1 //===-- Local.cpp - Functions to perform local transformations ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This family of functions perform various local transformations to the
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Utils/Local.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/SmallPtrSet.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/Analysis/InstructionSimplify.h"
21 #include "llvm/Analysis/LibCallSemantics.h"
22 #include "llvm/Analysis/MemoryBuiltins.h"
23 #include "llvm/Analysis/ValueTracking.h"
24 #include "llvm/IR/CFG.h"
25 #include "llvm/IR/Constants.h"
26 #include "llvm/IR/DIBuilder.h"
27 #include "llvm/IR/DataLayout.h"
28 #include "llvm/IR/DebugInfo.h"
29 #include "llvm/IR/DerivedTypes.h"
30 #include "llvm/IR/Dominators.h"
31 #include "llvm/IR/GetElementPtrTypeIterator.h"
32 #include "llvm/IR/GlobalAlias.h"
33 #include "llvm/IR/GlobalVariable.h"
34 #include "llvm/IR/IRBuilder.h"
35 #include "llvm/IR/Instructions.h"
36 #include "llvm/IR/IntrinsicInst.h"
37 #include "llvm/IR/Intrinsics.h"
38 #include "llvm/IR/MDBuilder.h"
39 #include "llvm/IR/Metadata.h"
40 #include "llvm/IR/Operator.h"
41 #include "llvm/IR/ValueHandle.h"
42 #include "llvm/Support/Debug.h"
43 #include "llvm/Support/MathExtras.h"
44 #include "llvm/Support/raw_ostream.h"
47 #define DEBUG_TYPE "local"
49 STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
51 //===----------------------------------------------------------------------===//
52 // Local constant propagation.
55 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
56 /// constant value, convert it into an unconditional branch to the constant
57 /// destination. This is a nontrivial operation because the successors of this
58 /// basic block must have their PHI nodes updated.
59 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
60 /// conditions and indirectbr addresses this might make dead if
61 /// DeleteDeadConditions is true.
62 bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
63 const TargetLibraryInfo *TLI) {
64 TerminatorInst *T = BB->getTerminator();
65 IRBuilder<> Builder(T);
67 // Branch - See if we are conditional jumping on constant
68 if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
69 if (BI->isUnconditional()) return false; // Can't optimize uncond branch
70 BasicBlock *Dest1 = BI->getSuccessor(0);
71 BasicBlock *Dest2 = BI->getSuccessor(1);
73 if (ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
74 // Are we branching on constant?
75 // YES. Change to unconditional branch...
76 BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
77 BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
79 //cerr << "Function: " << T->getParent()->getParent()
80 // << "\nRemoving branch from " << T->getParent()
81 // << "\n\nTo: " << OldDest << endl;
83 // Let the basic block know that we are letting go of it. Based on this,
84 // it will adjust it's PHI nodes.
85 OldDest->removePredecessor(BB);
87 // Replace the conditional branch with an unconditional one.
88 Builder.CreateBr(Destination);
89 BI->eraseFromParent();
93 if (Dest2 == Dest1) { // Conditional branch to same location?
94 // This branch matches something like this:
95 // br bool %cond, label %Dest, label %Dest
96 // and changes it into: br label %Dest
98 // Let the basic block know that we are letting go of one copy of it.
99 assert(BI->getParent() && "Terminator not inserted in block!");
100 Dest1->removePredecessor(BI->getParent());
102 // Replace the conditional branch with an unconditional one.
103 Builder.CreateBr(Dest1);
104 Value *Cond = BI->getCondition();
105 BI->eraseFromParent();
106 if (DeleteDeadConditions)
107 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
113 if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
114 // If we are switching on a constant, we can convert the switch to an
115 // unconditional branch.
116 ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
117 BasicBlock *DefaultDest = SI->getDefaultDest();
118 BasicBlock *TheOnlyDest = DefaultDest;
120 // If the default is unreachable, ignore it when searching for TheOnlyDest.
121 if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) &&
122 SI->getNumCases() > 0) {
123 TheOnlyDest = SI->case_begin().getCaseSuccessor();
126 // Figure out which case it goes to.
127 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
129 // Found case matching a constant operand?
130 if (i.getCaseValue() == CI) {
131 TheOnlyDest = i.getCaseSuccessor();
135 // Check to see if this branch is going to the same place as the default
136 // dest. If so, eliminate it as an explicit compare.
137 if (i.getCaseSuccessor() == DefaultDest) {
138 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
139 unsigned NCases = SI->getNumCases();
140 // Fold the case metadata into the default if there will be any branches
141 // left, unless the metadata doesn't match the switch.
142 if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) {
143 // Collect branch weights into a vector.
144 SmallVector<uint32_t, 8> Weights;
145 for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;
148 mdconst::dyn_extract<ConstantInt>(MD->getOperand(MD_i));
150 Weights.push_back(CI->getValue().getZExtValue());
152 // Merge weight of this case to the default weight.
153 unsigned idx = i.getCaseIndex();
154 Weights[0] += Weights[idx+1];
155 // Remove weight for this case.
156 std::swap(Weights[idx+1], Weights.back());
158 SI->setMetadata(LLVMContext::MD_prof,
159 MDBuilder(BB->getContext()).
160 createBranchWeights(Weights));
162 // Remove this entry.
163 DefaultDest->removePredecessor(SI->getParent());
169 // Otherwise, check to see if the switch only branches to one destination.
170 // We do this by reseting "TheOnlyDest" to null when we find two non-equal
172 if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = nullptr;
175 if (CI && !TheOnlyDest) {
176 // Branching on a constant, but not any of the cases, go to the default
178 TheOnlyDest = SI->getDefaultDest();
181 // If we found a single destination that we can fold the switch into, do so
184 // Insert the new branch.
185 Builder.CreateBr(TheOnlyDest);
186 BasicBlock *BB = SI->getParent();
188 // Remove entries from PHI nodes which we no longer branch to...
189 for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {
190 // Found case matching a constant operand?
191 BasicBlock *Succ = SI->getSuccessor(i);
192 if (Succ == TheOnlyDest)
193 TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest
195 Succ->removePredecessor(BB);
198 // Delete the old switch.
199 Value *Cond = SI->getCondition();
200 SI->eraseFromParent();
201 if (DeleteDeadConditions)
202 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
206 if (SI->getNumCases() == 1) {
207 // Otherwise, we can fold this switch into a conditional branch
208 // instruction if it has only one non-default destination.
209 SwitchInst::CaseIt FirstCase = SI->case_begin();
210 Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
211 FirstCase.getCaseValue(), "cond");
213 // Insert the new branch.
214 BranchInst *NewBr = Builder.CreateCondBr(Cond,
215 FirstCase.getCaseSuccessor(),
216 SI->getDefaultDest());
217 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
218 if (MD && MD->getNumOperands() == 3) {
219 ConstantInt *SICase =
220 mdconst::dyn_extract<ConstantInt>(MD->getOperand(2));
222 mdconst::dyn_extract<ConstantInt>(MD->getOperand(1));
223 assert(SICase && SIDef);
224 // The TrueWeight should be the weight for the single case of SI.
225 NewBr->setMetadata(LLVMContext::MD_prof,
226 MDBuilder(BB->getContext()).
227 createBranchWeights(SICase->getValue().getZExtValue(),
228 SIDef->getValue().getZExtValue()));
231 // Delete the old switch.
232 SI->eraseFromParent();
238 if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(T)) {
239 // indirectbr blockaddress(@F, @BB) -> br label @BB
240 if (BlockAddress *BA =
241 dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
242 BasicBlock *TheOnlyDest = BA->getBasicBlock();
243 // Insert the new branch.
244 Builder.CreateBr(TheOnlyDest);
246 for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
247 if (IBI->getDestination(i) == TheOnlyDest)
248 TheOnlyDest = nullptr;
250 IBI->getDestination(i)->removePredecessor(IBI->getParent());
252 Value *Address = IBI->getAddress();
253 IBI->eraseFromParent();
254 if (DeleteDeadConditions)
255 RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
257 // If we didn't find our destination in the IBI successor list, then we
258 // have undefined behavior. Replace the unconditional branch with an
259 // 'unreachable' instruction.
261 BB->getTerminator()->eraseFromParent();
262 new UnreachableInst(BB->getContext(), BB);
273 //===----------------------------------------------------------------------===//
274 // Local dead code elimination.
277 /// isInstructionTriviallyDead - Return true if the result produced by the
278 /// instruction is not used, and the instruction has no side effects.
280 bool llvm::isInstructionTriviallyDead(Instruction *I,
281 const TargetLibraryInfo *TLI) {
282 if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
284 // We don't want the landingpad instruction removed by anything this general.
285 if (isa<LandingPadInst>(I))
288 // We don't want debug info removed by anything this general, unless
289 // debug info is empty.
290 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
291 if (DDI->getAddress())
295 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
301 if (!I->mayHaveSideEffects()) return true;
303 // Special case intrinsics that "may have side effects" but can be deleted
305 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
306 // Safe to delete llvm.stacksave if dead.
307 if (II->getIntrinsicID() == Intrinsic::stacksave)
310 // Lifetime intrinsics are dead when their right-hand is undef.
311 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
312 II->getIntrinsicID() == Intrinsic::lifetime_end)
313 return isa<UndefValue>(II->getArgOperand(1));
315 // Assumptions are dead if their condition is trivially true.
316 if (II->getIntrinsicID() == Intrinsic::assume) {
317 if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0)))
318 return !Cond->isZero();
324 if (isAllocLikeFn(I, TLI)) return true;
326 if (CallInst *CI = isFreeCall(I, TLI))
327 if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
328 return C->isNullValue() || isa<UndefValue>(C);
333 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
334 /// trivially dead instruction, delete it. If that makes any of its operands
335 /// trivially dead, delete them too, recursively. Return true if any
336 /// instructions were deleted.
338 llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V,
339 const TargetLibraryInfo *TLI) {
340 Instruction *I = dyn_cast<Instruction>(V);
341 if (!I || !I->use_empty() || !isInstructionTriviallyDead(I, TLI))
344 SmallVector<Instruction*, 16> DeadInsts;
345 DeadInsts.push_back(I);
348 I = DeadInsts.pop_back_val();
350 // Null out all of the instruction's operands to see if any operand becomes
352 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
353 Value *OpV = I->getOperand(i);
354 I->setOperand(i, nullptr);
356 if (!OpV->use_empty()) continue;
358 // If the operand is an instruction that became dead as we nulled out the
359 // operand, and if it is 'trivially' dead, delete it in a future loop
361 if (Instruction *OpI = dyn_cast<Instruction>(OpV))
362 if (isInstructionTriviallyDead(OpI, TLI))
363 DeadInsts.push_back(OpI);
366 I->eraseFromParent();
367 } while (!DeadInsts.empty());
372 /// areAllUsesEqual - Check whether the uses of a value are all the same.
373 /// This is similar to Instruction::hasOneUse() except this will also return
374 /// true when there are no uses or multiple uses that all refer to the same
376 static bool areAllUsesEqual(Instruction *I) {
377 Value::user_iterator UI = I->user_begin();
378 Value::user_iterator UE = I->user_end();
383 for (++UI; UI != UE; ++UI) {
390 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
391 /// dead PHI node, due to being a def-use chain of single-use nodes that
392 /// either forms a cycle or is terminated by a trivially dead instruction,
393 /// delete it. If that makes any of its operands trivially dead, delete them
394 /// too, recursively. Return true if a change was made.
395 bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN,
396 const TargetLibraryInfo *TLI) {
397 SmallPtrSet<Instruction*, 4> Visited;
398 for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
399 I = cast<Instruction>(*I->user_begin())) {
401 return RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
403 // If we find an instruction more than once, we're on a cycle that
404 // won't prove fruitful.
405 if (!Visited.insert(I).second) {
406 // Break the cycle and delete the instruction and its operands.
407 I->replaceAllUsesWith(UndefValue::get(I->getType()));
408 (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
415 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
416 /// simplify any instructions in it and recursively delete dead instructions.
418 /// This returns true if it changed the code, note that it can delete
419 /// instructions in other blocks as well in this block.
420 bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB,
421 const TargetLibraryInfo *TLI) {
422 bool MadeChange = false;
425 // In debug builds, ensure that the terminator of the block is never replaced
426 // or deleted by these simplifications. The idea of simplification is that it
427 // cannot introduce new instructions, and there is no way to replace the
428 // terminator of a block without introducing a new instruction.
429 AssertingVH<Instruction> TerminatorVH(--BB->end());
432 for (BasicBlock::iterator BI = BB->begin(), E = --BB->end(); BI != E; ) {
433 assert(!BI->isTerminator());
434 Instruction *Inst = BI++;
437 if (recursivelySimplifyInstruction(Inst, TLI)) {
444 MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI);
451 //===----------------------------------------------------------------------===//
452 // Control Flow Graph Restructuring.
456 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
457 /// method is called when we're about to delete Pred as a predecessor of BB. If
458 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
460 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
461 /// nodes that collapse into identity values. For example, if we have:
462 /// x = phi(1, 0, 0, 0)
465 /// .. and delete the predecessor corresponding to the '1', this will attempt to
466 /// recursively fold the and to 0.
467 void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred) {
468 // This only adjusts blocks with PHI nodes.
469 if (!isa<PHINode>(BB->begin()))
472 // Remove the entries for Pred from the PHI nodes in BB, but do not simplify
473 // them down. This will leave us with single entry phi nodes and other phis
474 // that can be removed.
475 BB->removePredecessor(Pred, true);
477 WeakVH PhiIt = &BB->front();
478 while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
479 PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
480 Value *OldPhiIt = PhiIt;
482 if (!recursivelySimplifyInstruction(PN))
485 // If recursive simplification ended up deleting the next PHI node we would
486 // iterate to, then our iterator is invalid, restart scanning from the top
488 if (PhiIt != OldPhiIt) PhiIt = &BB->front();
493 /// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
494 /// predecessor is known to have one successor (DestBB!). Eliminate the edge
495 /// between them, moving the instructions in the predecessor into DestBB and
496 /// deleting the predecessor block.
498 void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT) {
499 // If BB has single-entry PHI nodes, fold them.
500 while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
501 Value *NewVal = PN->getIncomingValue(0);
502 // Replace self referencing PHI with undef, it must be dead.
503 if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
504 PN->replaceAllUsesWith(NewVal);
505 PN->eraseFromParent();
508 BasicBlock *PredBB = DestBB->getSinglePredecessor();
509 assert(PredBB && "Block doesn't have a single predecessor!");
511 // Zap anything that took the address of DestBB. Not doing this will give the
512 // address an invalid value.
513 if (DestBB->hasAddressTaken()) {
514 BlockAddress *BA = BlockAddress::get(DestBB);
515 Constant *Replacement =
516 ConstantInt::get(llvm::Type::getInt32Ty(BA->getContext()), 1);
517 BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
519 BA->destroyConstant();
522 // Anything that branched to PredBB now branches to DestBB.
523 PredBB->replaceAllUsesWith(DestBB);
525 // Splice all the instructions from PredBB to DestBB.
526 PredBB->getTerminator()->eraseFromParent();
527 DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
529 // If the PredBB is the entry block of the function, move DestBB up to
530 // become the entry block after we erase PredBB.
531 if (PredBB == &DestBB->getParent()->getEntryBlock())
532 DestBB->moveAfter(PredBB);
535 BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
536 DT->changeImmediateDominator(DestBB, PredBBIDom);
537 DT->eraseNode(PredBB);
540 PredBB->eraseFromParent();
543 /// CanMergeValues - Return true if we can choose one of these values to use
544 /// in place of the other. Note that we will always choose the non-undef
546 static bool CanMergeValues(Value *First, Value *Second) {
547 return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second);
550 /// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
551 /// almost-empty BB ending in an unconditional branch to Succ, into Succ.
553 /// Assumption: Succ is the single successor for BB.
555 static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
556 assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
558 DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
559 << Succ->getName() << "\n");
560 // Shortcut, if there is only a single predecessor it must be BB and merging
562 if (Succ->getSinglePredecessor()) return true;
564 // Make a list of the predecessors of BB
565 SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
567 // Look at all the phi nodes in Succ, to see if they present a conflict when
568 // merging these blocks
569 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
570 PHINode *PN = cast<PHINode>(I);
572 // If the incoming value from BB is again a PHINode in
573 // BB which has the same incoming value for *PI as PN does, we can
574 // merge the phi nodes and then the blocks can still be merged
575 PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
576 if (BBPN && BBPN->getParent() == BB) {
577 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
578 BasicBlock *IBB = PN->getIncomingBlock(PI);
579 if (BBPreds.count(IBB) &&
580 !CanMergeValues(BBPN->getIncomingValueForBlock(IBB),
581 PN->getIncomingValue(PI))) {
582 DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
583 << Succ->getName() << " is conflicting with "
584 << BBPN->getName() << " with regard to common predecessor "
585 << IBB->getName() << "\n");
590 Value* Val = PN->getIncomingValueForBlock(BB);
591 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
592 // See if the incoming value for the common predecessor is equal to the
593 // one for BB, in which case this phi node will not prevent the merging
595 BasicBlock *IBB = PN->getIncomingBlock(PI);
596 if (BBPreds.count(IBB) &&
597 !CanMergeValues(Val, PN->getIncomingValue(PI))) {
598 DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
599 << Succ->getName() << " is conflicting with regard to common "
600 << "predecessor " << IBB->getName() << "\n");
610 typedef SmallVector<BasicBlock *, 16> PredBlockVector;
611 typedef DenseMap<BasicBlock *, Value *> IncomingValueMap;
613 /// \brief Determines the value to use as the phi node input for a block.
615 /// Select between \p OldVal any value that we know flows from \p BB
616 /// to a particular phi on the basis of which one (if either) is not
617 /// undef. Update IncomingValues based on the selected value.
619 /// \param OldVal The value we are considering selecting.
620 /// \param BB The block that the value flows in from.
621 /// \param IncomingValues A map from block-to-value for other phi inputs
622 /// that we have examined.
624 /// \returns the selected value.
625 static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB,
626 IncomingValueMap &IncomingValues) {
627 if (!isa<UndefValue>(OldVal)) {
628 assert((!IncomingValues.count(BB) ||
629 IncomingValues.find(BB)->second == OldVal) &&
630 "Expected OldVal to match incoming value from BB!");
632 IncomingValues.insert(std::make_pair(BB, OldVal));
636 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
637 if (It != IncomingValues.end()) return It->second;
642 /// \brief Create a map from block to value for the operands of a
645 /// Create a map from block to value for each non-undef value flowing
648 /// \param PN The phi we are collecting the map for.
649 /// \param IncomingValues [out] The map from block to value for this phi.
650 static void gatherIncomingValuesToPhi(PHINode *PN,
651 IncomingValueMap &IncomingValues) {
652 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
653 BasicBlock *BB = PN->getIncomingBlock(i);
654 Value *V = PN->getIncomingValue(i);
656 if (!isa<UndefValue>(V))
657 IncomingValues.insert(std::make_pair(BB, V));
661 /// \brief Replace the incoming undef values to a phi with the values
662 /// from a block-to-value map.
664 /// \param PN The phi we are replacing the undefs in.
665 /// \param IncomingValues A map from block to value.
666 static void replaceUndefValuesInPhi(PHINode *PN,
667 const IncomingValueMap &IncomingValues) {
668 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
669 Value *V = PN->getIncomingValue(i);
671 if (!isa<UndefValue>(V)) continue;
673 BasicBlock *BB = PN->getIncomingBlock(i);
674 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
675 if (It == IncomingValues.end()) continue;
677 PN->setIncomingValue(i, It->second);
681 /// \brief Replace a value flowing from a block to a phi with
682 /// potentially multiple instances of that value flowing from the
683 /// block's predecessors to the phi.
685 /// \param BB The block with the value flowing into the phi.
686 /// \param BBPreds The predecessors of BB.
687 /// \param PN The phi that we are updating.
688 static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB,
689 const PredBlockVector &BBPreds,
691 Value *OldVal = PN->removeIncomingValue(BB, false);
692 assert(OldVal && "No entry in PHI for Pred BB!");
694 IncomingValueMap IncomingValues;
696 // We are merging two blocks - BB, and the block containing PN - and
697 // as a result we need to redirect edges from the predecessors of BB
698 // to go to the block containing PN, and update PN
699 // accordingly. Since we allow merging blocks in the case where the
700 // predecessor and successor blocks both share some predecessors,
701 // and where some of those common predecessors might have undef
702 // values flowing into PN, we want to rewrite those values to be
703 // consistent with the non-undef values.
705 gatherIncomingValuesToPhi(PN, IncomingValues);
707 // If this incoming value is one of the PHI nodes in BB, the new entries
708 // in the PHI node are the entries from the old PHI.
709 if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
710 PHINode *OldValPN = cast<PHINode>(OldVal);
711 for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) {
712 // Note that, since we are merging phi nodes and BB and Succ might
713 // have common predecessors, we could end up with a phi node with
714 // identical incoming branches. This will be cleaned up later (and
715 // will trigger asserts if we try to clean it up now, without also
716 // simplifying the corresponding conditional branch).
717 BasicBlock *PredBB = OldValPN->getIncomingBlock(i);
718 Value *PredVal = OldValPN->getIncomingValue(i);
719 Value *Selected = selectIncomingValueForBlock(PredVal, PredBB,
722 // And add a new incoming value for this predecessor for the
723 // newly retargeted branch.
724 PN->addIncoming(Selected, PredBB);
727 for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) {
728 // Update existing incoming values in PN for this
729 // predecessor of BB.
730 BasicBlock *PredBB = BBPreds[i];
731 Value *Selected = selectIncomingValueForBlock(OldVal, PredBB,
734 // And add a new incoming value for this predecessor for the
735 // newly retargeted branch.
736 PN->addIncoming(Selected, PredBB);
740 replaceUndefValuesInPhi(PN, IncomingValues);
743 /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
744 /// unconditional branch, and contains no instructions other than PHI nodes,
745 /// potential side-effect free intrinsics and the branch. If possible,
746 /// eliminate BB by rewriting all the predecessors to branch to the successor
747 /// block and return true. If we can't transform, return false.
748 bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
749 assert(BB != &BB->getParent()->getEntryBlock() &&
750 "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
752 // We can't eliminate infinite loops.
753 BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
754 if (BB == Succ) return false;
756 // Check to see if merging these blocks would cause conflicts for any of the
757 // phi nodes in BB or Succ. If not, we can safely merge.
758 if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
760 // Check for cases where Succ has multiple predecessors and a PHI node in BB
761 // has uses which will not disappear when the PHI nodes are merged. It is
762 // possible to handle such cases, but difficult: it requires checking whether
763 // BB dominates Succ, which is non-trivial to calculate in the case where
764 // Succ has multiple predecessors. Also, it requires checking whether
765 // constructing the necessary self-referential PHI node doesn't introduce any
766 // conflicts; this isn't too difficult, but the previous code for doing this
769 // Note that if this check finds a live use, BB dominates Succ, so BB is
770 // something like a loop pre-header (or rarely, a part of an irreducible CFG);
771 // folding the branch isn't profitable in that case anyway.
772 if (!Succ->getSinglePredecessor()) {
773 BasicBlock::iterator BBI = BB->begin();
774 while (isa<PHINode>(*BBI)) {
775 for (Use &U : BBI->uses()) {
776 if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) {
777 if (PN->getIncomingBlock(U) != BB)
787 DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
789 if (isa<PHINode>(Succ->begin())) {
790 // If there is more than one pred of succ, and there are PHI nodes in
791 // the successor, then we need to add incoming edges for the PHI nodes
793 const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
795 // Loop over all of the PHI nodes in the successor of BB.
796 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
797 PHINode *PN = cast<PHINode>(I);
799 redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
803 if (Succ->getSinglePredecessor()) {
804 // BB is the only predecessor of Succ, so Succ will end up with exactly
805 // the same predecessors BB had.
807 // Copy over any phi, debug or lifetime instruction.
808 BB->getTerminator()->eraseFromParent();
809 Succ->getInstList().splice(Succ->getFirstNonPHI(), BB->getInstList());
811 while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
812 // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
813 assert(PN->use_empty() && "There shouldn't be any uses here!");
814 PN->eraseFromParent();
818 // Everything that jumped to BB now goes to Succ.
819 BB->replaceAllUsesWith(Succ);
820 if (!Succ->hasName()) Succ->takeName(BB);
821 BB->eraseFromParent(); // Delete the old basic block.
825 /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
826 /// nodes in this block. This doesn't try to be clever about PHI nodes
827 /// which differ only in the order of the incoming values, but instcombine
828 /// orders them so it usually won't matter.
830 bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
831 bool Changed = false;
833 // This implementation doesn't currently consider undef operands
834 // specially. Theoretically, two phis which are identical except for
835 // one having an undef where the other doesn't could be collapsed.
837 // Map from PHI hash values to PHI nodes. If multiple PHIs have
838 // the same hash value, the element is the first PHI in the
839 // linked list in CollisionMap.
840 DenseMap<uintptr_t, PHINode *> HashMap;
842 // Maintain linked lists of PHI nodes with common hash values.
843 DenseMap<PHINode *, PHINode *> CollisionMap;
846 for (BasicBlock::iterator I = BB->begin();
847 PHINode *PN = dyn_cast<PHINode>(I++); ) {
848 // Compute a hash value on the operands. Instcombine will likely have sorted
849 // them, which helps expose duplicates, but we have to check all the
850 // operands to be safe in case instcombine hasn't run.
852 // This hash algorithm is quite weak as hash functions go, but it seems
853 // to do a good enough job for this particular purpose, and is very quick.
854 for (User::op_iterator I = PN->op_begin(), E = PN->op_end(); I != E; ++I) {
855 Hash ^= reinterpret_cast<uintptr_t>(static_cast<Value *>(*I));
856 Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
858 for (PHINode::block_iterator I = PN->block_begin(), E = PN->block_end();
860 Hash ^= reinterpret_cast<uintptr_t>(static_cast<BasicBlock *>(*I));
861 Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
863 // Avoid colliding with the DenseMap sentinels ~0 and ~0-1.
865 // If we've never seen this hash value before, it's a unique PHI.
866 std::pair<DenseMap<uintptr_t, PHINode *>::iterator, bool> Pair =
867 HashMap.insert(std::make_pair(Hash, PN));
868 if (Pair.second) continue;
869 // Otherwise it's either a duplicate or a hash collision.
870 for (PHINode *OtherPN = Pair.first->second; ; ) {
871 if (OtherPN->isIdenticalTo(PN)) {
872 // A duplicate. Replace this PHI with its duplicate.
873 PN->replaceAllUsesWith(OtherPN);
874 PN->eraseFromParent();
878 // A non-duplicate hash collision.
879 DenseMap<PHINode *, PHINode *>::iterator I = CollisionMap.find(OtherPN);
880 if (I == CollisionMap.end()) {
881 // Set this PHI to be the head of the linked list of colliding PHIs.
882 PHINode *Old = Pair.first->second;
883 Pair.first->second = PN;
884 CollisionMap[PN] = Old;
887 // Proceed to the next PHI in the list.
895 /// enforceKnownAlignment - If the specified pointer points to an object that
896 /// we control, modify the object's alignment to PrefAlign. This isn't
897 /// often possible though. If alignment is important, a more reliable approach
898 /// is to simply align all global variables and allocation instructions to
899 /// their preferred alignment from the beginning.
901 static unsigned enforceKnownAlignment(Value *V, unsigned Align,
903 const DataLayout &DL) {
904 V = V->stripPointerCasts();
906 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
907 // If the preferred alignment is greater than the natural stack alignment
908 // then don't round up. This avoids dynamic stack realignment.
909 if (DL.exceedsNaturalStackAlignment(PrefAlign))
911 // If there is a requested alignment and if this is an alloca, round up.
912 if (AI->getAlignment() >= PrefAlign)
913 return AI->getAlignment();
914 AI->setAlignment(PrefAlign);
918 if (auto *GO = dyn_cast<GlobalObject>(V)) {
919 // If there is a large requested alignment and we can, bump up the alignment
921 if (GO->isDeclaration())
923 // If the memory we set aside for the global may not be the memory used by
924 // the final program then it is impossible for us to reliably enforce the
925 // preferred alignment.
926 if (GO->isWeakForLinker())
929 if (GO->getAlignment() >= PrefAlign)
930 return GO->getAlignment();
931 // We can only increase the alignment of the global if it has no alignment
932 // specified or if it is not assigned a section. If it is assigned a
933 // section, the global could be densely packed with other objects in the
934 // section, increasing the alignment could cause padding issues.
935 if (!GO->hasSection() || GO->getAlignment() == 0)
936 GO->setAlignment(PrefAlign);
937 return GO->getAlignment();
943 /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
944 /// we can determine, return it, otherwise return 0. If PrefAlign is specified,
945 /// and it is more than the alignment of the ultimate object, see if we can
946 /// increase the alignment of the ultimate object, making this check succeed.
947 unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
948 const DataLayout &DL,
949 const Instruction *CxtI,
951 const DominatorTree *DT) {
952 assert(V->getType()->isPointerTy() &&
953 "getOrEnforceKnownAlignment expects a pointer!");
954 unsigned BitWidth = DL.getPointerTypeSizeInBits(V->getType());
956 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
957 computeKnownBits(V, KnownZero, KnownOne, DL, 0, AC, CxtI, DT);
958 unsigned TrailZ = KnownZero.countTrailingOnes();
960 // Avoid trouble with ridiculously large TrailZ values, such as
961 // those computed from a null pointer.
962 TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
964 unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
966 // LLVM doesn't support alignments larger than this currently.
967 Align = std::min(Align, +Value::MaximumAlignment);
969 if (PrefAlign > Align)
970 Align = enforceKnownAlignment(V, Align, PrefAlign, DL);
972 // We don't need to make any adjustment.
976 ///===---------------------------------------------------------------------===//
977 /// Dbg Intrinsic utilities
980 /// See if there is a dbg.value intrinsic for DIVar before I.
981 static bool LdStHasDebugValue(const MDLocalVariable *DIVar, Instruction *I) {
982 // Since we can't guarantee that the original dbg.declare instrinsic
983 // is removed by LowerDbgDeclare(), we need to make sure that we are
984 // not inserting the same dbg.value intrinsic over and over.
985 llvm::BasicBlock::InstListType::iterator PrevI(I);
986 if (PrevI != I->getParent()->getInstList().begin()) {
988 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI))
989 if (DVI->getValue() == I->getOperand(0) &&
990 DVI->getOffset() == 0 &&
991 DVI->getVariable() == DIVar)
997 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
998 /// that has an associated llvm.dbg.decl intrinsic.
999 bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
1000 StoreInst *SI, DIBuilder &Builder) {
1001 auto *DIVar = DDI->getVariable();
1002 auto *DIExpr = DDI->getExpression();
1003 assert(DIVar && "Missing variable");
1005 if (LdStHasDebugValue(DIVar, SI))
1008 // If an argument is zero extended then use argument directly. The ZExt
1009 // may be zapped by an optimization pass in future.
1010 Argument *ExtendedArg = nullptr;
1011 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1012 ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
1013 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1014 ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
1016 Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, DIExpr,
1017 DDI->getDebugLoc(), SI);
1019 Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar, DIExpr,
1020 DDI->getDebugLoc(), SI);
1024 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
1025 /// that has an associated llvm.dbg.decl intrinsic.
1026 bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
1027 LoadInst *LI, DIBuilder &Builder) {
1028 auto *DIVar = DDI->getVariable();
1029 auto *DIExpr = DDI->getExpression();
1030 assert(DIVar && "Missing variable");
1032 if (LdStHasDebugValue(DIVar, LI))
1035 Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0, DIVar, DIExpr,
1036 DDI->getDebugLoc(), LI);
1040 /// Determine whether this alloca is either a VLA or an array.
1041 static bool isArray(AllocaInst *AI) {
1042 return AI->isArrayAllocation() ||
1043 AI->getType()->getElementType()->isArrayTy();
1046 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
1047 /// of llvm.dbg.value intrinsics.
1048 bool llvm::LowerDbgDeclare(Function &F) {
1049 DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
1050 SmallVector<DbgDeclareInst *, 4> Dbgs;
1052 for (BasicBlock::iterator BI : FI)
1053 if (auto DDI = dyn_cast<DbgDeclareInst>(BI))
1054 Dbgs.push_back(DDI);
1059 for (auto &I : Dbgs) {
1060 DbgDeclareInst *DDI = I;
1061 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
1062 // If this is an alloca for a scalar variable, insert a dbg.value
1063 // at each load and store to the alloca and erase the dbg.declare.
1064 // The dbg.values allow tracking a variable even if it is not
1065 // stored on the stack, while the dbg.declare can only describe
1066 // the stack slot (and at a lexical-scope granularity). Later
1067 // passes will attempt to elide the stack slot.
1068 if (AI && !isArray(AI)) {
1069 for (User *U : AI->users())
1070 if (StoreInst *SI = dyn_cast<StoreInst>(U))
1071 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
1072 else if (LoadInst *LI = dyn_cast<LoadInst>(U))
1073 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
1074 else if (CallInst *CI = dyn_cast<CallInst>(U)) {
1075 // This is a call by-value or some other instruction that
1076 // takes a pointer to the variable. Insert a *value*
1077 // intrinsic that describes the alloca.
1078 DIB.insertDbgValueIntrinsic(AI, 0, DDI->getVariable(),
1079 DDI->getExpression(), DDI->getDebugLoc(),
1082 DDI->eraseFromParent();
1088 /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the
1089 /// alloca 'V', if any.
1090 DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) {
1091 if (auto *L = LocalAsMetadata::getIfExists(V))
1092 if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
1093 for (User *U : MDV->users())
1094 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
1100 bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
1101 DIBuilder &Builder, bool Deref) {
1102 DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI);
1105 DebugLoc Loc = DDI->getDebugLoc();
1106 auto *DIVar = DDI->getVariable();
1107 auto *DIExpr = DDI->getExpression();
1108 assert(DIVar && "Missing variable");
1111 // Create a copy of the original DIDescriptor for user variable, prepending
1112 // "deref" operation to a list of address elements, as new llvm.dbg.declare
1113 // will take a value storing address of the memory for variable, not
1115 SmallVector<uint64_t, 4> NewDIExpr;
1116 NewDIExpr.push_back(dwarf::DW_OP_deref);
1118 NewDIExpr.append(DIExpr->elements_begin(), DIExpr->elements_end());
1119 DIExpr = Builder.createExpression(NewDIExpr);
1122 // Insert llvm.dbg.declare in the same basic block as the original alloca,
1123 // and remove old llvm.dbg.declare.
1124 BasicBlock *BB = AI->getParent();
1125 Builder.insertDeclare(NewAllocaAddress, DIVar, DIExpr, Loc, BB);
1126 DDI->eraseFromParent();
1130 /// changeToUnreachable - Insert an unreachable instruction before the specified
1131 /// instruction, making it and the rest of the code in the block dead.
1132 static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) {
1133 BasicBlock *BB = I->getParent();
1134 // Loop over all of the successors, removing BB's entry from any PHI
1136 for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
1137 (*SI)->removePredecessor(BB);
1139 // Insert a call to llvm.trap right before this. This turns the undefined
1140 // behavior into a hard fail instead of falling through into random code.
1143 Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
1144 CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
1145 CallTrap->setDebugLoc(I->getDebugLoc());
1147 new UnreachableInst(I->getContext(), I);
1149 // All instructions after this are dead.
1150 BasicBlock::iterator BBI = I, BBE = BB->end();
1151 while (BBI != BBE) {
1152 if (!BBI->use_empty())
1153 BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
1154 BB->getInstList().erase(BBI++);
1158 /// changeToCall - Convert the specified invoke into a normal call.
1159 static void changeToCall(InvokeInst *II) {
1160 SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
1161 CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
1162 NewCall->takeName(II);
1163 NewCall->setCallingConv(II->getCallingConv());
1164 NewCall->setAttributes(II->getAttributes());
1165 NewCall->setDebugLoc(II->getDebugLoc());
1166 II->replaceAllUsesWith(NewCall);
1168 // Follow the call by a branch to the normal destination.
1169 BranchInst::Create(II->getNormalDest(), II);
1171 // Update PHI nodes in the unwind destination
1172 II->getUnwindDest()->removePredecessor(II->getParent());
1173 II->eraseFromParent();
1176 static bool markAliveBlocks(BasicBlock *BB,
1177 SmallPtrSetImpl<BasicBlock*> &Reachable) {
1179 SmallVector<BasicBlock*, 128> Worklist;
1180 Worklist.push_back(BB);
1181 Reachable.insert(BB);
1182 bool Changed = false;
1184 BB = Worklist.pop_back_val();
1186 // Do a quick scan of the basic block, turning any obviously unreachable
1187 // instructions into LLVM unreachable insts. The instruction combining pass
1188 // canonicalizes unreachable insts into stores to null or undef.
1189 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
1190 // Assumptions that are known to be false are equivalent to unreachable.
1191 // Also, if the condition is undefined, then we make the choice most
1192 // beneficial to the optimizer, and choose that to also be unreachable.
1193 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
1194 if (II->getIntrinsicID() == Intrinsic::assume) {
1195 bool MakeUnreachable = false;
1196 if (isa<UndefValue>(II->getArgOperand(0)))
1197 MakeUnreachable = true;
1198 else if (ConstantInt *Cond =
1199 dyn_cast<ConstantInt>(II->getArgOperand(0)))
1200 MakeUnreachable = Cond->isZero();
1202 if (MakeUnreachable) {
1203 // Don't insert a call to llvm.trap right before the unreachable.
1204 changeToUnreachable(BBI, false);
1210 if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
1211 if (CI->doesNotReturn()) {
1212 // If we found a call to a no-return function, insert an unreachable
1213 // instruction after it. Make sure there isn't *already* one there
1216 if (!isa<UnreachableInst>(BBI)) {
1217 // Don't insert a call to llvm.trap right before the unreachable.
1218 changeToUnreachable(BBI, false);
1225 // Store to undef and store to null are undefined and used to signal that
1226 // they should be changed to unreachable by passes that can't modify the
1228 if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
1229 // Don't touch volatile stores.
1230 if (SI->isVolatile()) continue;
1232 Value *Ptr = SI->getOperand(1);
1234 if (isa<UndefValue>(Ptr) ||
1235 (isa<ConstantPointerNull>(Ptr) &&
1236 SI->getPointerAddressSpace() == 0)) {
1237 changeToUnreachable(SI, true);
1244 // Turn invokes that call 'nounwind' functions into ordinary calls.
1245 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
1246 Value *Callee = II->getCalledValue();
1247 if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
1248 changeToUnreachable(II, true);
1250 } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(II)) {
1251 if (II->use_empty() && II->onlyReadsMemory()) {
1252 // jump to the normal destination branch.
1253 BranchInst::Create(II->getNormalDest(), II);
1254 II->getUnwindDest()->removePredecessor(II->getParent());
1255 II->eraseFromParent();
1262 Changed |= ConstantFoldTerminator(BB, true);
1263 for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
1264 if (Reachable.insert(*SI).second)
1265 Worklist.push_back(*SI);
1266 } while (!Worklist.empty());
1270 /// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
1271 /// if they are in a dead cycle. Return true if a change was made, false
1273 bool llvm::removeUnreachableBlocks(Function &F) {
1274 SmallPtrSet<BasicBlock*, 128> Reachable;
1275 bool Changed = markAliveBlocks(F.begin(), Reachable);
1277 // If there are unreachable blocks in the CFG...
1278 if (Reachable.size() == F.size())
1281 assert(Reachable.size() < F.size());
1282 NumRemoved += F.size()-Reachable.size();
1284 // Loop over all of the basic blocks that are not reachable, dropping all of
1285 // their internal references...
1286 for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
1287 if (Reachable.count(BB))
1290 for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
1291 if (Reachable.count(*SI))
1292 (*SI)->removePredecessor(BB);
1293 BB->dropAllReferences();
1296 for (Function::iterator I = ++F.begin(); I != F.end();)
1297 if (!Reachable.count(I))
1298 I = F.getBasicBlockList().erase(I);
1305 void llvm::combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsigned> KnownIDs) {
1306 SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
1307 K->dropUnknownMetadata(KnownIDs);
1308 K->getAllMetadataOtherThanDebugLoc(Metadata);
1309 for (unsigned i = 0, n = Metadata.size(); i < n; ++i) {
1310 unsigned Kind = Metadata[i].first;
1311 MDNode *JMD = J->getMetadata(Kind);
1312 MDNode *KMD = Metadata[i].second;
1316 K->setMetadata(Kind, nullptr); // Remove unknown metadata
1318 case LLVMContext::MD_dbg:
1319 llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
1320 case LLVMContext::MD_tbaa:
1321 K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
1323 case LLVMContext::MD_alias_scope:
1324 K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
1326 case LLVMContext::MD_noalias:
1327 K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
1329 case LLVMContext::MD_range:
1330 K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD));
1332 case LLVMContext::MD_fpmath:
1333 K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
1335 case LLVMContext::MD_invariant_load:
1336 // Only set the !invariant.load if it is present in both instructions.
1337 K->setMetadata(Kind, JMD);
1339 case LLVMContext::MD_nonnull:
1340 // Only set the !nonnull if it is present in both instructions.
1341 K->setMetadata(Kind, JMD);