1 //===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass performs loop invariant code motion, attempting to remove as much
11 // code from the body of a loop as possible. It does this by either hoisting
12 // code into the preheader block, or by sinking code to the exit blocks if it is
13 // safe. This pass also promotes must-aliased memory locations in the loop to
14 // live in registers, thus hoisting and sinking "invariant" loads and stores.
16 // This pass uses alias analysis for two purposes:
18 // 1. Moving loop invariant loads and calls out of loops. If we can determine
19 // that a load or call inside of a loop never aliases anything stored to,
20 // we can hoist it or sink it like any other instruction.
21 // 2. Scalar Promotion of Memory - If there is a store instruction inside of
22 // the loop, we try to move the store to happen AFTER the loop instead of
23 // inside of the loop. This can only happen if a few conditions are true:
24 // A. The pointer stored through is loop invariant
25 // B. There are no stores or loads in the loop which _may_ alias the
26 // pointer. There are no calls in the loop which mod/ref the pointer.
27 // If these conditions are true, we can promote the loads and stores in the
28 // loop of the pointer to use a temporary alloca'd variable. We then use
29 // the SSAUpdater to construct the appropriate SSA form for the value.
31 //===----------------------------------------------------------------------===//
33 #include "llvm/Transforms/Scalar/LICM.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/Loads.h"
42 #include "llvm/Analysis/LoopInfo.h"
43 #include "llvm/Analysis/LoopPass.h"
44 #include "llvm/Analysis/MemoryBuiltins.h"
45 #include "llvm/Analysis/OptimizationDiagnosticInfo.h"
46 #include "llvm/Analysis/ScalarEvolution.h"
47 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
48 #include "llvm/Analysis/TargetLibraryInfo.h"
49 #include "llvm/Analysis/ValueTracking.h"
50 #include "llvm/IR/CFG.h"
51 #include "llvm/IR/Constants.h"
52 #include "llvm/IR/DataLayout.h"
53 #include "llvm/IR/DerivedTypes.h"
54 #include "llvm/IR/Dominators.h"
55 #include "llvm/IR/Instructions.h"
56 #include "llvm/IR/IntrinsicInst.h"
57 #include "llvm/IR/LLVMContext.h"
58 #include "llvm/IR/Metadata.h"
59 #include "llvm/IR/PredIteratorCache.h"
60 #include "llvm/Support/CommandLine.h"
61 #include "llvm/Support/Debug.h"
62 #include "llvm/Support/raw_ostream.h"
63 #include "llvm/Transforms/Scalar.h"
64 #include "llvm/Transforms/Scalar/LoopPassManager.h"
65 #include "llvm/Transforms/Utils/Local.h"
66 #include "llvm/Transforms/Utils/LoopUtils.h"
67 #include "llvm/Transforms/Utils/SSAUpdater.h"
72 #define DEBUG_TYPE "licm"
74 STATISTIC(NumSunk, "Number of instructions sunk out of loop");
75 STATISTIC(NumHoisted, "Number of instructions hoisted out of loop");
76 STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk");
77 STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk");
78 STATISTIC(NumPromoted, "Number of memory locations promoted to registers");
81 DisablePromotion("disable-licm-promotion", cl::Hidden,
82 cl::desc("Disable memory promotion in LICM pass"));
84 static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI);
85 static bool isNotUsedInLoop(const Instruction &I, const Loop *CurLoop,
86 const LoopSafetyInfo *SafetyInfo);
87 static bool hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
88 const LoopSafetyInfo *SafetyInfo,
89 OptimizationRemarkEmitter *ORE);
90 static bool sink(Instruction &I, const LoopInfo *LI, const DominatorTree *DT,
91 const Loop *CurLoop, AliasSetTracker *CurAST,
92 const LoopSafetyInfo *SafetyInfo,
93 OptimizationRemarkEmitter *ORE);
94 static bool isSafeToExecuteUnconditionally(Instruction &Inst,
95 const DominatorTree *DT,
97 const LoopSafetyInfo *SafetyInfo,
98 OptimizationRemarkEmitter *ORE,
99 const Instruction *CtxI = nullptr);
100 static bool pointerInvalidatedByLoop(Value *V, uint64_t Size,
101 const AAMDNodes &AAInfo,
102 AliasSetTracker *CurAST);
104 CloneInstructionInExitBlock(Instruction &I, BasicBlock &ExitBlock, PHINode &PN,
106 const LoopSafetyInfo *SafetyInfo);
109 struct LoopInvariantCodeMotion {
110 bool runOnLoop(Loop *L, AliasAnalysis *AA, LoopInfo *LI, DominatorTree *DT,
111 TargetLibraryInfo *TLI, ScalarEvolution *SE,
112 OptimizationRemarkEmitter *ORE, bool DeleteAST);
114 DenseMap<Loop *, AliasSetTracker *> &getLoopToAliasSetMap() {
115 return LoopToAliasSetMap;
119 DenseMap<Loop *, AliasSetTracker *> LoopToAliasSetMap;
121 AliasSetTracker *collectAliasInfoForLoop(Loop *L, LoopInfo *LI,
125 struct LegacyLICMPass : public LoopPass {
126 static char ID; // Pass identification, replacement for typeid
127 LegacyLICMPass() : LoopPass(ID) {
128 initializeLegacyLICMPassPass(*PassRegistry::getPassRegistry());
131 bool runOnLoop(Loop *L, LPPassManager &LPM) override {
133 // If we have run LICM on a previous loop but now we are skipping
134 // (because we've hit the opt-bisect limit), we need to clear the
135 // loop alias information.
136 for (auto <AS : LICM.getLoopToAliasSetMap())
138 LICM.getLoopToAliasSetMap().clear();
142 auto *SE = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
143 // For the old PM, we can't use OptimizationRemarkEmitter as an analysis
144 // pass. Function analyses need to be preserved across loop transformations
145 // but ORE cannot be preserved (see comment before the pass definition).
146 OptimizationRemarkEmitter ORE(L->getHeader()->getParent());
147 return LICM.runOnLoop(L,
148 &getAnalysis<AAResultsWrapperPass>().getAAResults(),
149 &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(),
150 &getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
151 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
152 SE ? &SE->getSE() : nullptr, &ORE, false);
155 /// This transformation requires natural loop information & requires that
156 /// loop preheaders be inserted into the CFG...
158 void getAnalysisUsage(AnalysisUsage &AU) const override {
159 AU.setPreservesCFG();
160 AU.addRequired<TargetLibraryInfoWrapperPass>();
161 getLoopAnalysisUsage(AU);
164 using llvm::Pass::doFinalization;
166 bool doFinalization() override {
167 assert(LICM.getLoopToAliasSetMap().empty() &&
168 "Didn't free loop alias sets");
173 LoopInvariantCodeMotion LICM;
175 /// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info.
176 void cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To,
179 /// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias
181 void deleteAnalysisValue(Value *V, Loop *L) override;
183 /// Simple Analysis hook. Delete loop L from alias set map.
184 void deleteAnalysisLoop(Loop *L) override;
188 PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM,
189 LoopStandardAnalysisResults &AR, LPMUpdater &) {
191 AM.getResult<FunctionAnalysisManagerLoopProxy>(L, AR).getManager();
192 Function *F = L.getHeader()->getParent();
194 auto *ORE = FAM.getCachedResult<OptimizationRemarkEmitterAnalysis>(*F);
195 // FIXME: This should probably be optional rather than required.
197 report_fatal_error("LICM: OptimizationRemarkEmitterAnalysis not "
198 "cached at a higher level");
200 LoopInvariantCodeMotion LICM;
201 if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, &AR.TLI, &AR.SE, ORE, true))
202 return PreservedAnalyses::all();
204 // FIXME: There is no setPreservesCFG in the new PM. When that becomes
205 // available, it should be used here.
206 return getLoopPassPreservedAnalyses();
209 char LegacyLICMPass::ID = 0;
210 INITIALIZE_PASS_BEGIN(LegacyLICMPass, "licm", "Loop Invariant Code Motion",
212 INITIALIZE_PASS_DEPENDENCY(LoopPass)
213 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
214 INITIALIZE_PASS_END(LegacyLICMPass, "licm", "Loop Invariant Code Motion", false,
217 Pass *llvm::createLICMPass() { return new LegacyLICMPass(); }
219 /// Hoist expressions out of the specified loop. Note, alias info for inner
220 /// loop is not preserved so it is not a good idea to run LICM multiple
221 /// times on one loop.
222 /// We should delete AST for inner loops in the new pass manager to avoid
225 bool LoopInvariantCodeMotion::runOnLoop(Loop *L, AliasAnalysis *AA,
226 LoopInfo *LI, DominatorTree *DT,
227 TargetLibraryInfo *TLI,
229 OptimizationRemarkEmitter *ORE,
231 bool Changed = false;
233 assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form.");
235 AliasSetTracker *CurAST = collectAliasInfoForLoop(L, LI, AA);
237 // Get the preheader block to move instructions into...
238 BasicBlock *Preheader = L->getLoopPreheader();
240 // Compute loop safety information.
241 LoopSafetyInfo SafetyInfo;
242 computeLoopSafetyInfo(&SafetyInfo, L);
244 // We want to visit all of the instructions in this loop... that are not parts
245 // of our subloops (they have already had their invariants hoisted out of
246 // their loop, into this loop, so there is no need to process the BODIES of
249 // Traverse the body of the loop in depth first order on the dominator tree so
250 // that we are guaranteed to see definitions before we see uses. This allows
251 // us to sink instructions in one pass, without iteration. After sinking
252 // instructions, we perform another pass to hoist them out of the loop.
254 if (L->hasDedicatedExits())
255 Changed |= sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, L,
256 CurAST, &SafetyInfo, ORE);
258 Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, L,
259 CurAST, &SafetyInfo, ORE);
261 // Now that all loop invariants have been removed from the loop, promote any
262 // memory references to scalars that we can.
263 // Don't sink stores from loops without dedicated block exits. Exits
264 // containing indirect branches are not transformed by loop simplify,
265 // make sure we catch that. An additional load may be generated in the
266 // preheader for SSA updater, so also avoid sinking when no preheader
268 if (!DisablePromotion && Preheader && L->hasDedicatedExits()) {
269 // Figure out the loop exits and their insertion points
270 SmallVector<BasicBlock *, 8> ExitBlocks;
271 L->getUniqueExitBlocks(ExitBlocks);
273 // We can't insert into a catchswitch.
274 bool HasCatchSwitch = llvm::any_of(ExitBlocks, [](BasicBlock *Exit) {
275 return isa<CatchSwitchInst>(Exit->getTerminator());
278 if (!HasCatchSwitch) {
279 SmallVector<Instruction *, 8> InsertPts;
280 InsertPts.reserve(ExitBlocks.size());
281 for (BasicBlock *ExitBlock : ExitBlocks)
282 InsertPts.push_back(&*ExitBlock->getFirstInsertionPt());
284 PredIteratorCache PIC;
286 bool Promoted = false;
288 // Loop over all of the alias sets in the tracker object.
289 for (AliasSet &AS : *CurAST)
291 promoteLoopAccessesToScalars(AS, ExitBlocks, InsertPts, PIC, LI, DT,
292 TLI, L, CurAST, &SafetyInfo, ORE);
294 // Once we have promoted values across the loop body we have to
295 // recursively reform LCSSA as any nested loop may now have values defined
296 // within the loop used in the outer loop.
297 // FIXME: This is really heavy handed. It would be a bit better to use an
298 // SSAUpdater strategy during promotion that was LCSSA aware and reformed
301 formLCSSARecursively(*L, *DT, LI, SE);
307 // Check that neither this loop nor its parent have had LCSSA broken. LICM is
308 // specifically moving instructions across the loop boundary and so it is
309 // especially in need of sanity checking here.
310 assert(L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!");
311 assert((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) &&
312 "Parent loop not left in LCSSA form after LICM!");
314 // If this loop is nested inside of another one, save the alias information
315 // for when we process the outer loop.
316 if (L->getParentLoop() && !DeleteAST)
317 LoopToAliasSetMap[L] = CurAST;
322 SE->forgetLoopDispositions(L);
326 /// Walk the specified region of the CFG (defined by all blocks dominated by
327 /// the specified block, and that are in the current loop) in reverse depth
328 /// first order w.r.t the DominatorTree. This allows us to visit uses before
329 /// definitions, allowing us to sink a loop body in one pass without iteration.
331 bool llvm::sinkRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
332 DominatorTree *DT, TargetLibraryInfo *TLI, Loop *CurLoop,
333 AliasSetTracker *CurAST, LoopSafetyInfo *SafetyInfo,
334 OptimizationRemarkEmitter *ORE) {
337 assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&
338 CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr &&
339 "Unexpected input to sinkRegion");
341 BasicBlock *BB = N->getBlock();
342 // If this subregion is not in the top level loop at all, exit.
343 if (!CurLoop->contains(BB))
346 // We are processing blocks in reverse dfo, so process children first.
347 bool Changed = false;
348 const std::vector<DomTreeNode *> &Children = N->getChildren();
349 for (DomTreeNode *Child : Children)
351 sinkRegion(Child, AA, LI, DT, TLI, CurLoop, CurAST, SafetyInfo, ORE);
353 // Only need to process the contents of this block if it is not part of a
354 // subloop (which would already have been processed).
355 if (inSubLoop(BB, CurLoop, LI))
358 for (BasicBlock::iterator II = BB->end(); II != BB->begin();) {
359 Instruction &I = *--II;
361 // If the instruction is dead, we would try to sink it because it isn't used
362 // in the loop, instead, just delete it.
363 if (isInstructionTriviallyDead(&I, TLI)) {
364 DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n');
366 CurAST->deleteValue(&I);
372 // Check to see if we can sink this instruction to the exit blocks
373 // of the loop. We can do this if the all users of the instruction are
374 // outside of the loop. In this case, it doesn't even matter if the
375 // operands of the instruction are loop invariant.
377 if (isNotUsedInLoop(I, CurLoop, SafetyInfo) &&
378 canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE)) {
380 Changed |= sink(I, LI, DT, CurLoop, CurAST, SafetyInfo, ORE);
386 /// Walk the specified region of the CFG (defined by all blocks dominated by
387 /// the specified block, and that are in the current loop) in depth first
388 /// order w.r.t the DominatorTree. This allows us to visit definitions before
389 /// uses, allowing us to hoist a loop body in one pass without iteration.
391 bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
392 DominatorTree *DT, TargetLibraryInfo *TLI, Loop *CurLoop,
393 AliasSetTracker *CurAST, LoopSafetyInfo *SafetyInfo,
394 OptimizationRemarkEmitter *ORE) {
396 assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr &&
397 CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr &&
398 "Unexpected input to hoistRegion");
400 BasicBlock *BB = N->getBlock();
402 // If this subregion is not in the top level loop at all, exit.
403 if (!CurLoop->contains(BB))
406 // Only need to process the contents of this block if it is not part of a
407 // subloop (which would already have been processed).
408 bool Changed = false;
409 if (!inSubLoop(BB, CurLoop, LI))
410 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) {
411 Instruction &I = *II++;
412 // Try constant folding this instruction. If all the operands are
413 // constants, it is technically hoistable, but it would be better to just
415 if (Constant *C = ConstantFoldInstruction(
416 &I, I.getModule()->getDataLayout(), TLI)) {
417 DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n');
418 CurAST->copyValue(&I, C);
419 I.replaceAllUsesWith(C);
420 if (isInstructionTriviallyDead(&I, TLI)) {
421 CurAST->deleteValue(&I);
428 // Try hoisting the instruction out to the preheader. We can only do this
429 // if all of the operands of the instruction are loop invariant and if it
430 // is safe to hoist the instruction.
432 if (CurLoop->hasLoopInvariantOperands(&I) &&
433 canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE) &&
434 isSafeToExecuteUnconditionally(
435 I, DT, CurLoop, SafetyInfo, ORE,
436 CurLoop->getLoopPreheader()->getTerminator()))
437 Changed |= hoist(I, DT, CurLoop, SafetyInfo, ORE);
440 const std::vector<DomTreeNode *> &Children = N->getChildren();
441 for (DomTreeNode *Child : Children)
443 hoistRegion(Child, AA, LI, DT, TLI, CurLoop, CurAST, SafetyInfo, ORE);
447 /// Computes loop safety information, checks loop body & header
448 /// for the possibility of may throw exception.
450 void llvm::computeLoopSafetyInfo(LoopSafetyInfo *SafetyInfo, Loop *CurLoop) {
451 assert(CurLoop != nullptr && "CurLoop cant be null");
452 BasicBlock *Header = CurLoop->getHeader();
453 // Setting default safety values.
454 SafetyInfo->MayThrow = false;
455 SafetyInfo->HeaderMayThrow = false;
456 // Iterate over header and compute safety info.
457 for (BasicBlock::iterator I = Header->begin(), E = Header->end();
458 (I != E) && !SafetyInfo->HeaderMayThrow; ++I)
459 SafetyInfo->HeaderMayThrow |=
460 !isGuaranteedToTransferExecutionToSuccessor(&*I);
462 SafetyInfo->MayThrow = SafetyInfo->HeaderMayThrow;
463 // Iterate over loop instructions and compute safety info.
464 for (Loop::block_iterator BB = CurLoop->block_begin(),
465 BBE = CurLoop->block_end();
466 (BB != BBE) && !SafetyInfo->MayThrow; ++BB)
467 for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end();
468 (I != E) && !SafetyInfo->MayThrow; ++I)
469 SafetyInfo->MayThrow |= !isGuaranteedToTransferExecutionToSuccessor(&*I);
471 // Compute funclet colors if we might sink/hoist in a function with a funclet
472 // personality routine.
473 Function *Fn = CurLoop->getHeader()->getParent();
474 if (Fn->hasPersonalityFn())
475 if (Constant *PersonalityFn = Fn->getPersonalityFn())
476 if (isFuncletEHPersonality(classifyEHPersonality(PersonalityFn)))
477 SafetyInfo->BlockColors = colorEHFunclets(*Fn);
480 bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
481 Loop *CurLoop, AliasSetTracker *CurAST,
482 LoopSafetyInfo *SafetyInfo,
483 OptimizationRemarkEmitter *ORE) {
484 // Loads have extra constraints we have to verify before we can hoist them.
485 if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
486 if (!LI->isUnordered())
487 return false; // Don't hoist volatile/atomic loads!
489 // Loads from constant memory are always safe to move, even if they end up
490 // in the same alias set as something that ends up being modified.
491 if (AA->pointsToConstantMemory(LI->getOperand(0)))
493 if (LI->getMetadata(LLVMContext::MD_invariant_load))
496 // Don't hoist loads which have may-aliased stores in loop.
498 if (LI->getType()->isSized())
499 Size = I.getModule()->getDataLayout().getTypeStoreSize(LI->getType());
502 LI->getAAMetadata(AAInfo);
505 pointerInvalidatedByLoop(LI->getOperand(0), Size, AAInfo, CurAST);
506 // Check loop-invariant address because this may also be a sinkable load
507 // whose address is not necessarily loop-invariant.
508 if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand()))
509 ORE->emit(OptimizationRemarkMissed(
510 DEBUG_TYPE, "LoadWithLoopInvariantAddressInvalidated", LI)
511 << "failed to move load with loop-invariant address "
512 "because the loop may invalidate its value");
515 } else if (CallInst *CI = dyn_cast<CallInst>(&I)) {
516 // Don't sink or hoist dbg info; it's legal, but not useful.
517 if (isa<DbgInfoIntrinsic>(I))
520 // Don't sink calls which can throw.
524 // Handle simple cases by querying alias analysis.
525 FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI);
526 if (Behavior == FMRB_DoesNotAccessMemory)
528 if (AliasAnalysis::onlyReadsMemory(Behavior)) {
529 // A readonly argmemonly function only reads from memory pointed to by
530 // it's arguments with arbitrary offsets. If we can prove there are no
531 // writes to this memory in the loop, we can hoist or sink.
532 if (AliasAnalysis::onlyAccessesArgPointees(Behavior)) {
533 for (Value *Op : CI->arg_operands())
534 if (Op->getType()->isPointerTy() &&
535 pointerInvalidatedByLoop(Op, MemoryLocation::UnknownSize,
536 AAMDNodes(), CurAST))
540 // If this call only reads from memory and there are no writes to memory
541 // in the loop, we can hoist or sink the call as appropriate.
542 bool FoundMod = false;
543 for (AliasSet &AS : *CurAST) {
544 if (!AS.isForwardingAliasSet() && AS.isMod()) {
553 // FIXME: This should use mod/ref information to see if we can hoist or
559 // Only these instructions are hoistable/sinkable.
560 if (!isa<BinaryOperator>(I) && !isa<CastInst>(I) && !isa<SelectInst>(I) &&
561 !isa<GetElementPtrInst>(I) && !isa<CmpInst>(I) &&
562 !isa<InsertElementInst>(I) && !isa<ExtractElementInst>(I) &&
563 !isa<ShuffleVectorInst>(I) && !isa<ExtractValueInst>(I) &&
564 !isa<InsertValueInst>(I))
567 // SafetyInfo is nullptr if we are checking for sinking from preheader to
568 // loop body. It will be always safe as there is no speculative execution.
572 // TODO: Plumb the context instruction through to make hoisting and sinking
573 // more powerful. Hoisting of loads already works due to the special casing
575 return isSafeToExecuteUnconditionally(I, DT, CurLoop, SafetyInfo, nullptr);
578 /// Returns true if a PHINode is a trivially replaceable with an
580 /// This is true when all incoming values are that instruction.
581 /// This pattern occurs most often with LCSSA PHI nodes.
583 static bool isTriviallyReplacablePHI(const PHINode &PN, const Instruction &I) {
584 for (const Value *IncValue : PN.incoming_values())
591 /// Return true if the only users of this instruction are outside of
592 /// the loop. If this is true, we can sink the instruction to the exit
593 /// blocks of the loop.
595 static bool isNotUsedInLoop(const Instruction &I, const Loop *CurLoop,
596 const LoopSafetyInfo *SafetyInfo) {
597 const auto &BlockColors = SafetyInfo->BlockColors;
598 for (const User *U : I.users()) {
599 const Instruction *UI = cast<Instruction>(U);
600 if (const PHINode *PN = dyn_cast<PHINode>(UI)) {
601 const BasicBlock *BB = PN->getParent();
602 // We cannot sink uses in catchswitches.
603 if (isa<CatchSwitchInst>(BB->getTerminator()))
606 // We need to sink a callsite to a unique funclet. Avoid sinking if the
607 // phi use is too muddled.
608 if (isa<CallInst>(I))
609 if (!BlockColors.empty() &&
610 BlockColors.find(const_cast<BasicBlock *>(BB))->second.size() != 1)
613 // A PHI node where all of the incoming values are this instruction are
614 // special -- they can just be RAUW'ed with the instruction and thus
615 // don't require a use in the predecessor. This is a particular important
616 // special case because it is the pattern found in LCSSA form.
617 if (isTriviallyReplacablePHI(*PN, I)) {
618 if (CurLoop->contains(PN))
624 // Otherwise, PHI node uses occur in predecessor blocks if the incoming
625 // values. Check for such a use being inside the loop.
626 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
627 if (PN->getIncomingValue(i) == &I)
628 if (CurLoop->contains(PN->getIncomingBlock(i)))
634 if (CurLoop->contains(UI))
641 CloneInstructionInExitBlock(Instruction &I, BasicBlock &ExitBlock, PHINode &PN,
643 const LoopSafetyInfo *SafetyInfo) {
645 if (auto *CI = dyn_cast<CallInst>(&I)) {
646 const auto &BlockColors = SafetyInfo->BlockColors;
648 // Sinking call-sites need to be handled differently from other
649 // instructions. The cloned call-site needs a funclet bundle operand
650 // appropriate for it's location in the CFG.
651 SmallVector<OperandBundleDef, 1> OpBundles;
652 for (unsigned BundleIdx = 0, BundleEnd = CI->getNumOperandBundles();
653 BundleIdx != BundleEnd; ++BundleIdx) {
654 OperandBundleUse Bundle = CI->getOperandBundleAt(BundleIdx);
655 if (Bundle.getTagID() == LLVMContext::OB_funclet)
658 OpBundles.emplace_back(Bundle);
661 if (!BlockColors.empty()) {
662 const ColorVector &CV = BlockColors.find(&ExitBlock)->second;
663 assert(CV.size() == 1 && "non-unique color for exit block!");
664 BasicBlock *BBColor = CV.front();
665 Instruction *EHPad = BBColor->getFirstNonPHI();
666 if (EHPad->isEHPad())
667 OpBundles.emplace_back("funclet", EHPad);
670 New = CallInst::Create(CI, OpBundles);
675 ExitBlock.getInstList().insert(ExitBlock.getFirstInsertionPt(), New);
676 if (!I.getName().empty())
677 New->setName(I.getName() + ".le");
679 // Build LCSSA PHI nodes for any in-loop operands. Note that this is
680 // particularly cheap because we can rip off the PHI node that we're
681 // replacing for the number and blocks of the predecessors.
682 // OPT: If this shows up in a profile, we can instead finish sinking all
683 // invariant instructions, and then walk their operands to re-establish
684 // LCSSA. That will eliminate creating PHI nodes just to nuke them when
685 // sinking bottom-up.
686 for (User::op_iterator OI = New->op_begin(), OE = New->op_end(); OI != OE;
688 if (Instruction *OInst = dyn_cast<Instruction>(*OI))
689 if (Loop *OLoop = LI->getLoopFor(OInst->getParent()))
690 if (!OLoop->contains(&PN)) {
692 PHINode::Create(OInst->getType(), PN.getNumIncomingValues(),
693 OInst->getName() + ".lcssa", &ExitBlock.front());
694 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
695 OpPN->addIncoming(OInst, PN.getIncomingBlock(i));
701 /// When an instruction is found to only be used outside of the loop, this
702 /// function moves it to the exit blocks and patches up SSA form as needed.
703 /// This method is guaranteed to remove the original instruction from its
704 /// position, and may either delete it or move it to outside of the loop.
706 static bool sink(Instruction &I, const LoopInfo *LI, const DominatorTree *DT,
707 const Loop *CurLoop, AliasSetTracker *CurAST,
708 const LoopSafetyInfo *SafetyInfo,
709 OptimizationRemarkEmitter *ORE) {
710 DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n");
711 ORE->emit(OptimizationRemark(DEBUG_TYPE, "InstSunk", &I)
712 << "sinking " << ore::NV("Inst", &I));
713 bool Changed = false;
714 if (isa<LoadInst>(I))
716 else if (isa<CallInst>(I))
722 SmallVector<BasicBlock *, 32> ExitBlocks;
723 CurLoop->getUniqueExitBlocks(ExitBlocks);
724 SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(),
728 // Clones of this instruction. Don't create more than one per exit block!
729 SmallDenseMap<BasicBlock *, Instruction *, 32> SunkCopies;
731 // If this instruction is only used outside of the loop, then all users are
732 // PHI nodes in exit blocks due to LCSSA form. Just RAUW them with clones of
734 while (!I.use_empty()) {
735 Value::user_iterator UI = I.user_begin();
736 auto *User = cast<Instruction>(*UI);
737 if (!DT->isReachableFromEntry(User->getParent())) {
738 User->replaceUsesOfWith(&I, UndefValue::get(I.getType()));
741 // The user must be a PHI node.
742 PHINode *PN = cast<PHINode>(User);
744 // Surprisingly, instructions can be used outside of loops without any
745 // exits. This can only happen in PHI nodes if the incoming block is
747 Use &U = UI.getUse();
748 BasicBlock *BB = PN->getIncomingBlock(U);
749 if (!DT->isReachableFromEntry(BB)) {
750 U = UndefValue::get(I.getType());
754 BasicBlock *ExitBlock = PN->getParent();
755 assert(ExitBlockSet.count(ExitBlock) &&
756 "The LCSSA PHI is not in an exit block!");
759 auto It = SunkCopies.find(ExitBlock);
760 if (It != SunkCopies.end())
763 New = SunkCopies[ExitBlock] =
764 CloneInstructionInExitBlock(I, *ExitBlock, *PN, LI, SafetyInfo);
766 PN->replaceAllUsesWith(New);
767 PN->eraseFromParent();
770 CurAST->deleteValue(&I);
775 /// When an instruction is found to only use loop invariant operands that
776 /// is safe to hoist, this instruction is called to do the dirty work.
778 static bool hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
779 const LoopSafetyInfo *SafetyInfo,
780 OptimizationRemarkEmitter *ORE) {
781 auto *Preheader = CurLoop->getLoopPreheader();
782 DEBUG(dbgs() << "LICM hoisting to " << Preheader->getName() << ": " << I
784 ORE->emit(OptimizationRemark(DEBUG_TYPE, "Hoisted", &I)
785 << "hosting " << ore::NV("Inst", &I));
787 // Metadata can be dependent on conditions we are hoisting above.
788 // Conservatively strip all metadata on the instruction unless we were
789 // guaranteed to execute I if we entered the loop, in which case the metadata
790 // is valid in the loop preheader.
791 if (I.hasMetadataOtherThanDebugLoc() &&
792 // The check on hasMetadataOtherThanDebugLoc is to prevent us from burning
793 // time in isGuaranteedToExecute if we don't actually have anything to
794 // drop. It is a compile time optimization, not required for correctness.
795 !isGuaranteedToExecute(I, DT, CurLoop, SafetyInfo))
796 I.dropUnknownNonDebugMetadata();
798 // Move the new node to the Preheader, before its terminator.
799 I.moveBefore(Preheader->getTerminator());
801 // Do not retain debug locations when we are moving instructions to different
802 // basic blocks, because we want to avoid jumpy line tables. Calls, however,
803 // need to retain their debug locs because they may be inlined.
804 // FIXME: How do we retain source locations without causing poor debugging
806 if (!isa<CallInst>(I))
807 I.setDebugLoc(DebugLoc());
809 if (isa<LoadInst>(I))
811 else if (isa<CallInst>(I))
817 /// Only sink or hoist an instruction if it is not a trapping instruction,
818 /// or if the instruction is known not to trap when moved to the preheader.
819 /// or if it is a trapping instruction and is guaranteed to execute.
820 static bool isSafeToExecuteUnconditionally(Instruction &Inst,
821 const DominatorTree *DT,
823 const LoopSafetyInfo *SafetyInfo,
824 OptimizationRemarkEmitter *ORE,
825 const Instruction *CtxI) {
826 if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT))
829 bool GuaranteedToExecute =
830 isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo);
832 if (!GuaranteedToExecute) {
833 auto *LI = dyn_cast<LoadInst>(&Inst);
834 if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand()))
835 ORE->emit(OptimizationRemarkMissed(
836 DEBUG_TYPE, "LoadWithLoopInvariantAddressCondExecuted", LI)
837 << "failed to hoist load with loop-invariant address "
838 "because load is conditionally executed");
841 return GuaranteedToExecute;
845 class LoopPromoter : public LoadAndStorePromoter {
846 Value *SomePtr; // Designated pointer to store to.
847 SmallPtrSetImpl<Value *> &PointerMustAliases;
848 SmallVectorImpl<BasicBlock *> &LoopExitBlocks;
849 SmallVectorImpl<Instruction *> &LoopInsertPts;
850 PredIteratorCache &PredCache;
851 AliasSetTracker &AST;
857 Value *maybeInsertLCSSAPHI(Value *V, BasicBlock *BB) const {
858 if (Instruction *I = dyn_cast<Instruction>(V))
859 if (Loop *L = LI.getLoopFor(I->getParent()))
860 if (!L->contains(BB)) {
861 // We need to create an LCSSA PHI node for the incoming value and
863 PHINode *PN = PHINode::Create(I->getType(), PredCache.size(BB),
864 I->getName() + ".lcssa", &BB->front());
865 for (BasicBlock *Pred : PredCache.get(BB))
866 PN->addIncoming(I, Pred);
873 LoopPromoter(Value *SP, ArrayRef<const Instruction *> Insts, SSAUpdater &S,
874 SmallPtrSetImpl<Value *> &PMA,
875 SmallVectorImpl<BasicBlock *> &LEB,
876 SmallVectorImpl<Instruction *> &LIP, PredIteratorCache &PIC,
877 AliasSetTracker &ast, LoopInfo &li, DebugLoc dl, int alignment,
878 const AAMDNodes &AATags)
879 : LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA),
880 LoopExitBlocks(LEB), LoopInsertPts(LIP), PredCache(PIC), AST(ast),
881 LI(li), DL(std::move(dl)), Alignment(alignment), AATags(AATags) {}
883 bool isInstInList(Instruction *I,
884 const SmallVectorImpl<Instruction *> &) const override {
886 if (LoadInst *LI = dyn_cast<LoadInst>(I))
887 Ptr = LI->getOperand(0);
889 Ptr = cast<StoreInst>(I)->getPointerOperand();
890 return PointerMustAliases.count(Ptr);
893 void doExtraRewritesBeforeFinalDeletion() const override {
894 // Insert stores after in the loop exit blocks. Each exit block gets a
895 // store of the live-out values that feed them. Since we've already told
896 // the SSA updater about the defs in the loop and the preheader
897 // definition, it is all set and we can start using it.
898 for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) {
899 BasicBlock *ExitBlock = LoopExitBlocks[i];
900 Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
901 LiveInValue = maybeInsertLCSSAPHI(LiveInValue, ExitBlock);
902 Value *Ptr = maybeInsertLCSSAPHI(SomePtr, ExitBlock);
903 Instruction *InsertPos = LoopInsertPts[i];
904 StoreInst *NewSI = new StoreInst(LiveInValue, Ptr, InsertPos);
905 NewSI->setAlignment(Alignment);
906 NewSI->setDebugLoc(DL);
908 NewSI->setAAMetadata(AATags);
912 void replaceLoadWithValue(LoadInst *LI, Value *V) const override {
913 // Update alias analysis.
914 AST.copyValue(LI, V);
916 void instructionDeleted(Instruction *I) const override { AST.deleteValue(I); }
918 } // end anon namespace
920 /// Try to promote memory values to scalars by sinking stores out of the
921 /// loop and moving loads to before the loop. We do this by looping over
922 /// the stores in the loop, looking for stores to Must pointers which are
925 bool llvm::promoteLoopAccessesToScalars(
926 AliasSet &AS, SmallVectorImpl<BasicBlock *> &ExitBlocks,
927 SmallVectorImpl<Instruction *> &InsertPts, PredIteratorCache &PIC,
928 LoopInfo *LI, DominatorTree *DT, const TargetLibraryInfo *TLI,
929 Loop *CurLoop, AliasSetTracker *CurAST, LoopSafetyInfo *SafetyInfo,
930 OptimizationRemarkEmitter *ORE) {
932 assert(LI != nullptr && DT != nullptr && CurLoop != nullptr &&
933 CurAST != nullptr && SafetyInfo != nullptr &&
934 "Unexpected Input to promoteLoopAccessesToScalars");
936 // We can promote this alias set if it has a store, if it is a "Must" alias
937 // set, if the pointer is loop invariant, and if we are not eliminating any
938 // volatile loads or stores.
939 if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() ||
940 AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue()))
943 assert(!AS.empty() &&
944 "Must alias set should have at least one pointer element in it!");
946 Value *SomePtr = AS.begin()->getValue();
947 BasicBlock *Preheader = CurLoop->getLoopPreheader();
949 // It isn't safe to promote a load/store from the loop if the load/store is
950 // conditional. For example, turning:
952 // for () { if (c) *P += 1; }
956 // tmp = *P; for () { if (c) tmp +=1; } *P = tmp;
958 // is not safe, because *P may only be valid to access if 'c' is true.
960 // The safety property divides into two parts:
961 // p1) The memory may not be dereferenceable on entry to the loop. In this
962 // case, we can't insert the required load in the preheader.
963 // p2) The memory model does not allow us to insert a store along any dynamic
964 // path which did not originally have one.
966 // If at least one store is guaranteed to execute, both properties are
967 // satisfied, and promotion is legal.
969 // This, however, is not a necessary condition. Even if no store/load is
970 // guaranteed to execute, we can still establish these properties.
971 // We can establish (p1) by proving that hoisting the load into the preheader
972 // is safe (i.e. proving dereferenceability on all paths through the loop). We
973 // can use any access within the alias set to prove dereferenceability,
974 // since they're all must alias.
976 // There are two ways establish (p2):
977 // a) Prove the location is thread-local. In this case the memory model
978 // requirement does not apply, and stores are safe to insert.
979 // b) Prove a store dominates every exit block. In this case, if an exit
980 // blocks is reached, the original dynamic path would have taken us through
981 // the store, so inserting a store into the exit block is safe. Note that this
982 // is different from the store being guaranteed to execute. For instance,
983 // if an exception is thrown on the first iteration of the loop, the original
984 // store is never executed, but the exit blocks are not executed either.
986 bool DereferenceableInPH = false;
987 bool SafeToInsertStore = false;
989 SmallVector<Instruction *, 64> LoopUses;
990 SmallPtrSet<Value *, 4> PointerMustAliases;
992 // We start with an alignment of one and try to find instructions that allow
993 // us to prove better alignment.
994 unsigned Alignment = 1;
997 const DataLayout &MDL = Preheader->getModule()->getDataLayout();
999 if (SafetyInfo->MayThrow) {
1000 // If a loop can throw, we have to insert a store along each unwind edge.
1001 // That said, we can't actually make the unwind edge explicit. Therefore,
1002 // we have to prove that the store is dead along the unwind edge.
1004 // Currently, this code just special-cases alloca instructions.
1005 if (!isa<AllocaInst>(GetUnderlyingObject(SomePtr, MDL)))
1009 // Check that all of the pointers in the alias set have the same type. We
1010 // cannot (yet) promote a memory location that is loaded and stored in
1011 // different sizes. While we are at it, collect alignment and AA info.
1012 for (const auto &ASI : AS) {
1013 Value *ASIV = ASI.getValue();
1014 PointerMustAliases.insert(ASIV);
1016 // Check that all of the pointers in the alias set have the same type. We
1017 // cannot (yet) promote a memory location that is loaded and stored in
1019 if (SomePtr->getType() != ASIV->getType())
1022 for (User *U : ASIV->users()) {
1023 // Ignore instructions that are outside the loop.
1024 Instruction *UI = dyn_cast<Instruction>(U);
1025 if (!UI || !CurLoop->contains(UI))
1028 // If there is an non-load/store instruction in the loop, we can't promote
1030 if (LoadInst *Load = dyn_cast<LoadInst>(UI)) {
1031 assert(!Load->isVolatile() && "AST broken");
1032 if (!Load->isSimple())
1035 if (!DereferenceableInPH)
1036 DereferenceableInPH = isSafeToExecuteUnconditionally(
1037 *Load, DT, CurLoop, SafetyInfo, ORE, Preheader->getTerminator());
1038 } else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) {
1039 // Stores *of* the pointer are not interesting, only stores *to* the
1041 if (UI->getOperand(1) != ASIV)
1043 assert(!Store->isVolatile() && "AST broken");
1044 if (!Store->isSimple())
1047 // If the store is guaranteed to execute, both properties are satisfied.
1048 // We may want to check if a store is guaranteed to execute even if we
1049 // already know that promotion is safe, since it may have higher
1050 // alignment than any other guaranteed stores, in which case we can
1051 // raise the alignment on the promoted store.
1052 unsigned InstAlignment = Store->getAlignment();
1055 MDL.getABITypeAlignment(Store->getValueOperand()->getType());
1057 if (!DereferenceableInPH || !SafeToInsertStore ||
1058 (InstAlignment > Alignment)) {
1059 if (isGuaranteedToExecute(*UI, DT, CurLoop, SafetyInfo)) {
1060 DereferenceableInPH = true;
1061 SafeToInsertStore = true;
1062 Alignment = std::max(Alignment, InstAlignment);
1066 // If a store dominates all exit blocks, it is safe to sink.
1067 // As explained above, if an exit block was executed, a dominating
1068 // store must have been been executed at least once, so we are not
1069 // introducing stores on paths that did not have them.
1070 // Note that this only looks at explicit exit blocks. If we ever
1071 // start sinking stores into unwind edges (see above), this will break.
1072 if (!SafeToInsertStore)
1073 SafeToInsertStore = llvm::all_of(ExitBlocks, [&](BasicBlock *Exit) {
1074 return DT->dominates(Store->getParent(), Exit);
1077 // If the store is not guaranteed to execute, we may still get
1078 // deref info through it.
1079 if (!DereferenceableInPH) {
1080 DereferenceableInPH = isDereferenceableAndAlignedPointer(
1081 Store->getPointerOperand(), Store->getAlignment(), MDL,
1082 Preheader->getTerminator(), DT);
1085 return false; // Not a load or store.
1087 // Merge the AA tags.
1088 if (LoopUses.empty()) {
1089 // On the first load/store, just take its AA tags.
1090 UI->getAAMetadata(AATags);
1091 } else if (AATags) {
1092 UI->getAAMetadata(AATags, /* Merge = */ true);
1095 LoopUses.push_back(UI);
1100 // If we couldn't prove we can hoist the load, bail.
1101 if (!DereferenceableInPH)
1104 // We know we can hoist the load, but don't have a guaranteed store.
1105 // Check whether the location is thread-local. If it is, then we can insert
1106 // stores along paths which originally didn't have them without violating the
1108 if (!SafeToInsertStore) {
1109 Value *Object = GetUnderlyingObject(SomePtr, MDL);
1111 (isAllocLikeFn(Object, TLI) || isa<AllocaInst>(Object)) &&
1112 !PointerMayBeCaptured(Object, true, true);
1115 // If we've still failed to prove we can sink the store, give up.
1116 if (!SafeToInsertStore)
1119 // Otherwise, this is safe to promote, lets do it!
1120 DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtr
1123 OptimizationRemark(DEBUG_TYPE, "PromoteLoopAccessesToScalar", LoopUses[0])
1124 << "Moving accesses to memory location out of the loop");
1127 // Grab a debug location for the inserted loads/stores; given that the
1128 // inserted loads/stores have little relation to the original loads/stores,
1129 // this code just arbitrarily picks a location from one, since any debug
1130 // location is better than none.
1131 DebugLoc DL = LoopUses[0]->getDebugLoc();
1133 // We use the SSAUpdater interface to insert phi nodes as required.
1134 SmallVector<PHINode *, 16> NewPHIs;
1135 SSAUpdater SSA(&NewPHIs);
1136 LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
1137 InsertPts, PIC, *CurAST, *LI, DL, Alignment, AATags);
1139 // Set up the preheader to have a definition of the value. It is the live-out
1140 // value from the preheader that uses in the loop will use.
1141 LoadInst *PreheaderLoad = new LoadInst(
1142 SomePtr, SomePtr->getName() + ".promoted", Preheader->getTerminator());
1143 PreheaderLoad->setAlignment(Alignment);
1144 PreheaderLoad->setDebugLoc(DL);
1146 PreheaderLoad->setAAMetadata(AATags);
1147 SSA.AddAvailableValue(Preheader, PreheaderLoad);
1149 // Rewrite all the loads in the loop and remember all the definitions from
1150 // stores in the loop.
1151 Promoter.run(LoopUses);
1153 // If the SSAUpdater didn't use the load in the preheader, just zap it now.
1154 if (PreheaderLoad->use_empty())
1155 PreheaderLoad->eraseFromParent();
1160 /// Returns an owning pointer to an alias set which incorporates aliasing info
1161 /// from L and all subloops of L.
1162 /// FIXME: In new pass manager, there is no helper function to handle loop
1163 /// analysis such as cloneBasicBlockAnalysis, so the AST needs to be recomputed
1164 /// from scratch for every loop. Hook up with the helper functions when
1165 /// available in the new pass manager to avoid redundant computation.
1167 LoopInvariantCodeMotion::collectAliasInfoForLoop(Loop *L, LoopInfo *LI,
1168 AliasAnalysis *AA) {
1169 AliasSetTracker *CurAST = nullptr;
1170 SmallVector<Loop *, 4> RecomputeLoops;
1171 for (Loop *InnerL : L->getSubLoops()) {
1172 auto MapI = LoopToAliasSetMap.find(InnerL);
1173 // If the AST for this inner loop is missing it may have been merged into
1174 // some other loop's AST and then that loop unrolled, and so we need to
1176 if (MapI == LoopToAliasSetMap.end()) {
1177 RecomputeLoops.push_back(InnerL);
1180 AliasSetTracker *InnerAST = MapI->second;
1182 if (CurAST != nullptr) {
1183 // What if InnerLoop was modified by other passes ?
1184 CurAST->add(*InnerAST);
1186 // Once we've incorporated the inner loop's AST into ours, we don't need
1187 // the subloop's anymore.
1192 LoopToAliasSetMap.erase(MapI);
1194 if (CurAST == nullptr)
1195 CurAST = new AliasSetTracker(*AA);
1197 auto mergeLoop = [&](Loop *L) {
1198 // Loop over the body of this loop, looking for calls, invokes, and stores.
1199 // Because subloops have already been incorporated into AST, we skip blocks
1201 for (BasicBlock *BB : L->blocks())
1202 if (LI->getLoopFor(BB) == L) // Ignore blocks in subloops.
1203 CurAST->add(*BB); // Incorporate the specified basic block
1206 // Add everything from the sub loops that are no longer directly available.
1207 for (Loop *InnerL : RecomputeLoops)
1210 // And merge in this loop.
1216 /// Simple analysis hook. Clone alias set info.
1218 void LegacyLICMPass::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To,
1220 AliasSetTracker *AST = LICM.getLoopToAliasSetMap().lookup(L);
1224 AST->copyValue(From, To);
1227 /// Simple Analysis hook. Delete value V from alias set
1229 void LegacyLICMPass::deleteAnalysisValue(Value *V, Loop *L) {
1230 AliasSetTracker *AST = LICM.getLoopToAliasSetMap().lookup(L);
1234 AST->deleteValue(V);
1237 /// Simple Analysis hook. Delete value L from alias set map.
1239 void LegacyLICMPass::deleteAnalysisLoop(Loop *L) {
1240 AliasSetTracker *AST = LICM.getLoopToAliasSetMap().lookup(L);
1245 LICM.getLoopToAliasSetMap().erase(L);
1248 /// Return true if the body of this loop may store into the memory
1249 /// location pointed to by V.
1251 static bool pointerInvalidatedByLoop(Value *V, uint64_t Size,
1252 const AAMDNodes &AAInfo,
1253 AliasSetTracker *CurAST) {
1254 // Check to see if any of the basic blocks in CurLoop invalidate *V.
1255 return CurAST->getAliasSetForPointer(V, Size, AAInfo).isMod();
1258 /// Little predicate that returns true if the specified basic block is in
1259 /// a subloop of the current one, not the current one itself.
1261 static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) {
1262 assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop");
1263 return LI->getLoopFor(BB) != CurLoop;