Bug Summary

File:lib/Transforms/Scalar/LICM.cpp
Warning:line 1153, column 41
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name LICM.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-9/lib/clang/9.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/include -I /build/llvm-toolchain-snapshot-9~svn362543/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/include/clang/9.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-9/lib/clang/9.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/lib/Transforms/Scalar -fdebug-prefix-map=/build/llvm-toolchain-snapshot-9~svn362543=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2019-06-05-060531-1271-1 -x c++ /build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp -faddrsig
1//===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===//
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 pass performs loop invariant code motion, attempting to remove as much
10// code from the body of a loop as possible. It does this by either hoisting
11// code into the preheader block, or by sinking code to the exit blocks if it is
12// safe. This pass also promotes must-aliased memory locations in the loop to
13// live in registers, thus hoisting and sinking "invariant" loads and stores.
14//
15// This pass uses alias analysis for two purposes:
16//
17// 1. Moving loop invariant loads and calls out of loops. If we can determine
18// that a load or call inside of a loop never aliases anything stored to,
19// we can hoist it or sink it like any other instruction.
20// 2. Scalar Promotion of Memory - If there is a store instruction inside of
21// the loop, we try to move the store to happen AFTER the loop instead of
22// inside of the loop. This can only happen if a few conditions are true:
23// A. The pointer stored through is loop invariant
24// B. There are no stores or loads in the loop which _may_ alias the
25// pointer. There are no calls in the loop which mod/ref the pointer.
26// If these conditions are true, we can promote the loads and stores in the
27// loop of the pointer to use a temporary alloca'd variable. We then use
28// the SSAUpdater to construct the appropriate SSA form for the value.
29//
30//===----------------------------------------------------------------------===//
31
32#include "llvm/Transforms/Scalar/LICM.h"
33#include "llvm/ADT/SetOperations.h"
34#include "llvm/ADT/Statistic.h"
35#include "llvm/Analysis/AliasAnalysis.h"
36#include "llvm/Analysis/AliasSetTracker.h"
37#include "llvm/Analysis/BasicAliasAnalysis.h"
38#include "llvm/Analysis/CaptureTracking.h"
39#include "llvm/Analysis/ConstantFolding.h"
40#include "llvm/Analysis/GlobalsModRef.h"
41#include "llvm/Analysis/GuardUtils.h"
42#include "llvm/Analysis/Loads.h"
43#include "llvm/Analysis/LoopInfo.h"
44#include "llvm/Analysis/LoopIterator.h"
45#include "llvm/Analysis/LoopPass.h"
46#include "llvm/Analysis/MemoryBuiltins.h"
47#include "llvm/Analysis/MemorySSA.h"
48#include "llvm/Analysis/MemorySSAUpdater.h"
49#include "llvm/Analysis/OptimizationRemarkEmitter.h"
50#include "llvm/Analysis/ScalarEvolution.h"
51#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
52#include "llvm/Analysis/TargetLibraryInfo.h"
53#include "llvm/Analysis/ValueTracking.h"
54#include "llvm/IR/CFG.h"
55#include "llvm/IR/Constants.h"
56#include "llvm/IR/DataLayout.h"
57#include "llvm/IR/DebugInfoMetadata.h"
58#include "llvm/IR/DerivedTypes.h"
59#include "llvm/IR/Dominators.h"
60#include "llvm/IR/Instructions.h"
61#include "llvm/IR/IntrinsicInst.h"
62#include "llvm/IR/LLVMContext.h"
63#include "llvm/IR/Metadata.h"
64#include "llvm/IR/PatternMatch.h"
65#include "llvm/IR/PredIteratorCache.h"
66#include "llvm/Support/CommandLine.h"
67#include "llvm/Support/Debug.h"
68#include "llvm/Support/raw_ostream.h"
69#include "llvm/Transforms/Scalar.h"
70#include "llvm/Transforms/Scalar/LoopPassManager.h"
71#include "llvm/Transforms/Utils/BasicBlockUtils.h"
72#include "llvm/Transforms/Utils/Local.h"
73#include "llvm/Transforms/Utils/LoopUtils.h"
74#include "llvm/Transforms/Utils/SSAUpdater.h"
75#include <algorithm>
76#include <utility>
77using namespace llvm;
78
79#define DEBUG_TYPE"licm" "licm"
80
81STATISTIC(NumCreatedBlocks, "Number of blocks created")static llvm::Statistic NumCreatedBlocks = {"licm", "NumCreatedBlocks"
, "Number of blocks created", {0}, {false}}
;
82STATISTIC(NumClonedBranches, "Number of branches cloned")static llvm::Statistic NumClonedBranches = {"licm", "NumClonedBranches"
, "Number of branches cloned", {0}, {false}}
;
83STATISTIC(NumSunk, "Number of instructions sunk out of loop")static llvm::Statistic NumSunk = {"licm", "NumSunk", "Number of instructions sunk out of loop"
, {0}, {false}}
;
84STATISTIC(NumHoisted, "Number of instructions hoisted out of loop")static llvm::Statistic NumHoisted = {"licm", "NumHoisted", "Number of instructions hoisted out of loop"
, {0}, {false}}
;
85STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk")static llvm::Statistic NumMovedLoads = {"licm", "NumMovedLoads"
, "Number of load insts hoisted or sunk", {0}, {false}}
;
86STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk")static llvm::Statistic NumMovedCalls = {"licm", "NumMovedCalls"
, "Number of call insts hoisted or sunk", {0}, {false}}
;
87STATISTIC(NumPromoted, "Number of memory locations promoted to registers")static llvm::Statistic NumPromoted = {"licm", "NumPromoted", "Number of memory locations promoted to registers"
, {0}, {false}}
;
88
89/// Memory promotion is enabled by default.
90static cl::opt<bool>
91 DisablePromotion("disable-licm-promotion", cl::Hidden, cl::init(false),
92 cl::desc("Disable memory promotion in LICM pass"));
93
94static cl::opt<bool> ControlFlowHoisting(
95 "licm-control-flow-hoisting", cl::Hidden, cl::init(false),
96 cl::desc("Enable control flow (and PHI) hoisting in LICM"));
97
98static cl::opt<uint32_t> MaxNumUsesTraversed(
99 "licm-max-num-uses-traversed", cl::Hidden, cl::init(8),
100 cl::desc("Max num uses visited for identifying load "
101 "invariance in loop using invariant start (default = 8)"));
102
103// Default value of zero implies we use the regular alias set tracker mechanism
104// instead of the cross product using AA to identify aliasing of the memory
105// location we are interested in.
106static cl::opt<int>
107LICMN2Theshold("licm-n2-threshold", cl::Hidden, cl::init(0),
108 cl::desc("How many instruction to cross product using AA"));
109
110// Experimental option to allow imprecision in LICM in pathological cases, in
111// exchange for faster compile. This is to be removed if MemorySSA starts to
112// address the same issue. This flag applies only when LICM uses MemorySSA
113// instead on AliasSetTracker. LICM calls MemorySSAWalker's
114// getClobberingMemoryAccess, up to the value of the Cap, getting perfect
115// accuracy. Afterwards, LICM will call into MemorySSA's getDefiningAccess,
116// which may not be precise, since optimizeUses is capped. The result is
117// correct, but we may not get as "far up" as possible to get which access is
118// clobbering the one queried.
119cl::opt<unsigned> llvm::SetLicmMssaOptCap(
120 "licm-mssa-optimization-cap", cl::init(100), cl::Hidden,
121 cl::desc("Enable imprecision in LICM in pathological cases, in exchange "
122 "for faster compile. Caps the MemorySSA clobbering calls."));
123
124// Experimentally, memory promotion carries less importance than sinking and
125// hoisting. Limit when we do promotion when using MemorySSA, in order to save
126// compile time.
127cl::opt<unsigned> llvm::SetLicmMssaNoAccForPromotionCap(
128 "licm-mssa-max-acc-promotion", cl::init(250), cl::Hidden,
129 cl::desc("[LICM & MemorySSA] When MSSA in LICM is disabled, this has no "
130 "effect. When MSSA in LICM is enabled, then this is the maximum "
131 "number of accesses allowed to be present in a loop in order to "
132 "enable memory promotion."));
133
134static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI);
135static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop,
136 const LoopSafetyInfo *SafetyInfo,
137 TargetTransformInfo *TTI, bool &FreeInLoop);
138static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
139 BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo,
140 MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE);
141static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
142 const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo,
143 MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE);
144static bool isSafeToExecuteUnconditionally(Instruction &Inst,
145 const DominatorTree *DT,
146 const Loop *CurLoop,
147 const LoopSafetyInfo *SafetyInfo,
148 OptimizationRemarkEmitter *ORE,
149 const Instruction *CtxI = nullptr);
150static bool pointerInvalidatedByLoop(MemoryLocation MemLoc,
151 AliasSetTracker *CurAST, Loop *CurLoop,
152 AliasAnalysis *AA);
153static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU,
154 Loop *CurLoop,
155 SinkAndHoistLICMFlags &Flags);
156static Instruction *CloneInstructionInExitBlock(
157 Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI,
158 const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU);
159
160static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
161 AliasSetTracker *AST, MemorySSAUpdater *MSSAU);
162
163static void moveInstructionBefore(Instruction &I, Instruction &Dest,
164 ICFLoopSafetyInfo &SafetyInfo,
165 MemorySSAUpdater *MSSAU);
166
167namespace {
168struct LoopInvariantCodeMotion {
169 using ASTrackerMapTy = DenseMap<Loop *, std::unique_ptr<AliasSetTracker>>;
170 bool runOnLoop(Loop *L, AliasAnalysis *AA, LoopInfo *LI, DominatorTree *DT,
171 TargetLibraryInfo *TLI, TargetTransformInfo *TTI,
172 ScalarEvolution *SE, MemorySSA *MSSA,
173 OptimizationRemarkEmitter *ORE, bool DeleteAST);
174
175 ASTrackerMapTy &getLoopToAliasSetMap() { return LoopToAliasSetMap; }
176 LoopInvariantCodeMotion(unsigned LicmMssaOptCap,
177 unsigned LicmMssaNoAccForPromotionCap)
178 : LicmMssaOptCap(LicmMssaOptCap),
179 LicmMssaNoAccForPromotionCap(LicmMssaNoAccForPromotionCap) {}
180
181private:
182 ASTrackerMapTy LoopToAliasSetMap;
183 unsigned LicmMssaOptCap;
184 unsigned LicmMssaNoAccForPromotionCap;
185
186 std::unique_ptr<AliasSetTracker>
187 collectAliasInfoForLoop(Loop *L, LoopInfo *LI, AliasAnalysis *AA);
188 std::unique_ptr<AliasSetTracker>
189 collectAliasInfoForLoopWithMSSA(Loop *L, AliasAnalysis *AA,
190 MemorySSAUpdater *MSSAU);
191};
192
193struct LegacyLICMPass : public LoopPass {
194 static char ID; // Pass identification, replacement for typeid
195 LegacyLICMPass(
196 unsigned LicmMssaOptCap = SetLicmMssaOptCap,
197 unsigned LicmMssaNoAccForPromotionCap = SetLicmMssaNoAccForPromotionCap)
198 : LoopPass(ID), LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap) {
199 initializeLegacyLICMPassPass(*PassRegistry::getPassRegistry());
200 }
201
202 bool runOnLoop(Loop *L, LPPassManager &LPM) override {
203 if (skipLoop(L)) {
204 // If we have run LICM on a previous loop but now we are skipping
205 // (because we've hit the opt-bisect limit), we need to clear the
206 // loop alias information.
207 LICM.getLoopToAliasSetMap().clear();
208 return false;
209 }
210
211 auto *SE = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
212 MemorySSA *MSSA = EnableMSSALoopDependency
213 ? (&getAnalysis<MemorySSAWrapperPass>().getMSSA())
214 : nullptr;
215 // For the old PM, we can't use OptimizationRemarkEmitter as an analysis
216 // pass. Function analyses need to be preserved across loop transformations
217 // but ORE cannot be preserved (see comment before the pass definition).
218 OptimizationRemarkEmitter ORE(L->getHeader()->getParent());
219 return LICM.runOnLoop(L,
220 &getAnalysis<AAResultsWrapperPass>().getAAResults(),
221 &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(),
222 &getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
223 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
224 &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
225 *L->getHeader()->getParent()),
226 SE ? &SE->getSE() : nullptr, MSSA, &ORE, false);
227 }
228
229 /// This transformation requires natural loop information & requires that
230 /// loop preheaders be inserted into the CFG...
231 ///
232 void getAnalysisUsage(AnalysisUsage &AU) const override {
233 AU.addPreserved<DominatorTreeWrapperPass>();
234 AU.addPreserved<LoopInfoWrapperPass>();
235 AU.addRequired<TargetLibraryInfoWrapperPass>();
236 if (EnableMSSALoopDependency) {
237 AU.addRequired<MemorySSAWrapperPass>();
238 AU.addPreserved<MemorySSAWrapperPass>();
239 }
240 AU.addRequired<TargetTransformInfoWrapperPass>();
241 getLoopAnalysisUsage(AU);
242 }
243
244 using llvm::Pass::doFinalization;
245
246 bool doFinalization() override {
247 auto &AliasSetMap = LICM.getLoopToAliasSetMap();
248 // All loops in the AliasSetMap should be cleaned up already. The only case
249 // where we fail to do so is if an outer loop gets deleted before LICM
250 // visits it.
251 assert(all_of(AliasSetMap,((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy
::value_type &KV) { return !KV.first->getParentLoop();
}) && "Didn't free loop alias sets") ? static_cast<
void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 255, __PRETTY_FUNCTION__))
252 [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) {((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy
::value_type &KV) { return !KV.first->getParentLoop();
}) && "Didn't free loop alias sets") ? static_cast<
void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 255, __PRETTY_FUNCTION__))
253 return !KV.first->getParentLoop();((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy
::value_type &KV) { return !KV.first->getParentLoop();
}) && "Didn't free loop alias sets") ? static_cast<
void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 255, __PRETTY_FUNCTION__))
254 }) &&((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy
::value_type &KV) { return !KV.first->getParentLoop();
}) && "Didn't free loop alias sets") ? static_cast<
void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 255, __PRETTY_FUNCTION__))
255 "Didn't free loop alias sets")((all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy
::value_type &KV) { return !KV.first->getParentLoop();
}) && "Didn't free loop alias sets") ? static_cast<
void> (0) : __assert_fail ("all_of(AliasSetMap, [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { return !KV.first->getParentLoop(); }) && \"Didn't free loop alias sets\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 255, __PRETTY_FUNCTION__))
;
256 AliasSetMap.clear();
257 return false;
258 }
259
260private:
261 LoopInvariantCodeMotion LICM;
262
263 /// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info.
264 void cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To,
265 Loop *L) override;
266
267 /// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias
268 /// set.
269 void deleteAnalysisValue(Value *V, Loop *L) override;
270
271 /// Simple Analysis hook. Delete loop L from alias set map.
272 void deleteAnalysisLoop(Loop *L) override;
273};
274} // namespace
275
276PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM,
277 LoopStandardAnalysisResults &AR, LPMUpdater &) {
278 const auto &FAM =
279 AM.getResult<FunctionAnalysisManagerLoopProxy>(L, AR).getManager();
280 Function *F = L.getHeader()->getParent();
281
282 auto *ORE = FAM.getCachedResult<OptimizationRemarkEmitterAnalysis>(*F);
283 // FIXME: This should probably be optional rather than required.
284 if (!ORE)
285 report_fatal_error("LICM: OptimizationRemarkEmitterAnalysis not "
286 "cached at a higher level");
287
288 LoopInvariantCodeMotion LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap);
289 if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, &AR.TLI, &AR.TTI, &AR.SE,
290 AR.MSSA, ORE, true))
291 return PreservedAnalyses::all();
292
293 auto PA = getLoopPassPreservedAnalyses();
294
295 PA.preserve<DominatorTreeAnalysis>();
296 PA.preserve<LoopAnalysis>();
297
298 return PA;
299}
300
301char LegacyLICMPass::ID = 0;
302INITIALIZE_PASS_BEGIN(LegacyLICMPass, "licm", "Loop Invariant Code Motion",static void *initializeLegacyLICMPassPassOnce(PassRegistry &
Registry) {
303 false, false)static void *initializeLegacyLICMPassPassOnce(PassRegistry &
Registry) {
304INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry);
305INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry);
306INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
307INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry);
308INITIALIZE_PASS_END(LegacyLICMPass, "licm", "Loop Invariant Code Motion", false,PassInfo *PI = new PassInfo( "Loop Invariant Code Motion", "licm"
, &LegacyLICMPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LegacyLICMPass>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeLegacyLICMPassPassFlag
; void llvm::initializeLegacyLICMPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeLegacyLICMPassPassFlag, initializeLegacyLICMPassPassOnce
, std::ref(Registry)); }
309 false)PassInfo *PI = new PassInfo( "Loop Invariant Code Motion", "licm"
, &LegacyLICMPass::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LegacyLICMPass>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeLegacyLICMPassPassFlag
; void llvm::initializeLegacyLICMPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeLegacyLICMPassPassFlag, initializeLegacyLICMPassPassOnce
, std::ref(Registry)); }
310
311Pass *llvm::createLICMPass() { return new LegacyLICMPass(); }
312Pass *llvm::createLICMPass(unsigned LicmMssaOptCap,
313 unsigned LicmMssaNoAccForPromotionCap) {
314 return new LegacyLICMPass(LicmMssaOptCap, LicmMssaNoAccForPromotionCap);
315}
316
317/// Hoist expressions out of the specified loop. Note, alias info for inner
318/// loop is not preserved so it is not a good idea to run LICM multiple
319/// times on one loop.
320/// We should delete AST for inner loops in the new pass manager to avoid
321/// memory leak.
322///
323bool LoopInvariantCodeMotion::runOnLoop(
324 Loop *L, AliasAnalysis *AA, LoopInfo *LI, DominatorTree *DT,
325 TargetLibraryInfo *TLI, TargetTransformInfo *TTI, ScalarEvolution *SE,
326 MemorySSA *MSSA, OptimizationRemarkEmitter *ORE, bool DeleteAST) {
327 bool Changed = false;
328
329 assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form.")((L->isLCSSAForm(*DT) && "Loop is not in LCSSA form."
) ? static_cast<void> (0) : __assert_fail ("L->isLCSSAForm(*DT) && \"Loop is not in LCSSA form.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 329, __PRETTY_FUNCTION__))
;
330
331 std::unique_ptr<AliasSetTracker> CurAST;
332 std::unique_ptr<MemorySSAUpdater> MSSAU;
333 bool NoOfMemAccTooLarge = false;
334 unsigned LicmMssaOptCounter = 0;
335
336 if (!MSSA) {
337 LLVM_DEBUG(dbgs() << "LICM: Using Alias Set Tracker.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM: Using Alias Set Tracker.\n"
; } } while (false)
;
338 CurAST = collectAliasInfoForLoop(L, LI, AA);
339 } else {
340 LLVM_DEBUG(dbgs() << "LICM: Using MemorySSA.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM: Using MemorySSA.\n"; } } while
(false)
;
341 MSSAU = make_unique<MemorySSAUpdater>(MSSA);
342
343 unsigned AccessCapCount = 0;
344 for (auto *BB : L->getBlocks()) {
345 if (auto *Accesses = MSSA->getBlockAccesses(BB)) {
346 for (const auto &MA : *Accesses) {
347 (void)MA;
348 AccessCapCount++;
349 if (AccessCapCount > LicmMssaNoAccForPromotionCap) {
350 NoOfMemAccTooLarge = true;
351 break;
352 }
353 }
354 }
355 if (NoOfMemAccTooLarge)
356 break;
357 }
358 }
359
360 // Get the preheader block to move instructions into...
361 BasicBlock *Preheader = L->getLoopPreheader();
362
363 // Compute loop safety information.
364 ICFLoopSafetyInfo SafetyInfo(DT);
365 SafetyInfo.computeLoopSafetyInfo(L);
366
367 // We want to visit all of the instructions in this loop... that are not parts
368 // of our subloops (they have already had their invariants hoisted out of
369 // their loop, into this loop, so there is no need to process the BODIES of
370 // the subloops).
371 //
372 // Traverse the body of the loop in depth first order on the dominator tree so
373 // that we are guaranteed to see definitions before we see uses. This allows
374 // us to sink instructions in one pass, without iteration. After sinking
375 // instructions, we perform another pass to hoist them out of the loop.
376 SinkAndHoistLICMFlags Flags = {NoOfMemAccTooLarge, LicmMssaOptCounter,
377 LicmMssaOptCap, LicmMssaNoAccForPromotionCap};
378 if (L->hasDedicatedExits())
379 Changed |= sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, TTI, L,
380 CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE);
381 if (Preheader)
382 Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, L,
383 CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE);
384
385 // Now that all loop invariants have been removed from the loop, promote any
386 // memory references to scalars that we can.
387 // Don't sink stores from loops without dedicated block exits. Exits
388 // containing indirect branches are not transformed by loop simplify,
389 // make sure we catch that. An additional load may be generated in the
390 // preheader for SSA updater, so also avoid sinking when no preheader
391 // is available.
392 if (!DisablePromotion && Preheader && L->hasDedicatedExits() &&
393 !NoOfMemAccTooLarge) {
394 // Figure out the loop exits and their insertion points
395 SmallVector<BasicBlock *, 8> ExitBlocks;
396 L->getUniqueExitBlocks(ExitBlocks);
397
398 // We can't insert into a catchswitch.
399 bool HasCatchSwitch = llvm::any_of(ExitBlocks, [](BasicBlock *Exit) {
400 return isa<CatchSwitchInst>(Exit->getTerminator());
401 });
402
403 if (!HasCatchSwitch) {
404 SmallVector<Instruction *, 8> InsertPts;
405 SmallVector<MemoryAccess *, 8> MSSAInsertPts;
406 InsertPts.reserve(ExitBlocks.size());
407 if (MSSAU)
408 MSSAInsertPts.reserve(ExitBlocks.size());
409 for (BasicBlock *ExitBlock : ExitBlocks) {
410 InsertPts.push_back(&*ExitBlock->getFirstInsertionPt());
411 if (MSSAU)
412 MSSAInsertPts.push_back(nullptr);
413 }
414
415 PredIteratorCache PIC;
416
417 bool Promoted = false;
418
419 // Build an AST using MSSA.
420 if (!CurAST.get())
421 CurAST = collectAliasInfoForLoopWithMSSA(L, AA, MSSAU.get());
422
423 // Loop over all of the alias sets in the tracker object.
424 for (AliasSet &AS : *CurAST) {
425 // We can promote this alias set if it has a store, if it is a "Must"
426 // alias set, if the pointer is loop invariant, and if we are not
427 // eliminating any volatile loads or stores.
428 if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() ||
429 !L->isLoopInvariant(AS.begin()->getValue()))
430 continue;
431
432 assert(((!AS.empty() && "Must alias set should have at least one pointer element in it!"
) ? static_cast<void> (0) : __assert_fail ("!AS.empty() && \"Must alias set should have at least one pointer element in it!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 434, __PRETTY_FUNCTION__))
433 !AS.empty() &&((!AS.empty() && "Must alias set should have at least one pointer element in it!"
) ? static_cast<void> (0) : __assert_fail ("!AS.empty() && \"Must alias set should have at least one pointer element in it!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 434, __PRETTY_FUNCTION__))
434 "Must alias set should have at least one pointer element in it!")((!AS.empty() && "Must alias set should have at least one pointer element in it!"
) ? static_cast<void> (0) : __assert_fail ("!AS.empty() && \"Must alias set should have at least one pointer element in it!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 434, __PRETTY_FUNCTION__))
;
435
436 SmallSetVector<Value *, 8> PointerMustAliases;
437 for (const auto &ASI : AS)
438 PointerMustAliases.insert(ASI.getValue());
439
440 Promoted |= promoteLoopAccessesToScalars(
441 PointerMustAliases, ExitBlocks, InsertPts, MSSAInsertPts, PIC, LI,
442 DT, TLI, L, CurAST.get(), MSSAU.get(), &SafetyInfo, ORE);
443 }
444
445 // Once we have promoted values across the loop body we have to
446 // recursively reform LCSSA as any nested loop may now have values defined
447 // within the loop used in the outer loop.
448 // FIXME: This is really heavy handed. It would be a bit better to use an
449 // SSAUpdater strategy during promotion that was LCSSA aware and reformed
450 // it as it went.
451 if (Promoted)
452 formLCSSARecursively(*L, *DT, LI, SE);
453
454 Changed |= Promoted;
455 }
456 }
457
458 // Check that neither this loop nor its parent have had LCSSA broken. LICM is
459 // specifically moving instructions across the loop boundary and so it is
460 // especially in need of sanity checking here.
461 assert(L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!")((L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!"
) ? static_cast<void> (0) : __assert_fail ("L->isLCSSAForm(*DT) && \"Loop not left in LCSSA form after LICM!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 461, __PRETTY_FUNCTION__))
;
462 assert((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) &&(((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm
(*DT)) && "Parent loop not left in LCSSA form after LICM!"
) ? static_cast<void> (0) : __assert_fail ("(!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) && \"Parent loop not left in LCSSA form after LICM!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 463, __PRETTY_FUNCTION__))
463 "Parent loop not left in LCSSA form after LICM!")(((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm
(*DT)) && "Parent loop not left in LCSSA form after LICM!"
) ? static_cast<void> (0) : __assert_fail ("(!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) && \"Parent loop not left in LCSSA form after LICM!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 463, __PRETTY_FUNCTION__))
;
464
465 // If this loop is nested inside of another one, save the alias information
466 // for when we process the outer loop.
467 if (!MSSAU.get() && CurAST.get() && L->getParentLoop() && !DeleteAST)
468 LoopToAliasSetMap[L] = std::move(CurAST);
469
470 if (MSSAU.get() && VerifyMemorySSA)
471 MSSAU->getMemorySSA()->verifyMemorySSA();
472
473 if (Changed && SE)
474 SE->forgetLoopDispositions(L);
475 return Changed;
476}
477
478/// Walk the specified region of the CFG (defined by all blocks dominated by
479/// the specified block, and that are in the current loop) in reverse depth
480/// first order w.r.t the DominatorTree. This allows us to visit uses before
481/// definitions, allowing us to sink a loop body in one pass without iteration.
482///
483bool llvm::sinkRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
484 DominatorTree *DT, TargetLibraryInfo *TLI,
485 TargetTransformInfo *TTI, Loop *CurLoop,
486 AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU,
487 ICFLoopSafetyInfo *SafetyInfo,
488 SinkAndHoistLICMFlags &Flags,
489 OptimizationRemarkEmitter *ORE) {
490
491 // Verify inputs.
492 assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr
&& DT != nullptr && CurLoop != nullptr &&
SafetyInfo != nullptr && "Unexpected input to sinkRegion."
) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to sinkRegion.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 494, __PRETTY_FUNCTION__))
493 CurLoop != nullptr && SafetyInfo != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr
&& DT != nullptr && CurLoop != nullptr &&
SafetyInfo != nullptr && "Unexpected input to sinkRegion."
) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to sinkRegion.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 494, __PRETTY_FUNCTION__))
494 "Unexpected input to sinkRegion.")((N != nullptr && AA != nullptr && LI != nullptr
&& DT != nullptr && CurLoop != nullptr &&
SafetyInfo != nullptr && "Unexpected input to sinkRegion."
) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to sinkRegion.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 494, __PRETTY_FUNCTION__))
;
495 assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized."
) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 496, __PRETTY_FUNCTION__))
496 "Either AliasSetTracker or MemorySSA should be initialized.")((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized."
) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 496, __PRETTY_FUNCTION__))
;
497
498 // We want to visit children before parents. We will enque all the parents
499 // before their children in the worklist and process the worklist in reverse
500 // order.
501 SmallVector<DomTreeNode *, 16> Worklist = collectChildrenInLoop(N, CurLoop);
502
503 bool Changed = false;
504 for (DomTreeNode *DTN : reverse(Worklist)) {
505 BasicBlock *BB = DTN->getBlock();
506 // Only need to process the contents of this block if it is not part of a
507 // subloop (which would already have been processed).
508 if (inSubLoop(BB, CurLoop, LI))
509 continue;
510
511 for (BasicBlock::iterator II = BB->end(); II != BB->begin();) {
512 Instruction &I = *--II;
513
514 // If the instruction is dead, we would try to sink it because it isn't
515 // used in the loop, instead, just delete it.
516 if (isInstructionTriviallyDead(&I, TLI)) {
517 LLVM_DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM deleting dead inst: " <<
I << '\n'; } } while (false)
;
518 salvageDebugInfo(I);
519 ++II;
520 eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
521 Changed = true;
522 continue;
523 }
524
525 // Check to see if we can sink this instruction to the exit blocks
526 // of the loop. We can do this if the all users of the instruction are
527 // outside of the loop. In this case, it doesn't even matter if the
528 // operands of the instruction are loop invariant.
529 //
530 bool FreeInLoop = false;
531 if (isNotUsedOrFreeInLoop(I, CurLoop, SafetyInfo, TTI, FreeInLoop) &&
532 canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags,
533 ORE) &&
534 !I.mayHaveSideEffects()) {
535 if (sink(I, LI, DT, CurLoop, SafetyInfo, MSSAU, ORE)) {
536 if (!FreeInLoop) {
537 ++II;
538 eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
539 }
540 Changed = true;
541 }
542 }
543 }
544 }
545 if (MSSAU && VerifyMemorySSA)
546 MSSAU->getMemorySSA()->verifyMemorySSA();
547 return Changed;
548}
549
550namespace {
551// This is a helper class for hoistRegion to make it able to hoist control flow
552// in order to be able to hoist phis. The way this works is that we initially
553// start hoisting to the loop preheader, and when we see a loop invariant branch
554// we make note of this. When we then come to hoist an instruction that's
555// conditional on such a branch we duplicate the branch and the relevant control
556// flow, then hoist the instruction into the block corresponding to its original
557// block in the duplicated control flow.
558class ControlFlowHoister {
559private:
560 // Information about the loop we are hoisting from
561 LoopInfo *LI;
562 DominatorTree *DT;
563 Loop *CurLoop;
564 MemorySSAUpdater *MSSAU;
565
566 // A map of blocks in the loop to the block their instructions will be hoisted
567 // to.
568 DenseMap<BasicBlock *, BasicBlock *> HoistDestinationMap;
569
570 // The branches that we can hoist, mapped to the block that marks a
571 // convergence point of their control flow.
572 DenseMap<BranchInst *, BasicBlock *> HoistableBranches;
573
574public:
575 ControlFlowHoister(LoopInfo *LI, DominatorTree *DT, Loop *CurLoop,
576 MemorySSAUpdater *MSSAU)
577 : LI(LI), DT(DT), CurLoop(CurLoop), MSSAU(MSSAU) {}
578
579 void registerPossiblyHoistableBranch(BranchInst *BI) {
580 // We can only hoist conditional branches with loop invariant operands.
581 if (!ControlFlowHoisting || !BI->isConditional() ||
582 !CurLoop->hasLoopInvariantOperands(BI))
583 return;
584
585 // The branch destinations need to be in the loop, and we don't gain
586 // anything by duplicating conditional branches with duplicate successors,
587 // as it's essentially the same as an unconditional branch.
588 BasicBlock *TrueDest = BI->getSuccessor(0);
589 BasicBlock *FalseDest = BI->getSuccessor(1);
590 if (!CurLoop->contains(TrueDest) || !CurLoop->contains(FalseDest) ||
591 TrueDest == FalseDest)
592 return;
593
594 // We can hoist BI if one branch destination is the successor of the other,
595 // or both have common successor which we check by seeing if the
596 // intersection of their successors is non-empty.
597 // TODO: This could be expanded to allowing branches where both ends
598 // eventually converge to a single block.
599 SmallPtrSet<BasicBlock *, 4> TrueDestSucc, FalseDestSucc;
600 TrueDestSucc.insert(succ_begin(TrueDest), succ_end(TrueDest));
601 FalseDestSucc.insert(succ_begin(FalseDest), succ_end(FalseDest));
602 BasicBlock *CommonSucc = nullptr;
603 if (TrueDestSucc.count(FalseDest)) {
604 CommonSucc = FalseDest;
605 } else if (FalseDestSucc.count(TrueDest)) {
606 CommonSucc = TrueDest;
607 } else {
608 set_intersect(TrueDestSucc, FalseDestSucc);
609 // If there's one common successor use that.
610 if (TrueDestSucc.size() == 1)
611 CommonSucc = *TrueDestSucc.begin();
612 // If there's more than one pick whichever appears first in the block list
613 // (we can't use the value returned by TrueDestSucc.begin() as it's
614 // unpredicatable which element gets returned).
615 else if (!TrueDestSucc.empty()) {
616 Function *F = TrueDest->getParent();
617 auto IsSucc = [&](BasicBlock &BB) { return TrueDestSucc.count(&BB); };
618 auto It = std::find_if(F->begin(), F->end(), IsSucc);
619 assert(It != F->end() && "Could not find successor in function")((It != F->end() && "Could not find successor in function"
) ? static_cast<void> (0) : __assert_fail ("It != F->end() && \"Could not find successor in function\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 619, __PRETTY_FUNCTION__))
;
620 CommonSucc = &*It;
621 }
622 }
623 // The common successor has to be dominated by the branch, as otherwise
624 // there will be some other path to the successor that will not be
625 // controlled by this branch so any phi we hoist would be controlled by the
626 // wrong condition. This also takes care of avoiding hoisting of loop back
627 // edges.
628 // TODO: In some cases this could be relaxed if the successor is dominated
629 // by another block that's been hoisted and we can guarantee that the
630 // control flow has been replicated exactly.
631 if (CommonSucc && DT->dominates(BI, CommonSucc))
632 HoistableBranches[BI] = CommonSucc;
633 }
634
635 bool canHoistPHI(PHINode *PN) {
636 // The phi must have loop invariant operands.
637 if (!ControlFlowHoisting || !CurLoop->hasLoopInvariantOperands(PN))
638 return false;
639 // We can hoist phis if the block they are in is the target of hoistable
640 // branches which cover all of the predecessors of the block.
641 SmallPtrSet<BasicBlock *, 8> PredecessorBlocks;
642 BasicBlock *BB = PN->getParent();
643 for (BasicBlock *PredBB : predecessors(BB))
644 PredecessorBlocks.insert(PredBB);
645 // If we have less predecessor blocks than predecessors then the phi will
646 // have more than one incoming value for the same block which we can't
647 // handle.
648 // TODO: This could be handled be erasing some of the duplicate incoming
649 // values.
650 if (PredecessorBlocks.size() != pred_size(BB))
651 return false;
652 for (auto &Pair : HoistableBranches) {
653 if (Pair.second == BB) {
654 // Which blocks are predecessors via this branch depends on if the
655 // branch is triangle-like or diamond-like.
656 if (Pair.first->getSuccessor(0) == BB) {
657 PredecessorBlocks.erase(Pair.first->getParent());
658 PredecessorBlocks.erase(Pair.first->getSuccessor(1));
659 } else if (Pair.first->getSuccessor(1) == BB) {
660 PredecessorBlocks.erase(Pair.first->getParent());
661 PredecessorBlocks.erase(Pair.first->getSuccessor(0));
662 } else {
663 PredecessorBlocks.erase(Pair.first->getSuccessor(0));
664 PredecessorBlocks.erase(Pair.first->getSuccessor(1));
665 }
666 }
667 }
668 // PredecessorBlocks will now be empty if for every predecessor of BB we
669 // found a hoistable branch source.
670 return PredecessorBlocks.empty();
671 }
672
673 BasicBlock *getOrCreateHoistedBlock(BasicBlock *BB) {
674 if (!ControlFlowHoisting)
675 return CurLoop->getLoopPreheader();
676 // If BB has already been hoisted, return that
677 if (HoistDestinationMap.count(BB))
678 return HoistDestinationMap[BB];
679
680 // Check if this block is conditional based on a pending branch
681 auto HasBBAsSuccessor =
682 [&](DenseMap<BranchInst *, BasicBlock *>::value_type &Pair) {
683 return BB != Pair.second && (Pair.first->getSuccessor(0) == BB ||
684 Pair.first->getSuccessor(1) == BB);
685 };
686 auto It = std::find_if(HoistableBranches.begin(), HoistableBranches.end(),
687 HasBBAsSuccessor);
688
689 // If not involved in a pending branch, hoist to preheader
690 BasicBlock *InitialPreheader = CurLoop->getLoopPreheader();
691 if (It == HoistableBranches.end()) {
692 LLVM_DEBUG(dbgs() << "LICM using " << InitialPreheader->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM using " << InitialPreheader
->getName() << " as hoist destination for " <<
BB->getName() << "\n"; } } while (false)
693 << " as hoist destination for " << BB->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM using " << InitialPreheader
->getName() << " as hoist destination for " <<
BB->getName() << "\n"; } } while (false)
694 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM using " << InitialPreheader
->getName() << " as hoist destination for " <<
BB->getName() << "\n"; } } while (false)
;
695 HoistDestinationMap[BB] = InitialPreheader;
696 return InitialPreheader;
697 }
698 BranchInst *BI = It->first;
699 assert(std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) ==((std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor
) == HoistableBranches.end() && "BB is expected to be the target of at most one branch"
) ? static_cast<void> (0) : __assert_fail ("std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) == HoistableBranches.end() && \"BB is expected to be the target of at most one branch\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 701, __PRETTY_FUNCTION__))
700 HoistableBranches.end() &&((std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor
) == HoistableBranches.end() && "BB is expected to be the target of at most one branch"
) ? static_cast<void> (0) : __assert_fail ("std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) == HoistableBranches.end() && \"BB is expected to be the target of at most one branch\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 701, __PRETTY_FUNCTION__))
701 "BB is expected to be the target of at most one branch")((std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor
) == HoistableBranches.end() && "BB is expected to be the target of at most one branch"
) ? static_cast<void> (0) : __assert_fail ("std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) == HoistableBranches.end() && \"BB is expected to be the target of at most one branch\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 701, __PRETTY_FUNCTION__))
;
702
703 LLVMContext &C = BB->getContext();
704 BasicBlock *TrueDest = BI->getSuccessor(0);
705 BasicBlock *FalseDest = BI->getSuccessor(1);
706 BasicBlock *CommonSucc = HoistableBranches[BI];
707 BasicBlock *HoistTarget = getOrCreateHoistedBlock(BI->getParent());
708
709 // Create hoisted versions of blocks that currently don't have them
710 auto CreateHoistedBlock = [&](BasicBlock *Orig) {
711 if (HoistDestinationMap.count(Orig))
712 return HoistDestinationMap[Orig];
713 BasicBlock *New =
714 BasicBlock::Create(C, Orig->getName() + ".licm", Orig->getParent());
715 HoistDestinationMap[Orig] = New;
716 DT->addNewBlock(New, HoistTarget);
717 if (CurLoop->getParentLoop())
718 CurLoop->getParentLoop()->addBasicBlockToLoop(New, *LI);
719 ++NumCreatedBlocks;
720 LLVM_DEBUG(dbgs() << "LICM created " << New->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM created " << New->
getName() << " as hoist destination for " << Orig
->getName() << "\n"; } } while (false)
721 << " as hoist destination for " << Orig->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM created " << New->
getName() << " as hoist destination for " << Orig
->getName() << "\n"; } } while (false)
722 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM created " << New->
getName() << " as hoist destination for " << Orig
->getName() << "\n"; } } while (false)
;
723 return New;
724 };
725 BasicBlock *HoistTrueDest = CreateHoistedBlock(TrueDest);
726 BasicBlock *HoistFalseDest = CreateHoistedBlock(FalseDest);
727 BasicBlock *HoistCommonSucc = CreateHoistedBlock(CommonSucc);
728
729 // Link up these blocks with branches.
730 if (!HoistCommonSucc->getTerminator()) {
731 // The new common successor we've generated will branch to whatever that
732 // hoist target branched to.
733 BasicBlock *TargetSucc = HoistTarget->getSingleSuccessor();
734 assert(TargetSucc && "Expected hoist target to have a single successor")((TargetSucc && "Expected hoist target to have a single successor"
) ? static_cast<void> (0) : __assert_fail ("TargetSucc && \"Expected hoist target to have a single successor\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 734, __PRETTY_FUNCTION__))
;
735 HoistCommonSucc->moveBefore(TargetSucc);
736 BranchInst::Create(TargetSucc, HoistCommonSucc);
737 }
738 if (!HoistTrueDest->getTerminator()) {
739 HoistTrueDest->moveBefore(HoistCommonSucc);
740 BranchInst::Create(HoistCommonSucc, HoistTrueDest);
741 }
742 if (!HoistFalseDest->getTerminator()) {
743 HoistFalseDest->moveBefore(HoistCommonSucc);
744 BranchInst::Create(HoistCommonSucc, HoistFalseDest);
745 }
746
747 // If BI is being cloned to what was originally the preheader then
748 // HoistCommonSucc will now be the new preheader.
749 if (HoistTarget == InitialPreheader) {
750 // Phis in the loop header now need to use the new preheader.
751 InitialPreheader->replaceSuccessorsPhiUsesWith(HoistCommonSucc);
752 if (MSSAU)
753 MSSAU->wireOldPredecessorsToNewImmediatePredecessor(
754 HoistTarget->getSingleSuccessor(), HoistCommonSucc, {HoistTarget});
755 // The new preheader dominates the loop header.
756 DomTreeNode *PreheaderNode = DT->getNode(HoistCommonSucc);
757 DomTreeNode *HeaderNode = DT->getNode(CurLoop->getHeader());
758 DT->changeImmediateDominator(HeaderNode, PreheaderNode);
759 // The preheader hoist destination is now the new preheader, with the
760 // exception of the hoist destination of this branch.
761 for (auto &Pair : HoistDestinationMap)
762 if (Pair.second == InitialPreheader && Pair.first != BI->getParent())
763 Pair.second = HoistCommonSucc;
764 }
765
766 // Now finally clone BI.
767 ReplaceInstWithInst(
768 HoistTarget->getTerminator(),
769 BranchInst::Create(HoistTrueDest, HoistFalseDest, BI->getCondition()));
770 ++NumClonedBranches;
771
772 assert(CurLoop->getLoopPreheader() &&((CurLoop->getLoopPreheader() && "Hoisting blocks should not have destroyed preheader"
) ? static_cast<void> (0) : __assert_fail ("CurLoop->getLoopPreheader() && \"Hoisting blocks should not have destroyed preheader\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 773, __PRETTY_FUNCTION__))
773 "Hoisting blocks should not have destroyed preheader")((CurLoop->getLoopPreheader() && "Hoisting blocks should not have destroyed preheader"
) ? static_cast<void> (0) : __assert_fail ("CurLoop->getLoopPreheader() && \"Hoisting blocks should not have destroyed preheader\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 773, __PRETTY_FUNCTION__))
;
774 return HoistDestinationMap[BB];
775 }
776};
777} // namespace
778
779/// Walk the specified region of the CFG (defined by all blocks dominated by
780/// the specified block, and that are in the current loop) in depth first
781/// order w.r.t the DominatorTree. This allows us to visit definitions before
782/// uses, allowing us to hoist a loop body in one pass without iteration.
783///
784bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
785 DominatorTree *DT, TargetLibraryInfo *TLI, Loop *CurLoop,
786 AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU,
787 ICFLoopSafetyInfo *SafetyInfo,
788 SinkAndHoistLICMFlags &Flags,
789 OptimizationRemarkEmitter *ORE) {
790 // Verify inputs.
791 assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr
&& DT != nullptr && CurLoop != nullptr &&
SafetyInfo != nullptr && "Unexpected input to hoistRegion."
) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to hoistRegion.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 793, __PRETTY_FUNCTION__))
792 CurLoop != nullptr && SafetyInfo != nullptr &&((N != nullptr && AA != nullptr && LI != nullptr
&& DT != nullptr && CurLoop != nullptr &&
SafetyInfo != nullptr && "Unexpected input to hoistRegion."
) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to hoistRegion.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 793, __PRETTY_FUNCTION__))
793 "Unexpected input to hoistRegion.")((N != nullptr && AA != nullptr && LI != nullptr
&& DT != nullptr && CurLoop != nullptr &&
SafetyInfo != nullptr && "Unexpected input to hoistRegion."
) ? static_cast<void> (0) : __assert_fail ("N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && CurLoop != nullptr && SafetyInfo != nullptr && \"Unexpected input to hoistRegion.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 793, __PRETTY_FUNCTION__))
;
794 assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) &&((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized."
) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 795, __PRETTY_FUNCTION__))
795 "Either AliasSetTracker or MemorySSA should be initialized.")((((CurAST != nullptr) ^ (MSSAU != nullptr)) && "Either AliasSetTracker or MemorySSA should be initialized."
) ? static_cast<void> (0) : __assert_fail ("((CurAST != nullptr) ^ (MSSAU != nullptr)) && \"Either AliasSetTracker or MemorySSA should be initialized.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 795, __PRETTY_FUNCTION__))
;
796
797 ControlFlowHoister CFH(LI, DT, CurLoop, MSSAU);
798
799 // Keep track of instructions that have been hoisted, as they may need to be
800 // re-hoisted if they end up not dominating all of their uses.
801 SmallVector<Instruction *, 16> HoistedInstructions;
802
803 // For PHI hoisting to work we need to hoist blocks before their successors.
804 // We can do this by iterating through the blocks in the loop in reverse
805 // post-order.
806 LoopBlocksRPO Worklist(CurLoop);
807 Worklist.perform(LI);
808 bool Changed = false;
809 for (BasicBlock *BB : Worklist) {
810 // Only need to process the contents of this block if it is not part of a
811 // subloop (which would already have been processed).
812 if (inSubLoop(BB, CurLoop, LI))
813 continue;
814
815 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) {
816 Instruction &I = *II++;
817 // Try constant folding this instruction. If all the operands are
818 // constants, it is technically hoistable, but it would be better to
819 // just fold it.
820 if (Constant *C = ConstantFoldInstruction(
821 &I, I.getModule()->getDataLayout(), TLI)) {
822 LLVM_DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *Cdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM folding inst: " << I <<
" --> " << *C << '\n'; } } while (false)
823 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM folding inst: " << I <<
" --> " << *C << '\n'; } } while (false)
;
824 if (CurAST)
825 CurAST->copyValue(&I, C);
826 // FIXME MSSA: Such replacements may make accesses unoptimized (D51960).
827 I.replaceAllUsesWith(C);
828 if (isInstructionTriviallyDead(&I, TLI))
829 eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
830 Changed = true;
831 continue;
832 }
833
834 // Try hoisting the instruction out to the preheader. We can only do
835 // this if all of the operands of the instruction are loop invariant and
836 // if it is safe to hoist the instruction.
837 // TODO: It may be safe to hoist if we are hoisting to a conditional block
838 // and we have accurately duplicated the control flow from the loop header
839 // to that block.
840 if (CurLoop->hasLoopInvariantOperands(&I) &&
841 canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags,
842 ORE) &&
843 isSafeToExecuteUnconditionally(
844 I, DT, CurLoop, SafetyInfo, ORE,
845 CurLoop->getLoopPreheader()->getTerminator())) {
846 hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
847 MSSAU, ORE);
848 HoistedInstructions.push_back(&I);
849 Changed = true;
850 continue;
851 }
852
853 // Attempt to remove floating point division out of the loop by
854 // converting it to a reciprocal multiplication.
855 if (I.getOpcode() == Instruction::FDiv &&
856 CurLoop->isLoopInvariant(I.getOperand(1)) &&
857 I.hasAllowReciprocal()) {
858 auto Divisor = I.getOperand(1);
859 auto One = llvm::ConstantFP::get(Divisor->getType(), 1.0);
860 auto ReciprocalDivisor = BinaryOperator::CreateFDiv(One, Divisor);
861 ReciprocalDivisor->setFastMathFlags(I.getFastMathFlags());
862 SafetyInfo->insertInstructionTo(ReciprocalDivisor, I.getParent());
863 ReciprocalDivisor->insertBefore(&I);
864
865 auto Product =
866 BinaryOperator::CreateFMul(I.getOperand(0), ReciprocalDivisor);
867 Product->setFastMathFlags(I.getFastMathFlags());
868 SafetyInfo->insertInstructionTo(Product, I.getParent());
869 Product->insertAfter(&I);
870 I.replaceAllUsesWith(Product);
871 eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
872
873 hoist(*ReciprocalDivisor, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB),
874 SafetyInfo, MSSAU, ORE);
875 HoistedInstructions.push_back(ReciprocalDivisor);
876 Changed = true;
877 continue;
878 }
879
880 auto IsInvariantStart = [&](Instruction &I) {
881 using namespace PatternMatch;
882 return I.use_empty() &&
883 match(&I, m_Intrinsic<Intrinsic::invariant_start>());
884 };
885 auto MustExecuteWithoutWritesBefore = [&](Instruction &I) {
886 return SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop) &&
887 SafetyInfo->doesNotWriteMemoryBefore(I, CurLoop);
888 };
889 if ((IsInvariantStart(I) || isGuard(&I)) &&
890 CurLoop->hasLoopInvariantOperands(&I) &&
891 MustExecuteWithoutWritesBefore(I)) {
892 hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
893 MSSAU, ORE);
894 HoistedInstructions.push_back(&I);
895 Changed = true;
896 continue;
897 }
898
899 if (PHINode *PN = dyn_cast<PHINode>(&I)) {
900 if (CFH.canHoistPHI(PN)) {
901 // Redirect incoming blocks first to ensure that we create hoisted
902 // versions of those blocks before we hoist the phi.
903 for (unsigned int i = 0; i < PN->getNumIncomingValues(); ++i)
904 PN->setIncomingBlock(
905 i, CFH.getOrCreateHoistedBlock(PN->getIncomingBlock(i)));
906 hoist(*PN, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
907 MSSAU, ORE);
908 assert(DT->dominates(PN, BB) && "Conditional PHIs not expected")((DT->dominates(PN, BB) && "Conditional PHIs not expected"
) ? static_cast<void> (0) : __assert_fail ("DT->dominates(PN, BB) && \"Conditional PHIs not expected\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 908, __PRETTY_FUNCTION__))
;
909 Changed = true;
910 continue;
911 }
912 }
913
914 // Remember possibly hoistable branches so we can actually hoist them
915 // later if needed.
916 if (BranchInst *BI = dyn_cast<BranchInst>(&I))
917 CFH.registerPossiblyHoistableBranch(BI);
918 }
919 }
920
921 // If we hoisted instructions to a conditional block they may not dominate
922 // their uses that weren't hoisted (such as phis where some operands are not
923 // loop invariant). If so make them unconditional by moving them to their
924 // immediate dominator. We iterate through the instructions in reverse order
925 // which ensures that when we rehoist an instruction we rehoist its operands,
926 // and also keep track of where in the block we are rehoisting to to make sure
927 // that we rehoist instructions before the instructions that use them.
928 Instruction *HoistPoint = nullptr;
929 if (ControlFlowHoisting) {
930 for (Instruction *I : reverse(HoistedInstructions)) {
931 if (!llvm::all_of(I->uses(),
932 [&](Use &U) { return DT->dominates(I, U); })) {
933 BasicBlock *Dominator =
934 DT->getNode(I->getParent())->getIDom()->getBlock();
935 if (!HoistPoint || !DT->dominates(HoistPoint->getParent(), Dominator)) {
936 if (HoistPoint)
937 assert(DT->dominates(Dominator, HoistPoint->getParent()) &&((DT->dominates(Dominator, HoistPoint->getParent()) &&
"New hoist point expected to dominate old hoist point") ? static_cast
<void> (0) : __assert_fail ("DT->dominates(Dominator, HoistPoint->getParent()) && \"New hoist point expected to dominate old hoist point\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 938, __PRETTY_FUNCTION__))
938 "New hoist point expected to dominate old hoist point")((DT->dominates(Dominator, HoistPoint->getParent()) &&
"New hoist point expected to dominate old hoist point") ? static_cast
<void> (0) : __assert_fail ("DT->dominates(Dominator, HoistPoint->getParent()) && \"New hoist point expected to dominate old hoist point\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 938, __PRETTY_FUNCTION__))
;
939 HoistPoint = Dominator->getTerminator();
940 }
941 LLVM_DEBUG(dbgs() << "LICM rehoisting to "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM rehoisting to " << HoistPoint
->getParent()->getName() << ": " << *I <<
"\n"; } } while (false)
942 << HoistPoint->getParent()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM rehoisting to " << HoistPoint
->getParent()->getName() << ": " << *I <<
"\n"; } } while (false)
943 << ": " << *I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM rehoisting to " << HoistPoint
->getParent()->getName() << ": " << *I <<
"\n"; } } while (false)
;
944 moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU);
945 HoistPoint = I;
946 Changed = true;
947 }
948 }
949 }
950 if (MSSAU && VerifyMemorySSA)
951 MSSAU->getMemorySSA()->verifyMemorySSA();
952
953 // Now that we've finished hoisting make sure that LI and DT are still
954 // valid.
955#ifndef NDEBUG
956 if (Changed) {
957 assert(DT->verify(DominatorTree::VerificationLevel::Fast) &&((DT->verify(DominatorTree::VerificationLevel::Fast) &&
"Dominator tree verification failed") ? static_cast<void>
(0) : __assert_fail ("DT->verify(DominatorTree::VerificationLevel::Fast) && \"Dominator tree verification failed\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 958, __PRETTY_FUNCTION__))
958 "Dominator tree verification failed")((DT->verify(DominatorTree::VerificationLevel::Fast) &&
"Dominator tree verification failed") ? static_cast<void>
(0) : __assert_fail ("DT->verify(DominatorTree::VerificationLevel::Fast) && \"Dominator tree verification failed\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 958, __PRETTY_FUNCTION__))
;
959 LI->verify(*DT);
960 }
961#endif
962
963 return Changed;
964}
965
966// Return true if LI is invariant within scope of the loop. LI is invariant if
967// CurLoop is dominated by an invariant.start representing the same memory
968// location and size as the memory location LI loads from, and also the
969// invariant.start has no uses.
970static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT,
971 Loop *CurLoop) {
972 Value *Addr = LI->getOperand(0);
973 const DataLayout &DL = LI->getModule()->getDataLayout();
974 const uint32_t LocSizeInBits = DL.getTypeSizeInBits(
975 cast<PointerType>(Addr->getType())->getElementType());
976
977 // if the type is i8 addrspace(x)*, we know this is the type of
978 // llvm.invariant.start operand
979 auto *PtrInt8Ty = PointerType::get(Type::getInt8Ty(LI->getContext()),
980 LI->getPointerAddressSpace());
981 unsigned BitcastsVisited = 0;
982 // Look through bitcasts until we reach the i8* type (this is invariant.start
983 // operand type).
984 while (Addr->getType() != PtrInt8Ty) {
985 auto *BC = dyn_cast<BitCastInst>(Addr);
986 // Avoid traversing high number of bitcast uses.
987 if (++BitcastsVisited > MaxNumUsesTraversed || !BC)
988 return false;
989 Addr = BC->getOperand(0);
990 }
991
992 unsigned UsesVisited = 0;
993 // Traverse all uses of the load operand value, to see if invariant.start is
994 // one of the uses, and whether it dominates the load instruction.
995 for (auto *U : Addr->users()) {
996 // Avoid traversing for Load operand with high number of users.
997 if (++UsesVisited > MaxNumUsesTraversed)
998 return false;
999 IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
1000 // If there are escaping uses of invariant.start instruction, the load maybe
1001 // non-invariant.
1002 if (!II || II->getIntrinsicID() != Intrinsic::invariant_start ||
1003 !II->use_empty())
1004 continue;
1005 unsigned InvariantSizeInBits =
1006 cast<ConstantInt>(II->getArgOperand(0))->getSExtValue() * 8;
1007 // Confirm the invariant.start location size contains the load operand size
1008 // in bits. Also, the invariant.start should dominate the load, and we
1009 // should not hoist the load out of a loop that contains this dominating
1010 // invariant.start.
1011 if (LocSizeInBits <= InvariantSizeInBits &&
1012 DT->properlyDominates(II->getParent(), CurLoop->getHeader()))
1013 return true;
1014 }
1015
1016 return false;
1017}
1018
1019namespace {
1020/// Return true if-and-only-if we know how to (mechanically) both hoist and
1021/// sink a given instruction out of a loop. Does not address legality
1022/// concerns such as aliasing or speculation safety.
1023bool isHoistableAndSinkableInst(Instruction &I) {
1024 // Only these instructions are hoistable/sinkable.
1025 return (isa<LoadInst>(I) || isa<StoreInst>(I) || isa<CallInst>(I) ||
1026 isa<FenceInst>(I) || isa<BinaryOperator>(I) || isa<CastInst>(I) ||
1027 isa<SelectInst>(I) || isa<GetElementPtrInst>(I) || isa<CmpInst>(I) ||
1028 isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) ||
1029 isa<ShuffleVectorInst>(I) || isa<ExtractValueInst>(I) ||
1030 isa<InsertValueInst>(I));
1031}
1032/// Return true if all of the alias sets within this AST are known not to
1033/// contain a Mod, or if MSSA knows thare are no MemoryDefs in the loop.
1034bool isReadOnly(AliasSetTracker *CurAST, const MemorySSAUpdater *MSSAU,
1035 const Loop *L) {
1036 if (CurAST) {
1037 for (AliasSet &AS : *CurAST) {
1038 if (!AS.isForwardingAliasSet() && AS.isMod()) {
1039 return false;
1040 }
1041 }
1042 return true;
1043 } else { /*MSSAU*/
1044 for (auto *BB : L->getBlocks())
1045 if (MSSAU->getMemorySSA()->getBlockDefs(BB))
1046 return false;
1047 return true;
1048 }
1049}
1050
1051/// Return true if I is the only Instruction with a MemoryAccess in L.
1052bool isOnlyMemoryAccess(const Instruction *I, const Loop *L,
1053 const MemorySSAUpdater *MSSAU) {
1054 for (auto *BB : L->getBlocks())
1055 if (auto *Accs = MSSAU->getMemorySSA()->getBlockAccesses(BB)) {
1056 int NotAPhi = 0;
1057 for (const auto &Acc : *Accs) {
1058 if (isa<MemoryPhi>(&Acc))
1059 continue;
1060 const auto *MUD = cast<MemoryUseOrDef>(&Acc);
1061 if (MUD->getMemoryInst() != I || NotAPhi++ == 1)
1062 return false;
1063 }
1064 }
1065 return true;
1066}
1067}
1068
1069bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
1070 Loop *CurLoop, AliasSetTracker *CurAST,
1071 MemorySSAUpdater *MSSAU,
1072 bool TargetExecutesOncePerLoop,
1073 SinkAndHoistLICMFlags *Flags,
1074 OptimizationRemarkEmitter *ORE) {
1075 // If we don't understand the instruction, bail early.
1076 if (!isHoistableAndSinkableInst(I))
1
Taking false branch
1077 return false;
1078
1079 MemorySSA *MSSA = MSSAU ? MSSAU->getMemorySSA() : nullptr;
2
Assuming 'MSSAU' is non-null
3
'?' condition is true
4
'MSSA' initialized here
1080 if (MSSA)
5
Assuming 'MSSA' is null
6
Taking false branch
1081 assert(Flags != nullptr && "Flags cannot be null.")((Flags != nullptr && "Flags cannot be null.") ? static_cast
<void> (0) : __assert_fail ("Flags != nullptr && \"Flags cannot be null.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1081, __PRETTY_FUNCTION__))
;
1082
1083 // Loads have extra constraints we have to verify before we can hoist them.
1084 if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
7
Taking false branch
1085 if (!LI->isUnordered())
1086 return false; // Don't sink/hoist volatile or ordered atomic loads!
1087
1088 // Loads from constant memory are always safe to move, even if they end up
1089 // in the same alias set as something that ends up being modified.
1090 if (AA->pointsToConstantMemory(LI->getOperand(0)))
1091 return true;
1092 if (LI->getMetadata(LLVMContext::MD_invariant_load))
1093 return true;
1094
1095 if (LI->isAtomic() && !TargetExecutesOncePerLoop)
1096 return false; // Don't risk duplicating unordered loads
1097
1098 // This checks for an invariant.start dominating the load.
1099 if (isLoadInvariantInLoop(LI, DT, CurLoop))
1100 return true;
1101
1102 bool Invalidated;
1103 if (CurAST)
1104 Invalidated = pointerInvalidatedByLoop(MemoryLocation::get(LI), CurAST,
1105 CurLoop, AA);
1106 else
1107 Invalidated = pointerInvalidatedByLoopWithMSSA(
1108 MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(LI)), CurLoop, *Flags);
1109 // Check loop-invariant address because this may also be a sinkable load
1110 // whose address is not necessarily loop-invariant.
1111 if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand()))
1112 ORE->emit([&]() {
1113 return OptimizationRemarkMissed(
1114 DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressInvalidated", LI)
1115 << "failed to move load with loop-invariant address "
1116 "because the loop may invalidate its value";
1117 });
1118
1119 return !Invalidated;
1120 } else if (CallInst *CI = dyn_cast<CallInst>(&I)) {
8
Taking true branch
1121 // Don't sink or hoist dbg info; it's legal, but not useful.
1122 if (isa<DbgInfoIntrinsic>(I))
9
Taking false branch
1123 return false;
1124
1125 // Don't sink calls which can throw.
1126 if (CI->mayThrow())
10
Assuming the condition is false
11
Taking false branch
1127 return false;
1128
1129 using namespace PatternMatch;
1130 if (match(CI, m_Intrinsic<Intrinsic::assume>()))
12
Taking false branch
1131 // Assumes don't actually alias anything or throw
1132 return true;
1133
1134 // Handle simple cases by querying alias analysis.
1135 FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI);
1136 if (Behavior == FMRB_DoesNotAccessMemory)
13
Assuming 'Behavior' is not equal to FMRB_DoesNotAccessMemory
14
Taking false branch
1137 return true;
1138 if (AliasAnalysis::onlyReadsMemory(Behavior)) {
15
Taking true branch
1139 // A readonly argmemonly function only reads from memory pointed to by
1140 // it's arguments with arbitrary offsets. If we can prove there are no
1141 // writes to this memory in the loop, we can hoist or sink.
1142 if (AliasAnalysis::onlyAccessesArgPointees(Behavior)) {
16
Taking true branch
1143 // TODO: expand to writeable arguments
1144 for (Value *Op : CI->arg_operands())
17
Assuming '__begin5' is not equal to '__end5'
1145 if (Op->getType()->isPointerTy()) {
18
Taking true branch
1146 bool Invalidated;
1147 if (CurAST)
19
Assuming 'CurAST' is null
20
Taking false branch
1148 Invalidated = pointerInvalidatedByLoop(
1149 MemoryLocation(Op, LocationSize::unknown(), AAMDNodes()),
1150 CurAST, CurLoop, AA);
1151 else
1152 Invalidated = pointerInvalidatedByLoopWithMSSA(
1153 MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(CI)), CurLoop,
21
Called C++ object pointer is null
1154 *Flags);
1155 if (Invalidated)
1156 return false;
1157 }
1158 return true;
1159 }
1160
1161 // If this call only reads from memory and there are no writes to memory
1162 // in the loop, we can hoist or sink the call as appropriate.
1163 if (isReadOnly(CurAST, MSSAU, CurLoop))
1164 return true;
1165 }
1166
1167 // FIXME: This should use mod/ref information to see if we can hoist or
1168 // sink the call.
1169
1170 return false;
1171 } else if (auto *FI = dyn_cast<FenceInst>(&I)) {
1172 // Fences alias (most) everything to provide ordering. For the moment,
1173 // just give up if there are any other memory operations in the loop.
1174 if (CurAST) {
1175 auto Begin = CurAST->begin();
1176 assert(Begin != CurAST->end() && "must contain FI")((Begin != CurAST->end() && "must contain FI") ? static_cast
<void> (0) : __assert_fail ("Begin != CurAST->end() && \"must contain FI\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1176, __PRETTY_FUNCTION__))
;
1177 if (std::next(Begin) != CurAST->end())
1178 // constant memory for instance, TODO: handle better
1179 return false;
1180 auto *UniqueI = Begin->getUniqueInstruction();
1181 if (!UniqueI)
1182 // other memory op, give up
1183 return false;
1184 (void)FI; // suppress unused variable warning
1185 assert(UniqueI == FI && "AS must contain FI")((UniqueI == FI && "AS must contain FI") ? static_cast
<void> (0) : __assert_fail ("UniqueI == FI && \"AS must contain FI\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1185, __PRETTY_FUNCTION__))
;
1186 return true;
1187 } else // MSSAU
1188 return isOnlyMemoryAccess(FI, CurLoop, MSSAU);
1189 } else if (auto *SI = dyn_cast<StoreInst>(&I)) {
1190 if (!SI->isUnordered())
1191 return false; // Don't sink/hoist volatile or ordered atomic store!
1192
1193 // We can only hoist a store that we can prove writes a value which is not
1194 // read or overwritten within the loop. For those cases, we fallback to
1195 // load store promotion instead. TODO: We can extend this to cases where
1196 // there is exactly one write to the location and that write dominates an
1197 // arbitrary number of reads in the loop.
1198 if (CurAST) {
1199 auto &AS = CurAST->getAliasSetFor(MemoryLocation::get(SI));
1200
1201 if (AS.isRef() || !AS.isMustAlias())
1202 // Quick exit test, handled by the full path below as well.
1203 return false;
1204 auto *UniqueI = AS.getUniqueInstruction();
1205 if (!UniqueI)
1206 // other memory op, give up
1207 return false;
1208 assert(UniqueI == SI && "AS must contain SI")((UniqueI == SI && "AS must contain SI") ? static_cast
<void> (0) : __assert_fail ("UniqueI == SI && \"AS must contain SI\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1208, __PRETTY_FUNCTION__))
;
1209 return true;
1210 } else { // MSSAU
1211 if (isOnlyMemoryAccess(SI, CurLoop, MSSAU))
1212 return true;
1213 // If there are more accesses than the Promotion cap, give up, we're not
1214 // walking a list that long.
1215 if (Flags->NoOfMemAccTooLarge)
1216 return false;
1217 // Check store only if there's still "quota" to check clobber.
1218 if (Flags->LicmMssaOptCounter >= Flags->LicmMssaOptCap)
1219 return false;
1220 // If there are interfering Uses (i.e. their defining access is in the
1221 // loop), or ordered loads (stored as Defs!), don't move this store.
1222 // Could do better here, but this is conservatively correct.
1223 // TODO: Cache set of Uses on the first walk in runOnLoop, update when
1224 // moving accesses. Can also extend to dominating uses.
1225 for (auto *BB : CurLoop->getBlocks())
1226 if (auto *Accesses = MSSA->getBlockAccesses(BB)) {
1227 for (const auto &MA : *Accesses)
1228 if (const auto *MU = dyn_cast<MemoryUse>(&MA)) {
1229 auto *MD = MU->getDefiningAccess();
1230 if (!MSSA->isLiveOnEntryDef(MD) &&
1231 CurLoop->contains(MD->getBlock()))
1232 return false;
1233 } else if (const auto *MD = dyn_cast<MemoryDef>(&MA))
1234 if (auto *LI = dyn_cast<LoadInst>(MD->getMemoryInst())) {
1235 (void)LI; // Silence warning.
1236 assert(!LI->isUnordered() && "Expected unordered load")((!LI->isUnordered() && "Expected unordered load")
? static_cast<void> (0) : __assert_fail ("!LI->isUnordered() && \"Expected unordered load\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1236, __PRETTY_FUNCTION__))
;
1237 return false;
1238 }
1239 }
1240
1241 auto *Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(SI);
1242 Flags->LicmMssaOptCounter++;
1243 // If there are no clobbering Defs in the loop, store is safe to hoist.
1244 return MSSA->isLiveOnEntryDef(Source) ||
1245 !CurLoop->contains(Source->getBlock());
1246 }
1247 }
1248
1249 assert(!I.mayReadOrWriteMemory() && "unhandled aliasing")((!I.mayReadOrWriteMemory() && "unhandled aliasing") ?
static_cast<void> (0) : __assert_fail ("!I.mayReadOrWriteMemory() && \"unhandled aliasing\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1249, __PRETTY_FUNCTION__))
;
1250
1251 // We've established mechanical ability and aliasing, it's up to the caller
1252 // to check fault safety
1253 return true;
1254}
1255
1256/// Returns true if a PHINode is a trivially replaceable with an
1257/// Instruction.
1258/// This is true when all incoming values are that instruction.
1259/// This pattern occurs most often with LCSSA PHI nodes.
1260///
1261static bool isTriviallyReplaceablePHI(const PHINode &PN, const Instruction &I) {
1262 for (const Value *IncValue : PN.incoming_values())
1263 if (IncValue != &I)
1264 return false;
1265
1266 return true;
1267}
1268
1269/// Return true if the instruction is free in the loop.
1270static bool isFreeInLoop(const Instruction &I, const Loop *CurLoop,
1271 const TargetTransformInfo *TTI) {
1272
1273 if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&I)) {
1274 if (TTI->getUserCost(GEP) != TargetTransformInfo::TCC_Free)
1275 return false;
1276 // For a GEP, we cannot simply use getUserCost because currently it
1277 // optimistically assume that a GEP will fold into addressing mode
1278 // regardless of its users.
1279 const BasicBlock *BB = GEP->getParent();
1280 for (const User *U : GEP->users()) {
1281 const Instruction *UI = cast<Instruction>(U);
1282 if (CurLoop->contains(UI) &&
1283 (BB != UI->getParent() ||
1284 (!isa<StoreInst>(UI) && !isa<LoadInst>(UI))))
1285 return false;
1286 }
1287 return true;
1288 } else
1289 return TTI->getUserCost(&I) == TargetTransformInfo::TCC_Free;
1290}
1291
1292/// Return true if the only users of this instruction are outside of
1293/// the loop. If this is true, we can sink the instruction to the exit
1294/// blocks of the loop.
1295///
1296/// We also return true if the instruction could be folded away in lowering.
1297/// (e.g., a GEP can be folded into a load as an addressing mode in the loop).
1298static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop,
1299 const LoopSafetyInfo *SafetyInfo,
1300 TargetTransformInfo *TTI, bool &FreeInLoop) {
1301 const auto &BlockColors = SafetyInfo->getBlockColors();
1302 bool IsFree = isFreeInLoop(I, CurLoop, TTI);
1303 for (const User *U : I.users()) {
1304 const Instruction *UI = cast<Instruction>(U);
1305 if (const PHINode *PN = dyn_cast<PHINode>(UI)) {
1306 const BasicBlock *BB = PN->getParent();
1307 // We cannot sink uses in catchswitches.
1308 if (isa<CatchSwitchInst>(BB->getTerminator()))
1309 return false;
1310
1311 // We need to sink a callsite to a unique funclet. Avoid sinking if the
1312 // phi use is too muddled.
1313 if (isa<CallInst>(I))
1314 if (!BlockColors.empty() &&
1315 BlockColors.find(const_cast<BasicBlock *>(BB))->second.size() != 1)
1316 return false;
1317 }
1318
1319 if (CurLoop->contains(UI)) {
1320 if (IsFree) {
1321 FreeInLoop = true;
1322 continue;
1323 }
1324 return false;
1325 }
1326 }
1327 return true;
1328}
1329
1330static Instruction *CloneInstructionInExitBlock(
1331 Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI,
1332 const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU) {
1333 Instruction *New;
1334 if (auto *CI = dyn_cast<CallInst>(&I)) {
1335 const auto &BlockColors = SafetyInfo->getBlockColors();
1336
1337 // Sinking call-sites need to be handled differently from other
1338 // instructions. The cloned call-site needs a funclet bundle operand
1339 // appropriate for its location in the CFG.
1340 SmallVector<OperandBundleDef, 1> OpBundles;
1341 for (unsigned BundleIdx = 0, BundleEnd = CI->getNumOperandBundles();
1342 BundleIdx != BundleEnd; ++BundleIdx) {
1343 OperandBundleUse Bundle = CI->getOperandBundleAt(BundleIdx);
1344 if (Bundle.getTagID() == LLVMContext::OB_funclet)
1345 continue;
1346
1347 OpBundles.emplace_back(Bundle);
1348 }
1349
1350 if (!BlockColors.empty()) {
1351 const ColorVector &CV = BlockColors.find(&ExitBlock)->second;
1352 assert(CV.size() == 1 && "non-unique color for exit block!")((CV.size() == 1 && "non-unique color for exit block!"
) ? static_cast<void> (0) : __assert_fail ("CV.size() == 1 && \"non-unique color for exit block!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1352, __PRETTY_FUNCTION__))
;
1353 BasicBlock *BBColor = CV.front();
1354 Instruction *EHPad = BBColor->getFirstNonPHI();
1355 if (EHPad->isEHPad())
1356 OpBundles.emplace_back("funclet", EHPad);
1357 }
1358
1359 New = CallInst::Create(CI, OpBundles);
1360 } else {
1361 New = I.clone();
1362 }
1363
1364 ExitBlock.getInstList().insert(ExitBlock.getFirstInsertionPt(), New);
1365 if (!I.getName().empty())
1366 New->setName(I.getName() + ".le");
1367
1368 MemoryAccess *OldMemAcc;
1369 if (MSSAU && (OldMemAcc = MSSAU->getMemorySSA()->getMemoryAccess(&I))) {
1370 // Create a new MemoryAccess and let MemorySSA set its defining access.
1371 MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB(
1372 New, nullptr, New->getParent(), MemorySSA::Beginning);
1373 if (NewMemAcc) {
1374 if (auto *MemDef = dyn_cast<MemoryDef>(NewMemAcc))
1375 MSSAU->insertDef(MemDef, /*RenameUses=*/true);
1376 else {
1377 auto *MemUse = cast<MemoryUse>(NewMemAcc);
1378 MSSAU->insertUse(MemUse);
1379 }
1380 }
1381 }
1382
1383 // Build LCSSA PHI nodes for any in-loop operands. Note that this is
1384 // particularly cheap because we can rip off the PHI node that we're
1385 // replacing for the number and blocks of the predecessors.
1386 // OPT: If this shows up in a profile, we can instead finish sinking all
1387 // invariant instructions, and then walk their operands to re-establish
1388 // LCSSA. That will eliminate creating PHI nodes just to nuke them when
1389 // sinking bottom-up.
1390 for (User::op_iterator OI = New->op_begin(), OE = New->op_end(); OI != OE;
1391 ++OI)
1392 if (Instruction *OInst = dyn_cast<Instruction>(*OI))
1393 if (Loop *OLoop = LI->getLoopFor(OInst->getParent()))
1394 if (!OLoop->contains(&PN)) {
1395 PHINode *OpPN =
1396 PHINode::Create(OInst->getType(), PN.getNumIncomingValues(),
1397 OInst->getName() + ".lcssa", &ExitBlock.front());
1398 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1399 OpPN->addIncoming(OInst, PN.getIncomingBlock(i));
1400 *OI = OpPN;
1401 }
1402 return New;
1403}
1404
1405static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
1406 AliasSetTracker *AST, MemorySSAUpdater *MSSAU) {
1407 if (AST)
1408 AST->deleteValue(&I);
1409 if (MSSAU)
1410 MSSAU->removeMemoryAccess(&I);
1411 SafetyInfo.removeInstruction(&I);
1412 I.eraseFromParent();
1413}
1414
1415static void moveInstructionBefore(Instruction &I, Instruction &Dest,
1416 ICFLoopSafetyInfo &SafetyInfo,
1417 MemorySSAUpdater *MSSAU) {
1418 SafetyInfo.removeInstruction(&I);
1419 SafetyInfo.insertInstructionTo(&I, Dest.getParent());
1420 I.moveBefore(&Dest);
1421 if (MSSAU)
1422 if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>(
1423 MSSAU->getMemorySSA()->getMemoryAccess(&I)))
1424 MSSAU->moveToPlace(OldMemAcc, Dest.getParent(), MemorySSA::End);
1425}
1426
1427static Instruction *sinkThroughTriviallyReplaceablePHI(
1428 PHINode *TPN, Instruction *I, LoopInfo *LI,
1429 SmallDenseMap<BasicBlock *, Instruction *, 32> &SunkCopies,
1430 const LoopSafetyInfo *SafetyInfo, const Loop *CurLoop,
1431 MemorySSAUpdater *MSSAU) {
1432 assert(isTriviallyReplaceablePHI(*TPN, *I) &&((isTriviallyReplaceablePHI(*TPN, *I) && "Expect only trivially replaceable PHI"
) ? static_cast<void> (0) : __assert_fail ("isTriviallyReplaceablePHI(*TPN, *I) && \"Expect only trivially replaceable PHI\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1433, __PRETTY_FUNCTION__))
1433 "Expect only trivially replaceable PHI")((isTriviallyReplaceablePHI(*TPN, *I) && "Expect only trivially replaceable PHI"
) ? static_cast<void> (0) : __assert_fail ("isTriviallyReplaceablePHI(*TPN, *I) && \"Expect only trivially replaceable PHI\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1433, __PRETTY_FUNCTION__))
;
1434 BasicBlock *ExitBlock = TPN->getParent();
1435 Instruction *New;
1436 auto It = SunkCopies.find(ExitBlock);
1437 if (It != SunkCopies.end())
1438 New = It->second;
1439 else
1440 New = SunkCopies[ExitBlock] = CloneInstructionInExitBlock(
1441 *I, *ExitBlock, *TPN, LI, SafetyInfo, MSSAU);
1442 return New;
1443}
1444
1445static bool canSplitPredecessors(PHINode *PN, LoopSafetyInfo *SafetyInfo) {
1446 BasicBlock *BB = PN->getParent();
1447 if (!BB->canSplitPredecessors())
1448 return false;
1449 // It's not impossible to split EHPad blocks, but if BlockColors already exist
1450 // it require updating BlockColors for all offspring blocks accordingly. By
1451 // skipping such corner case, we can make updating BlockColors after splitting
1452 // predecessor fairly simple.
1453 if (!SafetyInfo->getBlockColors().empty() && BB->getFirstNonPHI()->isEHPad())
1454 return false;
1455 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
1456 BasicBlock *BBPred = *PI;
1457 if (isa<IndirectBrInst>(BBPred->getTerminator()))
1458 return false;
1459 }
1460 return true;
1461}
1462
1463static void splitPredecessorsOfLoopExit(PHINode *PN, DominatorTree *DT,
1464 LoopInfo *LI, const Loop *CurLoop,
1465 LoopSafetyInfo *SafetyInfo,
1466 MemorySSAUpdater *MSSAU) {
1467#ifndef NDEBUG
1468 SmallVector<BasicBlock *, 32> ExitBlocks;
1469 CurLoop->getUniqueExitBlocks(ExitBlocks);
1470 SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(),
1471 ExitBlocks.end());
1472#endif
1473 BasicBlock *ExitBB = PN->getParent();
1474 assert(ExitBlockSet.count(ExitBB) && "Expect the PHI is in an exit block.")((ExitBlockSet.count(ExitBB) && "Expect the PHI is in an exit block."
) ? static_cast<void> (0) : __assert_fail ("ExitBlockSet.count(ExitBB) && \"Expect the PHI is in an exit block.\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1474, __PRETTY_FUNCTION__))
;
1475
1476 // Split predecessors of the loop exit to make instructions in the loop are
1477 // exposed to exit blocks through trivially replaceable PHIs while keeping the
1478 // loop in the canonical form where each predecessor of each exit block should
1479 // be contained within the loop. For example, this will convert the loop below
1480 // from
1481 //
1482 // LB1:
1483 // %v1 =
1484 // br %LE, %LB2
1485 // LB2:
1486 // %v2 =
1487 // br %LE, %LB1
1488 // LE:
1489 // %p = phi [%v1, %LB1], [%v2, %LB2] <-- non-trivially replaceable
1490 //
1491 // to
1492 //
1493 // LB1:
1494 // %v1 =
1495 // br %LE.split, %LB2
1496 // LB2:
1497 // %v2 =
1498 // br %LE.split2, %LB1
1499 // LE.split:
1500 // %p1 = phi [%v1, %LB1] <-- trivially replaceable
1501 // br %LE
1502 // LE.split2:
1503 // %p2 = phi [%v2, %LB2] <-- trivially replaceable
1504 // br %LE
1505 // LE:
1506 // %p = phi [%p1, %LE.split], [%p2, %LE.split2]
1507 //
1508 const auto &BlockColors = SafetyInfo->getBlockColors();
1509 SmallSetVector<BasicBlock *, 8> PredBBs(pred_begin(ExitBB), pred_end(ExitBB));
1510 while (!PredBBs.empty()) {
1511 BasicBlock *PredBB = *PredBBs.begin();
1512 assert(CurLoop->contains(PredBB) &&((CurLoop->contains(PredBB) && "Expect all predecessors are in the loop"
) ? static_cast<void> (0) : __assert_fail ("CurLoop->contains(PredBB) && \"Expect all predecessors are in the loop\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1513, __PRETTY_FUNCTION__))
1513 "Expect all predecessors are in the loop")((CurLoop->contains(PredBB) && "Expect all predecessors are in the loop"
) ? static_cast<void> (0) : __assert_fail ("CurLoop->contains(PredBB) && \"Expect all predecessors are in the loop\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1513, __PRETTY_FUNCTION__))
;
1514 if (PN->getBasicBlockIndex(PredBB) >= 0) {
1515 BasicBlock *NewPred = SplitBlockPredecessors(
1516 ExitBB, PredBB, ".split.loop.exit", DT, LI, MSSAU, true);
1517 // Since we do not allow splitting EH-block with BlockColors in
1518 // canSplitPredecessors(), we can simply assign predecessor's color to
1519 // the new block.
1520 if (!BlockColors.empty())
1521 // Grab a reference to the ColorVector to be inserted before getting the
1522 // reference to the vector we are copying because inserting the new
1523 // element in BlockColors might cause the map to be reallocated.
1524 SafetyInfo->copyColors(NewPred, PredBB);
1525 }
1526 PredBBs.remove(PredBB);
1527 }
1528}
1529
1530/// When an instruction is found to only be used outside of the loop, this
1531/// function moves it to the exit blocks and patches up SSA form as needed.
1532/// This method is guaranteed to remove the original instruction from its
1533/// position, and may either delete it or move it to outside of the loop.
1534///
1535static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
1536 const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo,
1537 MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE) {
1538 LLVM_DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM sinking instruction: " <<
I << "\n"; } } while (false)
;
1539 ORE->emit([&]() {
1540 return OptimizationRemark(DEBUG_TYPE"licm", "InstSunk", &I)
1541 << "sinking " << ore::NV("Inst", &I);
1542 });
1543 bool Changed = false;
1544 if (isa<LoadInst>(I))
1545 ++NumMovedLoads;
1546 else if (isa<CallInst>(I))
1547 ++NumMovedCalls;
1548 ++NumSunk;
1549
1550 // Iterate over users to be ready for actual sinking. Replace users via
1551 // unreachable blocks with undef and make all user PHIs trivially replaceable.
1552 SmallPtrSet<Instruction *, 8> VisitedUsers;
1553 for (Value::user_iterator UI = I.user_begin(), UE = I.user_end(); UI != UE;) {
1554 auto *User = cast<Instruction>(*UI);
1555 Use &U = UI.getUse();
1556 ++UI;
1557
1558 if (VisitedUsers.count(User) || CurLoop->contains(User))
1559 continue;
1560
1561 if (!DT->isReachableFromEntry(User->getParent())) {
1562 U = UndefValue::get(I.getType());
1563 Changed = true;
1564 continue;
1565 }
1566
1567 // The user must be a PHI node.
1568 PHINode *PN = cast<PHINode>(User);
1569
1570 // Surprisingly, instructions can be used outside of loops without any
1571 // exits. This can only happen in PHI nodes if the incoming block is
1572 // unreachable.
1573 BasicBlock *BB = PN->getIncomingBlock(U);
1574 if (!DT->isReachableFromEntry(BB)) {
1575 U = UndefValue::get(I.getType());
1576 Changed = true;
1577 continue;
1578 }
1579
1580 VisitedUsers.insert(PN);
1581 if (isTriviallyReplaceablePHI(*PN, I))
1582 continue;
1583
1584 if (!canSplitPredecessors(PN, SafetyInfo))
1585 return Changed;
1586
1587 // Split predecessors of the PHI so that we can make users trivially
1588 // replaceable.
1589 splitPredecessorsOfLoopExit(PN, DT, LI, CurLoop, SafetyInfo, MSSAU);
1590
1591 // Should rebuild the iterators, as they may be invalidated by
1592 // splitPredecessorsOfLoopExit().
1593 UI = I.user_begin();
1594 UE = I.user_end();
1595 }
1596
1597 if (VisitedUsers.empty())
1598 return Changed;
1599
1600#ifndef NDEBUG
1601 SmallVector<BasicBlock *, 32> ExitBlocks;
1602 CurLoop->getUniqueExitBlocks(ExitBlocks);
1603 SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(),
1604 ExitBlocks.end());
1605#endif
1606
1607 // Clones of this instruction. Don't create more than one per exit block!
1608 SmallDenseMap<BasicBlock *, Instruction *, 32> SunkCopies;
1609
1610 // If this instruction is only used outside of the loop, then all users are
1611 // PHI nodes in exit blocks due to LCSSA form. Just RAUW them with clones of
1612 // the instruction.
1613 SmallSetVector<User*, 8> Users(I.user_begin(), I.user_end());
1614 for (auto *UI : Users) {
1615 auto *User = cast<Instruction>(UI);
1616
1617 if (CurLoop->contains(User))
1618 continue;
1619
1620 PHINode *PN = cast<PHINode>(User);
1621 assert(ExitBlockSet.count(PN->getParent()) &&((ExitBlockSet.count(PN->getParent()) && "The LCSSA PHI is not in an exit block!"
) ? static_cast<void> (0) : __assert_fail ("ExitBlockSet.count(PN->getParent()) && \"The LCSSA PHI is not in an exit block!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1622, __PRETTY_FUNCTION__))
1622 "The LCSSA PHI is not in an exit block!")((ExitBlockSet.count(PN->getParent()) && "The LCSSA PHI is not in an exit block!"
) ? static_cast<void> (0) : __assert_fail ("ExitBlockSet.count(PN->getParent()) && \"The LCSSA PHI is not in an exit block!\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1622, __PRETTY_FUNCTION__))
;
1623 // The PHI must be trivially replaceable.
1624 Instruction *New = sinkThroughTriviallyReplaceablePHI(
1625 PN, &I, LI, SunkCopies, SafetyInfo, CurLoop, MSSAU);
1626 PN->replaceAllUsesWith(New);
1627 eraseInstruction(*PN, *SafetyInfo, nullptr, nullptr);
1628 Changed = true;
1629 }
1630 return Changed;
1631}
1632
1633/// When an instruction is found to only use loop invariant operands that
1634/// is safe to hoist, this instruction is called to do the dirty work.
1635///
1636static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
1637 BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo,
1638 MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE) {
1639 LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getName() << ": " << Ido { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM hoisting to " << Dest
->getName() << ": " << I << "\n"; } } while
(false)
1640 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM hoisting to " << Dest
->getName() << ": " << I << "\n"; } } while
(false)
;
1641 ORE->emit([&]() {
1642 return OptimizationRemark(DEBUG_TYPE"licm", "Hoisted", &I) << "hoisting "
1643 << ore::NV("Inst", &I);
1644 });
1645
1646 // Metadata can be dependent on conditions we are hoisting above.
1647 // Conservatively strip all metadata on the instruction unless we were
1648 // guaranteed to execute I if we entered the loop, in which case the metadata
1649 // is valid in the loop preheader.
1650 if (I.hasMetadataOtherThanDebugLoc() &&
1651 // The check on hasMetadataOtherThanDebugLoc is to prevent us from burning
1652 // time in isGuaranteedToExecute if we don't actually have anything to
1653 // drop. It is a compile time optimization, not required for correctness.
1654 !SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop))
1655 I.dropUnknownNonDebugMetadata();
1656
1657 if (isa<PHINode>(I))
1658 // Move the new node to the end of the phi list in the destination block.
1659 moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU);
1660 else
1661 // Move the new node to the destination block, before its terminator.
1662 moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU);
1663
1664 // Apply line 0 debug locations when we are moving instructions to different
1665 // basic blocks because we want to avoid jumpy line tables.
1666 if (const DebugLoc &DL = I.getDebugLoc())
1667 I.setDebugLoc(DebugLoc::get(0, 0, DL.getScope(), DL.getInlinedAt()));
1668
1669 if (isa<LoadInst>(I))
1670 ++NumMovedLoads;
1671 else if (isa<CallInst>(I))
1672 ++NumMovedCalls;
1673 ++NumHoisted;
1674}
1675
1676/// Only sink or hoist an instruction if it is not a trapping instruction,
1677/// or if the instruction is known not to trap when moved to the preheader.
1678/// or if it is a trapping instruction and is guaranteed to execute.
1679static bool isSafeToExecuteUnconditionally(Instruction &Inst,
1680 const DominatorTree *DT,
1681 const Loop *CurLoop,
1682 const LoopSafetyInfo *SafetyInfo,
1683 OptimizationRemarkEmitter *ORE,
1684 const Instruction *CtxI) {
1685 if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT))
1686 return true;
1687
1688 bool GuaranteedToExecute =
1689 SafetyInfo->isGuaranteedToExecute(Inst, DT, CurLoop);
1690
1691 if (!GuaranteedToExecute) {
1692 auto *LI = dyn_cast<LoadInst>(&Inst);
1693 if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand()))
1694 ORE->emit([&]() {
1695 return OptimizationRemarkMissed(
1696 DEBUG_TYPE"licm", "LoadWithLoopInvariantAddressCondExecuted", LI)
1697 << "failed to hoist load with loop-invariant address "
1698 "because load is conditionally executed";
1699 });
1700 }
1701
1702 return GuaranteedToExecute;
1703}
1704
1705namespace {
1706class LoopPromoter : public LoadAndStorePromoter {
1707 Value *SomePtr; // Designated pointer to store to.
1708 const SmallSetVector<Value *, 8> &PointerMustAliases;
1709 SmallVectorImpl<BasicBlock *> &LoopExitBlocks;
1710 SmallVectorImpl<Instruction *> &LoopInsertPts;
1711 SmallVectorImpl<MemoryAccess *> &MSSAInsertPts;
1712 PredIteratorCache &PredCache;
1713 AliasSetTracker &AST;
1714 MemorySSAUpdater *MSSAU;
1715 LoopInfo &LI;
1716 DebugLoc DL;
1717 int Alignment;
1718 bool UnorderedAtomic;
1719 AAMDNodes AATags;
1720 ICFLoopSafetyInfo &SafetyInfo;
1721
1722 Value *maybeInsertLCSSAPHI(Value *V, BasicBlock *BB) const {
1723 if (Instruction *I = dyn_cast<Instruction>(V))
1724 if (Loop *L = LI.getLoopFor(I->getParent()))
1725 if (!L->contains(BB)) {
1726 // We need to create an LCSSA PHI node for the incoming value and
1727 // store that.
1728 PHINode *PN = PHINode::Create(I->getType(), PredCache.size(BB),
1729 I->getName() + ".lcssa", &BB->front());
1730 for (BasicBlock *Pred : PredCache.get(BB))
1731 PN->addIncoming(I, Pred);
1732 return PN;
1733 }
1734 return V;
1735 }
1736
1737public:
1738 LoopPromoter(Value *SP, ArrayRef<const Instruction *> Insts, SSAUpdater &S,
1739 const SmallSetVector<Value *, 8> &PMA,
1740 SmallVectorImpl<BasicBlock *> &LEB,
1741 SmallVectorImpl<Instruction *> &LIP,
1742 SmallVectorImpl<MemoryAccess *> &MSSAIP, PredIteratorCache &PIC,
1743 AliasSetTracker &ast, MemorySSAUpdater *MSSAU, LoopInfo &li,
1744 DebugLoc dl, int alignment, bool UnorderedAtomic,
1745 const AAMDNodes &AATags, ICFLoopSafetyInfo &SafetyInfo)
1746 : LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA),
1747 LoopExitBlocks(LEB), LoopInsertPts(LIP), MSSAInsertPts(MSSAIP),
1748 PredCache(PIC), AST(ast), MSSAU(MSSAU), LI(li), DL(std::move(dl)),
1749 Alignment(alignment), UnorderedAtomic(UnorderedAtomic), AATags(AATags),
1750 SafetyInfo(SafetyInfo) {}
1751
1752 bool isInstInList(Instruction *I,
1753 const SmallVectorImpl<Instruction *> &) const override {
1754 Value *Ptr;
1755 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1756 Ptr = LI->getOperand(0);
1757 else
1758 Ptr = cast<StoreInst>(I)->getPointerOperand();
1759 return PointerMustAliases.count(Ptr);
1760 }
1761
1762 void doExtraRewritesBeforeFinalDeletion() override {
1763 // Insert stores after in the loop exit blocks. Each exit block gets a
1764 // store of the live-out values that feed them. Since we've already told
1765 // the SSA updater about the defs in the loop and the preheader
1766 // definition, it is all set and we can start using it.
1767 for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) {
1768 BasicBlock *ExitBlock = LoopExitBlocks[i];
1769 Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
1770 LiveInValue = maybeInsertLCSSAPHI(LiveInValue, ExitBlock);
1771 Value *Ptr = maybeInsertLCSSAPHI(SomePtr, ExitBlock);
1772 Instruction *InsertPos = LoopInsertPts[i];
1773 StoreInst *NewSI = new StoreInst(LiveInValue, Ptr, InsertPos);
1774 if (UnorderedAtomic)
1775 NewSI->setOrdering(AtomicOrdering::Unordered);
1776 NewSI->setAlignment(Alignment);
1777 NewSI->setDebugLoc(DL);
1778 if (AATags)
1779 NewSI->setAAMetadata(AATags);
1780
1781 if (MSSAU) {
1782 MemoryAccess *MSSAInsertPoint = MSSAInsertPts[i];
1783 MemoryAccess *NewMemAcc;
1784 if (!MSSAInsertPoint) {
1785 NewMemAcc = MSSAU->createMemoryAccessInBB(
1786 NewSI, nullptr, NewSI->getParent(), MemorySSA::Beginning);
1787 } else {
1788 NewMemAcc =
1789 MSSAU->createMemoryAccessAfter(NewSI, nullptr, MSSAInsertPoint);
1790 }
1791 MSSAInsertPts[i] = NewMemAcc;
1792 MSSAU->insertDef(cast<MemoryDef>(NewMemAcc), true);
1793 // FIXME: true for safety, false may still be correct.
1794 }
1795 }
1796 }
1797
1798 void replaceLoadWithValue(LoadInst *LI, Value *V) const override {
1799 // Update alias analysis.
1800 AST.copyValue(LI, V);
1801 }
1802 void instructionDeleted(Instruction *I) const override {
1803 SafetyInfo.removeInstruction(I);
1804 AST.deleteValue(I);
1805 if (MSSAU)
1806 MSSAU->removeMemoryAccess(I);
1807 }
1808};
1809
1810
1811/// Return true iff we can prove that a caller of this function can not inspect
1812/// the contents of the provided object in a well defined program.
1813bool isKnownNonEscaping(Value *Object, const TargetLibraryInfo *TLI) {
1814 if (isa<AllocaInst>(Object))
1815 // Since the alloca goes out of scope, we know the caller can't retain a
1816 // reference to it and be well defined. Thus, we don't need to check for
1817 // capture.
1818 return true;
1819
1820 // For all other objects we need to know that the caller can't possibly
1821 // have gotten a reference to the object. There are two components of
1822 // that:
1823 // 1) Object can't be escaped by this function. This is what
1824 // PointerMayBeCaptured checks.
1825 // 2) Object can't have been captured at definition site. For this, we
1826 // need to know the return value is noalias. At the moment, we use a
1827 // weaker condition and handle only AllocLikeFunctions (which are
1828 // known to be noalias). TODO
1829 return isAllocLikeFn(Object, TLI) &&
1830 !PointerMayBeCaptured(Object, true, true);
1831}
1832
1833} // namespace
1834
1835/// Try to promote memory values to scalars by sinking stores out of the
1836/// loop and moving loads to before the loop. We do this by looping over
1837/// the stores in the loop, looking for stores to Must pointers which are
1838/// loop invariant.
1839///
1840bool llvm::promoteLoopAccessesToScalars(
1841 const SmallSetVector<Value *, 8> &PointerMustAliases,
1842 SmallVectorImpl<BasicBlock *> &ExitBlocks,
1843 SmallVectorImpl<Instruction *> &InsertPts,
1844 SmallVectorImpl<MemoryAccess *> &MSSAInsertPts, PredIteratorCache &PIC,
1845 LoopInfo *LI, DominatorTree *DT, const TargetLibraryInfo *TLI,
1846 Loop *CurLoop, AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU,
1847 ICFLoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE) {
1848 // Verify inputs.
1849 assert(LI != nullptr && DT != nullptr && CurLoop != nullptr &&((LI != nullptr && DT != nullptr && CurLoop !=
nullptr && CurAST != nullptr && SafetyInfo !=
nullptr && "Unexpected Input to promoteLoopAccessesToScalars"
) ? static_cast<void> (0) : __assert_fail ("LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && \"Unexpected Input to promoteLoopAccessesToScalars\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1851, __PRETTY_FUNCTION__))
1850 CurAST != nullptr && SafetyInfo != nullptr &&((LI != nullptr && DT != nullptr && CurLoop !=
nullptr && CurAST != nullptr && SafetyInfo !=
nullptr && "Unexpected Input to promoteLoopAccessesToScalars"
) ? static_cast<void> (0) : __assert_fail ("LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && \"Unexpected Input to promoteLoopAccessesToScalars\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1851, __PRETTY_FUNCTION__))
1851 "Unexpected Input to promoteLoopAccessesToScalars")((LI != nullptr && DT != nullptr && CurLoop !=
nullptr && CurAST != nullptr && SafetyInfo !=
nullptr && "Unexpected Input to promoteLoopAccessesToScalars"
) ? static_cast<void> (0) : __assert_fail ("LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && \"Unexpected Input to promoteLoopAccessesToScalars\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 1851, __PRETTY_FUNCTION__))
;
1852
1853 Value *SomePtr = *PointerMustAliases.begin();
1854 BasicBlock *Preheader = CurLoop->getLoopPreheader();
1855
1856 // It is not safe to promote a load/store from the loop if the load/store is
1857 // conditional. For example, turning:
1858 //
1859 // for () { if (c) *P += 1; }
1860 //
1861 // into:
1862 //
1863 // tmp = *P; for () { if (c) tmp +=1; } *P = tmp;
1864 //
1865 // is not safe, because *P may only be valid to access if 'c' is true.
1866 //
1867 // The safety property divides into two parts:
1868 // p1) The memory may not be dereferenceable on entry to the loop. In this
1869 // case, we can't insert the required load in the preheader.
1870 // p2) The memory model does not allow us to insert a store along any dynamic
1871 // path which did not originally have one.
1872 //
1873 // If at least one store is guaranteed to execute, both properties are
1874 // satisfied, and promotion is legal.
1875 //
1876 // This, however, is not a necessary condition. Even if no store/load is
1877 // guaranteed to execute, we can still establish these properties.
1878 // We can establish (p1) by proving that hoisting the load into the preheader
1879 // is safe (i.e. proving dereferenceability on all paths through the loop). We
1880 // can use any access within the alias set to prove dereferenceability,
1881 // since they're all must alias.
1882 //
1883 // There are two ways establish (p2):
1884 // a) Prove the location is thread-local. In this case the memory model
1885 // requirement does not apply, and stores are safe to insert.
1886 // b) Prove a store dominates every exit block. In this case, if an exit
1887 // blocks is reached, the original dynamic path would have taken us through
1888 // the store, so inserting a store into the exit block is safe. Note that this
1889 // is different from the store being guaranteed to execute. For instance,
1890 // if an exception is thrown on the first iteration of the loop, the original
1891 // store is never executed, but the exit blocks are not executed either.
1892
1893 bool DereferenceableInPH = false;
1894 bool SafeToInsertStore = false;
1895
1896 SmallVector<Instruction *, 64> LoopUses;
1897
1898 // We start with an alignment of one and try to find instructions that allow
1899 // us to prove better alignment.
1900 unsigned Alignment = 1;
1901 // Keep track of which types of access we see
1902 bool SawUnorderedAtomic = false;
1903 bool SawNotAtomic = false;
1904 AAMDNodes AATags;
1905
1906 const DataLayout &MDL = Preheader->getModule()->getDataLayout();
1907
1908 bool IsKnownThreadLocalObject = false;
1909 if (SafetyInfo->anyBlockMayThrow()) {
1910 // If a loop can throw, we have to insert a store along each unwind edge.
1911 // That said, we can't actually make the unwind edge explicit. Therefore,
1912 // we have to prove that the store is dead along the unwind edge. We do
1913 // this by proving that the caller can't have a reference to the object
1914 // after return and thus can't possibly load from the object.
1915 Value *Object = GetUnderlyingObject(SomePtr, MDL);
1916 if (!isKnownNonEscaping(Object, TLI))
1917 return false;
1918 // Subtlety: Alloca's aren't visible to callers, but *are* potentially
1919 // visible to other threads if captured and used during their lifetimes.
1920 IsKnownThreadLocalObject = !isa<AllocaInst>(Object);
1921 }
1922
1923 // Check that all of the pointers in the alias set have the same type. We
1924 // cannot (yet) promote a memory location that is loaded and stored in
1925 // different sizes. While we are at it, collect alignment and AA info.
1926 for (Value *ASIV : PointerMustAliases) {
1927 // Check that all of the pointers in the alias set have the same type. We
1928 // cannot (yet) promote a memory location that is loaded and stored in
1929 // different sizes.
1930 if (SomePtr->getType() != ASIV->getType())
1931 return false;
1932
1933 for (User *U : ASIV->users()) {
1934 // Ignore instructions that are outside the loop.
1935 Instruction *UI = dyn_cast<Instruction>(U);
1936 if (!UI || !CurLoop->contains(UI))
1937 continue;
1938
1939 // If there is an non-load/store instruction in the loop, we can't promote
1940 // it.
1941 if (LoadInst *Load = dyn_cast<LoadInst>(UI)) {
1942 if (!Load->isUnordered())
1943 return false;
1944
1945 SawUnorderedAtomic |= Load->isAtomic();
1946 SawNotAtomic |= !Load->isAtomic();
1947
1948 unsigned InstAlignment = Load->getAlignment();
1949 if (!InstAlignment)
1950 InstAlignment =
1951 MDL.getABITypeAlignment(Load->getType());
1952
1953 // Note that proving a load safe to speculate requires proving
1954 // sufficient alignment at the target location. Proving it guaranteed
1955 // to execute does as well. Thus we can increase our guaranteed
1956 // alignment as well.
1957 if (!DereferenceableInPH || (InstAlignment > Alignment))
1958 if (isSafeToExecuteUnconditionally(*Load, DT, CurLoop, SafetyInfo,
1959 ORE, Preheader->getTerminator())) {
1960 DereferenceableInPH = true;
1961 Alignment = std::max(Alignment, InstAlignment);
1962 }
1963 } else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) {
1964 // Stores *of* the pointer are not interesting, only stores *to* the
1965 // pointer.
1966 if (UI->getOperand(1) != ASIV)
1967 continue;
1968 if (!Store->isUnordered())
1969 return false;
1970
1971 SawUnorderedAtomic |= Store->isAtomic();
1972 SawNotAtomic |= !Store->isAtomic();
1973
1974 // If the store is guaranteed to execute, both properties are satisfied.
1975 // We may want to check if a store is guaranteed to execute even if we
1976 // already know that promotion is safe, since it may have higher
1977 // alignment than any other guaranteed stores, in which case we can
1978 // raise the alignment on the promoted store.
1979 unsigned InstAlignment = Store->getAlignment();
1980 if (!InstAlignment)
1981 InstAlignment =
1982 MDL.getABITypeAlignment(Store->getValueOperand()->getType());
1983
1984 if (!DereferenceableInPH || !SafeToInsertStore ||
1985 (InstAlignment > Alignment)) {
1986 if (SafetyInfo->isGuaranteedToExecute(*UI, DT, CurLoop)) {
1987 DereferenceableInPH = true;
1988 SafeToInsertStore = true;
1989 Alignment = std::max(Alignment, InstAlignment);
1990 }
1991 }
1992
1993 // If a store dominates all exit blocks, it is safe to sink.
1994 // As explained above, if an exit block was executed, a dominating
1995 // store must have been executed at least once, so we are not
1996 // introducing stores on paths that did not have them.
1997 // Note that this only looks at explicit exit blocks. If we ever
1998 // start sinking stores into unwind edges (see above), this will break.
1999 if (!SafeToInsertStore)
2000 SafeToInsertStore = llvm::all_of(ExitBlocks, [&](BasicBlock *Exit) {
2001 return DT->dominates(Store->getParent(), Exit);
2002 });
2003
2004 // If the store is not guaranteed to execute, we may still get
2005 // deref info through it.
2006 if (!DereferenceableInPH) {
2007 DereferenceableInPH = isDereferenceableAndAlignedPointer(
2008 Store->getPointerOperand(), Store->getAlignment(), MDL,
2009 Preheader->getTerminator(), DT);
2010 }
2011 } else
2012 return false; // Not a load or store.
2013
2014 // Merge the AA tags.
2015 if (LoopUses.empty()) {
2016 // On the first load/store, just take its AA tags.
2017 UI->getAAMetadata(AATags);
2018 } else if (AATags) {
2019 UI->getAAMetadata(AATags, /* Merge = */ true);
2020 }
2021
2022 LoopUses.push_back(UI);
2023 }
2024 }
2025
2026 // If we found both an unordered atomic instruction and a non-atomic memory
2027 // access, bail. We can't blindly promote non-atomic to atomic since we
2028 // might not be able to lower the result. We can't downgrade since that
2029 // would violate memory model. Also, align 0 is an error for atomics.
2030 if (SawUnorderedAtomic && SawNotAtomic)
2031 return false;
2032
2033 // If we're inserting an atomic load in the preheader, we must be able to
2034 // lower it. We're only guaranteed to be able to lower naturally aligned
2035 // atomics.
2036 auto *SomePtrElemType = SomePtr->getType()->getPointerElementType();
2037 if (SawUnorderedAtomic &&
2038 Alignment < MDL.getTypeStoreSize(SomePtrElemType))
2039 return false;
2040
2041 // If we couldn't prove we can hoist the load, bail.
2042 if (!DereferenceableInPH)
2043 return false;
2044
2045 // We know we can hoist the load, but don't have a guaranteed store.
2046 // Check whether the location is thread-local. If it is, then we can insert
2047 // stores along paths which originally didn't have them without violating the
2048 // memory model.
2049 if (!SafeToInsertStore) {
2050 if (IsKnownThreadLocalObject)
2051 SafeToInsertStore = true;
2052 else {
2053 Value *Object = GetUnderlyingObject(SomePtr, MDL);
2054 SafeToInsertStore =
2055 (isAllocLikeFn(Object, TLI) || isa<AllocaInst>(Object)) &&
2056 !PointerMayBeCaptured(Object, true, true);
2057 }
2058 }
2059
2060 // If we've still failed to prove we can sink the store, give up.
2061 if (!SafeToInsertStore)
2062 return false;
2063
2064 // Otherwise, this is safe to promote, lets do it!
2065 LLVM_DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtrdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM: Promoting value stored to in loop: "
<< *SomePtr << '\n'; } } while (false)
2066 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "LICM: Promoting value stored to in loop: "
<< *SomePtr << '\n'; } } while (false)
;
2067 ORE->emit([&]() {
2068 return OptimizationRemark(DEBUG_TYPE"licm", "PromoteLoopAccessesToScalar",
2069 LoopUses[0])
2070 << "Moving accesses to memory location out of the loop";
2071 });
2072 ++NumPromoted;
2073
2074 // Grab a debug location for the inserted loads/stores; given that the
2075 // inserted loads/stores have little relation to the original loads/stores,
2076 // this code just arbitrarily picks a location from one, since any debug
2077 // location is better than none.
2078 DebugLoc DL = LoopUses[0]->getDebugLoc();
2079
2080 // We use the SSAUpdater interface to insert phi nodes as required.
2081 SmallVector<PHINode *, 16> NewPHIs;
2082 SSAUpdater SSA(&NewPHIs);
2083 LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
2084 InsertPts, MSSAInsertPts, PIC, *CurAST, MSSAU, *LI, DL,
2085 Alignment, SawUnorderedAtomic, AATags, *SafetyInfo);
2086
2087 // Set up the preheader to have a definition of the value. It is the live-out
2088 // value from the preheader that uses in the loop will use.
2089 LoadInst *PreheaderLoad = new LoadInst(
2090 SomePtr->getType()->getPointerElementType(), SomePtr,
2091 SomePtr->getName() + ".promoted", Preheader->getTerminator());
2092 if (SawUnorderedAtomic)
2093 PreheaderLoad->setOrdering(AtomicOrdering::Unordered);
2094 PreheaderLoad->setAlignment(Alignment);
2095 PreheaderLoad->setDebugLoc(DL);
2096 if (AATags)
2097 PreheaderLoad->setAAMetadata(AATags);
2098 SSA.AddAvailableValue(Preheader, PreheaderLoad);
2099
2100 MemoryAccess *PreheaderLoadMemoryAccess;
2101 if (MSSAU) {
2102 PreheaderLoadMemoryAccess = MSSAU->createMemoryAccessInBB(
2103 PreheaderLoad, nullptr, PreheaderLoad->getParent(), MemorySSA::End);
2104 MemoryUse *NewMemUse = cast<MemoryUse>(PreheaderLoadMemoryAccess);
2105 MSSAU->insertUse(NewMemUse);
2106 }
2107
2108 // Rewrite all the loads in the loop and remember all the definitions from
2109 // stores in the loop.
2110 Promoter.run(LoopUses);
2111
2112 if (MSSAU && VerifyMemorySSA)
2113 MSSAU->getMemorySSA()->verifyMemorySSA();
2114 // If the SSAUpdater didn't use the load in the preheader, just zap it now.
2115 if (PreheaderLoad->use_empty())
2116 eraseInstruction(*PreheaderLoad, *SafetyInfo, CurAST, MSSAU);
2117
2118 return true;
2119}
2120
2121/// Returns an owning pointer to an alias set which incorporates aliasing info
2122/// from L and all subloops of L.
2123/// FIXME: In new pass manager, there is no helper function to handle loop
2124/// analysis such as cloneBasicBlockAnalysis, so the AST needs to be recomputed
2125/// from scratch for every loop. Hook up with the helper functions when
2126/// available in the new pass manager to avoid redundant computation.
2127std::unique_ptr<AliasSetTracker>
2128LoopInvariantCodeMotion::collectAliasInfoForLoop(Loop *L, LoopInfo *LI,
2129 AliasAnalysis *AA) {
2130 std::unique_ptr<AliasSetTracker> CurAST;
2131 SmallVector<Loop *, 4> RecomputeLoops;
2132 for (Loop *InnerL : L->getSubLoops()) {
2133 auto MapI = LoopToAliasSetMap.find(InnerL);
2134 // If the AST for this inner loop is missing it may have been merged into
2135 // some other loop's AST and then that loop unrolled, and so we need to
2136 // recompute it.
2137 if (MapI == LoopToAliasSetMap.end()) {
2138 RecomputeLoops.push_back(InnerL);
2139 continue;
2140 }
2141 std::unique_ptr<AliasSetTracker> InnerAST = std::move(MapI->second);
2142
2143 if (CurAST) {
2144 // What if InnerLoop was modified by other passes ?
2145 // Once we've incorporated the inner loop's AST into ours, we don't need
2146 // the subloop's anymore.
2147 CurAST->add(*InnerAST);
2148 } else {
2149 CurAST = std::move(InnerAST);
2150 }
2151 LoopToAliasSetMap.erase(MapI);
2152 }
2153 if (!CurAST)
2154 CurAST = make_unique<AliasSetTracker>(*AA);
2155
2156 // Add everything from the sub loops that are no longer directly available.
2157 for (Loop *InnerL : RecomputeLoops)
2158 for (BasicBlock *BB : InnerL->blocks())
2159 CurAST->add(*BB);
2160
2161 // And merge in this loop (without anything from inner loops).
2162 for (BasicBlock *BB : L->blocks())
2163 if (LI->getLoopFor(BB) == L)
2164 CurAST->add(*BB);
2165
2166 return CurAST;
2167}
2168
2169std::unique_ptr<AliasSetTracker>
2170LoopInvariantCodeMotion::collectAliasInfoForLoopWithMSSA(
2171 Loop *L, AliasAnalysis *AA, MemorySSAUpdater *MSSAU) {
2172 auto *MSSA = MSSAU->getMemorySSA();
2173 auto CurAST = make_unique<AliasSetTracker>(*AA, MSSA, L);
2174 CurAST->addAllInstructionsInLoopUsingMSSA();
2175 return CurAST;
2176}
2177
2178/// Simple analysis hook. Clone alias set info.
2179///
2180void LegacyLICMPass::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To,
2181 Loop *L) {
2182 auto ASTIt = LICM.getLoopToAliasSetMap().find(L);
2183 if (ASTIt == LICM.getLoopToAliasSetMap().end())
2184 return;
2185
2186 ASTIt->second->copyValue(From, To);
2187}
2188
2189/// Simple Analysis hook. Delete value V from alias set
2190///
2191void LegacyLICMPass::deleteAnalysisValue(Value *V, Loop *L) {
2192 auto ASTIt = LICM.getLoopToAliasSetMap().find(L);
2193 if (ASTIt == LICM.getLoopToAliasSetMap().end())
2194 return;
2195
2196 ASTIt->second->deleteValue(V);
2197}
2198
2199/// Simple Analysis hook. Delete value L from alias set map.
2200///
2201void LegacyLICMPass::deleteAnalysisLoop(Loop *L) {
2202 if (!LICM.getLoopToAliasSetMap().count(L))
2203 return;
2204
2205 LICM.getLoopToAliasSetMap().erase(L);
2206}
2207
2208static bool pointerInvalidatedByLoop(MemoryLocation MemLoc,
2209 AliasSetTracker *CurAST, Loop *CurLoop,
2210 AliasAnalysis *AA) {
2211 // First check to see if any of the basic blocks in CurLoop invalidate *V.
2212 bool isInvalidatedAccordingToAST = CurAST->getAliasSetFor(MemLoc).isMod();
2213
2214 if (!isInvalidatedAccordingToAST || !LICMN2Theshold)
2215 return isInvalidatedAccordingToAST;
2216
2217 // Check with a diagnostic analysis if we can refine the information above.
2218 // This is to identify the limitations of using the AST.
2219 // The alias set mechanism used by LICM has a major weakness in that it
2220 // combines all things which may alias into a single set *before* asking
2221 // modref questions. As a result, a single readonly call within a loop will
2222 // collapse all loads and stores into a single alias set and report
2223 // invalidation if the loop contains any store. For example, readonly calls
2224 // with deopt states have this form and create a general alias set with all
2225 // loads and stores. In order to get any LICM in loops containing possible
2226 // deopt states we need a more precise invalidation of checking the mod ref
2227 // info of each instruction within the loop and LI. This has a complexity of
2228 // O(N^2), so currently, it is used only as a diagnostic tool since the
2229 // default value of LICMN2Threshold is zero.
2230
2231 // Don't look at nested loops.
2232 if (CurLoop->begin() != CurLoop->end())
2233 return true;
2234
2235 int N = 0;
2236 for (BasicBlock *BB : CurLoop->getBlocks())
2237 for (Instruction &I : *BB) {
2238 if (N >= LICMN2Theshold) {
2239 LLVM_DEBUG(dbgs() << "Alasing N2 threshold exhausted for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "Alasing N2 threshold exhausted for "
<< *(MemLoc.Ptr) << "\n"; } } while (false)
2240 << *(MemLoc.Ptr) << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "Alasing N2 threshold exhausted for "
<< *(MemLoc.Ptr) << "\n"; } } while (false)
;
2241 return true;
2242 }
2243 N++;
2244 auto Res = AA->getModRefInfo(&I, MemLoc);
2245 if (isModSet(Res)) {
2246 LLVM_DEBUG(dbgs() << "Aliasing failed on " << I << " for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "Aliasing failed on " << I <<
" for " << *(MemLoc.Ptr) << "\n"; } } while (false
)
2247 << *(MemLoc.Ptr) << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "Aliasing failed on " << I <<
" for " << *(MemLoc.Ptr) << "\n"; } } while (false
)
;
2248 return true;
2249 }
2250 }
2251 LLVM_DEBUG(dbgs() << "Aliasing okay for " << *(MemLoc.Ptr) << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("licm")) { dbgs() << "Aliasing okay for " << *(MemLoc
.Ptr) << "\n"; } } while (false)
;
2252 return false;
2253}
2254
2255static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU,
2256 Loop *CurLoop,
2257 SinkAndHoistLICMFlags &Flags) {
2258 MemoryAccess *Source;
2259 // See declaration of SetLicmMssaOptCap for usage details.
2260 if (Flags.LicmMssaOptCounter >= Flags.LicmMssaOptCap)
2261 Source = MU->getDefiningAccess();
2262 else {
2263 Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(MU);
2264 Flags.LicmMssaOptCounter++;
2265 }
2266 return !MSSA->isLiveOnEntryDef(Source) &&
2267 CurLoop->contains(Source->getBlock());
2268}
2269
2270/// Little predicate that returns true if the specified basic block is in
2271/// a subloop of the current one, not the current one itself.
2272///
2273static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) {
2274 assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop")((CurLoop->contains(BB) && "Only valid if BB is IN the loop"
) ? static_cast<void> (0) : __assert_fail ("CurLoop->contains(BB) && \"Only valid if BB is IN the loop\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Transforms/Scalar/LICM.cpp"
, 2274, __PRETTY_FUNCTION__))
;
2275 return LI->getLoopFor(BB) != CurLoop;
2276}