1 //===- Local.cpp - Functions to perform local transformations -------------===//
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
7 //===----------------------------------------------------------------------===//
9 // This family of functions perform various local transformations to the
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Transforms/Utils/Local.h"
15 #include "llvm/ADT/APInt.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/DenseMapInfo.h"
18 #include "llvm/ADT/DenseSet.h"
19 #include "llvm/ADT/Hashing.h"
20 #include "llvm/ADT/None.h"
21 #include "llvm/ADT/Optional.h"
22 #include "llvm/ADT/STLExtras.h"
23 #include "llvm/ADT/SetVector.h"
24 #include "llvm/ADT/SmallPtrSet.h"
25 #include "llvm/ADT/SmallVector.h"
26 #include "llvm/ADT/Statistic.h"
27 #include "llvm/ADT/TinyPtrVector.h"
28 #include "llvm/Analysis/ConstantFolding.h"
29 #include "llvm/Analysis/DomTreeUpdater.h"
30 #include "llvm/Analysis/EHPersonalities.h"
31 #include "llvm/Analysis/InstructionSimplify.h"
32 #include "llvm/Analysis/LazyValueInfo.h"
33 #include "llvm/Analysis/MemoryBuiltins.h"
34 #include "llvm/Analysis/MemorySSAUpdater.h"
35 #include "llvm/Analysis/TargetLibraryInfo.h"
36 #include "llvm/Analysis/ValueTracking.h"
37 #include "llvm/Analysis/VectorUtils.h"
38 #include "llvm/BinaryFormat/Dwarf.h"
39 #include "llvm/IR/Argument.h"
40 #include "llvm/IR/Attributes.h"
41 #include "llvm/IR/BasicBlock.h"
42 #include "llvm/IR/CFG.h"
43 #include "llvm/IR/CallSite.h"
44 #include "llvm/IR/Constant.h"
45 #include "llvm/IR/ConstantRange.h"
46 #include "llvm/IR/Constants.h"
47 #include "llvm/IR/DIBuilder.h"
48 #include "llvm/IR/DataLayout.h"
49 #include "llvm/IR/DebugInfoMetadata.h"
50 #include "llvm/IR/DebugLoc.h"
51 #include "llvm/IR/DerivedTypes.h"
52 #include "llvm/IR/Dominators.h"
53 #include "llvm/IR/Function.h"
54 #include "llvm/IR/GetElementPtrTypeIterator.h"
55 #include "llvm/IR/GlobalObject.h"
56 #include "llvm/IR/IRBuilder.h"
57 #include "llvm/IR/InstrTypes.h"
58 #include "llvm/IR/Instruction.h"
59 #include "llvm/IR/Instructions.h"
60 #include "llvm/IR/IntrinsicInst.h"
61 #include "llvm/IR/Intrinsics.h"
62 #include "llvm/IR/LLVMContext.h"
63 #include "llvm/IR/MDBuilder.h"
64 #include "llvm/IR/Metadata.h"
65 #include "llvm/IR/Module.h"
66 #include "llvm/IR/Operator.h"
67 #include "llvm/IR/PatternMatch.h"
68 #include "llvm/IR/Type.h"
69 #include "llvm/IR/Use.h"
70 #include "llvm/IR/User.h"
71 #include "llvm/IR/Value.h"
72 #include "llvm/IR/ValueHandle.h"
73 #include "llvm/Support/Casting.h"
74 #include "llvm/Support/Debug.h"
75 #include "llvm/Support/ErrorHandling.h"
76 #include "llvm/Support/KnownBits.h"
77 #include "llvm/Support/raw_ostream.h"
78 #include "llvm/Transforms/Utils/ValueMapper.h"
88 using namespace llvm::PatternMatch;
90 #define DEBUG_TYPE "local"
92 STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
94 // Max recursion depth for collectBitParts used when detecting bswap and
96 static const unsigned BitPartRecursionMaxDepth = 64;
98 //===----------------------------------------------------------------------===//
99 // Local constant propagation.
102 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
103 /// constant value, convert it into an unconditional branch to the constant
104 /// destination. This is a nontrivial operation because the successors of this
105 /// basic block must have their PHI nodes updated.
106 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
107 /// conditions and indirectbr addresses this might make dead if
108 /// DeleteDeadConditions is true.
109 bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
110 const TargetLibraryInfo *TLI,
111 DomTreeUpdater *DTU) {
112 Instruction *T = BB->getTerminator();
113 IRBuilder<> Builder(T);
115 // Branch - See if we are conditional jumping on constant
116 if (auto *BI = dyn_cast<BranchInst>(T)) {
117 if (BI->isUnconditional()) return false; // Can't optimize uncond branch
118 BasicBlock *Dest1 = BI->getSuccessor(0);
119 BasicBlock *Dest2 = BI->getSuccessor(1);
121 if (auto *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
122 // Are we branching on constant?
123 // YES. Change to unconditional branch...
124 BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
125 BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
127 // Let the basic block know that we are letting go of it. Based on this,
128 // it will adjust it's PHI nodes.
129 OldDest->removePredecessor(BB);
131 // Replace the conditional branch with an unconditional one.
132 Builder.CreateBr(Destination);
133 BI->eraseFromParent();
135 DTU->applyUpdatesPermissive({{DominatorTree::Delete, BB, OldDest}});
139 if (Dest2 == Dest1) { // Conditional branch to same location?
140 // This branch matches something like this:
141 // br bool %cond, label %Dest, label %Dest
142 // and changes it into: br label %Dest
144 // Let the basic block know that we are letting go of one copy of it.
145 assert(BI->getParent() && "Terminator not inserted in block!");
146 Dest1->removePredecessor(BI->getParent());
148 // Replace the conditional branch with an unconditional one.
149 Builder.CreateBr(Dest1);
150 Value *Cond = BI->getCondition();
151 BI->eraseFromParent();
152 if (DeleteDeadConditions)
153 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
159 if (auto *SI = dyn_cast<SwitchInst>(T)) {
160 // If we are switching on a constant, we can convert the switch to an
161 // unconditional branch.
162 auto *CI = dyn_cast<ConstantInt>(SI->getCondition());
163 BasicBlock *DefaultDest = SI->getDefaultDest();
164 BasicBlock *TheOnlyDest = DefaultDest;
166 // If the default is unreachable, ignore it when searching for TheOnlyDest.
167 if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) &&
168 SI->getNumCases() > 0) {
169 TheOnlyDest = SI->case_begin()->getCaseSuccessor();
172 // Figure out which case it goes to.
173 for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) {
174 // Found case matching a constant operand?
175 if (i->getCaseValue() == CI) {
176 TheOnlyDest = i->getCaseSuccessor();
180 // Check to see if this branch is going to the same place as the default
181 // dest. If so, eliminate it as an explicit compare.
182 if (i->getCaseSuccessor() == DefaultDest) {
183 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
184 unsigned NCases = SI->getNumCases();
185 // Fold the case metadata into the default if there will be any branches
186 // left, unless the metadata doesn't match the switch.
187 if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) {
188 // Collect branch weights into a vector.
189 SmallVector<uint32_t, 8> Weights;
190 for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;
192 auto *CI = mdconst::extract<ConstantInt>(MD->getOperand(MD_i));
193 Weights.push_back(CI->getValue().getZExtValue());
195 // Merge weight of this case to the default weight.
196 unsigned idx = i->getCaseIndex();
197 Weights[0] += Weights[idx+1];
198 // Remove weight for this case.
199 std::swap(Weights[idx+1], Weights.back());
201 SI->setMetadata(LLVMContext::MD_prof,
202 MDBuilder(BB->getContext()).
203 createBranchWeights(Weights));
205 // Remove this entry.
206 BasicBlock *ParentBB = SI->getParent();
207 DefaultDest->removePredecessor(ParentBB);
208 i = SI->removeCase(i);
211 DTU->applyUpdatesPermissive(
212 {{DominatorTree::Delete, ParentBB, DefaultDest}});
216 // Otherwise, check to see if the switch only branches to one destination.
217 // We do this by reseting "TheOnlyDest" to null when we find two non-equal
219 if (i->getCaseSuccessor() != TheOnlyDest)
220 TheOnlyDest = nullptr;
222 // Increment this iterator as we haven't removed the case.
226 if (CI && !TheOnlyDest) {
227 // Branching on a constant, but not any of the cases, go to the default
229 TheOnlyDest = SI->getDefaultDest();
232 // If we found a single destination that we can fold the switch into, do so
235 // Insert the new branch.
236 Builder.CreateBr(TheOnlyDest);
237 BasicBlock *BB = SI->getParent();
238 std::vector <DominatorTree::UpdateType> Updates;
240 Updates.reserve(SI->getNumSuccessors() - 1);
242 // Remove entries from PHI nodes which we no longer branch to...
243 for (BasicBlock *Succ : successors(SI)) {
244 // Found case matching a constant operand?
245 if (Succ == TheOnlyDest) {
246 TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest
248 Succ->removePredecessor(BB);
250 Updates.push_back({DominatorTree::Delete, BB, Succ});
254 // Delete the old switch.
255 Value *Cond = SI->getCondition();
256 SI->eraseFromParent();
257 if (DeleteDeadConditions)
258 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
260 DTU->applyUpdatesPermissive(Updates);
264 if (SI->getNumCases() == 1) {
265 // Otherwise, we can fold this switch into a conditional branch
266 // instruction if it has only one non-default destination.
267 auto FirstCase = *SI->case_begin();
268 Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
269 FirstCase.getCaseValue(), "cond");
271 // Insert the new branch.
272 BranchInst *NewBr = Builder.CreateCondBr(Cond,
273 FirstCase.getCaseSuccessor(),
274 SI->getDefaultDest());
275 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
276 if (MD && MD->getNumOperands() == 3) {
277 ConstantInt *SICase =
278 mdconst::dyn_extract<ConstantInt>(MD->getOperand(2));
280 mdconst::dyn_extract<ConstantInt>(MD->getOperand(1));
281 assert(SICase && SIDef);
282 // The TrueWeight should be the weight for the single case of SI.
283 NewBr->setMetadata(LLVMContext::MD_prof,
284 MDBuilder(BB->getContext()).
285 createBranchWeights(SICase->getValue().getZExtValue(),
286 SIDef->getValue().getZExtValue()));
289 // Update make.implicit metadata to the newly-created conditional branch.
290 MDNode *MakeImplicitMD = SI->getMetadata(LLVMContext::MD_make_implicit);
292 NewBr->setMetadata(LLVMContext::MD_make_implicit, MakeImplicitMD);
294 // Delete the old switch.
295 SI->eraseFromParent();
301 if (auto *IBI = dyn_cast<IndirectBrInst>(T)) {
302 // indirectbr blockaddress(@F, @BB) -> br label @BB
304 dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
305 BasicBlock *TheOnlyDest = BA->getBasicBlock();
306 std::vector <DominatorTree::UpdateType> Updates;
308 Updates.reserve(IBI->getNumDestinations() - 1);
310 // Insert the new branch.
311 Builder.CreateBr(TheOnlyDest);
313 for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
314 if (IBI->getDestination(i) == TheOnlyDest) {
315 TheOnlyDest = nullptr;
317 BasicBlock *ParentBB = IBI->getParent();
318 BasicBlock *DestBB = IBI->getDestination(i);
319 DestBB->removePredecessor(ParentBB);
321 Updates.push_back({DominatorTree::Delete, ParentBB, DestBB});
324 Value *Address = IBI->getAddress();
325 IBI->eraseFromParent();
326 if (DeleteDeadConditions)
327 RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
329 // If we didn't find our destination in the IBI successor list, then we
330 // have undefined behavior. Replace the unconditional branch with an
331 // 'unreachable' instruction.
333 BB->getTerminator()->eraseFromParent();
334 new UnreachableInst(BB->getContext(), BB);
338 DTU->applyUpdatesPermissive(Updates);
346 //===----------------------------------------------------------------------===//
347 // Local dead code elimination.
350 /// isInstructionTriviallyDead - Return true if the result produced by the
351 /// instruction is not used, and the instruction has no side effects.
353 bool llvm::isInstructionTriviallyDead(Instruction *I,
354 const TargetLibraryInfo *TLI) {
357 return wouldInstructionBeTriviallyDead(I, TLI);
360 bool llvm::wouldInstructionBeTriviallyDead(Instruction *I,
361 const TargetLibraryInfo *TLI) {
362 if (I->isTerminator())
365 // We don't want the landingpad-like instructions removed by anything this
370 // We don't want debug info removed by anything this general, unless
371 // debug info is empty.
372 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
373 if (DDI->getAddress())
377 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
382 if (DbgLabelInst *DLI = dyn_cast<DbgLabelInst>(I)) {
388 if (!I->mayHaveSideEffects())
391 // Special case intrinsics that "may have side effects" but can be deleted
393 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
394 // Safe to delete llvm.stacksave and launder.invariant.group if dead.
395 if (II->getIntrinsicID() == Intrinsic::stacksave ||
396 II->getIntrinsicID() == Intrinsic::launder_invariant_group)
399 // Lifetime intrinsics are dead when their right-hand is undef.
400 if (II->isLifetimeStartOrEnd())
401 return isa<UndefValue>(II->getArgOperand(1));
403 // Assumptions are dead if their condition is trivially true. Guards on
404 // true are operationally no-ops. In the future we can consider more
405 // sophisticated tradeoffs for guards considering potential for check
406 // widening, but for now we keep things simple.
407 if (II->getIntrinsicID() == Intrinsic::assume ||
408 II->getIntrinsicID() == Intrinsic::experimental_guard) {
409 if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0)))
410 return !Cond->isZero();
416 if (isAllocLikeFn(I, TLI))
419 if (CallInst *CI = isFreeCall(I, TLI))
420 if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
421 return C->isNullValue() || isa<UndefValue>(C);
423 if (auto *Call = dyn_cast<CallBase>(I))
424 if (isMathLibCallNoop(Call, TLI))
430 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
431 /// trivially dead instruction, delete it. If that makes any of its operands
432 /// trivially dead, delete them too, recursively. Return true if any
433 /// instructions were deleted.
434 bool llvm::RecursivelyDeleteTriviallyDeadInstructions(
435 Value *V, const TargetLibraryInfo *TLI, MemorySSAUpdater *MSSAU) {
436 Instruction *I = dyn_cast<Instruction>(V);
437 if (!I || !isInstructionTriviallyDead(I, TLI))
440 SmallVector<Instruction*, 16> DeadInsts;
441 DeadInsts.push_back(I);
442 RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI, MSSAU);
447 void llvm::RecursivelyDeleteTriviallyDeadInstructions(
448 SmallVectorImpl<Instruction *> &DeadInsts, const TargetLibraryInfo *TLI,
449 MemorySSAUpdater *MSSAU) {
450 // Process the dead instruction list until empty.
451 while (!DeadInsts.empty()) {
452 Instruction &I = *DeadInsts.pop_back_val();
453 assert(I.use_empty() && "Instructions with uses are not dead.");
454 assert(isInstructionTriviallyDead(&I, TLI) &&
455 "Live instruction found in dead worklist!");
457 // Don't lose the debug info while deleting the instructions.
460 // Null out all of the instruction's operands to see if any operand becomes
462 for (Use &OpU : I.operands()) {
463 Value *OpV = OpU.get();
466 if (!OpV->use_empty())
469 // If the operand is an instruction that became dead as we nulled out the
470 // operand, and if it is 'trivially' dead, delete it in a future loop
472 if (Instruction *OpI = dyn_cast<Instruction>(OpV))
473 if (isInstructionTriviallyDead(OpI, TLI))
474 DeadInsts.push_back(OpI);
477 MSSAU->removeMemoryAccess(&I);
483 bool llvm::replaceDbgUsesWithUndef(Instruction *I) {
484 SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
485 findDbgUsers(DbgUsers, I);
486 for (auto *DII : DbgUsers) {
487 Value *Undef = UndefValue::get(I->getType());
488 DII->setOperand(0, MetadataAsValue::get(DII->getContext(),
489 ValueAsMetadata::get(Undef)));
491 return !DbgUsers.empty();
494 /// areAllUsesEqual - Check whether the uses of a value are all the same.
495 /// This is similar to Instruction::hasOneUse() except this will also return
496 /// true when there are no uses or multiple uses that all refer to the same
498 static bool areAllUsesEqual(Instruction *I) {
499 Value::user_iterator UI = I->user_begin();
500 Value::user_iterator UE = I->user_end();
505 for (++UI; UI != UE; ++UI) {
512 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
513 /// dead PHI node, due to being a def-use chain of single-use nodes that
514 /// either forms a cycle or is terminated by a trivially dead instruction,
515 /// delete it. If that makes any of its operands trivially dead, delete them
516 /// too, recursively. Return true if a change was made.
517 bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN,
518 const TargetLibraryInfo *TLI) {
519 SmallPtrSet<Instruction*, 4> Visited;
520 for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
521 I = cast<Instruction>(*I->user_begin())) {
523 return RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
525 // If we find an instruction more than once, we're on a cycle that
526 // won't prove fruitful.
527 if (!Visited.insert(I).second) {
528 // Break the cycle and delete the instruction and its operands.
529 I->replaceAllUsesWith(UndefValue::get(I->getType()));
530 (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
538 simplifyAndDCEInstruction(Instruction *I,
539 SmallSetVector<Instruction *, 16> &WorkList,
540 const DataLayout &DL,
541 const TargetLibraryInfo *TLI) {
542 if (isInstructionTriviallyDead(I, TLI)) {
543 salvageDebugInfo(*I);
545 // Null out all of the instruction's operands to see if any operand becomes
547 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
548 Value *OpV = I->getOperand(i);
549 I->setOperand(i, nullptr);
551 if (!OpV->use_empty() || I == OpV)
554 // If the operand is an instruction that became dead as we nulled out the
555 // operand, and if it is 'trivially' dead, delete it in a future loop
557 if (Instruction *OpI = dyn_cast<Instruction>(OpV))
558 if (isInstructionTriviallyDead(OpI, TLI))
559 WorkList.insert(OpI);
562 I->eraseFromParent();
567 if (Value *SimpleV = SimplifyInstruction(I, DL)) {
568 // Add the users to the worklist. CAREFUL: an instruction can use itself,
569 // in the case of a phi node.
570 for (User *U : I->users()) {
572 WorkList.insert(cast<Instruction>(U));
576 // Replace the instruction with its simplified value.
577 bool Changed = false;
578 if (!I->use_empty()) {
579 I->replaceAllUsesWith(SimpleV);
582 if (isInstructionTriviallyDead(I, TLI)) {
583 I->eraseFromParent();
591 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
592 /// simplify any instructions in it and recursively delete dead instructions.
594 /// This returns true if it changed the code, note that it can delete
595 /// instructions in other blocks as well in this block.
596 bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB,
597 const TargetLibraryInfo *TLI) {
598 bool MadeChange = false;
599 const DataLayout &DL = BB->getModule()->getDataLayout();
602 // In debug builds, ensure that the terminator of the block is never replaced
603 // or deleted by these simplifications. The idea of simplification is that it
604 // cannot introduce new instructions, and there is no way to replace the
605 // terminator of a block without introducing a new instruction.
606 AssertingVH<Instruction> TerminatorVH(&BB->back());
609 SmallSetVector<Instruction *, 16> WorkList;
610 // Iterate over the original function, only adding insts to the worklist
611 // if they actually need to be revisited. This avoids having to pre-init
612 // the worklist with the entire function's worth of instructions.
613 for (BasicBlock::iterator BI = BB->begin(), E = std::prev(BB->end());
615 assert(!BI->isTerminator());
616 Instruction *I = &*BI;
619 // We're visiting this instruction now, so make sure it's not in the
620 // worklist from an earlier visit.
621 if (!WorkList.count(I))
622 MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
625 while (!WorkList.empty()) {
626 Instruction *I = WorkList.pop_back_val();
627 MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
632 //===----------------------------------------------------------------------===//
633 // Control Flow Graph Restructuring.
636 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
637 /// method is called when we're about to delete Pred as a predecessor of BB. If
638 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
640 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
641 /// nodes that collapse into identity values. For example, if we have:
642 /// x = phi(1, 0, 0, 0)
645 /// .. and delete the predecessor corresponding to the '1', this will attempt to
646 /// recursively fold the and to 0.
647 void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
648 DomTreeUpdater *DTU) {
649 // This only adjusts blocks with PHI nodes.
650 if (!isa<PHINode>(BB->begin()))
653 // Remove the entries for Pred from the PHI nodes in BB, but do not simplify
654 // them down. This will leave us with single entry phi nodes and other phis
655 // that can be removed.
656 BB->removePredecessor(Pred, true);
658 WeakTrackingVH PhiIt = &BB->front();
659 while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
660 PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
661 Value *OldPhiIt = PhiIt;
663 if (!recursivelySimplifyInstruction(PN))
666 // If recursive simplification ended up deleting the next PHI node we would
667 // iterate to, then our iterator is invalid, restart scanning from the top
669 if (PhiIt != OldPhiIt) PhiIt = &BB->front();
672 DTU->applyUpdatesPermissive({{DominatorTree::Delete, Pred, BB}});
675 /// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
676 /// predecessor is known to have one successor (DestBB!). Eliminate the edge
677 /// between them, moving the instructions in the predecessor into DestBB and
678 /// deleting the predecessor block.
679 void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB,
680 DomTreeUpdater *DTU) {
682 // If BB has single-entry PHI nodes, fold them.
683 while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
684 Value *NewVal = PN->getIncomingValue(0);
685 // Replace self referencing PHI with undef, it must be dead.
686 if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
687 PN->replaceAllUsesWith(NewVal);
688 PN->eraseFromParent();
691 BasicBlock *PredBB = DestBB->getSinglePredecessor();
692 assert(PredBB && "Block doesn't have a single predecessor!");
694 bool ReplaceEntryBB = false;
695 if (PredBB == &DestBB->getParent()->getEntryBlock())
696 ReplaceEntryBB = true;
698 // DTU updates: Collect all the edges that enter
699 // PredBB. These dominator edges will be redirected to DestBB.
700 SmallVector<DominatorTree::UpdateType, 32> Updates;
703 Updates.push_back({DominatorTree::Delete, PredBB, DestBB});
704 for (auto I = pred_begin(PredBB), E = pred_end(PredBB); I != E; ++I) {
705 Updates.push_back({DominatorTree::Delete, *I, PredBB});
706 // This predecessor of PredBB may already have DestBB as a successor.
707 if (llvm::find(successors(*I), DestBB) == succ_end(*I))
708 Updates.push_back({DominatorTree::Insert, *I, DestBB});
712 // Zap anything that took the address of DestBB. Not doing this will give the
713 // address an invalid value.
714 if (DestBB->hasAddressTaken()) {
715 BlockAddress *BA = BlockAddress::get(DestBB);
716 Constant *Replacement =
717 ConstantInt::get(Type::getInt32Ty(BA->getContext()), 1);
718 BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
720 BA->destroyConstant();
723 // Anything that branched to PredBB now branches to DestBB.
724 PredBB->replaceAllUsesWith(DestBB);
726 // Splice all the instructions from PredBB to DestBB.
727 PredBB->getTerminator()->eraseFromParent();
728 DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
729 new UnreachableInst(PredBB->getContext(), PredBB);
731 // If the PredBB is the entry block of the function, move DestBB up to
732 // become the entry block after we erase PredBB.
734 DestBB->moveAfter(PredBB);
737 assert(PredBB->getInstList().size() == 1 &&
738 isa<UnreachableInst>(PredBB->getTerminator()) &&
739 "The successor list of PredBB isn't empty before "
740 "applying corresponding DTU updates.");
741 DTU->applyUpdatesPermissive(Updates);
742 DTU->deleteBB(PredBB);
743 // Recalculation of DomTree is needed when updating a forward DomTree and
744 // the Entry BB is replaced.
745 if (ReplaceEntryBB && DTU->hasDomTree()) {
746 // The entry block was removed and there is no external interface for
747 // the dominator tree to be notified of this change. In this corner-case
748 // we recalculate the entire tree.
749 DTU->recalculate(*(DestBB->getParent()));
754 PredBB->eraseFromParent(); // Nuke BB if DTU is nullptr.
758 /// CanMergeValues - Return true if we can choose one of these values to use
759 /// in place of the other. Note that we will always choose the non-undef
761 static bool CanMergeValues(Value *First, Value *Second) {
762 return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second);
765 /// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
766 /// almost-empty BB ending in an unconditional branch to Succ, into Succ.
768 /// Assumption: Succ is the single successor for BB.
769 static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
770 assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
772 LLVM_DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
773 << Succ->getName() << "\n");
774 // Shortcut, if there is only a single predecessor it must be BB and merging
776 if (Succ->getSinglePredecessor()) return true;
778 // Make a list of the predecessors of BB
779 SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
781 // Look at all the phi nodes in Succ, to see if they present a conflict when
782 // merging these blocks
783 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
784 PHINode *PN = cast<PHINode>(I);
786 // If the incoming value from BB is again a PHINode in
787 // BB which has the same incoming value for *PI as PN does, we can
788 // merge the phi nodes and then the blocks can still be merged
789 PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
790 if (BBPN && BBPN->getParent() == BB) {
791 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
792 BasicBlock *IBB = PN->getIncomingBlock(PI);
793 if (BBPreds.count(IBB) &&
794 !CanMergeValues(BBPN->getIncomingValueForBlock(IBB),
795 PN->getIncomingValue(PI))) {
797 << "Can't fold, phi node " << PN->getName() << " in "
798 << Succ->getName() << " is conflicting with "
799 << BBPN->getName() << " with regard to common predecessor "
800 << IBB->getName() << "\n");
805 Value* Val = PN->getIncomingValueForBlock(BB);
806 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
807 // See if the incoming value for the common predecessor is equal to the
808 // one for BB, in which case this phi node will not prevent the merging
810 BasicBlock *IBB = PN->getIncomingBlock(PI);
811 if (BBPreds.count(IBB) &&
812 !CanMergeValues(Val, PN->getIncomingValue(PI))) {
813 LLVM_DEBUG(dbgs() << "Can't fold, phi node " << PN->getName()
814 << " in " << Succ->getName()
815 << " is conflicting with regard to common "
816 << "predecessor " << IBB->getName() << "\n");
826 using PredBlockVector = SmallVector<BasicBlock *, 16>;
827 using IncomingValueMap = DenseMap<BasicBlock *, Value *>;
829 /// Determines the value to use as the phi node input for a block.
831 /// Select between \p OldVal any value that we know flows from \p BB
832 /// to a particular phi on the basis of which one (if either) is not
833 /// undef. Update IncomingValues based on the selected value.
835 /// \param OldVal The value we are considering selecting.
836 /// \param BB The block that the value flows in from.
837 /// \param IncomingValues A map from block-to-value for other phi inputs
838 /// that we have examined.
840 /// \returns the selected value.
841 static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB,
842 IncomingValueMap &IncomingValues) {
843 if (!isa<UndefValue>(OldVal)) {
844 assert((!IncomingValues.count(BB) ||
845 IncomingValues.find(BB)->second == OldVal) &&
846 "Expected OldVal to match incoming value from BB!");
848 IncomingValues.insert(std::make_pair(BB, OldVal));
852 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
853 if (It != IncomingValues.end()) return It->second;
858 /// Create a map from block to value for the operands of a
861 /// Create a map from block to value for each non-undef value flowing
864 /// \param PN The phi we are collecting the map for.
865 /// \param IncomingValues [out] The map from block to value for this phi.
866 static void gatherIncomingValuesToPhi(PHINode *PN,
867 IncomingValueMap &IncomingValues) {
868 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
869 BasicBlock *BB = PN->getIncomingBlock(i);
870 Value *V = PN->getIncomingValue(i);
872 if (!isa<UndefValue>(V))
873 IncomingValues.insert(std::make_pair(BB, V));
877 /// Replace the incoming undef values to a phi with the values
878 /// from a block-to-value map.
880 /// \param PN The phi we are replacing the undefs in.
881 /// \param IncomingValues A map from block to value.
882 static void replaceUndefValuesInPhi(PHINode *PN,
883 const IncomingValueMap &IncomingValues) {
884 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
885 Value *V = PN->getIncomingValue(i);
887 if (!isa<UndefValue>(V)) continue;
889 BasicBlock *BB = PN->getIncomingBlock(i);
890 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
891 if (It == IncomingValues.end()) continue;
893 PN->setIncomingValue(i, It->second);
897 /// Replace a value flowing from a block to a phi with
898 /// potentially multiple instances of that value flowing from the
899 /// block's predecessors to the phi.
901 /// \param BB The block with the value flowing into the phi.
902 /// \param BBPreds The predecessors of BB.
903 /// \param PN The phi that we are updating.
904 static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB,
905 const PredBlockVector &BBPreds,
907 Value *OldVal = PN->removeIncomingValue(BB, false);
908 assert(OldVal && "No entry in PHI for Pred BB!");
910 IncomingValueMap IncomingValues;
912 // We are merging two blocks - BB, and the block containing PN - and
913 // as a result we need to redirect edges from the predecessors of BB
914 // to go to the block containing PN, and update PN
915 // accordingly. Since we allow merging blocks in the case where the
916 // predecessor and successor blocks both share some predecessors,
917 // and where some of those common predecessors might have undef
918 // values flowing into PN, we want to rewrite those values to be
919 // consistent with the non-undef values.
921 gatherIncomingValuesToPhi(PN, IncomingValues);
923 // If this incoming value is one of the PHI nodes in BB, the new entries
924 // in the PHI node are the entries from the old PHI.
925 if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
926 PHINode *OldValPN = cast<PHINode>(OldVal);
927 for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) {
928 // Note that, since we are merging phi nodes and BB and Succ might
929 // have common predecessors, we could end up with a phi node with
930 // identical incoming branches. This will be cleaned up later (and
931 // will trigger asserts if we try to clean it up now, without also
932 // simplifying the corresponding conditional branch).
933 BasicBlock *PredBB = OldValPN->getIncomingBlock(i);
934 Value *PredVal = OldValPN->getIncomingValue(i);
935 Value *Selected = selectIncomingValueForBlock(PredVal, PredBB,
938 // And add a new incoming value for this predecessor for the
939 // newly retargeted branch.
940 PN->addIncoming(Selected, PredBB);
943 for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) {
944 // Update existing incoming values in PN for this
945 // predecessor of BB.
946 BasicBlock *PredBB = BBPreds[i];
947 Value *Selected = selectIncomingValueForBlock(OldVal, PredBB,
950 // And add a new incoming value for this predecessor for the
951 // newly retargeted branch.
952 PN->addIncoming(Selected, PredBB);
956 replaceUndefValuesInPhi(PN, IncomingValues);
959 /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
960 /// unconditional branch, and contains no instructions other than PHI nodes,
961 /// potential side-effect free intrinsics and the branch. If possible,
962 /// eliminate BB by rewriting all the predecessors to branch to the successor
963 /// block and return true. If we can't transform, return false.
964 bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
965 DomTreeUpdater *DTU) {
966 assert(BB != &BB->getParent()->getEntryBlock() &&
967 "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
969 // We can't eliminate infinite loops.
970 BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
971 if (BB == Succ) return false;
973 // Check to see if merging these blocks would cause conflicts for any of the
974 // phi nodes in BB or Succ. If not, we can safely merge.
975 if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
977 // Check for cases where Succ has multiple predecessors and a PHI node in BB
978 // has uses which will not disappear when the PHI nodes are merged. It is
979 // possible to handle such cases, but difficult: it requires checking whether
980 // BB dominates Succ, which is non-trivial to calculate in the case where
981 // Succ has multiple predecessors. Also, it requires checking whether
982 // constructing the necessary self-referential PHI node doesn't introduce any
983 // conflicts; this isn't too difficult, but the previous code for doing this
986 // Note that if this check finds a live use, BB dominates Succ, so BB is
987 // something like a loop pre-header (or rarely, a part of an irreducible CFG);
988 // folding the branch isn't profitable in that case anyway.
989 if (!Succ->getSinglePredecessor()) {
990 BasicBlock::iterator BBI = BB->begin();
991 while (isa<PHINode>(*BBI)) {
992 for (Use &U : BBI->uses()) {
993 if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) {
994 if (PN->getIncomingBlock(U) != BB)
1004 // We cannot fold the block if it's a branch to an already present callbr
1005 // successor because that creates duplicate successors.
1006 for (auto I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
1007 if (auto *CBI = dyn_cast<CallBrInst>((*I)->getTerminator())) {
1008 if (Succ == CBI->getDefaultDest())
1010 for (unsigned i = 0, e = CBI->getNumIndirectDests(); i != e; ++i)
1011 if (Succ == CBI->getIndirectDest(i))
1016 LLVM_DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
1018 SmallVector<DominatorTree::UpdateType, 32> Updates;
1020 Updates.push_back({DominatorTree::Delete, BB, Succ});
1021 // All predecessors of BB will be moved to Succ.
1022 for (auto I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
1023 Updates.push_back({DominatorTree::Delete, *I, BB});
1024 // This predecessor of BB may already have Succ as a successor.
1025 if (llvm::find(successors(*I), Succ) == succ_end(*I))
1026 Updates.push_back({DominatorTree::Insert, *I, Succ});
1030 if (isa<PHINode>(Succ->begin())) {
1031 // If there is more than one pred of succ, and there are PHI nodes in
1032 // the successor, then we need to add incoming edges for the PHI nodes
1034 const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
1036 // Loop over all of the PHI nodes in the successor of BB.
1037 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
1038 PHINode *PN = cast<PHINode>(I);
1040 redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
1044 if (Succ->getSinglePredecessor()) {
1045 // BB is the only predecessor of Succ, so Succ will end up with exactly
1046 // the same predecessors BB had.
1048 // Copy over any phi, debug or lifetime instruction.
1049 BB->getTerminator()->eraseFromParent();
1050 Succ->getInstList().splice(Succ->getFirstNonPHI()->getIterator(),
1053 while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
1054 // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
1055 assert(PN->use_empty() && "There shouldn't be any uses here!");
1056 PN->eraseFromParent();
1060 // If the unconditional branch we replaced contains llvm.loop metadata, we
1061 // add the metadata to the branch instructions in the predecessors.
1062 unsigned LoopMDKind = BB->getContext().getMDKindID("llvm.loop");
1063 Instruction *TI = BB->getTerminator();
1065 if (MDNode *LoopMD = TI->getMetadata(LoopMDKind))
1066 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
1067 BasicBlock *Pred = *PI;
1068 Pred->getTerminator()->setMetadata(LoopMDKind, LoopMD);
1071 // Everything that jumped to BB now goes to Succ.
1072 BB->replaceAllUsesWith(Succ);
1073 if (!Succ->hasName()) Succ->takeName(BB);
1075 // Clear the successor list of BB to match updates applying to DTU later.
1076 if (BB->getTerminator())
1077 BB->getInstList().pop_back();
1078 new UnreachableInst(BB->getContext(), BB);
1079 assert(succ_empty(BB) && "The successor list of BB isn't empty before "
1080 "applying corresponding DTU updates.");
1083 DTU->applyUpdatesPermissive(Updates);
1086 BB->eraseFromParent(); // Delete the old basic block.
1091 /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
1092 /// nodes in this block. This doesn't try to be clever about PHI nodes
1093 /// which differ only in the order of the incoming values, but instcombine
1094 /// orders them so it usually won't matter.
1095 bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
1096 // This implementation doesn't currently consider undef operands
1097 // specially. Theoretically, two phis which are identical except for
1098 // one having an undef where the other doesn't could be collapsed.
1100 struct PHIDenseMapInfo {
1101 static PHINode *getEmptyKey() {
1102 return DenseMapInfo<PHINode *>::getEmptyKey();
1105 static PHINode *getTombstoneKey() {
1106 return DenseMapInfo<PHINode *>::getTombstoneKey();
1109 static unsigned getHashValue(PHINode *PN) {
1110 // Compute a hash value on the operands. Instcombine will likely have
1111 // sorted them, which helps expose duplicates, but we have to check all
1112 // the operands to be safe in case instcombine hasn't run.
1113 return static_cast<unsigned>(hash_combine(
1114 hash_combine_range(PN->value_op_begin(), PN->value_op_end()),
1115 hash_combine_range(PN->block_begin(), PN->block_end())));
1118 static bool isEqual(PHINode *LHS, PHINode *RHS) {
1119 if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
1120 RHS == getEmptyKey() || RHS == getTombstoneKey())
1122 return LHS->isIdenticalTo(RHS);
1126 // Set of unique PHINodes.
1127 DenseSet<PHINode *, PHIDenseMapInfo> PHISet;
1129 // Examine each PHI.
1130 bool Changed = false;
1131 for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I++);) {
1132 auto Inserted = PHISet.insert(PN);
1133 if (!Inserted.second) {
1134 // A duplicate. Replace this PHI with its duplicate.
1135 PN->replaceAllUsesWith(*Inserted.first);
1136 PN->eraseFromParent();
1139 // The RAUW can change PHIs that we already visited. Start over from the
1149 /// enforceKnownAlignment - If the specified pointer points to an object that
1150 /// we control, modify the object's alignment to PrefAlign. This isn't
1151 /// often possible though. If alignment is important, a more reliable approach
1152 /// is to simply align all global variables and allocation instructions to
1153 /// their preferred alignment from the beginning.
1154 static unsigned enforceKnownAlignment(Value *V, unsigned Align,
1156 const DataLayout &DL) {
1157 assert(PrefAlign > Align);
1159 V = V->stripPointerCasts();
1161 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
1162 // TODO: ideally, computeKnownBits ought to have used
1163 // AllocaInst::getAlignment() in its computation already, making
1164 // the below max redundant. But, as it turns out,
1165 // stripPointerCasts recurses through infinite layers of bitcasts,
1166 // while computeKnownBits is not allowed to traverse more than 6
1168 Align = std::max(AI->getAlignment(), Align);
1169 if (PrefAlign <= Align)
1172 // If the preferred alignment is greater than the natural stack alignment
1173 // then don't round up. This avoids dynamic stack realignment.
1174 if (DL.exceedsNaturalStackAlignment(PrefAlign))
1176 AI->setAlignment(PrefAlign);
1180 if (auto *GO = dyn_cast<GlobalObject>(V)) {
1181 // TODO: as above, this shouldn't be necessary.
1182 Align = std::max(GO->getAlignment(), Align);
1183 if (PrefAlign <= Align)
1186 // If there is a large requested alignment and we can, bump up the alignment
1187 // of the global. If the memory we set aside for the global may not be the
1188 // memory used by the final program then it is impossible for us to reliably
1189 // enforce the preferred alignment.
1190 if (!GO->canIncreaseAlignment())
1193 GO->setAlignment(PrefAlign);
1200 unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
1201 const DataLayout &DL,
1202 const Instruction *CxtI,
1203 AssumptionCache *AC,
1204 const DominatorTree *DT) {
1205 assert(V->getType()->isPointerTy() &&
1206 "getOrEnforceKnownAlignment expects a pointer!");
1208 KnownBits Known = computeKnownBits(V, DL, 0, AC, CxtI, DT);
1209 unsigned TrailZ = Known.countMinTrailingZeros();
1211 // Avoid trouble with ridiculously large TrailZ values, such as
1212 // those computed from a null pointer.
1213 TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
1215 unsigned Align = 1u << std::min(Known.getBitWidth() - 1, TrailZ);
1217 // LLVM doesn't support alignments larger than this currently.
1218 Align = std::min(Align, +Value::MaximumAlignment);
1220 if (PrefAlign > Align)
1221 Align = enforceKnownAlignment(V, Align, PrefAlign, DL);
1223 // We don't need to make any adjustment.
1227 ///===---------------------------------------------------------------------===//
1228 /// Dbg Intrinsic utilities
1231 /// See if there is a dbg.value intrinsic for DIVar before I.
1232 static bool LdStHasDebugValue(DILocalVariable *DIVar, DIExpression *DIExpr,
1234 // Since we can't guarantee that the original dbg.declare instrinsic
1235 // is removed by LowerDbgDeclare(), we need to make sure that we are
1236 // not inserting the same dbg.value intrinsic over and over.
1237 BasicBlock::InstListType::iterator PrevI(I);
1238 if (PrevI != I->getParent()->getInstList().begin()) {
1240 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI))
1241 if (DVI->getValue() == I->getOperand(0) &&
1242 DVI->getVariable() == DIVar &&
1243 DVI->getExpression() == DIExpr)
1249 /// See if there is a dbg.value intrinsic for DIVar for the PHI node.
1250 static bool PhiHasDebugValue(DILocalVariable *DIVar,
1251 DIExpression *DIExpr,
1253 // Since we can't guarantee that the original dbg.declare instrinsic
1254 // is removed by LowerDbgDeclare(), we need to make sure that we are
1255 // not inserting the same dbg.value intrinsic over and over.
1256 SmallVector<DbgValueInst *, 1> DbgValues;
1257 findDbgValues(DbgValues, APN);
1258 for (auto *DVI : DbgValues) {
1259 assert(DVI->getValue() == APN);
1260 if ((DVI->getVariable() == DIVar) && (DVI->getExpression() == DIExpr))
1266 /// Check if the alloc size of \p ValTy is large enough to cover the variable
1267 /// (or fragment of the variable) described by \p DII.
1269 /// This is primarily intended as a helper for the different
1270 /// ConvertDebugDeclareToDebugValue functions. The dbg.declare/dbg.addr that is
1271 /// converted describes an alloca'd variable, so we need to use the
1272 /// alloc size of the value when doing the comparison. E.g. an i1 value will be
1273 /// identified as covering an n-bit fragment, if the store size of i1 is at
1275 static bool valueCoversEntireFragment(Type *ValTy, DbgVariableIntrinsic *DII) {
1276 const DataLayout &DL = DII->getModule()->getDataLayout();
1277 uint64_t ValueSize = DL.getTypeAllocSizeInBits(ValTy);
1278 if (auto FragmentSize = DII->getFragmentSizeInBits())
1279 return ValueSize >= *FragmentSize;
1280 // We can't always calculate the size of the DI variable (e.g. if it is a
1281 // VLA). Try to use the size of the alloca that the dbg intrinsic describes
1283 if (DII->isAddressOfVariable())
1284 if (auto *AI = dyn_cast_or_null<AllocaInst>(DII->getVariableLocation()))
1285 if (auto FragmentSize = AI->getAllocationSizeInBits(DL))
1286 return ValueSize >= *FragmentSize;
1287 // Could not determine size of variable. Conservatively return false.
1291 /// Produce a DebugLoc to use for each dbg.declare/inst pair that are promoted
1292 /// to a dbg.value. Because no machine insts can come from debug intrinsics,
1293 /// only the scope and inlinedAt is significant. Zero line numbers are used in
1294 /// case this DebugLoc leaks into any adjacent instructions.
1295 static DebugLoc getDebugValueLoc(DbgVariableIntrinsic *DII, Instruction *Src) {
1296 // Original dbg.declare must have a location.
1297 DebugLoc DeclareLoc = DII->getDebugLoc();
1298 MDNode *Scope = DeclareLoc.getScope();
1299 DILocation *InlinedAt = DeclareLoc.getInlinedAt();
1300 // Produce an unknown location with the correct scope / inlinedAt fields.
1301 return DebugLoc::get(0, 0, Scope, InlinedAt);
1304 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
1305 /// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic.
1306 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
1307 StoreInst *SI, DIBuilder &Builder) {
1308 assert(DII->isAddressOfVariable());
1309 auto *DIVar = DII->getVariable();
1310 assert(DIVar && "Missing variable");
1311 auto *DIExpr = DII->getExpression();
1312 Value *DV = SI->getValueOperand();
1314 DebugLoc NewLoc = getDebugValueLoc(DII, SI);
1316 if (!valueCoversEntireFragment(DV->getType(), DII)) {
1317 // FIXME: If storing to a part of the variable described by the dbg.declare,
1318 // then we want to insert a dbg.value for the corresponding fragment.
1319 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
1321 // For now, when there is a store to parts of the variable (but we do not
1322 // know which part) we insert an dbg.value instrinsic to indicate that we
1323 // know nothing about the variable's content.
1324 DV = UndefValue::get(DV->getType());
1325 if (!LdStHasDebugValue(DIVar, DIExpr, SI))
1326 Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
1330 if (!LdStHasDebugValue(DIVar, DIExpr, SI))
1331 Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
1334 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
1335 /// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic.
1336 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
1337 LoadInst *LI, DIBuilder &Builder) {
1338 auto *DIVar = DII->getVariable();
1339 auto *DIExpr = DII->getExpression();
1340 assert(DIVar && "Missing variable");
1342 if (LdStHasDebugValue(DIVar, DIExpr, LI))
1345 if (!valueCoversEntireFragment(LI->getType(), DII)) {
1346 // FIXME: If only referring to a part of the variable described by the
1347 // dbg.declare, then we want to insert a dbg.value for the corresponding
1349 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
1354 DebugLoc NewLoc = getDebugValueLoc(DII, nullptr);
1356 // We are now tracking the loaded value instead of the address. In the
1357 // future if multi-location support is added to the IR, it might be
1358 // preferable to keep tracking both the loaded value and the original
1359 // address in case the alloca can not be elided.
1360 Instruction *DbgValue = Builder.insertDbgValueIntrinsic(
1361 LI, DIVar, DIExpr, NewLoc, (Instruction *)nullptr);
1362 DbgValue->insertAfter(LI);
1365 /// Inserts a llvm.dbg.value intrinsic after a phi that has an associated
1366 /// llvm.dbg.declare or llvm.dbg.addr intrinsic.
1367 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
1368 PHINode *APN, DIBuilder &Builder) {
1369 auto *DIVar = DII->getVariable();
1370 auto *DIExpr = DII->getExpression();
1371 assert(DIVar && "Missing variable");
1373 if (PhiHasDebugValue(DIVar, DIExpr, APN))
1376 if (!valueCoversEntireFragment(APN->getType(), DII)) {
1377 // FIXME: If only referring to a part of the variable described by the
1378 // dbg.declare, then we want to insert a dbg.value for the corresponding
1380 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
1385 BasicBlock *BB = APN->getParent();
1386 auto InsertionPt = BB->getFirstInsertionPt();
1388 DebugLoc NewLoc = getDebugValueLoc(DII, nullptr);
1390 // The block may be a catchswitch block, which does not have a valid
1392 // FIXME: Insert dbg.value markers in the successors when appropriate.
1393 if (InsertionPt != BB->end())
1394 Builder.insertDbgValueIntrinsic(APN, DIVar, DIExpr, NewLoc, &*InsertionPt);
1397 /// Determine whether this alloca is either a VLA or an array.
1398 static bool isArray(AllocaInst *AI) {
1399 return AI->isArrayAllocation() ||
1400 AI->getType()->getElementType()->isArrayTy();
1403 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
1404 /// of llvm.dbg.value intrinsics.
1405 bool llvm::LowerDbgDeclare(Function &F) {
1406 DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
1407 SmallVector<DbgDeclareInst *, 4> Dbgs;
1409 for (Instruction &BI : FI)
1410 if (auto DDI = dyn_cast<DbgDeclareInst>(&BI))
1411 Dbgs.push_back(DDI);
1416 for (auto &I : Dbgs) {
1417 DbgDeclareInst *DDI = I;
1418 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
1419 // If this is an alloca for a scalar variable, insert a dbg.value
1420 // at each load and store to the alloca and erase the dbg.declare.
1421 // The dbg.values allow tracking a variable even if it is not
1422 // stored on the stack, while the dbg.declare can only describe
1423 // the stack slot (and at a lexical-scope granularity). Later
1424 // passes will attempt to elide the stack slot.
1425 if (!AI || isArray(AI))
1428 // A volatile load/store means that the alloca can't be elided anyway.
1429 if (llvm::any_of(AI->users(), [](User *U) -> bool {
1430 if (LoadInst *LI = dyn_cast<LoadInst>(U))
1431 return LI->isVolatile();
1432 if (StoreInst *SI = dyn_cast<StoreInst>(U))
1433 return SI->isVolatile();
1438 for (auto &AIUse : AI->uses()) {
1439 User *U = AIUse.getUser();
1440 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1441 if (AIUse.getOperandNo() == 1)
1442 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
1443 } else if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1444 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
1445 } else if (CallInst *CI = dyn_cast<CallInst>(U)) {
1446 // This is a call by-value or some other instruction that takes a
1447 // pointer to the variable. Insert a *value* intrinsic that describes
1448 // the variable by dereferencing the alloca.
1449 DebugLoc NewLoc = getDebugValueLoc(DDI, nullptr);
1451 DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref);
1452 DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), DerefExpr, NewLoc,
1456 DDI->eraseFromParent();
1461 /// Propagate dbg.value intrinsics through the newly inserted PHIs.
1462 void llvm::insertDebugValuesForPHIs(BasicBlock *BB,
1463 SmallVectorImpl<PHINode *> &InsertedPHIs) {
1464 assert(BB && "No BasicBlock to clone dbg.value(s) from.");
1465 if (InsertedPHIs.size() == 0)
1468 // Map existing PHI nodes to their dbg.values.
1469 ValueToValueMapTy DbgValueMap;
1470 for (auto &I : *BB) {
1471 if (auto DbgII = dyn_cast<DbgVariableIntrinsic>(&I)) {
1472 if (auto *Loc = dyn_cast_or_null<PHINode>(DbgII->getVariableLocation()))
1473 DbgValueMap.insert({Loc, DbgII});
1476 if (DbgValueMap.size() == 0)
1479 // Then iterate through the new PHIs and look to see if they use one of the
1480 // previously mapped PHIs. If so, insert a new dbg.value intrinsic that will
1481 // propagate the info through the new PHI.
1482 LLVMContext &C = BB->getContext();
1483 for (auto PHI : InsertedPHIs) {
1484 BasicBlock *Parent = PHI->getParent();
1485 // Avoid inserting an intrinsic into an EH block.
1486 if (Parent->getFirstNonPHI()->isEHPad())
1488 auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI));
1489 for (auto VI : PHI->operand_values()) {
1490 auto V = DbgValueMap.find(VI);
1491 if (V != DbgValueMap.end()) {
1492 auto *DbgII = cast<DbgVariableIntrinsic>(V->second);
1493 Instruction *NewDbgII = DbgII->clone();
1494 NewDbgII->setOperand(0, PhiMAV);
1495 auto InsertionPt = Parent->getFirstInsertionPt();
1496 assert(InsertionPt != Parent->end() && "Ill-formed basic block");
1497 NewDbgII->insertBefore(&*InsertionPt);
1503 /// Finds all intrinsics declaring local variables as living in the memory that
1504 /// 'V' points to. This may include a mix of dbg.declare and
1505 /// dbg.addr intrinsics.
1506 TinyPtrVector<DbgVariableIntrinsic *> llvm::FindDbgAddrUses(Value *V) {
1507 // This function is hot. Check whether the value has any metadata to avoid a
1509 if (!V->isUsedByMetadata())
1511 auto *L = LocalAsMetadata::getIfExists(V);
1514 auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L);
1518 TinyPtrVector<DbgVariableIntrinsic *> Declares;
1519 for (User *U : MDV->users()) {
1520 if (auto *DII = dyn_cast<DbgVariableIntrinsic>(U))
1521 if (DII->isAddressOfVariable())
1522 Declares.push_back(DII);
1528 void llvm::findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V) {
1529 // This function is hot. Check whether the value has any metadata to avoid a
1531 if (!V->isUsedByMetadata())
1533 if (auto *L = LocalAsMetadata::getIfExists(V))
1534 if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
1535 for (User *U : MDV->users())
1536 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U))
1537 DbgValues.push_back(DVI);
1540 void llvm::findDbgUsers(SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers,
1542 // This function is hot. Check whether the value has any metadata to avoid a
1544 if (!V->isUsedByMetadata())
1546 if (auto *L = LocalAsMetadata::getIfExists(V))
1547 if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
1548 for (User *U : MDV->users())
1549 if (DbgVariableIntrinsic *DII = dyn_cast<DbgVariableIntrinsic>(U))
1550 DbgUsers.push_back(DII);
1553 bool llvm::replaceDbgDeclare(Value *Address, Value *NewAddress,
1554 Instruction *InsertBefore, DIBuilder &Builder,
1555 uint8_t DIExprFlags, int Offset) {
1556 auto DbgAddrs = FindDbgAddrUses(Address);
1557 for (DbgVariableIntrinsic *DII : DbgAddrs) {
1558 DebugLoc Loc = DII->getDebugLoc();
1559 auto *DIVar = DII->getVariable();
1560 auto *DIExpr = DII->getExpression();
1561 assert(DIVar && "Missing variable");
1562 DIExpr = DIExpression::prepend(DIExpr, DIExprFlags, Offset);
1563 // Insert llvm.dbg.declare immediately before InsertBefore, and remove old
1564 // llvm.dbg.declare.
1565 Builder.insertDeclare(NewAddress, DIVar, DIExpr, Loc, InsertBefore);
1566 if (DII == InsertBefore)
1567 InsertBefore = InsertBefore->getNextNode();
1568 DII->eraseFromParent();
1570 return !DbgAddrs.empty();
1573 bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
1574 DIBuilder &Builder, uint8_t DIExprFlags,
1576 return replaceDbgDeclare(AI, NewAllocaAddress, AI->getNextNode(), Builder,
1577 DIExprFlags, Offset);
1580 static void replaceOneDbgValueForAlloca(DbgValueInst *DVI, Value *NewAddress,
1581 DIBuilder &Builder, int Offset) {
1582 DebugLoc Loc = DVI->getDebugLoc();
1583 auto *DIVar = DVI->getVariable();
1584 auto *DIExpr = DVI->getExpression();
1585 assert(DIVar && "Missing variable");
1587 // This is an alloca-based llvm.dbg.value. The first thing it should do with
1588 // the alloca pointer is dereference it. Otherwise we don't know how to handle
1590 if (!DIExpr || DIExpr->getNumElements() < 1 ||
1591 DIExpr->getElement(0) != dwarf::DW_OP_deref)
1594 // Insert the offset immediately after the first deref.
1595 // We could just change the offset argument of dbg.value, but it's unsigned...
1597 SmallVector<uint64_t, 4> Ops;
1598 Ops.push_back(dwarf::DW_OP_deref);
1599 DIExpression::appendOffset(Ops, Offset);
1600 Ops.append(DIExpr->elements_begin() + 1, DIExpr->elements_end());
1601 DIExpr = Builder.createExpression(Ops);
1604 Builder.insertDbgValueIntrinsic(NewAddress, DIVar, DIExpr, Loc, DVI);
1605 DVI->eraseFromParent();
1608 void llvm::replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
1609 DIBuilder &Builder, int Offset) {
1610 if (auto *L = LocalAsMetadata::getIfExists(AI))
1611 if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L))
1612 for (auto UI = MDV->use_begin(), UE = MDV->use_end(); UI != UE;) {
1614 if (auto *DVI = dyn_cast<DbgValueInst>(U.getUser()))
1615 replaceOneDbgValueForAlloca(DVI, NewAllocaAddress, Builder, Offset);
1619 /// Wrap \p V in a ValueAsMetadata instance.
1620 static MetadataAsValue *wrapValueInMetadata(LLVMContext &C, Value *V) {
1621 return MetadataAsValue::get(C, ValueAsMetadata::get(V));
1624 bool llvm::salvageDebugInfo(Instruction &I) {
1625 SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
1626 findDbgUsers(DbgUsers, &I);
1627 if (DbgUsers.empty())
1630 return salvageDebugInfoForDbgValues(I, DbgUsers);
1633 bool llvm::salvageDebugInfoForDbgValues(
1634 Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers) {
1635 auto &Ctx = I.getContext();
1636 auto wrapMD = [&](Value *V) { return wrapValueInMetadata(Ctx, V); };
1638 for (auto *DII : DbgUsers) {
1639 // Do not add DW_OP_stack_value for DbgDeclare and DbgAddr, because they
1640 // are implicitly pointing out the value as a DWARF memory location
1642 bool StackValue = isa<DbgValueInst>(DII);
1644 DIExpression *DIExpr =
1645 salvageDebugInfoImpl(I, DII->getExpression(), StackValue);
1647 // salvageDebugInfoImpl should fail on examining the first element of
1648 // DbgUsers, or none of them.
1652 DII->setOperand(0, wrapMD(I.getOperand(0)));
1653 DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr));
1654 LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
1660 DIExpression *llvm::salvageDebugInfoImpl(Instruction &I,
1661 DIExpression *SrcDIExpr,
1662 bool WithStackValue) {
1663 auto &M = *I.getModule();
1664 auto &DL = M.getDataLayout();
1666 // Apply a vector of opcodes to the source DIExpression.
1667 auto doSalvage = [&](SmallVectorImpl<uint64_t> &Ops) -> DIExpression * {
1668 DIExpression *DIExpr = SrcDIExpr;
1670 DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, WithStackValue);
1675 // Apply the given offset to the source DIExpression.
1676 auto applyOffset = [&](uint64_t Offset) -> DIExpression * {
1677 SmallVector<uint64_t, 8> Ops;
1678 DIExpression::appendOffset(Ops, Offset);
1679 return doSalvage(Ops);
1682 // initializer-list helper for applying operators to the source DIExpression.
1684 [&](std::initializer_list<uint64_t> Opcodes) -> DIExpression * {
1685 SmallVector<uint64_t, 8> Ops(Opcodes);
1686 return doSalvage(Ops);
1689 if (auto *CI = dyn_cast<CastInst>(&I)) {
1690 // No-op casts and zexts are irrelevant for debug info.
1691 if (CI->isNoopCast(DL) || isa<ZExtInst>(&I))
1694 } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
1696 M.getDataLayout().getIndexSizeInBits(GEP->getPointerAddressSpace());
1697 // Rewrite a constant GEP into a DIExpression.
1698 APInt Offset(BitWidth, 0);
1699 if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
1700 return applyOffset(Offset.getSExtValue());
1704 } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
1705 // Rewrite binary operations with constant integer operands.
1706 auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1));
1707 if (!ConstInt || ConstInt->getBitWidth() > 64)
1710 uint64_t Val = ConstInt->getSExtValue();
1711 switch (BI->getOpcode()) {
1712 case Instruction::Add:
1713 return applyOffset(Val);
1714 case Instruction::Sub:
1715 return applyOffset(-int64_t(Val));
1716 case Instruction::Mul:
1717 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mul});
1718 case Instruction::SDiv:
1719 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_div});
1720 case Instruction::SRem:
1721 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mod});
1722 case Instruction::Or:
1723 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_or});
1724 case Instruction::And:
1725 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_and});
1726 case Instruction::Xor:
1727 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_xor});
1728 case Instruction::Shl:
1729 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shl});
1730 case Instruction::LShr:
1731 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shr});
1732 case Instruction::AShr:
1733 return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shra});
1735 // TODO: Salvage constants from each kind of binop we know about.
1738 // *Not* to do: we should not attempt to salvage load instructions,
1739 // because the validity and lifetime of a dbg.value containing
1740 // DW_OP_deref becomes difficult to analyze. See PR40628 for examples.
1745 /// A replacement for a dbg.value expression.
1746 using DbgValReplacement = Optional<DIExpression *>;
1748 /// Point debug users of \p From to \p To using exprs given by \p RewriteExpr,
1749 /// possibly moving/deleting users to prevent use-before-def. Returns true if
1750 /// changes are made.
1751 static bool rewriteDebugUsers(
1752 Instruction &From, Value &To, Instruction &DomPoint, DominatorTree &DT,
1753 function_ref<DbgValReplacement(DbgVariableIntrinsic &DII)> RewriteExpr) {
1754 // Find debug users of From.
1755 SmallVector<DbgVariableIntrinsic *, 1> Users;
1756 findDbgUsers(Users, &From);
1760 // Prevent use-before-def of To.
1761 bool Changed = false;
1762 SmallPtrSet<DbgVariableIntrinsic *, 1> DeleteOrSalvage;
1763 if (isa<Instruction>(&To)) {
1764 bool DomPointAfterFrom = From.getNextNonDebugInstruction() == &DomPoint;
1766 for (auto *DII : Users) {
1767 // It's common to see a debug user between From and DomPoint. Move it
1768 // after DomPoint to preserve the variable update without any reordering.
1769 if (DomPointAfterFrom && DII->getNextNonDebugInstruction() == &DomPoint) {
1770 LLVM_DEBUG(dbgs() << "MOVE: " << *DII << '\n');
1771 DII->moveAfter(&DomPoint);
1774 // Users which otherwise aren't dominated by the replacement value must
1775 // be salvaged or deleted.
1776 } else if (!DT.dominates(&DomPoint, DII)) {
1777 DeleteOrSalvage.insert(DII);
1782 // Update debug users without use-before-def risk.
1783 for (auto *DII : Users) {
1784 if (DeleteOrSalvage.count(DII))
1787 LLVMContext &Ctx = DII->getContext();
1788 DbgValReplacement DVR = RewriteExpr(*DII);
1792 DII->setOperand(0, wrapValueInMetadata(Ctx, &To));
1793 DII->setOperand(2, MetadataAsValue::get(Ctx, *DVR));
1794 LLVM_DEBUG(dbgs() << "REWRITE: " << *DII << '\n');
1798 if (!DeleteOrSalvage.empty()) {
1799 // Try to salvage the remaining debug users.
1800 Changed |= salvageDebugInfo(From);
1802 // Delete the debug users which weren't salvaged.
1803 for (auto *DII : DeleteOrSalvage) {
1804 if (DII->getVariableLocation() == &From) {
1805 LLVM_DEBUG(dbgs() << "Erased UseBeforeDef: " << *DII << '\n');
1806 DII->eraseFromParent();
1815 /// Check if a bitcast between a value of type \p FromTy to type \p ToTy would
1816 /// losslessly preserve the bits and semantics of the value. This predicate is
1817 /// symmetric, i.e swapping \p FromTy and \p ToTy should give the same result.
1819 /// Note that Type::canLosslesslyBitCastTo is not suitable here because it
1820 /// allows semantically unequivalent bitcasts, such as <2 x i64> -> <4 x i32>,
1821 /// and also does not allow lossless pointer <-> integer conversions.
1822 static bool isBitCastSemanticsPreserving(const DataLayout &DL, Type *FromTy,
1824 // Trivially compatible types.
1828 // Handle compatible pointer <-> integer conversions.
1829 if (FromTy->isIntOrPtrTy() && ToTy->isIntOrPtrTy()) {
1830 bool SameSize = DL.getTypeSizeInBits(FromTy) == DL.getTypeSizeInBits(ToTy);
1831 bool LosslessConversion = !DL.isNonIntegralPointerType(FromTy) &&
1832 !DL.isNonIntegralPointerType(ToTy);
1833 return SameSize && LosslessConversion;
1836 // TODO: This is not exhaustive.
1840 bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To,
1841 Instruction &DomPoint, DominatorTree &DT) {
1842 // Exit early if From has no debug users.
1843 if (!From.isUsedByMetadata())
1846 assert(&From != &To && "Can't replace something with itself");
1848 Type *FromTy = From.getType();
1849 Type *ToTy = To.getType();
1851 auto Identity = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement {
1852 return DII.getExpression();
1855 // Handle no-op conversions.
1856 Module &M = *From.getModule();
1857 const DataLayout &DL = M.getDataLayout();
1858 if (isBitCastSemanticsPreserving(DL, FromTy, ToTy))
1859 return rewriteDebugUsers(From, To, DomPoint, DT, Identity);
1861 // Handle integer-to-integer widening and narrowing.
1862 // FIXME: Use DW_OP_convert when it's available everywhere.
1863 if (FromTy->isIntegerTy() && ToTy->isIntegerTy()) {
1864 uint64_t FromBits = FromTy->getPrimitiveSizeInBits();
1865 uint64_t ToBits = ToTy->getPrimitiveSizeInBits();
1866 assert(FromBits != ToBits && "Unexpected no-op conversion");
1868 // When the width of the result grows, assume that a debugger will only
1869 // access the low `FromBits` bits when inspecting the source variable.
1870 if (FromBits < ToBits)
1871 return rewriteDebugUsers(From, To, DomPoint, DT, Identity);
1873 // The width of the result has shrunk. Use sign/zero extension to describe
1874 // the source variable's high bits.
1875 auto SignOrZeroExt = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement {
1876 DILocalVariable *Var = DII.getVariable();
1878 // Without knowing signedness, sign/zero extension isn't possible.
1879 auto Signedness = Var->getSignedness();
1883 bool Signed = *Signedness == DIBasicType::Signedness::Signed;
1884 dwarf::TypeKind TK = Signed ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned;
1885 SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_LLVM_convert, ToBits, TK,
1886 dwarf::DW_OP_LLVM_convert, FromBits, TK});
1887 return DIExpression::appendToStack(DII.getExpression(), Ops);
1889 return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt);
1892 // TODO: Floating-point conversions, vectors.
1896 unsigned llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) {
1897 unsigned NumDeadInst = 0;
1898 // Delete the instructions backwards, as it has a reduced likelihood of
1899 // having to update as many def-use and use-def chains.
1900 Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
1901 while (EndInst != &BB->front()) {
1902 // Delete the next to last instruction.
1903 Instruction *Inst = &*--EndInst->getIterator();
1904 if (!Inst->use_empty() && !Inst->getType()->isTokenTy())
1905 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
1906 if (Inst->isEHPad() || Inst->getType()->isTokenTy()) {
1910 if (!isa<DbgInfoIntrinsic>(Inst))
1912 Inst->eraseFromParent();
1917 unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap,
1918 bool PreserveLCSSA, DomTreeUpdater *DTU,
1919 MemorySSAUpdater *MSSAU) {
1920 BasicBlock *BB = I->getParent();
1921 std::vector <DominatorTree::UpdateType> Updates;
1924 MSSAU->changeToUnreachable(I);
1926 // Loop over all of the successors, removing BB's entry from any PHI
1929 Updates.reserve(BB->getTerminator()->getNumSuccessors());
1930 for (BasicBlock *Successor : successors(BB)) {
1931 Successor->removePredecessor(BB, PreserveLCSSA);
1933 Updates.push_back({DominatorTree::Delete, BB, Successor});
1935 // Insert a call to llvm.trap right before this. This turns the undefined
1936 // behavior into a hard fail instead of falling through into random code.
1939 Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
1940 CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
1941 CallTrap->setDebugLoc(I->getDebugLoc());
1943 auto *UI = new UnreachableInst(I->getContext(), I);
1944 UI->setDebugLoc(I->getDebugLoc());
1946 // All instructions after this are dead.
1947 unsigned NumInstrsRemoved = 0;
1948 BasicBlock::iterator BBI = I->getIterator(), BBE = BB->end();
1949 while (BBI != BBE) {
1950 if (!BBI->use_empty())
1951 BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
1952 BB->getInstList().erase(BBI++);
1956 DTU->applyUpdatesPermissive(Updates);
1957 return NumInstrsRemoved;
1960 /// changeToCall - Convert the specified invoke into a normal call.
1961 static void changeToCall(InvokeInst *II, DomTreeUpdater *DTU = nullptr) {
1962 SmallVector<Value*, 8> Args(II->arg_begin(), II->arg_end());
1963 SmallVector<OperandBundleDef, 1> OpBundles;
1964 II->getOperandBundlesAsDefs(OpBundles);
1965 CallInst *NewCall = CallInst::Create(
1966 II->getFunctionType(), II->getCalledValue(), Args, OpBundles, "", II);
1967 NewCall->takeName(II);
1968 NewCall->setCallingConv(II->getCallingConv());
1969 NewCall->setAttributes(II->getAttributes());
1970 NewCall->setDebugLoc(II->getDebugLoc());
1971 NewCall->copyMetadata(*II);
1972 II->replaceAllUsesWith(NewCall);
1974 // Follow the call by a branch to the normal destination.
1975 BasicBlock *NormalDestBB = II->getNormalDest();
1976 BranchInst::Create(NormalDestBB, II);
1978 // Update PHI nodes in the unwind destination
1979 BasicBlock *BB = II->getParent();
1980 BasicBlock *UnwindDestBB = II->getUnwindDest();
1981 UnwindDestBB->removePredecessor(BB);
1982 II->eraseFromParent();
1984 DTU->applyUpdatesPermissive({{DominatorTree::Delete, BB, UnwindDestBB}});
1987 BasicBlock *llvm::changeToInvokeAndSplitBasicBlock(CallInst *CI,
1988 BasicBlock *UnwindEdge) {
1989 BasicBlock *BB = CI->getParent();
1991 // Convert this function call into an invoke instruction. First, split the
1994 BB->splitBasicBlock(CI->getIterator(), CI->getName() + ".noexc");
1996 // Delete the unconditional branch inserted by splitBasicBlock
1997 BB->getInstList().pop_back();
1999 // Create the new invoke instruction.
2000 SmallVector<Value *, 8> InvokeArgs(CI->arg_begin(), CI->arg_end());
2001 SmallVector<OperandBundleDef, 1> OpBundles;
2003 CI->getOperandBundlesAsDefs(OpBundles);
2005 // Note: we're round tripping operand bundles through memory here, and that
2006 // can potentially be avoided with a cleverer API design that we do not have
2010 InvokeInst::Create(CI->getFunctionType(), CI->getCalledValue(), Split,
2011 UnwindEdge, InvokeArgs, OpBundles, CI->getName(), BB);
2012 II->setDebugLoc(CI->getDebugLoc());
2013 II->setCallingConv(CI->getCallingConv());
2014 II->setAttributes(CI->getAttributes());
2016 // Make sure that anything using the call now uses the invoke! This also
2017 // updates the CallGraph if present, because it uses a WeakTrackingVH.
2018 CI->replaceAllUsesWith(II);
2020 // Delete the original call
2021 Split->getInstList().pop_front();
2025 static bool markAliveBlocks(Function &F,
2026 SmallPtrSetImpl<BasicBlock *> &Reachable,
2027 DomTreeUpdater *DTU = nullptr) {
2028 SmallVector<BasicBlock*, 128> Worklist;
2029 BasicBlock *BB = &F.front();
2030 Worklist.push_back(BB);
2031 Reachable.insert(BB);
2032 bool Changed = false;
2034 BB = Worklist.pop_back_val();
2036 // Do a quick scan of the basic block, turning any obviously unreachable
2037 // instructions into LLVM unreachable insts. The instruction combining pass
2038 // canonicalizes unreachable insts into stores to null or undef.
2039 for (Instruction &I : *BB) {
2040 if (auto *CI = dyn_cast<CallInst>(&I)) {
2041 Value *Callee = CI->getCalledValue();
2042 // Handle intrinsic calls.
2043 if (Function *F = dyn_cast<Function>(Callee)) {
2044 auto IntrinsicID = F->getIntrinsicID();
2045 // Assumptions that are known to be false are equivalent to
2046 // unreachable. Also, if the condition is undefined, then we make the
2047 // choice most beneficial to the optimizer, and choose that to also be
2049 if (IntrinsicID == Intrinsic::assume) {
2050 if (match(CI->getArgOperand(0), m_CombineOr(m_Zero(), m_Undef()))) {
2051 // Don't insert a call to llvm.trap right before the unreachable.
2052 changeToUnreachable(CI, false, false, DTU);
2056 } else if (IntrinsicID == Intrinsic::experimental_guard) {
2057 // A call to the guard intrinsic bails out of the current
2058 // compilation unit if the predicate passed to it is false. If the
2059 // predicate is a constant false, then we know the guard will bail
2060 // out of the current compile unconditionally, so all code following
2063 // Note: unlike in llvm.assume, it is not "obviously profitable" for
2064 // guards to treat `undef` as `false` since a guard on `undef` can
2065 // still be useful for widening.
2066 if (match(CI->getArgOperand(0), m_Zero()))
2067 if (!isa<UnreachableInst>(CI->getNextNode())) {
2068 changeToUnreachable(CI->getNextNode(), /*UseLLVMTrap=*/false,
2074 } else if ((isa<ConstantPointerNull>(Callee) &&
2075 !NullPointerIsDefined(CI->getFunction())) ||
2076 isa<UndefValue>(Callee)) {
2077 changeToUnreachable(CI, /*UseLLVMTrap=*/false, false, DTU);
2081 if (CI->doesNotReturn() && !CI->isMustTailCall()) {
2082 // If we found a call to a no-return function, insert an unreachable
2083 // instruction after it. Make sure there isn't *already* one there
2085 if (!isa<UnreachableInst>(CI->getNextNode())) {
2086 // Don't insert a call to llvm.trap right before the unreachable.
2087 changeToUnreachable(CI->getNextNode(), false, false, DTU);
2092 } else if (auto *SI = dyn_cast<StoreInst>(&I)) {
2093 // Store to undef and store to null are undefined and used to signal
2094 // that they should be changed to unreachable by passes that can't
2097 // Don't touch volatile stores.
2098 if (SI->isVolatile()) continue;
2100 Value *Ptr = SI->getOperand(1);
2102 if (isa<UndefValue>(Ptr) ||
2103 (isa<ConstantPointerNull>(Ptr) &&
2104 !NullPointerIsDefined(SI->getFunction(),
2105 SI->getPointerAddressSpace()))) {
2106 changeToUnreachable(SI, true, false, DTU);
2113 Instruction *Terminator = BB->getTerminator();
2114 if (auto *II = dyn_cast<InvokeInst>(Terminator)) {
2115 // Turn invokes that call 'nounwind' functions into ordinary calls.
2116 Value *Callee = II->getCalledValue();
2117 if ((isa<ConstantPointerNull>(Callee) &&
2118 !NullPointerIsDefined(BB->getParent())) ||
2119 isa<UndefValue>(Callee)) {
2120 changeToUnreachable(II, true, false, DTU);
2122 } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) {
2123 if (II->use_empty() && II->onlyReadsMemory()) {
2124 // jump to the normal destination branch.
2125 BasicBlock *NormalDestBB = II->getNormalDest();
2126 BasicBlock *UnwindDestBB = II->getUnwindDest();
2127 BranchInst::Create(NormalDestBB, II);
2128 UnwindDestBB->removePredecessor(II->getParent());
2129 II->eraseFromParent();
2131 DTU->applyUpdatesPermissive(
2132 {{DominatorTree::Delete, BB, UnwindDestBB}});
2134 changeToCall(II, DTU);
2137 } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Terminator)) {
2138 // Remove catchpads which cannot be reached.
2139 struct CatchPadDenseMapInfo {
2140 static CatchPadInst *getEmptyKey() {
2141 return DenseMapInfo<CatchPadInst *>::getEmptyKey();
2144 static CatchPadInst *getTombstoneKey() {
2145 return DenseMapInfo<CatchPadInst *>::getTombstoneKey();
2148 static unsigned getHashValue(CatchPadInst *CatchPad) {
2149 return static_cast<unsigned>(hash_combine_range(
2150 CatchPad->value_op_begin(), CatchPad->value_op_end()));
2153 static bool isEqual(CatchPadInst *LHS, CatchPadInst *RHS) {
2154 if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
2155 RHS == getEmptyKey() || RHS == getTombstoneKey())
2157 return LHS->isIdenticalTo(RHS);
2161 // Set of unique CatchPads.
2162 SmallDenseMap<CatchPadInst *, detail::DenseSetEmpty, 4,
2163 CatchPadDenseMapInfo, detail::DenseSetPair<CatchPadInst *>>
2165 detail::DenseSetEmpty Empty;
2166 for (CatchSwitchInst::handler_iterator I = CatchSwitch->handler_begin(),
2167 E = CatchSwitch->handler_end();
2169 BasicBlock *HandlerBB = *I;
2170 auto *CatchPad = cast<CatchPadInst>(HandlerBB->getFirstNonPHI());
2171 if (!HandlerSet.insert({CatchPad, Empty}).second) {
2172 CatchSwitch->removeHandler(I);
2180 Changed |= ConstantFoldTerminator(BB, true, nullptr, DTU);
2181 for (BasicBlock *Successor : successors(BB))
2182 if (Reachable.insert(Successor).second)
2183 Worklist.push_back(Successor);
2184 } while (!Worklist.empty());
2188 void llvm::removeUnwindEdge(BasicBlock *BB, DomTreeUpdater *DTU) {
2189 Instruction *TI = BB->getTerminator();
2191 if (auto *II = dyn_cast<InvokeInst>(TI)) {
2192 changeToCall(II, DTU);
2197 BasicBlock *UnwindDest;
2199 if (auto *CRI = dyn_cast<CleanupReturnInst>(TI)) {
2200 NewTI = CleanupReturnInst::Create(CRI->getCleanupPad(), nullptr, CRI);
2201 UnwindDest = CRI->getUnwindDest();
2202 } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(TI)) {
2203 auto *NewCatchSwitch = CatchSwitchInst::Create(
2204 CatchSwitch->getParentPad(), nullptr, CatchSwitch->getNumHandlers(),
2205 CatchSwitch->getName(), CatchSwitch);
2206 for (BasicBlock *PadBB : CatchSwitch->handlers())
2207 NewCatchSwitch->addHandler(PadBB);
2209 NewTI = NewCatchSwitch;
2210 UnwindDest = CatchSwitch->getUnwindDest();
2212 llvm_unreachable("Could not find unwind successor");
2215 NewTI->takeName(TI);
2216 NewTI->setDebugLoc(TI->getDebugLoc());
2217 UnwindDest->removePredecessor(BB);
2218 TI->replaceAllUsesWith(NewTI);
2219 TI->eraseFromParent();
2221 DTU->applyUpdatesPermissive({{DominatorTree::Delete, BB, UnwindDest}});
2224 /// removeUnreachableBlocks - Remove blocks that are not reachable, even
2225 /// if they are in a dead cycle. Return true if a change was made, false
2226 /// otherwise. If `LVI` is passed, this function preserves LazyValueInfo
2227 /// after modifying the CFG.
2228 bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI,
2229 DomTreeUpdater *DTU,
2230 MemorySSAUpdater *MSSAU) {
2231 SmallPtrSet<BasicBlock*, 16> Reachable;
2232 bool Changed = markAliveBlocks(F, Reachable, DTU);
2234 // If there are unreachable blocks in the CFG...
2235 if (Reachable.size() == F.size())
2238 assert(Reachable.size() < F.size());
2239 NumRemoved += F.size()-Reachable.size();
2241 SmallSetVector<BasicBlock *, 8> DeadBlockSet;
2242 for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ++I) {
2244 if (Reachable.count(BB))
2246 DeadBlockSet.insert(BB);
2250 MSSAU->removeBlocks(DeadBlockSet);
2252 // Loop over all of the basic blocks that are not reachable, dropping all of
2253 // their internal references. Update DTU and LVI if available.
2254 std::vector<DominatorTree::UpdateType> Updates;
2255 for (auto *BB : DeadBlockSet) {
2256 for (BasicBlock *Successor : successors(BB)) {
2257 if (!DeadBlockSet.count(Successor))
2258 Successor->removePredecessor(BB);
2260 Updates.push_back({DominatorTree::Delete, BB, Successor});
2263 LVI->eraseBlock(BB);
2264 BB->dropAllReferences();
2266 for (Function::iterator I = ++F.begin(); I != F.end();) {
2268 if (Reachable.count(BB)) {
2273 // Remove the terminator of BB to clear the successor list of BB.
2274 if (BB->getTerminator())
2275 BB->getInstList().pop_back();
2276 new UnreachableInst(BB->getContext(), BB);
2277 assert(succ_empty(BB) && "The successor list of BB isn't empty before "
2278 "applying corresponding DTU updates.");
2281 I = F.getBasicBlockList().erase(I);
2286 DTU->applyUpdatesPermissive(Updates);
2287 bool Deleted = false;
2288 for (auto *BB : DeadBlockSet) {
2289 if (DTU->isBBPendingDeletion(BB))
2301 void llvm::combineMetadata(Instruction *K, const Instruction *J,
2302 ArrayRef<unsigned> KnownIDs, bool DoesKMove) {
2303 SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
2304 K->dropUnknownNonDebugMetadata(KnownIDs);
2305 K->getAllMetadataOtherThanDebugLoc(Metadata);
2306 for (const auto &MD : Metadata) {
2307 unsigned Kind = MD.first;
2308 MDNode *JMD = J->getMetadata(Kind);
2309 MDNode *KMD = MD.second;
2313 K->setMetadata(Kind, nullptr); // Remove unknown metadata
2315 case LLVMContext::MD_dbg:
2316 llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
2317 case LLVMContext::MD_tbaa:
2318 K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
2320 case LLVMContext::MD_alias_scope:
2321 K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
2323 case LLVMContext::MD_noalias:
2324 case LLVMContext::MD_mem_parallel_loop_access:
2325 K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
2327 case LLVMContext::MD_access_group:
2328 K->setMetadata(LLVMContext::MD_access_group,
2329 intersectAccessGroups(K, J));
2331 case LLVMContext::MD_range:
2333 // If K does move, use most generic range. Otherwise keep the range of
2336 // FIXME: If K does move, we should drop the range info and nonnull.
2337 // Currently this function is used with DoesKMove in passes
2338 // doing hoisting/sinking and the current behavior of using the
2339 // most generic range is correct in those cases.
2340 K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD));
2342 case LLVMContext::MD_fpmath:
2343 K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
2345 case LLVMContext::MD_invariant_load:
2346 // Only set the !invariant.load if it is present in both instructions.
2347 K->setMetadata(Kind, JMD);
2349 case LLVMContext::MD_nonnull:
2350 // If K does move, keep nonull if it is present in both instructions.
2352 K->setMetadata(Kind, JMD);
2354 case LLVMContext::MD_invariant_group:
2355 // Preserve !invariant.group in K.
2357 case LLVMContext::MD_align:
2358 K->setMetadata(Kind,
2359 MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD));
2361 case LLVMContext::MD_dereferenceable:
2362 case LLVMContext::MD_dereferenceable_or_null:
2363 K->setMetadata(Kind,
2364 MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD));
2368 // Set !invariant.group from J if J has it. If both instructions have it
2369 // then we will just pick it from J - even when they are different.
2370 // Also make sure that K is load or store - f.e. combining bitcast with load
2371 // could produce bitcast with invariant.group metadata, which is invalid.
2372 // FIXME: we should try to preserve both invariant.group md if they are
2373 // different, but right now instruction can only have one invariant.group.
2374 if (auto *JMD = J->getMetadata(LLVMContext::MD_invariant_group))
2375 if (isa<LoadInst>(K) || isa<StoreInst>(K))
2376 K->setMetadata(LLVMContext::MD_invariant_group, JMD);
2379 void llvm::combineMetadataForCSE(Instruction *K, const Instruction *J,
2381 unsigned KnownIDs[] = {
2382 LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
2383 LLVMContext::MD_noalias, LLVMContext::MD_range,
2384 LLVMContext::MD_invariant_load, LLVMContext::MD_nonnull,
2385 LLVMContext::MD_invariant_group, LLVMContext::MD_align,
2386 LLVMContext::MD_dereferenceable,
2387 LLVMContext::MD_dereferenceable_or_null,
2388 LLVMContext::MD_access_group};
2389 combineMetadata(K, J, KnownIDs, KDominatesJ);
2392 void llvm::patchReplacementInstruction(Instruction *I, Value *Repl) {
2393 auto *ReplInst = dyn_cast<Instruction>(Repl);
2397 // Patch the replacement so that it is not more restrictive than the value
2399 // Note that if 'I' is a load being replaced by some operation,
2400 // for example, by an arithmetic operation, then andIRFlags()
2401 // would just erase all math flags from the original arithmetic
2402 // operation, which is clearly not wanted and not needed.
2403 if (!isa<LoadInst>(I))
2404 ReplInst->andIRFlags(I);
2406 // FIXME: If both the original and replacement value are part of the
2407 // same control-flow region (meaning that the execution of one
2408 // guarantees the execution of the other), then we can combine the
2409 // noalias scopes here and do better than the general conservative
2410 // answer used in combineMetadata().
2412 // In general, GVN unifies expressions over different control-flow
2413 // regions, and so we need a conservative combination of the noalias
2415 static const unsigned KnownIDs[] = {
2416 LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
2417 LLVMContext::MD_noalias, LLVMContext::MD_range,
2418 LLVMContext::MD_fpmath, LLVMContext::MD_invariant_load,
2419 LLVMContext::MD_invariant_group, LLVMContext::MD_nonnull,
2420 LLVMContext::MD_access_group};
2421 combineMetadata(ReplInst, I, KnownIDs, false);
2424 template <typename RootType, typename DominatesFn>
2425 static unsigned replaceDominatedUsesWith(Value *From, Value *To,
2426 const RootType &Root,
2427 const DominatesFn &Dominates) {
2428 assert(From->getType() == To->getType());
2431 for (Value::use_iterator UI = From->use_begin(), UE = From->use_end();
2434 if (!Dominates(Root, U))
2437 LLVM_DEBUG(dbgs() << "Replace dominated use of '" << From->getName()
2438 << "' as " << *To << " in " << *U << "\n");
2444 unsigned llvm::replaceNonLocalUsesWith(Instruction *From, Value *To) {
2445 assert(From->getType() == To->getType());
2446 auto *BB = From->getParent();
2449 for (Value::use_iterator UI = From->use_begin(), UE = From->use_end();
2452 auto *I = cast<Instruction>(U.getUser());
2453 if (I->getParent() == BB)
2461 unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
2463 const BasicBlockEdge &Root) {
2464 auto Dominates = [&DT](const BasicBlockEdge &Root, const Use &U) {
2465 return DT.dominates(Root, U);
2467 return ::replaceDominatedUsesWith(From, To, Root, Dominates);
2470 unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
2472 const BasicBlock *BB) {
2473 auto ProperlyDominates = [&DT](const BasicBlock *BB, const Use &U) {
2474 auto *I = cast<Instruction>(U.getUser())->getParent();
2475 return DT.properlyDominates(BB, I);
2477 return ::replaceDominatedUsesWith(From, To, BB, ProperlyDominates);
2480 bool llvm::callsGCLeafFunction(const CallBase *Call,
2481 const TargetLibraryInfo &TLI) {
2482 // Check if the function is specifically marked as a gc leaf function.
2483 if (Call->hasFnAttr("gc-leaf-function"))
2485 if (const Function *F = Call->getCalledFunction()) {
2486 if (F->hasFnAttribute("gc-leaf-function"))
2489 if (auto IID = F->getIntrinsicID())
2490 // Most LLVM intrinsics do not take safepoints.
2491 return IID != Intrinsic::experimental_gc_statepoint &&
2492 IID != Intrinsic::experimental_deoptimize;
2495 // Lib calls can be materialized by some passes, and won't be
2496 // marked as 'gc-leaf-function.' All available Libcalls are
2499 if (TLI.getLibFunc(ImmutableCallSite(Call), LF)) {
2506 void llvm::copyNonnullMetadata(const LoadInst &OldLI, MDNode *N,
2508 auto *NewTy = NewLI.getType();
2510 // This only directly applies if the new type is also a pointer.
2511 if (NewTy->isPointerTy()) {
2512 NewLI.setMetadata(LLVMContext::MD_nonnull, N);
2516 // The only other translation we can do is to integral loads with !range
2518 if (!NewTy->isIntegerTy())
2521 MDBuilder MDB(NewLI.getContext());
2522 const Value *Ptr = OldLI.getPointerOperand();
2523 auto *ITy = cast<IntegerType>(NewTy);
2524 auto *NullInt = ConstantExpr::getPtrToInt(
2525 ConstantPointerNull::get(cast<PointerType>(Ptr->getType())), ITy);
2526 auto *NonNullInt = ConstantExpr::getAdd(NullInt, ConstantInt::get(ITy, 1));
2527 NewLI.setMetadata(LLVMContext::MD_range,
2528 MDB.createRange(NonNullInt, NullInt));
2531 void llvm::copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI,
2532 MDNode *N, LoadInst &NewLI) {
2533 auto *NewTy = NewLI.getType();
2535 // Give up unless it is converted to a pointer where there is a single very
2536 // valuable mapping we can do reliably.
2537 // FIXME: It would be nice to propagate this in more ways, but the type
2538 // conversions make it hard.
2539 if (!NewTy->isPointerTy())
2542 unsigned BitWidth = DL.getIndexTypeSizeInBits(NewTy);
2543 if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
2544 MDNode *NN = MDNode::get(OldLI.getContext(), None);
2545 NewLI.setMetadata(LLVMContext::MD_nonnull, NN);
2549 void llvm::dropDebugUsers(Instruction &I) {
2550 SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
2551 findDbgUsers(DbgUsers, &I);
2552 for (auto *DII : DbgUsers)
2553 DII->eraseFromParent();
2556 void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
2558 // Since we are moving the instructions out of its basic block, we do not
2559 // retain their original debug locations (DILocations) and debug intrinsic
2562 // Doing so would degrade the debugging experience and adversely affect the
2563 // accuracy of profiling information.
2565 // Currently, when hoisting the instructions, we take the following actions:
2566 // - Remove their debug intrinsic instructions.
2567 // - Set their debug locations to the values from the insertion point.
2569 // As per PR39141 (comment #8), the more fundamental reason why the dbg.values
2570 // need to be deleted, is because there will not be any instructions with a
2571 // DILocation in either branch left after performing the transformation. We
2572 // can only insert a dbg.value after the two branches are joined again.
2574 // See PR38762, PR39243 for more details.
2576 // TODO: Extend llvm.dbg.value to take more than one SSA Value (PR39141) to
2577 // encode predicated DIExpressions that yield different results on different
2579 for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) {
2580 Instruction *I = &*II;
2581 I->dropUnknownNonDebugMetadata();
2582 if (I->isUsedByMetadata())
2584 if (isa<DbgInfoIntrinsic>(I)) {
2585 // Remove DbgInfo Intrinsics.
2586 II = I->eraseFromParent();
2589 I->setDebugLoc(InsertPt->getDebugLoc());
2592 DomBlock->getInstList().splice(InsertPt->getIterator(), BB->getInstList(),
2594 BB->getTerminator()->getIterator());
2599 /// A potential constituent of a bitreverse or bswap expression. See
2600 /// collectBitParts for a fuller explanation.
2602 BitPart(Value *P, unsigned BW) : Provider(P) {
2603 Provenance.resize(BW);
2606 /// The Value that this is a bitreverse/bswap of.
2609 /// The "provenance" of each bit. Provenance[A] = B means that bit A
2610 /// in Provider becomes bit B in the result of this expression.
2611 SmallVector<int8_t, 32> Provenance; // int8_t means max size is i128.
2613 enum { Unset = -1 };
2616 } // end anonymous namespace
2618 /// Analyze the specified subexpression and see if it is capable of providing
2619 /// pieces of a bswap or bitreverse. The subexpression provides a potential
2620 /// piece of a bswap or bitreverse if it can be proven that each non-zero bit in
2621 /// the output of the expression came from a corresponding bit in some other
2622 /// value. This function is recursive, and the end result is a mapping of
2623 /// bitnumber to bitnumber. It is the caller's responsibility to validate that
2624 /// the bitnumber to bitnumber mapping is correct for a bswap or bitreverse.
2626 /// For example, if the current subexpression if "(shl i32 %X, 24)" then we know
2627 /// that the expression deposits the low byte of %X into the high byte of the
2628 /// result and that all other bits are zero. This expression is accepted and a
2629 /// BitPart is returned with Provider set to %X and Provenance[24-31] set to
2632 /// To avoid revisiting values, the BitPart results are memoized into the
2633 /// provided map. To avoid unnecessary copying of BitParts, BitParts are
2634 /// constructed in-place in the \c BPS map. Because of this \c BPS needs to
2635 /// store BitParts objects, not pointers. As we need the concept of a nullptr
2636 /// BitParts (Value has been analyzed and the analysis failed), we an Optional
2637 /// type instead to provide the same functionality.
2639 /// Because we pass around references into \c BPS, we must use a container that
2640 /// does not invalidate internal references (std::map instead of DenseMap).
2641 static const Optional<BitPart> &
2642 collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals,
2643 std::map<Value *, Optional<BitPart>> &BPS, int Depth) {
2644 auto I = BPS.find(V);
2648 auto &Result = BPS[V] = None;
2649 auto BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
2651 // Prevent stack overflow by limiting the recursion depth
2652 if (Depth == BitPartRecursionMaxDepth) {
2653 LLVM_DEBUG(dbgs() << "collectBitParts max recursion depth reached.\n");
2657 if (Instruction *I = dyn_cast<Instruction>(V)) {
2658 // If this is an or instruction, it may be an inner node of the bswap.
2659 if (I->getOpcode() == Instruction::Or) {
2660 auto &A = collectBitParts(I->getOperand(0), MatchBSwaps,
2661 MatchBitReversals, BPS, Depth + 1);
2662 auto &B = collectBitParts(I->getOperand(1), MatchBSwaps,
2663 MatchBitReversals, BPS, Depth + 1);
2667 // Try and merge the two together.
2668 if (!A->Provider || A->Provider != B->Provider)
2671 Result = BitPart(A->Provider, BitWidth);
2672 for (unsigned i = 0; i < A->Provenance.size(); ++i) {
2673 if (A->Provenance[i] != BitPart::Unset &&
2674 B->Provenance[i] != BitPart::Unset &&
2675 A->Provenance[i] != B->Provenance[i])
2676 return Result = None;
2678 if (A->Provenance[i] == BitPart::Unset)
2679 Result->Provenance[i] = B->Provenance[i];
2681 Result->Provenance[i] = A->Provenance[i];
2687 // If this is a logical shift by a constant, recurse then shift the result.
2688 if (I->isLogicalShift() && isa<ConstantInt>(I->getOperand(1))) {
2690 cast<ConstantInt>(I->getOperand(1))->getLimitedValue(~0U);
2691 // Ensure the shift amount is defined.
2692 if (BitShift > BitWidth)
2695 auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
2696 MatchBitReversals, BPS, Depth + 1);
2701 // Perform the "shift" on BitProvenance.
2702 auto &P = Result->Provenance;
2703 if (I->getOpcode() == Instruction::Shl) {
2704 P.erase(std::prev(P.end(), BitShift), P.end());
2705 P.insert(P.begin(), BitShift, BitPart::Unset);
2707 P.erase(P.begin(), std::next(P.begin(), BitShift));
2708 P.insert(P.end(), BitShift, BitPart::Unset);
2714 // If this is a logical 'and' with a mask that clears bits, recurse then
2715 // unset the appropriate bits.
2716 if (I->getOpcode() == Instruction::And &&
2717 isa<ConstantInt>(I->getOperand(1))) {
2718 APInt Bit(I->getType()->getPrimitiveSizeInBits(), 1);
2719 const APInt &AndMask = cast<ConstantInt>(I->getOperand(1))->getValue();
2721 // Check that the mask allows a multiple of 8 bits for a bswap, for an
2723 unsigned NumMaskedBits = AndMask.countPopulation();
2724 if (!MatchBitReversals && NumMaskedBits % 8 != 0)
2727 auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
2728 MatchBitReversals, BPS, Depth + 1);
2733 for (unsigned i = 0; i < BitWidth; ++i, Bit <<= 1)
2734 // If the AndMask is zero for this bit, clear the bit.
2735 if ((AndMask & Bit) == 0)
2736 Result->Provenance[i] = BitPart::Unset;
2740 // If this is a zext instruction zero extend the result.
2741 if (I->getOpcode() == Instruction::ZExt) {
2742 auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
2743 MatchBitReversals, BPS, Depth + 1);
2747 Result = BitPart(Res->Provider, BitWidth);
2748 auto NarrowBitWidth =
2749 cast<IntegerType>(cast<ZExtInst>(I)->getSrcTy())->getBitWidth();
2750 for (unsigned i = 0; i < NarrowBitWidth; ++i)
2751 Result->Provenance[i] = Res->Provenance[i];
2752 for (unsigned i = NarrowBitWidth; i < BitWidth; ++i)
2753 Result->Provenance[i] = BitPart::Unset;
2758 // Okay, we got to something that isn't a shift, 'or' or 'and'. This must be
2759 // the input value to the bswap/bitreverse.
2760 Result = BitPart(V, BitWidth);
2761 for (unsigned i = 0; i < BitWidth; ++i)
2762 Result->Provenance[i] = i;
2766 static bool bitTransformIsCorrectForBSwap(unsigned From, unsigned To,
2767 unsigned BitWidth) {
2768 if (From % 8 != To % 8)
2770 // Convert from bit indices to byte indices and check for a byte reversal.
2774 return From == BitWidth - To - 1;
2777 static bool bitTransformIsCorrectForBitReverse(unsigned From, unsigned To,
2778 unsigned BitWidth) {
2779 return From == BitWidth - To - 1;
2782 bool llvm::recognizeBSwapOrBitReverseIdiom(
2783 Instruction *I, bool MatchBSwaps, bool MatchBitReversals,
2784 SmallVectorImpl<Instruction *> &InsertedInsts) {
2785 if (Operator::getOpcode(I) != Instruction::Or)
2787 if (!MatchBSwaps && !MatchBitReversals)
2789 IntegerType *ITy = dyn_cast<IntegerType>(I->getType());
2790 if (!ITy || ITy->getBitWidth() > 128)
2791 return false; // Can't do vectors or integers > 128 bits.
2792 unsigned BW = ITy->getBitWidth();
2794 unsigned DemandedBW = BW;
2795 IntegerType *DemandedTy = ITy;
2796 if (I->hasOneUse()) {
2797 if (TruncInst *Trunc = dyn_cast<TruncInst>(I->user_back())) {
2798 DemandedTy = cast<IntegerType>(Trunc->getType());
2799 DemandedBW = DemandedTy->getBitWidth();
2803 // Try to find all the pieces corresponding to the bswap.
2804 std::map<Value *, Optional<BitPart>> BPS;
2805 auto Res = collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS, 0);
2808 auto &BitProvenance = Res->Provenance;
2810 // Now, is the bit permutation correct for a bswap or a bitreverse? We can
2811 // only byteswap values with an even number of bytes.
2812 bool OKForBSwap = DemandedBW % 16 == 0, OKForBitReverse = true;
2813 for (unsigned i = 0; i < DemandedBW; ++i) {
2815 bitTransformIsCorrectForBSwap(BitProvenance[i], i, DemandedBW);
2817 bitTransformIsCorrectForBitReverse(BitProvenance[i], i, DemandedBW);
2820 Intrinsic::ID Intrin;
2821 if (OKForBSwap && MatchBSwaps)
2822 Intrin = Intrinsic::bswap;
2823 else if (OKForBitReverse && MatchBitReversals)
2824 Intrin = Intrinsic::bitreverse;
2828 if (ITy != DemandedTy) {
2829 Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, DemandedTy);
2830 Value *Provider = Res->Provider;
2831 IntegerType *ProviderTy = cast<IntegerType>(Provider->getType());
2832 // We may need to truncate the provider.
2833 if (DemandedTy != ProviderTy) {
2834 auto *Trunc = CastInst::Create(Instruction::Trunc, Provider, DemandedTy,
2836 InsertedInsts.push_back(Trunc);
2839 auto *CI = CallInst::Create(F, Provider, "rev", I);
2840 InsertedInsts.push_back(CI);
2841 auto *ExtInst = CastInst::Create(Instruction::ZExt, CI, ITy, "zext", I);
2842 InsertedInsts.push_back(ExtInst);
2846 Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, ITy);
2847 InsertedInsts.push_back(CallInst::Create(F, Res->Provider, "rev", I));
2851 // CodeGen has special handling for some string functions that may replace
2852 // them with target-specific intrinsics. Since that'd skip our interceptors
2853 // in ASan/MSan/TSan/DFSan, and thus make us miss some memory accesses,
2854 // we mark affected calls as NoBuiltin, which will disable optimization
2856 void llvm::maybeMarkSanitizerLibraryCallNoBuiltin(
2857 CallInst *CI, const TargetLibraryInfo *TLI) {
2858 Function *F = CI->getCalledFunction();
2860 if (F && !F->hasLocalLinkage() && F->hasName() &&
2861 TLI->getLibFunc(F->getName(), Func) && TLI->hasOptimizedCodeGen(Func) &&
2862 !F->doesNotAccessMemory())
2863 CI->addAttribute(AttributeList::FunctionIndex, Attribute::NoBuiltin);
2866 bool llvm::canReplaceOperandWithVariable(const Instruction *I, unsigned OpIdx) {
2867 // We can't have a PHI with a metadata type.
2868 if (I->getOperand(OpIdx)->getType()->isMetadataTy())
2872 if (!isa<Constant>(I->getOperand(OpIdx)))
2875 switch (I->getOpcode()) {
2878 case Instruction::Call:
2879 case Instruction::Invoke:
2880 // Can't handle inline asm. Skip it.
2881 if (isa<InlineAsm>(ImmutableCallSite(I).getCalledValue()))
2883 // Many arithmetic intrinsics have no issue taking a
2884 // variable, however it's hard to distingish these from
2885 // specials such as @llvm.frameaddress that require a constant.
2886 if (isa<IntrinsicInst>(I))
2889 // Constant bundle operands may need to retain their constant-ness for
2891 if (ImmutableCallSite(I).isBundleOperand(OpIdx))
2894 case Instruction::ShuffleVector:
2895 // Shufflevector masks are constant.
2897 case Instruction::Switch:
2898 case Instruction::ExtractValue:
2899 // All operands apart from the first are constant.
2901 case Instruction::InsertValue:
2902 // All operands apart from the first and the second are constant.
2904 case Instruction::Alloca:
2905 // Static allocas (constant size in the entry block) are handled by
2906 // prologue/epilogue insertion so they're free anyway. We definitely don't
2907 // want to make them non-constant.
2908 return !cast<AllocaInst>(I)->isStaticAlloca();
2909 case Instruction::GetElementPtr:
2912 gep_type_iterator It = gep_type_begin(I);
2913 for (auto E = std::next(It, OpIdx); It != E; ++It)
2920 using AllocaForValueMapTy = DenseMap<Value *, AllocaInst *>;
2921 AllocaInst *llvm::findAllocaForValue(Value *V,
2922 AllocaForValueMapTy &AllocaForValue) {
2923 if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
2925 // See if we've already calculated (or started to calculate) alloca for a
2927 AllocaForValueMapTy::iterator I = AllocaForValue.find(V);
2928 if (I != AllocaForValue.end())
2930 // Store 0 while we're calculating alloca for value V to avoid
2931 // infinite recursion if the value references itself.
2932 AllocaForValue[V] = nullptr;
2933 AllocaInst *Res = nullptr;
2934 if (CastInst *CI = dyn_cast<CastInst>(V))
2935 Res = findAllocaForValue(CI->getOperand(0), AllocaForValue);
2936 else if (PHINode *PN = dyn_cast<PHINode>(V)) {
2937 for (Value *IncValue : PN->incoming_values()) {
2938 // Allow self-referencing phi-nodes.
2941 AllocaInst *IncValueAI = findAllocaForValue(IncValue, AllocaForValue);
2942 // AI for incoming values should exist and should all be equal.
2943 if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res))
2947 } else if (GetElementPtrInst *EP = dyn_cast<GetElementPtrInst>(V)) {
2948 Res = findAllocaForValue(EP->getPointerOperand(), AllocaForValue);
2950 LLVM_DEBUG(dbgs() << "Alloca search cancelled on unknown instruction: "
2954 AllocaForValue[V] = Res;