt"); | ||||
2581 | BasicBlock *DeoptBlock = CheckBI->getSuccessor(1); | ||||
2582 | |||||
2583 | // We now have a new exit block. | ||||
2584 | ExitBlocks.push_back(CheckBI->getSuccessor(1)); | ||||
2585 | |||||
2586 | if (MSSAU) | ||||
2587 | MSSAU->moveAllAfterSpliceBlocks(CheckBB, GuardedBlock, GI); | ||||
2588 | |||||
2589 | GI->moveBefore(DeoptBlockTerm); | ||||
2590 | GI->setArgOperand(0, ConstantInt::getFalse(GI->getContext())); | ||||
2591 | |||||
2592 | // Add new successors of CheckBB into DomTree. | ||||
2593 | for (auto *Succ : successors(CheckBB)) | ||||
2594 | DTUpdates.push_back({DominatorTree::Insert, CheckBB, Succ}); | ||||
2595 | |||||
2596 | // Now the blocks that used to be CheckBB's successors are GuardedBlock's | ||||
2597 | // successors. | ||||
2598 | for (auto *Succ : Successors) | ||||
2599 | DTUpdates.push_back({DominatorTree::Insert, GuardedBlock, Succ}); | ||||
2600 | |||||
2601 | // Make proper changes to DT. | ||||
2602 | DT.applyUpdates(DTUpdates); | ||||
2603 | // Inform LI of a new loop block. | ||||
2604 | L.addBasicBlockToLoop(GuardedBlock, LI); | ||||
2605 | |||||
2606 | if (MSSAU) { | ||||
2607 | MemoryDef *MD = cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(GI)); | ||||
2608 | MSSAU->moveToPlace(MD, DeoptBlock, MemorySSA::BeforeTerminator); | ||||
2609 | if (VerifyMemorySSA) | ||||
2610 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||
2611 | } | ||||
2612 | |||||
2613 | ++NumGuards; | ||||
2614 | return CheckBI; | ||||
2615 | } | ||||
2616 | |||||
2617 | /// Cost multiplier is a way to limit potentially exponential behavior | ||||
2618 | /// of loop-unswitch. Cost is multipied in proportion of 2^number of unswitch | ||||
2619 | /// candidates available. Also accounting for the number of "sibling" loops with | ||||
2620 | /// the idea to account for previous unswitches that already happened on this | ||||
2621 | /// cluster of loops. There was an attempt to keep this formula simple, | ||||
2622 | /// just enough to limit the worst case behavior. Even if it is not that simple | ||||
2623 | /// now it is still not an attempt to provide a detailed heuristic size | ||||
2624 | /// prediction. | ||||
2625 | /// | ||||
2626 | /// TODO: Make a proper accounting of "explosion" effect for all kinds of | ||||
2627 | /// unswitch candidates, making adequate predictions instead of wild guesses. | ||||
2628 | /// That requires knowing not just the number of "remaining" candidates but | ||||
2629 | /// also costs of unswitching for each of these candidates. | ||||
2630 | static int CalculateUnswitchCostMultiplier( | ||||
2631 | Instruction &TI, Loop &L, LoopInfo &LI, DominatorTree &DT, | ||||
2632 | ArrayRef<std::pair<Instruction *, TinyPtrVector<Value *>>> | ||||
2633 | UnswitchCandidates) { | ||||
2634 | |||||
2635 | // Guards and other exiting conditions do not contribute to exponential | ||||
2636 | // explosion as soon as they dominate the latch (otherwise there might be | ||||
2637 | // another path to the latch remaining that does not allow to eliminate the | ||||
2638 | // loop copy on unswitch). | ||||
2639 | BasicBlock *Latch = L.getLoopLatch(); | ||||
2640 | BasicBlock *CondBlock = TI.getParent(); | ||||
2641 | if (DT.dominates(CondBlock, Latch) && | ||||
2642 | (isGuard(&TI) || | ||||
2643 | llvm::count_if(successors(&TI), [&L](BasicBlock *SuccBB) { | ||||
2644 | return L.contains(SuccBB); | ||||
2645 | }) <= 1)) { | ||||
2646 | NumCostMultiplierSkipped++; | ||||
2647 | return 1; | ||||
2648 | } | ||||
2649 | |||||
2650 | auto *ParentL = L.getParentLoop(); | ||||
2651 | int SiblingsCount = (ParentL ? ParentL->getSubLoopsVector().size() | ||||
2652 | : std::distance(LI.begin(), LI.end())); | ||||
2653 | // Count amount of clones that all the candidates might cause during | ||||
2654 | // unswitching. Branch/guard counts as 1, switch counts as log2 of its cases. | ||||
2655 | int UnswitchedClones = 0; | ||||
2656 | for (auto Candidate : UnswitchCandidates) { | ||||
2657 | Instruction *CI = Candidate.first; | ||||
2658 | BasicBlock *CondBlock = CI->getParent(); | ||||
2659 | bool SkipExitingSuccessors = DT.dominates(CondBlock, Latch); | ||||
2660 | if (isGuard(CI)) { | ||||
2661 | if (!SkipExitingSuccessors) | ||||
2662 | UnswitchedClones++; | ||||
2663 | continue; | ||||
2664 | } | ||||
2665 | int NonExitingSuccessors = llvm::count_if( | ||||
2666 | successors(CondBlock), [SkipExitingSuccessors, &L](BasicBlock *SuccBB) { | ||||
2667 | return !SkipExitingSuccessors || L.contains(SuccBB); | ||||
2668 | }); | ||||
2669 | UnswitchedClones += Log2_32(NonExitingSuccessors); | ||||
2670 | } | ||||
2671 | |||||
2672 | // Ignore up to the "unscaled candidates" number of unswitch candidates | ||||
2673 | // when calculating the power-of-two scaling of the cost. The main idea | ||||
2674 | // with this control is to allow a small number of unswitches to happen | ||||
2675 | // and rely more on siblings multiplier (see below) when the number | ||||
2676 | // of candidates is small. | ||||
2677 | unsigned ClonesPower = | ||||
2678 | std::max(UnswitchedClones - (int)UnswitchNumInitialUnscaledCandidates, 0); | ||||
2679 | |||||
2680 | // Allowing top-level loops to spread a bit more than nested ones. | ||||
2681 | int SiblingsMultiplier = | ||||
2682 | std::max((ParentL ? SiblingsCount | ||||
2683 | : SiblingsCount / (int)UnswitchSiblingsToplevelDiv), | ||||
2684 | 1); | ||||
2685 | // Compute the cost multiplier in a way that won't overflow by saturating | ||||
2686 | // at an upper bound. | ||||
2687 | int CostMultiplier; | ||||
2688 | if (ClonesPower > Log2_32(UnswitchThreshold) || | ||||
2689 | SiblingsMultiplier > UnswitchThreshold) | ||||
2690 | CostMultiplier = UnswitchThreshold; | ||||
2691 | else | ||||
2692 | CostMultiplier = std::min(SiblingsMultiplier * (1 << ClonesPower), | ||||
2693 | (int)UnswitchThreshold); | ||||
2694 | |||||
2695 | 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) | ||||
2696 | << " (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) | ||||
2697 | << (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) | ||||
2698 | << " 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); | ||||
2699 | return CostMultiplier; | ||||
2700 | } | ||||
2701 | |||||
2702 | static bool unswitchBestCondition( | ||||
2703 | Loop &L, DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | ||||
2704 | AAResults &AA, TargetTransformInfo &TTI, | ||||
2705 | function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB, | ||||
2706 | ScalarEvolution *SE, MemorySSAUpdater *MSSAU, | ||||
2707 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||
2708 | // Collect all invariant conditions within this loop (as opposed to an inner | ||||
2709 | // loop which would be handled when visiting that inner loop). | ||||
2710 | SmallVector<std::pair<Instruction *, TinyPtrVector<Value *>>, 4> | ||||
2711 | UnswitchCandidates; | ||||
2712 | |||||
2713 | // Whether or not we should also collect guards in the loop. | ||||
2714 | bool CollectGuards = false; | ||||
2715 | if (UnswitchGuards) { | ||||
| |||||
2716 | auto *GuardDecl = L.getHeader()->getParent()->getParent()->getFunction( | ||||
2717 | Intrinsic::getName(Intrinsic::experimental_guard)); | ||||
2718 | if (GuardDecl && !GuardDecl->use_empty()) | ||||
2719 | CollectGuards = true; | ||||
2720 | } | ||||
2721 | |||||
2722 | IVConditionInfo PartialIVInfo; | ||||
2723 | for (auto *BB : L.blocks()) { | ||||
2724 | if (LI.getLoopFor(BB) != &L) | ||||
2725 | continue; | ||||
2726 | |||||
2727 | if (CollectGuards) | ||||
2728 | for (auto &I : *BB) | ||||
2729 | if (isGuard(&I)) { | ||||
2730 | auto *Cond = cast<IntrinsicInst>(&I)->getArgOperand(0); | ||||
2731 | // TODO: Support AND, OR conditions and partial unswitching. | ||||
2732 | if (!isa<Constant>(Cond) && L.isLoopInvariant(Cond)) | ||||
2733 | UnswitchCandidates.push_back({&I, {Cond}}); | ||||
2734 | } | ||||
2735 | |||||
2736 | if (auto *SI = dyn_cast<SwitchInst>(BB->getTerminator())) { | ||||
2737 | // We can only consider fully loop-invariant switch conditions as we need | ||||
2738 | // to completely eliminate the switch after unswitching. | ||||
2739 | if (!isa<Constant>(SI->getCondition()) && | ||||
2740 | L.isLoopInvariant(SI->getCondition()) && !BB->getUniqueSuccessor()) | ||||
2741 | UnswitchCandidates.push_back({SI, {SI->getCondition()}}); | ||||
2742 | continue; | ||||
2743 | } | ||||
2744 | |||||
2745 | auto *BI = dyn_cast<BranchInst>(BB->getTerminator()); | ||||
2746 | if (!BI || !BI->isConditional() || isa<Constant>(BI->getCondition()) || | ||||
2747 | BI->getSuccessor(0) == BI->getSuccessor(1)) | ||||
2748 | continue; | ||||
2749 | |||||
2750 | // If BI's condition is 'select _, true, false', simplify it to confuse | ||||
2751 | // matchers | ||||
2752 | Value *Cond = BI->getCondition(), *CondNext; | ||||
2753 | while (match(Cond, m_Select(m_Value(CondNext), m_One(), m_Zero()))) | ||||
2754 | Cond = CondNext; | ||||
2755 | BI->setCondition(Cond); | ||||
2756 | |||||
2757 | if (isa<Constant>(Cond)) | ||||
2758 | continue; | ||||
2759 | |||||
2760 | if (L.isLoopInvariant(BI->getCondition())) { | ||||
2761 | UnswitchCandidates.push_back({BI, {BI->getCondition()}}); | ||||
2762 | continue; | ||||
2763 | } | ||||
2764 | |||||
2765 | Instruction &CondI = *cast<Instruction>(BI->getCondition()); | ||||
2766 | if (match(&CondI, m_CombineOr(m_LogicalAnd(), m_LogicalOr()))) { | ||||
2767 | TinyPtrVector<Value *> Invariants = | ||||
2768 | collectHomogenousInstGraphLoopInvariants(L, CondI, LI); | ||||
2769 | if (Invariants.empty()) | ||||
2770 | continue; | ||||
2771 | |||||
2772 | UnswitchCandidates.push_back({BI, std::move(Invariants)}); | ||||
2773 | continue; | ||||
2774 | } | ||||
2775 | } | ||||
2776 | |||||
2777 | Instruction *PartialIVCondBranch = nullptr; | ||||
2778 | if (MSSAU && !findOptionMDForLoop(&L, "llvm.loop.unswitch.partial.disable") && | ||||
2779 | !any_of(UnswitchCandidates, [&L](auto &TerminatorAndInvariants) { | ||||
2780 | return TerminatorAndInvariants.first == L.getHeader()->getTerminator(); | ||||
2781 | })) { | ||||
2782 | MemorySSA *MSSA = MSSAU->getMemorySSA(); | ||||
2783 | if (auto Info = hasPartialIVCondition(L, MSSAThreshold, *MSSA, AA)) { | ||||
2784 | 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) | ||||
2785 | 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) | ||||
2786 | << *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); | ||||
2787 | PartialIVInfo = *Info; | ||||
2788 | PartialIVCondBranch = L.getHeader()->getTerminator(); | ||||
2789 | TinyPtrVector<Value *> ValsToDuplicate; | ||||
2790 | for (auto *Inst : Info->InstToDuplicate) | ||||
2791 | ValsToDuplicate.push_back(Inst); | ||||
2792 | UnswitchCandidates.push_back( | ||||
2793 | {L.getHeader()->getTerminator(), std::move(ValsToDuplicate)}); | ||||
2794 | } | ||||
2795 | } | ||||
2796 | |||||
2797 | // If we didn't find any candidates, we're done. | ||||
2798 | if (UnswitchCandidates.empty()) | ||||
2799 | return false; | ||||
2800 | |||||
2801 | // Check if there are irreducible CFG cycles in this loop. If so, we cannot | ||||
2802 | // easily unswitch non-trivial edges out of the loop. Doing so might turn the | ||||
2803 | // irreducible control flow into reducible control flow and introduce new | ||||
2804 | // loops "out of thin air". If we ever discover important use cases for doing | ||||
2805 | // this, we can add support to loop unswitch, but it is a lot of complexity | ||||
2806 | // for what seems little or no real world benefit. | ||||
2807 | LoopBlocksRPO RPOT(&L); | ||||
2808 | RPOT.perform(&LI); | ||||
2809 | if (containsIrreducibleCFG<const BasicBlock *>(RPOT, LI)) | ||||
2810 | return false; | ||||
2811 | |||||
2812 | SmallVector<BasicBlock *, 4> ExitBlocks; | ||||
2813 | L.getUniqueExitBlocks(ExitBlocks); | ||||
2814 | |||||
2815 | // We cannot unswitch if exit blocks contain a cleanuppad/catchswitch | ||||
2816 | // instruction as we don't know how to split those exit blocks. | ||||
2817 | // FIXME: We should teach SplitBlock to handle this and remove this | ||||
2818 | // restriction. | ||||
2819 | for (auto *ExitBB : ExitBlocks) { | ||||
2820 | auto *I = ExitBB->getFirstNonPHI(); | ||||
2821 | if (isa<CleanupPadInst>(I) || isa<CatchSwitchInst>(I)) { | ||||
2822 | 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) | ||||
2823 | "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); | ||||
2824 | return false; | ||||
2825 | } | ||||
2826 | } | ||||
2827 | |||||
2828 | 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) | ||||
2829 | 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) | ||||
2830 | << " 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); | ||||
2831 | |||||
2832 | // Given that unswitching these terminators will require duplicating parts of | ||||
2833 | // the loop, so we need to be able to model that cost. Compute the ephemeral | ||||
2834 | // values and set up a data structure to hold per-BB costs. We cache each | ||||
2835 | // block's cost so that we don't recompute this when considering different | ||||
2836 | // subsets of the loop for duplication during unswitching. | ||||
2837 | SmallPtrSet<const Value *, 4> EphValues; | ||||
2838 | CodeMetrics::collectEphemeralValues(&L, &AC, EphValues); | ||||
2839 | SmallDenseMap<BasicBlock *, InstructionCost, 4> BBCostMap; | ||||
2840 | |||||
2841 | // Compute the cost of each block, as well as the total loop cost. Also, bail | ||||
2842 | // out if we see instructions which are incompatible with loop unswitching | ||||
2843 | // (convergent, noduplicate, or cross-basic-block tokens). | ||||
2844 | // FIXME: We might be able to safely handle some of these in non-duplicated | ||||
2845 | // regions. | ||||
2846 | TargetTransformInfo::TargetCostKind CostKind = | ||||
2847 | L.getHeader()->getParent()->hasMinSize() | ||||
2848 | ? TargetTransformInfo::TCK_CodeSize | ||||
2849 | : TargetTransformInfo::TCK_SizeAndLatency; | ||||
2850 | InstructionCost LoopCost = 0; | ||||
2851 | for (auto *BB : L.blocks()) { | ||||
2852 | InstructionCost Cost = 0; | ||||
2853 | for (auto &I : *BB) { | ||||
2854 | if (EphValues.count(&I)) | ||||
2855 | continue; | ||||
2856 | |||||
2857 | if (I.getType()->isTokenTy() && I.isUsedOutsideOfBlock(BB)) | ||||
2858 | return false; | ||||
2859 | if (auto *CB = dyn_cast<CallBase>(&I)) | ||||
2860 | if (CB->isConvergent() || CB->cannotDuplicate()) | ||||
2861 | return false; | ||||
2862 | |||||
2863 | Cost += TTI.getUserCost(&I, CostKind); | ||||
2864 | } | ||||
2865 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2865, __extension__ __PRETTY_FUNCTION__)); | ||||
2866 | LoopCost += Cost; | ||||
2867 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2867, __extension__ __PRETTY_FUNCTION__)); | ||||
2868 | BBCostMap[BB] = Cost; | ||||
2869 | } | ||||
2870 | 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); | ||||
2871 | |||||
2872 | // Now we find the best candidate by searching for the one with the following | ||||
2873 | // properties in order: | ||||
2874 | // | ||||
2875 | // 1) An unswitching cost below the threshold | ||||
2876 | // 2) The smallest number of duplicated unswitch candidates (to avoid | ||||
2877 | // creating redundant subsequent unswitching) | ||||
2878 | // 3) The smallest cost after unswitching. | ||||
2879 | // | ||||
2880 | // We prioritize reducing fanout of unswitch candidates provided the cost | ||||
2881 | // remains below the threshold because this has a multiplicative effect. | ||||
2882 | // | ||||
2883 | // This requires memoizing each dominator subtree to avoid redundant work. | ||||
2884 | // | ||||
2885 | // FIXME: Need to actually do the number of candidates part above. | ||||
2886 | SmallDenseMap<DomTreeNode *, InstructionCost, 4> DTCostMap; | ||||
2887 | // Given a terminator which might be unswitched, computes the non-duplicated | ||||
2888 | // cost for that terminator. | ||||
2889 | auto ComputeUnswitchedCost = [&](Instruction &TI, | ||||
2890 | bool FullUnswitch) -> InstructionCost { | ||||
2891 | BasicBlock &BB = *TI.getParent(); | ||||
2892 | SmallPtrSet<BasicBlock *, 4> Visited; | ||||
2893 | |||||
2894 | InstructionCost Cost = 0; | ||||
2895 | for (BasicBlock *SuccBB : successors(&BB)) { | ||||
2896 | // Don't count successors more than once. | ||||
2897 | if (!Visited.insert(SuccBB).second) | ||||
2898 | continue; | ||||
2899 | |||||
2900 | // If this is a partial unswitch candidate, then it must be a conditional | ||||
2901 | // branch with a condition of either `or`, `and`, their corresponding | ||||
2902 | // select forms or partially invariant instructions. In that case, one of | ||||
2903 | // the successors is necessarily duplicated, so don't even try to remove | ||||
2904 | // its cost. | ||||
2905 | if (!FullUnswitch
| ||||
2906 | auto &BI = cast<BranchInst>(TI); | ||||
2907 | if (match(BI.getCondition(), m_LogicalAnd())) { | ||||
2908 | if (SuccBB == BI.getSuccessor(1)) | ||||
2909 | continue; | ||||
2910 | } else if (match(BI.getCondition(), m_LogicalOr())) { | ||||
2911 | if (SuccBB == BI.getSuccessor(0)) | ||||
2912 | continue; | ||||
2913 | } else if ((PartialIVInfo.KnownValue->isOneValue() && | ||||
| |||||
2914 | SuccBB == BI.getSuccessor(0)) || | ||||
2915 | (!PartialIVInfo.KnownValue->isOneValue() && | ||||
2916 | SuccBB == BI.getSuccessor(1))) | ||||
2917 | continue; | ||||
2918 | } | ||||
2919 | |||||
2920 | // This successor's domtree will not need to be duplicated after | ||||
2921 | // unswitching if the edge to the successor dominates it (and thus the | ||||
2922 | // entire tree). This essentially means there is no other path into this | ||||
2923 | // subtree and so it will end up live in only one clone of the loop. | ||||
2924 | if (SuccBB->getUniquePredecessor() || | ||||
2925 | llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) { | ||||
2926 | return PredBB == &BB || DT.dominates(SuccBB, PredBB); | ||||
2927 | })) { | ||||
2928 | Cost += computeDomSubtreeCost(*DT[SuccBB], BBCostMap, DTCostMap); | ||||
2929 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2930, __extension__ __PRETTY_FUNCTION__)) | ||||
2930 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2930, __extension__ __PRETTY_FUNCTION__)); | ||||
2931 | } | ||||
2932 | } | ||||
2933 | |||||
2934 | // Now scale the cost by the number of unique successors minus one. We | ||||
2935 | // subtract one because there is already at least one copy of the entire | ||||
2936 | // loop. This is computing the new cost of unswitching a condition. | ||||
2937 | // Note that guards always have 2 unique successors that are implicit and | ||||
2938 | // will be materialized if we decide to unswitch it. | ||||
2939 | int SuccessorsCount = isGuard(&TI) ? 2 : Visited.size(); | ||||
2940 | 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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2941, __extension__ __PRETTY_FUNCTION__)) | ||||
2941 | "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!\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2941, __extension__ __PRETTY_FUNCTION__)); | ||||
2942 | return (LoopCost - Cost) * (SuccessorsCount - 1); | ||||
2943 | }; | ||||
2944 | Instruction *BestUnswitchTI = nullptr; | ||||
2945 | InstructionCost BestUnswitchCost = 0; | ||||
2946 | ArrayRef<Value *> BestUnswitchInvariants; | ||||
2947 | for (auto &TerminatorAndInvariants : UnswitchCandidates) { | ||||
2948 | Instruction &TI = *TerminatorAndInvariants.first; | ||||
2949 | ArrayRef<Value *> Invariants = TerminatorAndInvariants.second; | ||||
2950 | BranchInst *BI = dyn_cast<BranchInst>(&TI); | ||||
2951 | InstructionCost CandidateCost = ComputeUnswitchedCost( | ||||
2952 | TI, /*FullUnswitch*/ !BI
| ||||
2953 | Invariants[0] == BI->getCondition())); | ||||
2954 | // Calculate cost multiplier which is a tool to limit potentially | ||||
2955 | // exponential behavior of loop-unswitch. | ||||
2956 | if (EnableUnswitchCostMultiplier) { | ||||
2957 | int CostMultiplier = | ||||
2958 | CalculateUnswitchCostMultiplier(TI, L, LI, DT, UnswitchCandidates); | ||||
2959 | 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\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2961, __extension__ __PRETTY_FUNCTION__)) | ||||
2960 | (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\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2961, __extension__ __PRETTY_FUNCTION__)) | ||||
2961 | "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\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2961, __extension__ __PRETTY_FUNCTION__)); | ||||
2962 | CandidateCost *= CostMultiplier; | ||||
2963 | 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) | ||||
2964 | << " (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) | ||||
2965 | << " 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); | ||||
2966 | } else { | ||||
2967 | 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) | ||||
2968 | << " 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); | ||||
2969 | } | ||||
2970 | |||||
2971 | if (!BestUnswitchTI || CandidateCost < BestUnswitchCost) { | ||||
2972 | BestUnswitchTI = &TI; | ||||
2973 | BestUnswitchCost = CandidateCost; | ||||
2974 | BestUnswitchInvariants = Invariants; | ||||
2975 | } | ||||
2976 | } | ||||
2977 | 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\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 2977, __extension__ __PRETTY_FUNCTION__)); | ||||
2978 | |||||
2979 | if (BestUnswitchCost >= UnswitchThreshold) { | ||||
2980 | 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) | ||||
2981 | << BestUnswitchCost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Cannot unswitch, lowest cost found: " << BestUnswitchCost << "\n"; } } while (false); | ||||
2982 | return false; | ||||
2983 | } | ||||
2984 | |||||
2985 | if (BestUnswitchTI != PartialIVCondBranch) | ||||
2986 | PartialIVInfo.InstToDuplicate.clear(); | ||||
2987 | |||||
2988 | // If the best candidate is a guard, turn it into a branch. | ||||
2989 | if (isGuard(BestUnswitchTI)) | ||||
2990 | BestUnswitchTI = turnGuardIntoBranch(cast<IntrinsicInst>(BestUnswitchTI), L, | ||||
2991 | ExitBlocks, DT, LI, MSSAU); | ||||
2992 | |||||
2993 | 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) | ||||
2994 | << BestUnswitchCost << ") terminator: " << *BestUnswitchTIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Unswitching non-trivial (cost = " << BestUnswitchCost << ") terminator: " << *BestUnswitchTI << "\n"; } } while (false) | ||||
2995 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Unswitching non-trivial (cost = " << BestUnswitchCost << ") terminator: " << *BestUnswitchTI << "\n"; } } while (false); | ||||
2996 | unswitchNontrivialInvariants(L, *BestUnswitchTI, BestUnswitchInvariants, | ||||
2997 | ExitBlocks, PartialIVInfo, DT, LI, AC, | ||||
2998 | UnswitchCB, SE, MSSAU, DestroyLoopCB); | ||||
2999 | return true; | ||||
3000 | } | ||||
3001 | |||||
3002 | /// Unswitch control flow predicated on loop invariant conditions. | ||||
3003 | /// | ||||
3004 | /// This first hoists all branches or switches which are trivial (IE, do not | ||||
3005 | /// require duplicating any part of the loop) out of the loop body. It then | ||||
3006 | /// looks at other loop invariant control flows and tries to unswitch those as | ||||
3007 | /// well by cloning the loop if the result is small enough. | ||||
3008 | /// | ||||
3009 | /// The `DT`, `LI`, `AC`, `AA`, `TTI` parameters are required analyses that are | ||||
3010 | /// also updated based on the unswitch. The `MSSA` analysis is also updated if | ||||
3011 | /// valid (i.e. its use is enabled). | ||||
3012 | /// | ||||
3013 | /// If either `NonTrivial` is true or the flag `EnableNonTrivialUnswitch` is | ||||
3014 | /// true, we will attempt to do non-trivial unswitching as well as trivial | ||||
3015 | /// unswitching. | ||||
3016 | /// | ||||
3017 | /// The `UnswitchCB` callback provided will be run after unswitching is | ||||
3018 | /// complete, with the first parameter set to `true` if the provided loop | ||||
3019 | /// remains a loop, and a list of new sibling loops created. | ||||
3020 | /// | ||||
3021 | /// If `SE` is non-null, we will update that analysis based on the unswitching | ||||
3022 | /// done. | ||||
3023 | static bool | ||||
3024 | unswitchLoop(Loop &L, DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | ||||
3025 | AAResults &AA, TargetTransformInfo &TTI, bool Trivial, | ||||
3026 | bool NonTrivial, | ||||
3027 | function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB, | ||||
3028 | ScalarEvolution *SE, MemorySSAUpdater *MSSAU, | ||||
3029 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||
3030 | 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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 3031, __extension__ __PRETTY_FUNCTION__)) | ||||
3031 | "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.\"" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 3031, __extension__ __PRETTY_FUNCTION__)); | ||||
3032 | |||||
3033 | // Must be in loop simplified form: we need a preheader and dedicated exits. | ||||
3034 | if (!L.isLoopSimplifyForm()) | ||||
3035 | return false; | ||||
3036 | |||||
3037 | // Try trivial unswitch first before loop over other basic blocks in the loop. | ||||
3038 | if (Trivial && unswitchAllTrivialConditions(L, DT, LI, SE, MSSAU)) { | ||||
3039 | // If we unswitched successfully we will want to clean up the loop before | ||||
3040 | // processing it further so just mark it as unswitched and return. | ||||
3041 | UnswitchCB(/*CurrentLoopValid*/ true, false, {}); | ||||
3042 | return true; | ||||
3043 | } | ||||
3044 | |||||
3045 | // Check whether we should continue with non-trivial conditions. | ||||
3046 | // EnableNonTrivialUnswitch: Global variable that forces non-trivial | ||||
3047 | // unswitching for testing and debugging. | ||||
3048 | // NonTrivial: Parameter that enables non-trivial unswitching for this | ||||
3049 | // invocation of the transform. But this should be allowed only | ||||
3050 | // for targets without branch divergence. | ||||
3051 | // | ||||
3052 | // FIXME: If divergence analysis becomes available to a loop | ||||
3053 | // transform, we should allow unswitching for non-trivial uniform | ||||
3054 | // branches even on targets that have divergence. | ||||
3055 | // https://bugs.llvm.org/show_bug.cgi?id=48819 | ||||
3056 | bool ContinueWithNonTrivial = | ||||
3057 | EnableNonTrivialUnswitch || (NonTrivial && !TTI.hasBranchDivergence()); | ||||
3058 | if (!ContinueWithNonTrivial) | ||||
3059 | return false; | ||||
3060 | |||||
3061 | // Skip non-trivial unswitching for optsize functions. | ||||
3062 | if (L.getHeader()->getParent()->hasOptSize()) | ||||
3063 | return false; | ||||
3064 | |||||
3065 | // Skip non-trivial unswitching for loops that cannot be cloned. | ||||
3066 | if (!L.isSafeToClone()) | ||||
3067 | return false; | ||||
3068 | |||||
3069 | // For non-trivial unswitching, because it often creates new loops, we rely on | ||||
3070 | // the pass manager to iterate on the loops rather than trying to immediately | ||||
3071 | // reach a fixed point. There is no substantial advantage to iterating | ||||
3072 | // internally, and if any of the new loops are simplified enough to contain | ||||
3073 | // trivial unswitching we want to prefer those. | ||||
3074 | |||||
3075 | // Try to unswitch the best invariant condition. We prefer this full unswitch to | ||||
3076 | // a partial unswitch when possible below the threshold. | ||||
3077 | if (unswitchBestCondition(L, DT, LI, AC, AA, TTI, UnswitchCB, SE, MSSAU, | ||||
3078 | DestroyLoopCB)) | ||||
3079 | return true; | ||||
3080 | |||||
3081 | // No other opportunities to unswitch. | ||||
3082 | return false; | ||||
3083 | } | ||||
3084 | |||||
3085 | PreservedAnalyses SimpleLoopUnswitchPass::run(Loop &L, LoopAnalysisManager &AM, | ||||
3086 | LoopStandardAnalysisResults &AR, | ||||
3087 | LPMUpdater &U) { | ||||
3088 | Function &F = *L.getHeader()->getParent(); | ||||
3089 | (void)F; | ||||
3090 | |||||
3091 | 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) | ||||
3092 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << L << "\n"; } } while (false); | ||||
3093 | |||||
3094 | // Save the current loop name in a variable so that we can report it even | ||||
3095 | // after it has been deleted. | ||||
3096 | std::string LoopName = std::string(L.getName()); | ||||
3097 | |||||
3098 | auto UnswitchCB = [&L, &U, &LoopName](bool CurrentLoopValid, | ||||
3099 | bool PartiallyInvariant, | ||||
3100 | ArrayRef<Loop *> NewLoops) { | ||||
3101 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | ||||
3102 | if (!NewLoops.empty()) | ||||
3103 | U.addSiblingLoops(NewLoops); | ||||
3104 | |||||
3105 | // If the current loop remains valid, we should revisit it to catch any | ||||
3106 | // other unswitch opportunities. Otherwise, we need to mark it as deleted. | ||||
3107 | if (CurrentLoopValid) { | ||||
3108 | if (PartiallyInvariant) { | ||||
3109 | // Mark the new loop as partially unswitched, to avoid unswitching on | ||||
3110 | // the same condition again. | ||||
3111 | auto &Context = L.getHeader()->getContext(); | ||||
3112 | MDNode *DisableUnswitchMD = MDNode::get( | ||||
3113 | Context, | ||||
3114 | MDString::get(Context, "llvm.loop.unswitch.partial.disable")); | ||||
3115 | MDNode *NewLoopID = makePostTransformationMetadata( | ||||
3116 | Context, L.getLoopID(), {"llvm.loop.unswitch.partial"}, | ||||
3117 | {DisableUnswitchMD}); | ||||
3118 | L.setLoopID(NewLoopID); | ||||
3119 | } else | ||||
3120 | U.revisitCurrentLoop(); | ||||
3121 | } else | ||||
3122 | U.markLoopAsDeleted(L, LoopName); | ||||
3123 | }; | ||||
3124 | |||||
3125 | auto DestroyLoopCB = [&U](Loop &L, StringRef Name) { | ||||
3126 | U.markLoopAsDeleted(L, Name); | ||||
3127 | }; | ||||
3128 | |||||
3129 | Optional<MemorySSAUpdater> MSSAU; | ||||
3130 | if (AR.MSSA) { | ||||
3131 | MSSAU = MemorySSAUpdater(AR.MSSA); | ||||
3132 | if (VerifyMemorySSA) | ||||
3133 | AR.MSSA->verifyMemorySSA(); | ||||
3134 | } | ||||
3135 | if (!unswitchLoop(L, AR.DT, AR.LI, AR.AC, AR.AA, AR.TTI, Trivial, NonTrivial, | ||||
3136 | UnswitchCB, &AR.SE, | ||||
3137 | MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, | ||||
3138 | DestroyLoopCB)) | ||||
3139 | return PreservedAnalyses::all(); | ||||
3140 | |||||
3141 | if (AR.MSSA && VerifyMemorySSA) | ||||
3142 | AR.MSSA->verifyMemorySSA(); | ||||
3143 | |||||
3144 | // Historically this pass has had issues with the dominator tree so verify it | ||||
3145 | // in asserts builds. | ||||
3146 | 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)" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 3146, __extension__ __PRETTY_FUNCTION__)); | ||||
3147 | |||||
3148 | auto PA = getLoopPassPreservedAnalyses(); | ||||
3149 | if (AR.MSSA) | ||||
3150 | PA.preserve<MemorySSAAnalysis>(); | ||||
3151 | return PA; | ||||
3152 | } | ||||
3153 | |||||
3154 | void SimpleLoopUnswitchPass::printPipeline( | ||||
3155 | raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) { | ||||
3156 | static_cast<PassInfoMixin<SimpleLoopUnswitchPass> *>(this)->printPipeline( | ||||
3157 | OS, MapClassName2PassName); | ||||
3158 | |||||
3159 | OS << "<"; | ||||
3160 | OS << (NonTrivial ? "" : "no-") << "nontrivial;"; | ||||
3161 | OS << (Trivial ? "" : "no-") << "trivial"; | ||||
3162 | OS << ">"; | ||||
3163 | } | ||||
3164 | |||||
3165 | namespace { | ||||
3166 | |||||
3167 | class SimpleLoopUnswitchLegacyPass : public LoopPass { | ||||
3168 | bool NonTrivial; | ||||
3169 | |||||
3170 | public: | ||||
3171 | static char ID; // Pass ID, replacement for typeid | ||||
3172 | |||||
3173 | explicit SimpleLoopUnswitchLegacyPass(bool NonTrivial = false) | ||||
3174 | : LoopPass(ID), NonTrivial(NonTrivial) { | ||||
3175 | initializeSimpleLoopUnswitchLegacyPassPass( | ||||
3176 | *PassRegistry::getPassRegistry()); | ||||
3177 | } | ||||
3178 | |||||
3179 | bool runOnLoop(Loop *L, LPPassManager &LPM) override; | ||||
3180 | |||||
3181 | void getAnalysisUsage(AnalysisUsage &AU) const override { | ||||
3182 | AU.addRequired<AssumptionCacheTracker>(); | ||||
3183 | AU.addRequired<TargetTransformInfoWrapperPass>(); | ||||
3184 | AU.addRequired<MemorySSAWrapperPass>(); | ||||
3185 | AU.addPreserved<MemorySSAWrapperPass>(); | ||||
3186 | getLoopAnalysisUsage(AU); | ||||
3187 | } | ||||
3188 | }; | ||||
3189 | |||||
3190 | } // end anonymous namespace | ||||
3191 | |||||
3192 | bool SimpleLoopUnswitchLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) { | ||||
3193 | if (skipLoop(L)) | ||||
3194 | return false; | ||||
3195 | |||||
3196 | Function &F = *L->getHeader()->getParent(); | ||||
3197 | |||||
3198 | 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) | ||||
3199 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << *L << "\n" ; } } while (false); | ||||
3200 | |||||
3201 | auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); | ||||
3202 | auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); | ||||
3203 | auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); | ||||
3204 | auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults(); | ||||
3205 | auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F); | ||||
3206 | MemorySSA *MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA(); | ||||
3207 | MemorySSAUpdater MSSAU(MSSA); | ||||
3208 | |||||
3209 | auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>(); | ||||
3210 | auto *SE = SEWP ? &SEWP->getSE() : nullptr; | ||||
3211 | |||||
3212 | auto UnswitchCB = [&L, &LPM](bool CurrentLoopValid, bool PartiallyInvariant, | ||||
3213 | ArrayRef<Loop *> NewLoops) { | ||||
3214 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | ||||
3215 | for (auto *NewL : NewLoops) | ||||
3216 | LPM.addLoop(*NewL); | ||||
3217 | |||||
3218 | // If the current loop remains valid, re-add it to the queue. This is | ||||
3219 | // a little wasteful as we'll finish processing the current loop as well, | ||||
3220 | // but it is the best we can do in the old PM. | ||||
3221 | if (CurrentLoopValid) { | ||||
3222 | // If the current loop has been unswitched using a partially invariant | ||||
3223 | // condition, we should not re-add the current loop to avoid unswitching | ||||
3224 | // on the same condition again. | ||||
3225 | if (!PartiallyInvariant) | ||||
3226 | LPM.addLoop(*L); | ||||
3227 | } else | ||||
3228 | LPM.markLoopAsDeleted(*L); | ||||
3229 | }; | ||||
3230 | |||||
3231 | auto DestroyLoopCB = [&LPM](Loop &L, StringRef /* Name */) { | ||||
3232 | LPM.markLoopAsDeleted(L); | ||||
3233 | }; | ||||
3234 | |||||
3235 | if (VerifyMemorySSA) | ||||
3236 | MSSA->verifyMemorySSA(); | ||||
3237 | |||||
3238 | bool Changed = unswitchLoop(*L, DT, LI, AC, AA, TTI, true, NonTrivial, | ||||
3239 | UnswitchCB, SE, &MSSAU, DestroyLoopCB); | ||||
3240 | |||||
3241 | if (VerifyMemorySSA) | ||||
3242 | MSSA->verifyMemorySSA(); | ||||
3243 | |||||
3244 | // Historically this pass has had issues with the dominator tree so verify it | ||||
3245 | // in asserts builds. | ||||
3246 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp", 3246, __extension__ __PRETTY_FUNCTION__)); | ||||
3247 | |||||
3248 | return Changed; | ||||
3249 | } | ||||
3250 | |||||
3251 | char SimpleLoopUnswitchLegacyPass::ID = 0; | ||||
3252 | INITIALIZE_PASS_BEGIN(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | ||||
3253 | "Simple unswitch loops", false, false)static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | ||||
3254 | INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry); | ||||
3255 | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry); | ||||
3256 | INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry); | ||||
3257 | INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry); | ||||
3258 | INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry); | ||||
3259 | INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry); | ||||
3260 | INITIALIZE_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 )); } | ||||
3261 | "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 )); } | ||||
3262 | |||||
3263 | Pass *llvm::createSimpleLoopUnswitchLegacyPass(bool NonTrivial) { | ||||
3264 | return new SimpleLoopUnswitchLegacyPass(NonTrivial); | ||||
3265 | } |
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/Analysis/IVDescriptors.h" |
17 | #include "llvm/Transforms/Utils/ValueMapper.h" |
18 | |
19 | namespace llvm { |
20 | |
21 | template <typename T> class DomTreeNodeBase; |
22 | using DomTreeNode = DomTreeNodeBase<BasicBlock>; |
23 | class StringRef; |
24 | class AnalysisUsage; |
25 | class TargetTransformInfo; |
26 | class AAResults; |
27 | class BasicBlock; |
28 | class BlockFrequencyInfo; |
29 | class ICFLoopSafetyInfo; |
30 | class IRBuilderBase; |
31 | class Loop; |
32 | class LoopInfo; |
33 | class MemoryAccess; |
34 | class MemorySSA; |
35 | class MemorySSAUpdater; |
36 | class OptimizationRemarkEmitter; |
37 | class PredIteratorCache; |
38 | class ScalarEvolution; |
39 | class SCEV; |
40 | class SCEVExpander; |
41 | class TargetLibraryInfo; |
42 | class LPPassManager; |
43 | class Instruction; |
44 | struct RuntimeCheckingPtrGroup; |
45 | typedef std::pair<const RuntimeCheckingPtrGroup *, |
46 | const RuntimeCheckingPtrGroup *> |
47 | RuntimePointerCheck; |
48 | |
49 | template <typename T> class Optional; |
50 | template <typename T, unsigned N> class SmallSetVector; |
51 | template <typename T, unsigned N> class SmallPriorityWorklist; |
52 | |
53 | BasicBlock *InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, |
54 | MemorySSAUpdater *MSSAU, bool PreserveLCSSA); |
55 | |
56 | /// Ensure that all exit blocks of the loop are dedicated exits. |
57 | /// |
58 | /// For any loop exit block with non-loop predecessors, we split the loop |
59 | /// predecessors to use a dedicated loop exit block. We update the dominator |
60 | /// tree and loop info if provided, and will preserve LCSSA if requested. |
61 | bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI, |
62 | MemorySSAUpdater *MSSAU, bool PreserveLCSSA); |
63 | |
64 | /// Ensures LCSSA form for every instruction from the Worklist in the scope of |
65 | /// innermost containing loop. |
66 | /// |
67 | /// For the given instruction which have uses outside of the loop, an LCSSA PHI |
68 | /// node is inserted and the uses outside the loop are rewritten to use this |
69 | /// node. |
70 | /// |
71 | /// LoopInfo and DominatorTree are required and, since the routine makes no |
72 | /// changes to CFG, preserved. |
73 | /// |
74 | /// Returns true if any modifications are made. |
75 | /// |
76 | /// This function may introduce unused PHI nodes. If \p PHIsToRemove is not |
77 | /// nullptr, those are added to it (before removing, the caller has to check if |
78 | /// they still do not have any uses). Otherwise the PHIs are directly removed. |
79 | bool formLCSSAForInstructions( |
80 | SmallVectorImpl<Instruction *> &Worklist, const DominatorTree &DT, |
81 | const LoopInfo &LI, ScalarEvolution *SE, IRBuilderBase &Builder, |
82 | SmallVectorImpl<PHINode *> *PHIsToRemove = nullptr); |
83 | |
84 | /// Put loop into LCSSA form. |
85 | /// |
86 | /// Looks at all instructions in the loop which have uses outside of the |
87 | /// current loop. For each, an LCSSA PHI node is inserted and the uses outside |
88 | /// the loop are rewritten to use this node. Sub-loops must be in LCSSA form |
89 | /// already. |
90 | /// |
91 | /// LoopInfo and DominatorTree are required and preserved. |
92 | /// |
93 | /// If ScalarEvolution is passed in, it will be preserved. |
94 | /// |
95 | /// Returns true if any modifications are made to the loop. |
96 | bool formLCSSA(Loop &L, const DominatorTree &DT, const LoopInfo *LI, |
97 | ScalarEvolution *SE); |
98 | |
99 | /// Put a loop nest into LCSSA form. |
100 | /// |
101 | /// This recursively forms LCSSA for a loop nest. |
102 | /// |
103 | /// LoopInfo and DominatorTree are required and preserved. |
104 | /// |
105 | /// If ScalarEvolution is passed in, it will be preserved. |
106 | /// |
107 | /// Returns true if any modifications are made to the loop. |
108 | bool formLCSSARecursively(Loop &L, const DominatorTree &DT, const LoopInfo *LI, |
109 | ScalarEvolution *SE); |
110 | |
111 | /// Flags controlling how much is checked when sinking or hoisting |
112 | /// instructions. The number of memory access in the loop (and whether there |
113 | /// are too many) is determined in the constructors when using MemorySSA. |
114 | class SinkAndHoistLICMFlags { |
115 | public: |
116 | // Explicitly set limits. |
117 | SinkAndHoistLICMFlags(unsigned LicmMssaOptCap, |
118 | unsigned LicmMssaNoAccForPromotionCap, bool IsSink, |
119 | Loop *L = nullptr, MemorySSA *MSSA = nullptr); |
120 | // Use default limits. |
121 | SinkAndHoistLICMFlags(bool IsSink, Loop *L = nullptr, |
122 | MemorySSA *MSSA = nullptr); |
123 | |
124 | void setIsSink(bool B) { IsSink = B; } |
125 | bool getIsSink() { return IsSink; } |
126 | bool tooManyMemoryAccesses() { return NoOfMemAccTooLarge; } |
127 | bool tooManyClobberingCalls() { return LicmMssaOptCounter >= LicmMssaOptCap; } |
128 | void incrementClobberingCalls() { ++LicmMssaOptCounter; } |
129 | |
130 | protected: |
131 | bool NoOfMemAccTooLarge = false; |
132 | unsigned LicmMssaOptCounter = 0; |
133 | unsigned LicmMssaOptCap; |
134 | unsigned LicmMssaNoAccForPromotionCap; |
135 | bool IsSink; |
136 | }; |
137 | |
138 | /// Walk the specified region of the CFG (defined by all blocks |
139 | /// dominated by the specified block, and that are in the current loop) in |
140 | /// reverse depth first order w.r.t the DominatorTree. This allows us to visit |
141 | /// uses before definitions, allowing us to sink a loop body in one pass without |
142 | /// iteration. Takes DomTreeNode, AAResults, LoopInfo, DominatorTree, |
143 | /// BlockFrequencyInfo, TargetLibraryInfo, Loop, AliasSet information for all |
144 | /// instructions of the loop and loop safety information as |
145 | /// arguments. Diagnostics is emitted via \p ORE. It returns changed status. |
146 | /// \p CurLoop is a loop to do sinking on. \p OutermostLoop is used only when |
147 | /// this function is called by \p sinkRegionForLoopNest. |
148 | bool sinkRegion(DomTreeNode *, AAResults *, LoopInfo *, DominatorTree *, |
149 | BlockFrequencyInfo *, TargetLibraryInfo *, |
150 | TargetTransformInfo *, Loop *CurLoop, MemorySSAUpdater &, |
151 | ICFLoopSafetyInfo *, SinkAndHoistLICMFlags &, |
152 | OptimizationRemarkEmitter *, Loop *OutermostLoop = nullptr); |
153 | |
154 | /// Call sinkRegion on loops contained within the specified loop |
155 | /// in order from innermost to outermost. |
156 | bool sinkRegionForLoopNest(DomTreeNode *, AAResults *, LoopInfo *, |
157 | DominatorTree *, BlockFrequencyInfo *, |
158 | TargetLibraryInfo *, TargetTransformInfo *, Loop *, |
159 | MemorySSAUpdater &, ICFLoopSafetyInfo *, |
160 | SinkAndHoistLICMFlags &, |
161 | OptimizationRemarkEmitter *); |
162 | |
163 | /// Walk the specified region of the CFG (defined by all blocks |
164 | /// dominated by the specified block, and that are in the current loop) in depth |
165 | /// first order w.r.t the DominatorTree. This allows us to visit definitions |
166 | /// before uses, allowing us to hoist a loop body in one pass without iteration. |
167 | /// Takes DomTreeNode, AAResults, LoopInfo, DominatorTree, |
168 | /// BlockFrequencyInfo, TargetLibraryInfo, Loop, AliasSet information for all |
169 | /// instructions of the loop and loop safety information as arguments. |
170 | /// Diagnostics is emitted via \p ORE. It returns changed status. |
171 | /// \p AllowSpeculation is whether values should be hoisted even if they are not |
172 | /// guaranteed to execute in the loop, but are safe to speculatively execute. |
173 | bool hoistRegion(DomTreeNode *, AAResults *, LoopInfo *, DominatorTree *, |
174 | BlockFrequencyInfo *, TargetLibraryInfo *, Loop *, |
175 | MemorySSAUpdater &, ScalarEvolution *, ICFLoopSafetyInfo *, |
176 | SinkAndHoistLICMFlags &, OptimizationRemarkEmitter *, bool, |
177 | bool AllowSpeculation); |
178 | |
179 | /// This function deletes dead loops. The caller of this function needs to |
180 | /// guarantee that the loop is infact dead. |
181 | /// The function requires a bunch or prerequisites to be present: |
182 | /// - The loop needs to be in LCSSA form |
183 | /// - The loop needs to have a Preheader |
184 | /// - A unique dedicated exit block must exist |
185 | /// |
186 | /// This also updates the relevant analysis information in \p DT, \p SE, \p LI |
187 | /// and \p MSSA if pointers to those are provided. |
188 | /// It also updates the loop PM if an updater struct is provided. |
189 | |
190 | void deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE, |
191 | LoopInfo *LI, MemorySSA *MSSA = nullptr); |
192 | |
193 | /// Remove the backedge of the specified loop. Handles loop nests and general |
194 | /// loop structures subject to the precondition that the loop has no parent |
195 | /// loop and has a single latch block. Preserves all listed analyses. |
196 | void breakLoopBackedge(Loop *L, DominatorTree &DT, ScalarEvolution &SE, |
197 | LoopInfo &LI, MemorySSA *MSSA); |
198 | |
199 | /// Try to promote memory values to scalars by sinking stores out of |
200 | /// the loop and moving loads to before the loop. We do this by looping over |
201 | /// the stores in the loop, looking for stores to Must pointers which are |
202 | /// loop invariant. It takes a set of must-alias values, Loop exit blocks |
203 | /// vector, loop exit blocks insertion point vector, PredIteratorCache, |
204 | /// LoopInfo, DominatorTree, Loop, AliasSet information for all instructions |
205 | /// of the loop and loop safety information as arguments. |
206 | /// Diagnostics is emitted via \p ORE. It returns changed status. |
207 | /// \p AllowSpeculation is whether values should be hoisted even if they are not |
208 | /// guaranteed to execute in the loop, but are safe to speculatively execute. |
209 | bool promoteLoopAccessesToScalars( |
210 | const SmallSetVector<Value *, 8> &, SmallVectorImpl<BasicBlock *> &, |
211 | SmallVectorImpl<Instruction *> &, SmallVectorImpl<MemoryAccess *> &, |
212 | PredIteratorCache &, LoopInfo *, DominatorTree *, const TargetLibraryInfo *, |
213 | Loop *, MemorySSAUpdater &, ICFLoopSafetyInfo *, |
214 | OptimizationRemarkEmitter *, bool AllowSpeculation); |
215 | |
216 | /// Does a BFS from a given node to all of its children inside a given loop. |
217 | /// The returned vector of nodes includes the starting point. |
218 | SmallVector<DomTreeNode *, 16> collectChildrenInLoop(DomTreeNode *N, |
219 | const Loop *CurLoop); |
220 | |
221 | /// Returns the instructions that use values defined in the loop. |
222 | SmallVector<Instruction *, 8> findDefsUsedOutsideOfLoop(Loop *L); |
223 | |
224 | /// Find a combination of metadata ("llvm.loop.vectorize.width" and |
225 | /// "llvm.loop.vectorize.scalable.enable") for a loop and use it to construct a |
226 | /// ElementCount. If the metadata "llvm.loop.vectorize.width" cannot be found |
227 | /// then None is returned. |
228 | Optional<ElementCount> |
229 | getOptionalElementCountLoopAttribute(const Loop *TheLoop); |
230 | |
231 | /// Create a new loop identifier for a loop created from a loop transformation. |
232 | /// |
233 | /// @param OrigLoopID The loop ID of the loop before the transformation. |
234 | /// @param FollowupAttrs List of attribute names that contain attributes to be |
235 | /// added to the new loop ID. |
236 | /// @param InheritOptionsAttrsPrefix Selects which attributes should be inherited |
237 | /// from the original loop. The following values |
238 | /// are considered: |
239 | /// nullptr : Inherit all attributes from @p OrigLoopID. |
240 | /// "" : Do not inherit any attribute from @p OrigLoopID; only use |
241 | /// those specified by a followup attribute. |
242 | /// "<prefix>": Inherit all attributes except those which start with |
243 | /// <prefix>; commonly used to remove metadata for the |
244 | /// applied transformation. |
245 | /// @param AlwaysNew If true, do not try to reuse OrigLoopID and never return |
246 | /// None. |
247 | /// |
248 | /// @return The loop ID for the after-transformation loop. The following values |
249 | /// can be returned: |
250 | /// None : No followup attribute was found; it is up to the |
251 | /// transformation to choose attributes that make sense. |
252 | /// @p OrigLoopID: The original identifier can be reused. |
253 | /// nullptr : The new loop has no attributes. |
254 | /// MDNode* : A new unique loop identifier. |
255 | Optional<MDNode *> |
256 | makeFollowupLoopID(MDNode *OrigLoopID, ArrayRef<StringRef> FollowupAttrs, |
257 | const char *InheritOptionsAttrsPrefix = "", |
258 | bool AlwaysNew = false); |
259 | |
260 | /// Look for the loop attribute that disables all transformation heuristic. |
261 | bool hasDisableAllTransformsHint(const Loop *L); |
262 | |
263 | /// Look for the loop attribute that disables the LICM transformation heuristics. |
264 | bool hasDisableLICMTransformsHint(const Loop *L); |
265 | |
266 | /// The mode sets how eager a transformation should be applied. |
267 | enum TransformationMode { |
268 | /// The pass can use heuristics to determine whether a transformation should |
269 | /// be applied. |
270 | TM_Unspecified, |
271 | |
272 | /// The transformation should be applied without considering a cost model. |
273 | TM_Enable, |
274 | |
275 | /// The transformation should not be applied. |
276 | TM_Disable, |
277 | |
278 | /// Force is a flag and should not be used alone. |
279 | TM_Force = 0x04, |
280 | |
281 | /// The transformation was directed by the user, e.g. by a #pragma in |
282 | /// the source code. If the transformation could not be applied, a |
283 | /// warning should be emitted. |
284 | TM_ForcedByUser = TM_Enable | TM_Force, |
285 | |
286 | /// The transformation must not be applied. For instance, `#pragma clang loop |
287 | /// unroll(disable)` explicitly forbids any unrolling to take place. Unlike |
288 | /// general loop metadata, it must not be dropped. Most passes should not |
289 | /// behave differently under TM_Disable and TM_SuppressedByUser. |
290 | TM_SuppressedByUser = TM_Disable | TM_Force |
291 | }; |
292 | |
293 | /// @{ |
294 | /// Get the mode for LLVM's supported loop transformations. |
295 | TransformationMode hasUnrollTransformation(const Loop *L); |
296 | TransformationMode hasUnrollAndJamTransformation(const Loop *L); |
297 | TransformationMode hasVectorizeTransformation(const Loop *L); |
298 | TransformationMode hasDistributeTransformation(const Loop *L); |
299 | TransformationMode hasLICMVersioningTransformation(const Loop *L); |
300 | /// @} |
301 | |
302 | /// Set input string into loop metadata by keeping other values intact. |
303 | /// If the string is already in loop metadata update value if it is |
304 | /// different. |
305 | void addStringMetadataToLoop(Loop *TheLoop, const char *MDString, |
306 | unsigned V = 0); |
307 | |
308 | /// Returns a loop's estimated trip count based on branch weight metadata. |
309 | /// In addition if \p EstimatedLoopInvocationWeight is not null it is |
310 | /// initialized with weight of loop's latch leading to the exit. |
311 | /// Returns 0 when the count is estimated to be 0, or None when a meaningful |
312 | /// estimate can not be made. |
313 | Optional<unsigned> |
314 | getLoopEstimatedTripCount(Loop *L, |
315 | unsigned *EstimatedLoopInvocationWeight = nullptr); |
316 | |
317 | /// Set a loop's branch weight metadata to reflect that loop has \p |
318 | /// EstimatedTripCount iterations and \p EstimatedLoopInvocationWeight exits |
319 | /// through latch. Returns true if metadata is successfully updated, false |
320 | /// otherwise. Note that loop must have a latch block which controls loop exit |
321 | /// in order to succeed. |
322 | bool setLoopEstimatedTripCount(Loop *L, unsigned EstimatedTripCount, |
323 | unsigned EstimatedLoopInvocationWeight); |
324 | |
325 | /// Check inner loop (L) backedge count is known to be invariant on all |
326 | /// iterations of its outer loop. If the loop has no parent, this is trivially |
327 | /// true. |
328 | bool hasIterationCountInvariantInParent(Loop *L, ScalarEvolution &SE); |
329 | |
330 | /// Helper to consistently add the set of standard passes to a loop pass's \c |
331 | /// AnalysisUsage. |
332 | /// |
333 | /// All loop passes should call this as part of implementing their \c |
334 | /// getAnalysisUsage. |
335 | void getLoopAnalysisUsage(AnalysisUsage &AU); |
336 | |
337 | /// Returns true if is legal to hoist or sink this instruction disregarding the |
338 | /// possible introduction of faults. Reasoning about potential faulting |
339 | /// instructions is the responsibility of the caller since it is challenging to |
340 | /// do efficiently from within this routine. |
341 | /// \p TargetExecutesOncePerLoop is true only when it is guaranteed that the |
342 | /// target executes at most once per execution of the loop body. This is used |
343 | /// to assess the legality of duplicating atomic loads. Generally, this is |
344 | /// true when moving out of loop and not true when moving into loops. |
345 | /// If \p ORE is set use it to emit optimization remarks. |
346 | bool canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, |
347 | Loop *CurLoop, MemorySSAUpdater &MSSAU, |
348 | bool TargetExecutesOncePerLoop, |
349 | SinkAndHoistLICMFlags &LICMFlags, |
350 | OptimizationRemarkEmitter *ORE = nullptr); |
351 | |
352 | /// Returns the comparison predicate used when expanding a min/max reduction. |
353 | CmpInst::Predicate getMinMaxReductionPredicate(RecurKind RK); |
354 | |
355 | /// See RecurrenceDescriptor::isSelectCmpPattern for a description of the |
356 | /// pattern we are trying to match. In this pattern we are only ever selecting |
357 | /// between two values: 1) an initial PHI start value, and 2) a loop invariant |
358 | /// value. This function uses \p LoopExitInst to determine 2), which we then use |
359 | /// to select between \p Left and \p Right. Any lane value in \p Left that |
360 | /// matches 2) will be merged into \p Right. |
361 | Value *createSelectCmpOp(IRBuilderBase &Builder, Value *StartVal, RecurKind RK, |
362 | Value *Left, Value *Right); |
363 | |
364 | /// Returns a Min/Max operation corresponding to MinMaxRecurrenceKind. |
365 | /// The Builder's fast-math-flags must be set to propagate the expected values. |
366 | Value *createMinMaxOp(IRBuilderBase &Builder, RecurKind RK, Value *Left, |
367 | Value *Right); |
368 | |
369 | /// Generates an ordered vector reduction using extracts to reduce the value. |
370 | Value *getOrderedReduction(IRBuilderBase &Builder, Value *Acc, Value *Src, |
371 | unsigned Op, RecurKind MinMaxKind = RecurKind::None); |
372 | |
373 | /// Generates a vector reduction using shufflevectors to reduce the value. |
374 | /// Fast-math-flags are propagated using the IRBuilder's setting. |
375 | Value *getShuffleReduction(IRBuilderBase &Builder, Value *Src, unsigned Op, |
376 | RecurKind MinMaxKind = RecurKind::None); |
377 | |
378 | /// Create a target reduction of the given vector. The reduction operation |
379 | /// is described by the \p Opcode parameter. min/max reductions require |
380 | /// additional information supplied in \p RdxKind. |
381 | /// The target is queried to determine if intrinsics or shuffle sequences are |
382 | /// required to implement the reduction. |
383 | /// Fast-math-flags are propagated using the IRBuilder's setting. |
384 | Value *createSimpleTargetReduction(IRBuilderBase &B, |
385 | const TargetTransformInfo *TTI, Value *Src, |
386 | RecurKind RdxKind); |
387 | |
388 | /// Create a target reduction of the given vector \p Src for a reduction of the |
389 | /// kind RecurKind::SelectICmp or RecurKind::SelectFCmp. The reduction operation |
390 | /// is described by \p Desc. |
391 | Value *createSelectCmpTargetReduction(IRBuilderBase &B, |
392 | const TargetTransformInfo *TTI, |
393 | Value *Src, |
394 | const RecurrenceDescriptor &Desc, |
395 | PHINode *OrigPhi); |
396 | |
397 | /// Create a generic target reduction using a recurrence descriptor \p Desc |
398 | /// The target is queried to determine if intrinsics or shuffle sequences are |
399 | /// required to implement the reduction. |
400 | /// Fast-math-flags are propagated using the RecurrenceDescriptor. |
401 | Value *createTargetReduction(IRBuilderBase &B, const TargetTransformInfo *TTI, |
402 | const RecurrenceDescriptor &Desc, Value *Src, |
403 | PHINode *OrigPhi = nullptr); |
404 | |
405 | /// Create an ordered reduction intrinsic using the given recurrence |
406 | /// descriptor \p Desc. |
407 | Value *createOrderedReduction(IRBuilderBase &B, |
408 | const RecurrenceDescriptor &Desc, Value *Src, |
409 | Value *Start); |
410 | |
411 | /// Get the intersection (logical and) of all of the potential IR flags |
412 | /// of each scalar operation (VL) that will be converted into a vector (I). |
413 | /// If OpValue is non-null, we only consider operations similar to OpValue |
414 | /// when intersecting. |
415 | /// Flag set: NSW, NUW, exact, and all of fast-math. |
416 | void propagateIRFlags(Value *I, ArrayRef<Value *> VL, Value *OpValue = nullptr); |
417 | |
418 | /// Returns true if we can prove that \p S is defined and always negative in |
419 | /// loop \p L. |
420 | bool isKnownNegativeInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE); |
421 | |
422 | /// Returns true if we can prove that \p S is defined and always non-negative in |
423 | /// loop \p L. |
424 | bool isKnownNonNegativeInLoop(const SCEV *S, const Loop *L, |
425 | ScalarEvolution &SE); |
426 | |
427 | /// Returns true if \p S is defined and never is equal to signed/unsigned max. |
428 | bool cannotBeMaxInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE, |
429 | bool Signed); |
430 | |
431 | /// Returns true if \p S is defined and never is equal to signed/unsigned min. |
432 | bool cannotBeMinInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE, |
433 | bool Signed); |
434 | |
435 | enum ReplaceExitVal { NeverRepl, OnlyCheapRepl, NoHardUse, AlwaysRepl }; |
436 | |
437 | /// If the final value of any expressions that are recurrent in the loop can |
438 | /// be computed, substitute the exit values from the loop into any instructions |
439 | /// outside of the loop that use the final values of the current expressions. |
440 | /// Return the number of loop exit values that have been replaced, and the |
441 | /// corresponding phi node will be added to DeadInsts. |
442 | int rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI, |
443 | ScalarEvolution *SE, const TargetTransformInfo *TTI, |
444 | SCEVExpander &Rewriter, DominatorTree *DT, |
445 | ReplaceExitVal ReplaceExitValue, |
446 | SmallVector<WeakTrackingVH, 16> &DeadInsts); |
447 | |
448 | /// Set weights for \p UnrolledLoop and \p RemainderLoop based on weights for |
449 | /// \p OrigLoop and the following distribution of \p OrigLoop iteration among \p |
450 | /// UnrolledLoop and \p RemainderLoop. \p UnrolledLoop receives weights that |
451 | /// reflect TC/UF iterations, and \p RemainderLoop receives weights that reflect |
452 | /// the remaining TC%UF iterations. |
453 | /// |
454 | /// Note that \p OrigLoop may be equal to either \p UnrolledLoop or \p |
455 | /// RemainderLoop in which case weights for \p OrigLoop are updated accordingly. |
456 | /// Note also behavior is undefined if \p UnrolledLoop and \p RemainderLoop are |
457 | /// equal. \p UF must be greater than zero. |
458 | /// If \p OrigLoop has no profile info associated nothing happens. |
459 | /// |
460 | /// This utility may be useful for such optimizations as unroller and |
461 | /// vectorizer as it's typical transformation for them. |
462 | void setProfileInfoAfterUnrolling(Loop *OrigLoop, Loop *UnrolledLoop, |
463 | Loop *RemainderLoop, uint64_t UF); |
464 | |
465 | /// Utility that implements appending of loops onto a worklist given a range. |
466 | /// We want to process loops in postorder, but the worklist is a LIFO data |
467 | /// structure, so we append to it in *reverse* postorder. |
468 | /// For trees, a preorder traversal is a viable reverse postorder, so we |
469 | /// actually append using a preorder walk algorithm. |
470 | template <typename RangeT> |
471 | void appendLoopsToWorklist(RangeT &&, SmallPriorityWorklist<Loop *, 4> &); |
472 | /// Utility that implements appending of loops onto a worklist given a range. |
473 | /// It has the same behavior as appendLoopsToWorklist, but assumes the range of |
474 | /// loops has already been reversed, so it processes loops in the given order. |
475 | template <typename RangeT> |
476 | void appendReversedLoopsToWorklist(RangeT &&, |
477 | SmallPriorityWorklist<Loop *, 4> &); |
478 | |
479 | /// Utility that implements appending of loops onto a worklist given LoopInfo. |
480 | /// Calls the templated utility taking a Range of loops, handing it the Loops |
481 | /// in LoopInfo, iterated in reverse. This is because the loops are stored in |
482 | /// RPO w.r.t. the control flow graph in LoopInfo. For the purpose of unrolling, |
483 | /// loop deletion, and LICM, we largely want to work forward across the CFG so |
484 | /// that we visit defs before uses and can propagate simplifications from one |
485 | /// loop nest into the next. Calls appendReversedLoopsToWorklist with the |
486 | /// already reversed loops in LI. |
487 | /// FIXME: Consider changing the order in LoopInfo. |
488 | void appendLoopsToWorklist(LoopInfo &, SmallPriorityWorklist<Loop *, 4> &); |
489 | |
490 | /// Recursively clone the specified loop and all of its children, |
491 | /// mapping the blocks with the specified map. |
492 | Loop *cloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM, |
493 | LoopInfo *LI, LPPassManager *LPM); |
494 | |
495 | /// Add code that checks at runtime if the accessed arrays in \p PointerChecks |
496 | /// overlap. Returns the final comparator value or NULL if no check is needed. |
497 | Value * |
498 | addRuntimeChecks(Instruction *Loc, Loop *TheLoop, |
499 | const SmallVectorImpl<RuntimePointerCheck> &PointerChecks, |
500 | SCEVExpander &Expander); |
501 | |
502 | /// Struct to hold information about a partially invariant condition. |
503 | struct IVConditionInfo { |
504 | /// Instructions that need to be duplicated and checked for the unswitching |
505 | /// condition. |
506 | SmallVector<Instruction *> InstToDuplicate; |
507 | |
508 | /// Constant to indicate for which value the condition is invariant. |
509 | Constant *KnownValue = nullptr; |
510 | |
511 | /// True if the partially invariant path is no-op (=does not have any |
512 | /// side-effects and no loop value is used outside the loop). |
513 | bool PathIsNoop = true; |
514 | |
515 | /// If the partially invariant path reaches a single exit block, ExitForPath |
516 | /// is set to that block. Otherwise it is nullptr. |
517 | BasicBlock *ExitForPath = nullptr; |
518 | }; |
519 | |
520 | /// Check if the loop header has a conditional branch that is not |
521 | /// loop-invariant, because it involves load instructions. If all paths from |
522 | /// either the true or false successor to the header or loop exists do not |
523 | /// modify the memory feeding the condition, perform 'partial unswitching'. That |
524 | /// is, duplicate the instructions feeding the condition in the pre-header. Then |
525 | /// unswitch on the duplicated condition. The condition is now known in the |
526 | /// unswitched version for the 'invariant' path through the original loop. |
527 | /// |
528 | /// If the branch condition of the header is partially invariant, return a pair |
529 | /// containing the instructions to duplicate and a boolean Constant to update |
530 | /// the condition in the loops created for the true or false successors. |
531 | Optional<IVConditionInfo> hasPartialIVCondition(Loop &L, unsigned MSSAThreshold, |
532 | MemorySSA &MSSA, AAResults &AA); |
533 | |
534 | } // end namespace llvm |
535 | |
536 | #endif // LLVM_TRANSFORMS_UTILS_LOOPUTILS_H |