| //===-- Local.cpp - Functions to perform local transformations ------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This family of functions perform various local transformations to the |
| // program. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/ADT/Hashing.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/LibCallSemantics.h" |
| #include "llvm/Analysis/MemoryBuiltins.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/IR/CFG.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DIBuilder.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DebugInfo.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/Dominators.h" |
| #include "llvm/IR/GetElementPtrTypeIterator.h" |
| #include "llvm/IR/GlobalAlias.h" |
| #include "llvm/IR/GlobalVariable.h" |
| #include "llvm/IR/IRBuilder.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/Intrinsics.h" |
| #include "llvm/IR/MDBuilder.h" |
| #include "llvm/IR/Metadata.h" |
| #include "llvm/IR/Operator.h" |
| #include "llvm/IR/ValueHandle.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/raw_ostream.h" |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "local" |
| |
| STATISTIC(NumRemoved, "Number of unreachable basic blocks removed"); |
| |
| //===----------------------------------------------------------------------===// |
| // Local constant propagation. |
| // |
| |
| /// ConstantFoldTerminator - If a terminator instruction is predicated on a |
| /// constant value, convert it into an unconditional branch to the constant |
| /// destination. This is a nontrivial operation because the successors of this |
| /// basic block must have their PHI nodes updated. |
| /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch |
| /// conditions and indirectbr addresses this might make dead if |
| /// DeleteDeadConditions is true. |
| bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions, |
| const TargetLibraryInfo *TLI) { |
| TerminatorInst *T = BB->getTerminator(); |
| IRBuilder<> Builder(T); |
| |
| // Branch - See if we are conditional jumping on constant |
| if (BranchInst *BI = dyn_cast<BranchInst>(T)) { |
| if (BI->isUnconditional()) return false; // Can't optimize uncond branch |
| BasicBlock *Dest1 = BI->getSuccessor(0); |
| BasicBlock *Dest2 = BI->getSuccessor(1); |
| |
| if (ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition())) { |
| // Are we branching on constant? |
| // YES. Change to unconditional branch... |
| BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2; |
| BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1; |
| |
| //cerr << "Function: " << T->getParent()->getParent() |
| // << "\nRemoving branch from " << T->getParent() |
| // << "\n\nTo: " << OldDest << endl; |
| |
| // Let the basic block know that we are letting go of it. Based on this, |
| // it will adjust it's PHI nodes. |
| OldDest->removePredecessor(BB); |
| |
| // Replace the conditional branch with an unconditional one. |
| Builder.CreateBr(Destination); |
| BI->eraseFromParent(); |
| return true; |
| } |
| |
| if (Dest2 == Dest1) { // Conditional branch to same location? |
| // This branch matches something like this: |
| // br bool %cond, label %Dest, label %Dest |
| // and changes it into: br label %Dest |
| |
| // Let the basic block know that we are letting go of one copy of it. |
| assert(BI->getParent() && "Terminator not inserted in block!"); |
| Dest1->removePredecessor(BI->getParent()); |
| |
| // Replace the conditional branch with an unconditional one. |
| Builder.CreateBr(Dest1); |
| Value *Cond = BI->getCondition(); |
| BI->eraseFromParent(); |
| if (DeleteDeadConditions) |
| RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); |
| return true; |
| } |
| return false; |
| } |
| |
| if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) { |
| // If we are switching on a constant, we can convert the switch to an |
| // unconditional branch. |
| ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition()); |
| BasicBlock *DefaultDest = SI->getDefaultDest(); |
| BasicBlock *TheOnlyDest = DefaultDest; |
| |
| // If the default is unreachable, ignore it when searching for TheOnlyDest. |
| if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) && |
| SI->getNumCases() > 0) { |
| TheOnlyDest = SI->case_begin().getCaseSuccessor(); |
| } |
| |
| // Figure out which case it goes to. |
| for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); |
| i != e; ++i) { |
| // Found case matching a constant operand? |
| if (i.getCaseValue() == CI) { |
| TheOnlyDest = i.getCaseSuccessor(); |
| break; |
| } |
| |
| // Check to see if this branch is going to the same place as the default |
| // dest. If so, eliminate it as an explicit compare. |
| if (i.getCaseSuccessor() == DefaultDest) { |
| MDNode *MD = SI->getMetadata(LLVMContext::MD_prof); |
| unsigned NCases = SI->getNumCases(); |
| // Fold the case metadata into the default if there will be any branches |
| // left, unless the metadata doesn't match the switch. |
| if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) { |
| // Collect branch weights into a vector. |
| SmallVector<uint32_t, 8> Weights; |
| for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e; |
| ++MD_i) { |
| ConstantInt *CI = |
| mdconst::dyn_extract<ConstantInt>(MD->getOperand(MD_i)); |
| assert(CI); |
| Weights.push_back(CI->getValue().getZExtValue()); |
| } |
| // Merge weight of this case to the default weight. |
| unsigned idx = i.getCaseIndex(); |
| Weights[0] += Weights[idx+1]; |
| // Remove weight for this case. |
| std::swap(Weights[idx+1], Weights.back()); |
| Weights.pop_back(); |
| SI->setMetadata(LLVMContext::MD_prof, |
| MDBuilder(BB->getContext()). |
| createBranchWeights(Weights)); |
| } |
| // Remove this entry. |
| DefaultDest->removePredecessor(SI->getParent()); |
| SI->removeCase(i); |
| --i; --e; |
| continue; |
| } |
| |
| // Otherwise, check to see if the switch only branches to one destination. |
| // We do this by reseting "TheOnlyDest" to null when we find two non-equal |
| // destinations. |
| if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = nullptr; |
| } |
| |
| if (CI && !TheOnlyDest) { |
| // Branching on a constant, but not any of the cases, go to the default |
| // successor. |
| TheOnlyDest = SI->getDefaultDest(); |
| } |
| |
| // If we found a single destination that we can fold the switch into, do so |
| // now. |
| if (TheOnlyDest) { |
| // Insert the new branch. |
| Builder.CreateBr(TheOnlyDest); |
| BasicBlock *BB = SI->getParent(); |
| |
| // Remove entries from PHI nodes which we no longer branch to... |
| for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) { |
| // Found case matching a constant operand? |
| BasicBlock *Succ = SI->getSuccessor(i); |
| if (Succ == TheOnlyDest) |
| TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest |
| else |
| Succ->removePredecessor(BB); |
| } |
| |
| // Delete the old switch. |
| Value *Cond = SI->getCondition(); |
| SI->eraseFromParent(); |
| if (DeleteDeadConditions) |
| RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); |
| return true; |
| } |
| |
| if (SI->getNumCases() == 1) { |
| // Otherwise, we can fold this switch into a conditional branch |
| // instruction if it has only one non-default destination. |
| SwitchInst::CaseIt FirstCase = SI->case_begin(); |
| Value *Cond = Builder.CreateICmpEQ(SI->getCondition(), |
| FirstCase.getCaseValue(), "cond"); |
| |
| // Insert the new branch. |
| BranchInst *NewBr = Builder.CreateCondBr(Cond, |
| FirstCase.getCaseSuccessor(), |
| SI->getDefaultDest()); |
| MDNode *MD = SI->getMetadata(LLVMContext::MD_prof); |
| if (MD && MD->getNumOperands() == 3) { |
| ConstantInt *SICase = |
| mdconst::dyn_extract<ConstantInt>(MD->getOperand(2)); |
| ConstantInt *SIDef = |
| mdconst::dyn_extract<ConstantInt>(MD->getOperand(1)); |
| assert(SICase && SIDef); |
| // The TrueWeight should be the weight for the single case of SI. |
| NewBr->setMetadata(LLVMContext::MD_prof, |
| MDBuilder(BB->getContext()). |
| createBranchWeights(SICase->getValue().getZExtValue(), |
| SIDef->getValue().getZExtValue())); |
| } |
| |
| // Delete the old switch. |
| SI->eraseFromParent(); |
| return true; |
| } |
| return false; |
| } |
| |
| if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(T)) { |
| // indirectbr blockaddress(@F, @BB) -> br label @BB |
| if (BlockAddress *BA = |
| dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) { |
| BasicBlock *TheOnlyDest = BA->getBasicBlock(); |
| // Insert the new branch. |
| Builder.CreateBr(TheOnlyDest); |
| |
| for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) { |
| if (IBI->getDestination(i) == TheOnlyDest) |
| TheOnlyDest = nullptr; |
| else |
| IBI->getDestination(i)->removePredecessor(IBI->getParent()); |
| } |
| Value *Address = IBI->getAddress(); |
| IBI->eraseFromParent(); |
| if (DeleteDeadConditions) |
| RecursivelyDeleteTriviallyDeadInstructions(Address, TLI); |
| |
| // If we didn't find our destination in the IBI successor list, then we |
| // have undefined behavior. Replace the unconditional branch with an |
| // 'unreachable' instruction. |
| if (TheOnlyDest) { |
| BB->getTerminator()->eraseFromParent(); |
| new UnreachableInst(BB->getContext(), BB); |
| } |
| |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Local dead code elimination. |
| // |
| |
| /// isInstructionTriviallyDead - Return true if the result produced by the |
| /// instruction is not used, and the instruction has no side effects. |
| /// |
| bool llvm::isInstructionTriviallyDead(Instruction *I, |
| const TargetLibraryInfo *TLI) { |
| if (!I->use_empty() || isa<TerminatorInst>(I)) return false; |
| |
| // We don't want the landingpad instruction removed by anything this general. |
| if (isa<LandingPadInst>(I)) |
| return false; |
| |
| // We don't want debug info removed by anything this general, unless |
| // debug info is empty. |
| if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) { |
| if (DDI->getAddress()) |
| return false; |
| return true; |
| } |
| if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) { |
| if (DVI->getValue()) |
| return false; |
| return true; |
| } |
| |
| if (!I->mayHaveSideEffects()) return true; |
| |
| // Special case intrinsics that "may have side effects" but can be deleted |
| // when dead. |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { |
| // Safe to delete llvm.stacksave if dead. |
| if (II->getIntrinsicID() == Intrinsic::stacksave) |
| return true; |
| |
| // Lifetime intrinsics are dead when their right-hand is undef. |
| if (II->getIntrinsicID() == Intrinsic::lifetime_start || |
| II->getIntrinsicID() == Intrinsic::lifetime_end) |
| return isa<UndefValue>(II->getArgOperand(1)); |
| |
| // Assumptions are dead if their condition is trivially true. |
| if (II->getIntrinsicID() == Intrinsic::assume) { |
| if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0))) |
| return !Cond->isZero(); |
| |
| return false; |
| } |
| } |
| |
| if (isAllocLikeFn(I, TLI)) return true; |
| |
| if (CallInst *CI = isFreeCall(I, TLI)) |
| if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0))) |
| return C->isNullValue() || isa<UndefValue>(C); |
| |
| return false; |
| } |
| |
| /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a |
| /// trivially dead instruction, delete it. If that makes any of its operands |
| /// trivially dead, delete them too, recursively. Return true if any |
| /// instructions were deleted. |
| bool |
| llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V, |
| const TargetLibraryInfo *TLI) { |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I || !I->use_empty() || !isInstructionTriviallyDead(I, TLI)) |
| return false; |
| |
| SmallVector<Instruction*, 16> DeadInsts; |
| DeadInsts.push_back(I); |
| |
| do { |
| I = DeadInsts.pop_back_val(); |
| |
| // Null out all of the instruction's operands to see if any operand becomes |
| // dead as we go. |
| for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { |
| Value *OpV = I->getOperand(i); |
| I->setOperand(i, nullptr); |
| |
| if (!OpV->use_empty()) continue; |
| |
| // If the operand is an instruction that became dead as we nulled out the |
| // operand, and if it is 'trivially' dead, delete it in a future loop |
| // iteration. |
| if (Instruction *OpI = dyn_cast<Instruction>(OpV)) |
| if (isInstructionTriviallyDead(OpI, TLI)) |
| DeadInsts.push_back(OpI); |
| } |
| |
| I->eraseFromParent(); |
| } while (!DeadInsts.empty()); |
| |
| return true; |
| } |
| |
| /// areAllUsesEqual - Check whether the uses of a value are all the same. |
| /// This is similar to Instruction::hasOneUse() except this will also return |
| /// true when there are no uses or multiple uses that all refer to the same |
| /// value. |
| static bool areAllUsesEqual(Instruction *I) { |
| Value::user_iterator UI = I->user_begin(); |
| Value::user_iterator UE = I->user_end(); |
| if (UI == UE) |
| return true; |
| |
| User *TheUse = *UI; |
| for (++UI; UI != UE; ++UI) { |
| if (*UI != TheUse) |
| return false; |
| } |
| return true; |
| } |
| |
| /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively |
| /// dead PHI node, due to being a def-use chain of single-use nodes that |
| /// either forms a cycle or is terminated by a trivially dead instruction, |
| /// delete it. If that makes any of its operands trivially dead, delete them |
| /// too, recursively. Return true if a change was made. |
| bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN, |
| const TargetLibraryInfo *TLI) { |
| SmallPtrSet<Instruction*, 4> Visited; |
| for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects(); |
| I = cast<Instruction>(*I->user_begin())) { |
| if (I->use_empty()) |
| return RecursivelyDeleteTriviallyDeadInstructions(I, TLI); |
| |
| // If we find an instruction more than once, we're on a cycle that |
| // won't prove fruitful. |
| if (!Visited.insert(I).second) { |
| // Break the cycle and delete the instruction and its operands. |
| I->replaceAllUsesWith(UndefValue::get(I->getType())); |
| (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /// SimplifyInstructionsInBlock - Scan the specified basic block and try to |
| /// simplify any instructions in it and recursively delete dead instructions. |
| /// |
| /// This returns true if it changed the code, note that it can delete |
| /// instructions in other blocks as well in this block. |
| bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, |
| const TargetLibraryInfo *TLI) { |
| bool MadeChange = false; |
| |
| #ifndef NDEBUG |
| // In debug builds, ensure that the terminator of the block is never replaced |
| // or deleted by these simplifications. The idea of simplification is that it |
| // cannot introduce new instructions, and there is no way to replace the |
| // terminator of a block without introducing a new instruction. |
| AssertingVH<Instruction> TerminatorVH(--BB->end()); |
| #endif |
| |
| for (BasicBlock::iterator BI = BB->begin(), E = --BB->end(); BI != E; ) { |
| assert(!BI->isTerminator()); |
| Instruction *Inst = BI++; |
| |
| WeakVH BIHandle(BI); |
| if (recursivelySimplifyInstruction(Inst, TLI)) { |
| MadeChange = true; |
| if (BIHandle != BI) |
| BI = BB->begin(); |
| continue; |
| } |
| |
| MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI); |
| if (BIHandle != BI) |
| BI = BB->begin(); |
| } |
| return MadeChange; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Control Flow Graph Restructuring. |
| // |
| |
| |
| /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this |
| /// method is called when we're about to delete Pred as a predecessor of BB. If |
| /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred. |
| /// |
| /// Unlike the removePredecessor method, this attempts to simplify uses of PHI |
| /// nodes that collapse into identity values. For example, if we have: |
| /// x = phi(1, 0, 0, 0) |
| /// y = and x, z |
| /// |
| /// .. and delete the predecessor corresponding to the '1', this will attempt to |
| /// recursively fold the and to 0. |
| void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred) { |
| // This only adjusts blocks with PHI nodes. |
| if (!isa<PHINode>(BB->begin())) |
| return; |
| |
| // Remove the entries for Pred from the PHI nodes in BB, but do not simplify |
| // them down. This will leave us with single entry phi nodes and other phis |
| // that can be removed. |
| BB->removePredecessor(Pred, true); |
| |
| WeakVH PhiIt = &BB->front(); |
| while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) { |
| PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt)); |
| Value *OldPhiIt = PhiIt; |
| |
| if (!recursivelySimplifyInstruction(PN)) |
| continue; |
| |
| // If recursive simplification ended up deleting the next PHI node we would |
| // iterate to, then our iterator is invalid, restart scanning from the top |
| // of the block. |
| if (PhiIt != OldPhiIt) PhiIt = &BB->front(); |
| } |
| } |
| |
| |
| /// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its |
| /// predecessor is known to have one successor (DestBB!). Eliminate the edge |
| /// between them, moving the instructions in the predecessor into DestBB and |
| /// deleting the predecessor block. |
| /// |
| void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT) { |
| // If BB has single-entry PHI nodes, fold them. |
| while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) { |
| Value *NewVal = PN->getIncomingValue(0); |
| // Replace self referencing PHI with undef, it must be dead. |
| if (NewVal == PN) NewVal = UndefValue::get(PN->getType()); |
| PN->replaceAllUsesWith(NewVal); |
| PN->eraseFromParent(); |
| } |
| |
| BasicBlock *PredBB = DestBB->getSinglePredecessor(); |
| assert(PredBB && "Block doesn't have a single predecessor!"); |
| |
| // Zap anything that took the address of DestBB. Not doing this will give the |
| // address an invalid value. |
| if (DestBB->hasAddressTaken()) { |
| BlockAddress *BA = BlockAddress::get(DestBB); |
| Constant *Replacement = |
| ConstantInt::get(llvm::Type::getInt32Ty(BA->getContext()), 1); |
| BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement, |
| BA->getType())); |
| BA->destroyConstant(); |
| } |
| |
| // Anything that branched to PredBB now branches to DestBB. |
| PredBB->replaceAllUsesWith(DestBB); |
| |
| // Splice all the instructions from PredBB to DestBB. |
| PredBB->getTerminator()->eraseFromParent(); |
| DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList()); |
| |
| // If the PredBB is the entry block of the function, move DestBB up to |
| // become the entry block after we erase PredBB. |
| if (PredBB == &DestBB->getParent()->getEntryBlock()) |
| DestBB->moveAfter(PredBB); |
| |
| if (DT) { |
| BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock(); |
| DT->changeImmediateDominator(DestBB, PredBBIDom); |
| DT->eraseNode(PredBB); |
| } |
| // Nuke BB. |
| PredBB->eraseFromParent(); |
| } |
| |
| /// CanMergeValues - Return true if we can choose one of these values to use |
| /// in place of the other. Note that we will always choose the non-undef |
| /// value to keep. |
| static bool CanMergeValues(Value *First, Value *Second) { |
| return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second); |
| } |
| |
| /// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an |
| /// almost-empty BB ending in an unconditional branch to Succ, into Succ. |
| /// |
| /// Assumption: Succ is the single successor for BB. |
| /// |
| static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) { |
| assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!"); |
| |
| DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into " |
| << Succ->getName() << "\n"); |
| // Shortcut, if there is only a single predecessor it must be BB and merging |
| // is always safe |
| if (Succ->getSinglePredecessor()) return true; |
| |
| // Make a list of the predecessors of BB |
| SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB)); |
| |
| // Look at all the phi nodes in Succ, to see if they present a conflict when |
| // merging these blocks |
| for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) { |
| PHINode *PN = cast<PHINode>(I); |
| |
| // If the incoming value from BB is again a PHINode in |
| // BB which has the same incoming value for *PI as PN does, we can |
| // merge the phi nodes and then the blocks can still be merged |
| PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB)); |
| if (BBPN && BBPN->getParent() == BB) { |
| for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) { |
| BasicBlock *IBB = PN->getIncomingBlock(PI); |
| if (BBPreds.count(IBB) && |
| !CanMergeValues(BBPN->getIncomingValueForBlock(IBB), |
| PN->getIncomingValue(PI))) { |
| DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in " |
| << Succ->getName() << " is conflicting with " |
| << BBPN->getName() << " with regard to common predecessor " |
| << IBB->getName() << "\n"); |
| return false; |
| } |
| } |
| } else { |
| Value* Val = PN->getIncomingValueForBlock(BB); |
| for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) { |
| // See if the incoming value for the common predecessor is equal to the |
| // one for BB, in which case this phi node will not prevent the merging |
| // of the block. |
| BasicBlock *IBB = PN->getIncomingBlock(PI); |
| if (BBPreds.count(IBB) && |
| !CanMergeValues(Val, PN->getIncomingValue(PI))) { |
| DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in " |
| << Succ->getName() << " is conflicting with regard to common " |
| << "predecessor " << IBB->getName() << "\n"); |
| return false; |
| } |
| } |
| } |
| } |
| |
| return true; |
| } |
| |
| typedef SmallVector<BasicBlock *, 16> PredBlockVector; |
| typedef DenseMap<BasicBlock *, Value *> IncomingValueMap; |
| |
| /// \brief Determines the value to use as the phi node input for a block. |
| /// |
| /// Select between \p OldVal any value that we know flows from \p BB |
| /// to a particular phi on the basis of which one (if either) is not |
| /// undef. Update IncomingValues based on the selected value. |
| /// |
| /// \param OldVal The value we are considering selecting. |
| /// \param BB The block that the value flows in from. |
| /// \param IncomingValues A map from block-to-value for other phi inputs |
| /// that we have examined. |
| /// |
| /// \returns the selected value. |
| static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB, |
| IncomingValueMap &IncomingValues) { |
| if (!isa<UndefValue>(OldVal)) { |
| assert((!IncomingValues.count(BB) || |
| IncomingValues.find(BB)->second == OldVal) && |
| "Expected OldVal to match incoming value from BB!"); |
| |
| IncomingValues.insert(std::make_pair(BB, OldVal)); |
| return OldVal; |
| } |
| |
| IncomingValueMap::const_iterator It = IncomingValues.find(BB); |
| if (It != IncomingValues.end()) return It->second; |
| |
| return OldVal; |
| } |
| |
| /// \brief Create a map from block to value for the operands of a |
| /// given phi. |
| /// |
| /// Create a map from block to value for each non-undef value flowing |
| /// into \p PN. |
| /// |
| /// \param PN The phi we are collecting the map for. |
| /// \param IncomingValues [out] The map from block to value for this phi. |
| static void gatherIncomingValuesToPhi(PHINode *PN, |
| IncomingValueMap &IncomingValues) { |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| BasicBlock *BB = PN->getIncomingBlock(i); |
| Value *V = PN->getIncomingValue(i); |
| |
| if (!isa<UndefValue>(V)) |
| IncomingValues.insert(std::make_pair(BB, V)); |
| } |
| } |
| |
| /// \brief Replace the incoming undef values to a phi with the values |
| /// from a block-to-value map. |
| /// |
| /// \param PN The phi we are replacing the undefs in. |
| /// \param IncomingValues A map from block to value. |
| static void replaceUndefValuesInPhi(PHINode *PN, |
| const IncomingValueMap &IncomingValues) { |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| Value *V = PN->getIncomingValue(i); |
| |
| if (!isa<UndefValue>(V)) continue; |
| |
| BasicBlock *BB = PN->getIncomingBlock(i); |
| IncomingValueMap::const_iterator It = IncomingValues.find(BB); |
| if (It == IncomingValues.end()) continue; |
| |
| PN->setIncomingValue(i, It->second); |
| } |
| } |
| |
| /// \brief Replace a value flowing from a block to a phi with |
| /// potentially multiple instances of that value flowing from the |
| /// block's predecessors to the phi. |
| /// |
| /// \param BB The block with the value flowing into the phi. |
| /// \param BBPreds The predecessors of BB. |
| /// \param PN The phi that we are updating. |
| static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB, |
| const PredBlockVector &BBPreds, |
| PHINode *PN) { |
| Value *OldVal = PN->removeIncomingValue(BB, false); |
| assert(OldVal && "No entry in PHI for Pred BB!"); |
| |
| IncomingValueMap IncomingValues; |
| |
| // We are merging two blocks - BB, and the block containing PN - and |
| // as a result we need to redirect edges from the predecessors of BB |
| // to go to the block containing PN, and update PN |
| // accordingly. Since we allow merging blocks in the case where the |
| // predecessor and successor blocks both share some predecessors, |
| // and where some of those common predecessors might have undef |
| // values flowing into PN, we want to rewrite those values to be |
| // consistent with the non-undef values. |
| |
| gatherIncomingValuesToPhi(PN, IncomingValues); |
| |
| // If this incoming value is one of the PHI nodes in BB, the new entries |
| // in the PHI node are the entries from the old PHI. |
| if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) { |
| PHINode *OldValPN = cast<PHINode>(OldVal); |
| for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) { |
| // Note that, since we are merging phi nodes and BB and Succ might |
| // have common predecessors, we could end up with a phi node with |
| // identical incoming branches. This will be cleaned up later (and |
| // will trigger asserts if we try to clean it up now, without also |
| // simplifying the corresponding conditional branch). |
| BasicBlock *PredBB = OldValPN->getIncomingBlock(i); |
| Value *PredVal = OldValPN->getIncomingValue(i); |
| Value *Selected = selectIncomingValueForBlock(PredVal, PredBB, |
| IncomingValues); |
| |
| // And add a new incoming value for this predecessor for the |
| // newly retargeted branch. |
| PN->addIncoming(Selected, PredBB); |
| } |
| } else { |
| for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) { |
| // Update existing incoming values in PN for this |
| // predecessor of BB. |
| BasicBlock *PredBB = BBPreds[i]; |
| Value *Selected = selectIncomingValueForBlock(OldVal, PredBB, |
| IncomingValues); |
| |
| // And add a new incoming value for this predecessor for the |
| // newly retargeted branch. |
| PN->addIncoming(Selected, PredBB); |
| } |
| } |
| |
| replaceUndefValuesInPhi(PN, IncomingValues); |
| } |
| |
| /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an |
| /// unconditional branch, and contains no instructions other than PHI nodes, |
| /// potential side-effect free intrinsics and the branch. If possible, |
| /// eliminate BB by rewriting all the predecessors to branch to the successor |
| /// block and return true. If we can't transform, return false. |
| bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) { |
| assert(BB != &BB->getParent()->getEntryBlock() && |
| "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!"); |
| |
| // We can't eliminate infinite loops. |
| BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0); |
| if (BB == Succ) return false; |
| |
| // Check to see if merging these blocks would cause conflicts for any of the |
| // phi nodes in BB or Succ. If not, we can safely merge. |
| if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false; |
| |
| // Check for cases where Succ has multiple predecessors and a PHI node in BB |
| // has uses which will not disappear when the PHI nodes are merged. It is |
| // possible to handle such cases, but difficult: it requires checking whether |
| // BB dominates Succ, which is non-trivial to calculate in the case where |
| // Succ has multiple predecessors. Also, it requires checking whether |
| // constructing the necessary self-referential PHI node doesn't introduce any |
| // conflicts; this isn't too difficult, but the previous code for doing this |
| // was incorrect. |
| // |
| // Note that if this check finds a live use, BB dominates Succ, so BB is |
| // something like a loop pre-header (or rarely, a part of an irreducible CFG); |
| // folding the branch isn't profitable in that case anyway. |
| if (!Succ->getSinglePredecessor()) { |
| BasicBlock::iterator BBI = BB->begin(); |
| while (isa<PHINode>(*BBI)) { |
| for (Use &U : BBI->uses()) { |
| if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) { |
| if (PN->getIncomingBlock(U) != BB) |
| return false; |
| } else { |
| return false; |
| } |
| } |
| ++BBI; |
| } |
| } |
| |
| DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB); |
| |
| if (isa<PHINode>(Succ->begin())) { |
| // If there is more than one pred of succ, and there are PHI nodes in |
| // the successor, then we need to add incoming edges for the PHI nodes |
| // |
| const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB)); |
| |
| // Loop over all of the PHI nodes in the successor of BB. |
| for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) { |
| PHINode *PN = cast<PHINode>(I); |
| |
| redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN); |
| } |
| } |
| |
| if (Succ->getSinglePredecessor()) { |
| // BB is the only predecessor of Succ, so Succ will end up with exactly |
| // the same predecessors BB had. |
| |
| // Copy over any phi, debug or lifetime instruction. |
| BB->getTerminator()->eraseFromParent(); |
| Succ->getInstList().splice(Succ->getFirstNonPHI(), BB->getInstList()); |
| } else { |
| while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) { |
| // We explicitly check for such uses in CanPropagatePredecessorsForPHIs. |
| assert(PN->use_empty() && "There shouldn't be any uses here!"); |
| PN->eraseFromParent(); |
| } |
| } |
| |
| // Everything that jumped to BB now goes to Succ. |
| BB->replaceAllUsesWith(Succ); |
| if (!Succ->hasName()) Succ->takeName(BB); |
| BB->eraseFromParent(); // Delete the old basic block. |
| return true; |
| } |
| |
| /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI |
| /// nodes in this block. This doesn't try to be clever about PHI nodes |
| /// which differ only in the order of the incoming values, but instcombine |
| /// orders them so it usually won't matter. |
| /// |
| bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) { |
| // This implementation doesn't currently consider undef operands |
| // specially. Theoretically, two phis which are identical except for |
| // one having an undef where the other doesn't could be collapsed. |
| |
| struct PHIDenseMapInfo { |
| static PHINode *getEmptyKey() { |
| return DenseMapInfo<PHINode *>::getEmptyKey(); |
| } |
| static PHINode *getTombstoneKey() { |
| return DenseMapInfo<PHINode *>::getTombstoneKey(); |
| } |
| static unsigned getHashValue(PHINode *PN) { |
| // Compute a hash value on the operands. Instcombine will likely have |
| // sorted them, which helps expose duplicates, but we have to check all |
| // the operands to be safe in case instcombine hasn't run. |
| return static_cast<unsigned>(hash_combine( |
| hash_combine_range(PN->value_op_begin(), PN->value_op_end()), |
| hash_combine_range(PN->block_begin(), PN->block_end()))); |
| } |
| static bool isEqual(PHINode *LHS, PHINode *RHS) { |
| if (LHS == getEmptyKey() || LHS == getTombstoneKey() || |
| RHS == getEmptyKey() || RHS == getTombstoneKey()) |
| return LHS == RHS; |
| return LHS->isIdenticalTo(RHS); |
| } |
| }; |
| |
| // Set of unique PHINodes. |
| DenseSet<PHINode *, PHIDenseMapInfo> PHISet; |
| |
| // Examine each PHI. |
| bool Changed = false; |
| for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I++);) { |
| auto Inserted = PHISet.insert(PN); |
| if (!Inserted.second) { |
| // A duplicate. Replace this PHI with its duplicate. |
| PN->replaceAllUsesWith(*Inserted.first); |
| PN->eraseFromParent(); |
| Changed = true; |
| |
| // The RAUW can change PHIs that we already visited. Start over from the |
| // beginning. |
| PHISet.clear(); |
| I = BB->begin(); |
| } |
| } |
| |
| return Changed; |
| } |
| |
| /// enforceKnownAlignment - If the specified pointer points to an object that |
| /// we control, modify the object's alignment to PrefAlign. This isn't |
| /// often possible though. If alignment is important, a more reliable approach |
| /// is to simply align all global variables and allocation instructions to |
| /// their preferred alignment from the beginning. |
| /// |
| static unsigned enforceKnownAlignment(Value *V, unsigned Align, |
| unsigned PrefAlign, |
| const DataLayout &DL) { |
| V = V->stripPointerCasts(); |
| |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) { |
| // If the preferred alignment is greater than the natural stack alignment |
| // then don't round up. This avoids dynamic stack realignment. |
| if (DL.exceedsNaturalStackAlignment(PrefAlign)) |
| return Align; |
| // If there is a requested alignment and if this is an alloca, round up. |
| if (AI->getAlignment() >= PrefAlign) |
| return AI->getAlignment(); |
| AI->setAlignment(PrefAlign); |
| return PrefAlign; |
| } |
| |
| if (auto *GO = dyn_cast<GlobalObject>(V)) { |
| // If there is a large requested alignment and we can, bump up the alignment |
| // of the global. If the memory we set aside for the global may not be the |
| // memory used by the final program then it is impossible for us to reliably |
| // enforce the preferred alignment. |
| if (!GO->isStrongDefinitionForLinker()) |
| return Align; |
| |
| if (GO->getAlignment() >= PrefAlign) |
| return GO->getAlignment(); |
| // We can only increase the alignment of the global if it has no alignment |
| // specified or if it is not assigned a section. If it is assigned a |
| // section, the global could be densely packed with other objects in the |
| // section, increasing the alignment could cause padding issues. |
| if (!GO->hasSection() || GO->getAlignment() == 0) |
| GO->setAlignment(PrefAlign); |
| return GO->getAlignment(); |
| } |
| |
| return Align; |
| } |
| |
| /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that |
| /// we can determine, return it, otherwise return 0. If PrefAlign is specified, |
| /// and it is more than the alignment of the ultimate object, see if we can |
| /// increase the alignment of the ultimate object, making this check succeed. |
| unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign, |
| const DataLayout &DL, |
| const Instruction *CxtI, |
| AssumptionCache *AC, |
| const DominatorTree *DT) { |
| assert(V->getType()->isPointerTy() && |
| "getOrEnforceKnownAlignment expects a pointer!"); |
| unsigned BitWidth = DL.getPointerTypeSizeInBits(V->getType()); |
| |
| APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); |
| computeKnownBits(V, KnownZero, KnownOne, DL, 0, AC, CxtI, DT); |
| unsigned TrailZ = KnownZero.countTrailingOnes(); |
| |
| // Avoid trouble with ridiculously large TrailZ values, such as |
| // those computed from a null pointer. |
| TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1)); |
| |
| unsigned Align = 1u << std::min(BitWidth - 1, TrailZ); |
| |
| // LLVM doesn't support alignments larger than this currently. |
| Align = std::min(Align, +Value::MaximumAlignment); |
| |
| if (PrefAlign > Align) |
| Align = enforceKnownAlignment(V, Align, PrefAlign, DL); |
| |
| // We don't need to make any adjustment. |
| return Align; |
| } |
| |
| ///===---------------------------------------------------------------------===// |
| /// Dbg Intrinsic utilities |
| /// |
| |
| /// See if there is a dbg.value intrinsic for DIVar before I. |
| static bool LdStHasDebugValue(const DILocalVariable *DIVar, Instruction *I) { |
| // Since we can't guarantee that the original dbg.declare instrinsic |
| // is removed by LowerDbgDeclare(), we need to make sure that we are |
| // not inserting the same dbg.value intrinsic over and over. |
| llvm::BasicBlock::InstListType::iterator PrevI(I); |
| if (PrevI != I->getParent()->getInstList().begin()) { |
| --PrevI; |
| if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI)) |
| if (DVI->getValue() == I->getOperand(0) && |
| DVI->getOffset() == 0 && |
| DVI->getVariable() == DIVar) |
| return true; |
| } |
| return false; |
| } |
| |
| /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value |
| /// that has an associated llvm.dbg.decl intrinsic. |
| bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, |
| StoreInst *SI, DIBuilder &Builder) { |
| auto *DIVar = DDI->getVariable(); |
| auto *DIExpr = DDI->getExpression(); |
| assert(DIVar && "Missing variable"); |
| |
| if (LdStHasDebugValue(DIVar, SI)) |
| return true; |
| |
| // If an argument is zero extended then use argument directly. The ZExt |
| // may be zapped by an optimization pass in future. |
| Argument *ExtendedArg = nullptr; |
| if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0))) |
| ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0)); |
| if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0))) |
| ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0)); |
| if (ExtendedArg) |
| Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, DIExpr, |
| DDI->getDebugLoc(), SI); |
| else |
| Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar, DIExpr, |
| DDI->getDebugLoc(), SI); |
| return true; |
| } |
| |
| /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value |
| /// that has an associated llvm.dbg.decl intrinsic. |
| bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, |
| LoadInst *LI, DIBuilder &Builder) { |
| auto *DIVar = DDI->getVariable(); |
| auto *DIExpr = DDI->getExpression(); |
| assert(DIVar && "Missing variable"); |
| |
| if (LdStHasDebugValue(DIVar, LI)) |
| return true; |
| |
| Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0, DIVar, DIExpr, |
| DDI->getDebugLoc(), LI); |
| return true; |
| } |
| |
| /// Determine whether this alloca is either a VLA or an array. |
| static bool isArray(AllocaInst *AI) { |
| return AI->isArrayAllocation() || |
| AI->getType()->getElementType()->isArrayTy(); |
| } |
| |
| /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set |
| /// of llvm.dbg.value intrinsics. |
| bool llvm::LowerDbgDeclare(Function &F) { |
| DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false); |
| SmallVector<DbgDeclareInst *, 4> Dbgs; |
| for (auto &FI : F) |
| for (BasicBlock::iterator BI : FI) |
| if (auto DDI = dyn_cast<DbgDeclareInst>(BI)) |
| Dbgs.push_back(DDI); |
| |
| if (Dbgs.empty()) |
| return false; |
| |
| for (auto &I : Dbgs) { |
| DbgDeclareInst *DDI = I; |
| AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress()); |
| // If this is an alloca for a scalar variable, insert a dbg.value |
| // at each load and store to the alloca and erase the dbg.declare. |
| // The dbg.values allow tracking a variable even if it is not |
| // stored on the stack, while the dbg.declare can only describe |
| // the stack slot (and at a lexical-scope granularity). Later |
| // passes will attempt to elide the stack slot. |
| if (AI && !isArray(AI)) { |
| for (User *U : AI->users()) |
| if (StoreInst *SI = dyn_cast<StoreInst>(U)) |
| ConvertDebugDeclareToDebugValue(DDI, SI, DIB); |
| else if (LoadInst *LI = dyn_cast<LoadInst>(U)) |
| ConvertDebugDeclareToDebugValue(DDI, LI, DIB); |
| else if (CallInst *CI = dyn_cast<CallInst>(U)) { |
| // This is a call by-value or some other instruction that |
| // takes a pointer to the variable. Insert a *value* |
| // intrinsic that describes the alloca. |
| DIB.insertDbgValueIntrinsic(AI, 0, DDI->getVariable(), |
| DDI->getExpression(), DDI->getDebugLoc(), |
| CI); |
| } |
| DDI->eraseFromParent(); |
| } |
| } |
| return true; |
| } |
| |
| /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the |
| /// alloca 'V', if any. |
| DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) { |
| if (auto *L = LocalAsMetadata::getIfExists(V)) |
| if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L)) |
| for (User *U : MDV->users()) |
| if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U)) |
| return DDI; |
| |
| return nullptr; |
| } |
| |
| bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress, |
| DIBuilder &Builder, bool Deref) { |
| DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI); |
| if (!DDI) |
| return false; |
| DebugLoc Loc = DDI->getDebugLoc(); |
| auto *DIVar = DDI->getVariable(); |
| auto *DIExpr = DDI->getExpression(); |
| assert(DIVar && "Missing variable"); |
| |
| if (Deref) { |
| // Create a copy of the original DIDescriptor for user variable, prepending |
| // "deref" operation to a list of address elements, as new llvm.dbg.declare |
| // will take a value storing address of the memory for variable, not |
| // alloca itself. |
| SmallVector<uint64_t, 4> NewDIExpr; |
| NewDIExpr.push_back(dwarf::DW_OP_deref); |
| if (DIExpr) |
| NewDIExpr.append(DIExpr->elements_begin(), DIExpr->elements_end()); |
| DIExpr = Builder.createExpression(NewDIExpr); |
| } |
| |
| // Insert llvm.dbg.declare in the same basic block as the original alloca, |
| // and remove old llvm.dbg.declare. |
| BasicBlock *BB = AI->getParent(); |
| Builder.insertDeclare(NewAllocaAddress, DIVar, DIExpr, Loc, BB); |
| DDI->eraseFromParent(); |
| return true; |
| } |
| |
| /// changeToUnreachable - Insert an unreachable instruction before the specified |
| /// instruction, making it and the rest of the code in the block dead. |
| static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) { |
| BasicBlock *BB = I->getParent(); |
| // Loop over all of the successors, removing BB's entry from any PHI |
| // nodes. |
| for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) |
| (*SI)->removePredecessor(BB); |
| |
| // Insert a call to llvm.trap right before this. This turns the undefined |
| // behavior into a hard fail instead of falling through into random code. |
| if (UseLLVMTrap) { |
| Function *TrapFn = |
| Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap); |
| CallInst *CallTrap = CallInst::Create(TrapFn, "", I); |
| CallTrap->setDebugLoc(I->getDebugLoc()); |
| } |
| new UnreachableInst(I->getContext(), I); |
| |
| // All instructions after this are dead. |
| BasicBlock::iterator BBI = I, BBE = BB->end(); |
| while (BBI != BBE) { |
| if (!BBI->use_empty()) |
| BBI->replaceAllUsesWith(UndefValue::get(BBI->getType())); |
| BB->getInstList().erase(BBI++); |
| } |
| } |
| |
| /// changeToCall - Convert the specified invoke into a normal call. |
| static void changeToCall(InvokeInst *II) { |
| SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3); |
| CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II); |
| NewCall->takeName(II); |
| NewCall->setCallingConv(II->getCallingConv()); |
| NewCall->setAttributes(II->getAttributes()); |
| NewCall->setDebugLoc(II->getDebugLoc()); |
| II->replaceAllUsesWith(NewCall); |
| |
| // Follow the call by a branch to the normal destination. |
| BranchInst::Create(II->getNormalDest(), II); |
| |
| // Update PHI nodes in the unwind destination |
| II->getUnwindDest()->removePredecessor(II->getParent()); |
| II->eraseFromParent(); |
| } |
| |
| static bool markAliveBlocks(Function &F, |
| SmallPtrSetImpl<BasicBlock*> &Reachable) { |
| |
| SmallVector<BasicBlock*, 128> Worklist; |
| BasicBlock *BB = F.begin(); |
| Worklist.push_back(BB); |
| Reachable.insert(BB); |
| bool Changed = false; |
| do { |
| BB = Worklist.pop_back_val(); |
| |
| // Do a quick scan of the basic block, turning any obviously unreachable |
| // instructions into LLVM unreachable insts. The instruction combining pass |
| // canonicalizes unreachable insts into stores to null or undef. |
| for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){ |
| // Assumptions that are known to be false are equivalent to unreachable. |
| // Also, if the condition is undefined, then we make the choice most |
| // beneficial to the optimizer, and choose that to also be unreachable. |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI)) |
| if (II->getIntrinsicID() == Intrinsic::assume) { |
| bool MakeUnreachable = false; |
| if (isa<UndefValue>(II->getArgOperand(0))) |
| MakeUnreachable = true; |
| else if (ConstantInt *Cond = |
| dyn_cast<ConstantInt>(II->getArgOperand(0))) |
| MakeUnreachable = Cond->isZero(); |
| |
| if (MakeUnreachable) { |
| // Don't insert a call to llvm.trap right before the unreachable. |
| changeToUnreachable(BBI, false); |
| Changed = true; |
| break; |
| } |
| } |
| |
| if (CallInst *CI = dyn_cast<CallInst>(BBI)) { |
| if (CI->doesNotReturn()) { |
| // If we found a call to a no-return function, insert an unreachable |
| // instruction after it. Make sure there isn't *already* one there |
| // though. |
| ++BBI; |
| if (!isa<UnreachableInst>(BBI)) { |
| // Don't insert a call to llvm.trap right before the unreachable. |
| changeToUnreachable(BBI, false); |
| Changed = true; |
| } |
| break; |
| } |
| } |
| |
| // Store to undef and store to null are undefined and used to signal that |
| // they should be changed to unreachable by passes that can't modify the |
| // CFG. |
| if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) { |
| // Don't touch volatile stores. |
| if (SI->isVolatile()) continue; |
| |
| Value *Ptr = SI->getOperand(1); |
| |
| if (isa<UndefValue>(Ptr) || |
| (isa<ConstantPointerNull>(Ptr) && |
| SI->getPointerAddressSpace() == 0)) { |
| changeToUnreachable(SI, true); |
| Changed = true; |
| break; |
| } |
| } |
| } |
| |
| // Turn invokes that call 'nounwind' functions into ordinary calls. |
| if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { |
| Value *Callee = II->getCalledValue(); |
| if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) { |
| changeToUnreachable(II, true); |
| Changed = true; |
| } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) { |
| if (II->use_empty() && II->onlyReadsMemory()) { |
| // jump to the normal destination branch. |
| BranchInst::Create(II->getNormalDest(), II); |
| II->getUnwindDest()->removePredecessor(II->getParent()); |
| II->eraseFromParent(); |
| } else |
| changeToCall(II); |
| Changed = true; |
| } |
| } |
| |
| Changed |= ConstantFoldTerminator(BB, true); |
| for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) |
| if (Reachable.insert(*SI).second) |
| Worklist.push_back(*SI); |
| } while (!Worklist.empty()); |
| return Changed; |
| } |
| |
| /// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even |
| /// if they are in a dead cycle. Return true if a change was made, false |
| /// otherwise. |
| bool llvm::removeUnreachableBlocks(Function &F) { |
| SmallPtrSet<BasicBlock*, 128> Reachable; |
| bool Changed = markAliveBlocks(F, Reachable); |
| |
| // If there are unreachable blocks in the CFG... |
| if (Reachable.size() == F.size()) |
| return Changed; |
| |
| assert(Reachable.size() < F.size()); |
| NumRemoved += F.size()-Reachable.size(); |
| |
| // Loop over all of the basic blocks that are not reachable, dropping all of |
| // their internal references... |
| for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) { |
| if (Reachable.count(BB)) |
| continue; |
| |
| for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) |
| if (Reachable.count(*SI)) |
| (*SI)->removePredecessor(BB); |
| BB->dropAllReferences(); |
| } |
| |
| for (Function::iterator I = ++F.begin(); I != F.end();) |
| if (!Reachable.count(I)) |
| I = F.getBasicBlockList().erase(I); |
| else |
| ++I; |
| |
| return true; |
| } |
| |
| void llvm::combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsigned> KnownIDs) { |
| SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata; |
| K->dropUnknownMetadata(KnownIDs); |
| K->getAllMetadataOtherThanDebugLoc(Metadata); |
| for (unsigned i = 0, n = Metadata.size(); i < n; ++i) { |
| unsigned Kind = Metadata[i].first; |
| MDNode *JMD = J->getMetadata(Kind); |
| MDNode *KMD = Metadata[i].second; |
| |
| switch (Kind) { |
| default: |
| K->setMetadata(Kind, nullptr); // Remove unknown metadata |
| break; |
| case LLVMContext::MD_dbg: |
| llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg"); |
| case LLVMContext::MD_tbaa: |
| K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD)); |
| break; |
| case LLVMContext::MD_alias_scope: |
| K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD)); |
| break; |
| case LLVMContext::MD_noalias: |
| K->setMetadata(Kind, MDNode::intersect(JMD, KMD)); |
| break; |
| case LLVMContext::MD_range: |
| K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD)); |
| break; |
| case LLVMContext::MD_fpmath: |
| K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD)); |
| break; |
| case LLVMContext::MD_invariant_load: |
| // Only set the !invariant.load if it is present in both instructions. |
| K->setMetadata(Kind, JMD); |
| break; |
| case LLVMContext::MD_nonnull: |
| // Only set the !nonnull if it is present in both instructions. |
| K->setMetadata(Kind, JMD); |
| break; |
| } |
| } |
| } |
| |
| unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To, |
| DominatorTree &DT, |
| const BasicBlockEdge &Root) { |
| assert(From->getType() == To->getType()); |
| |
| unsigned Count = 0; |
| for (Value::use_iterator UI = From->use_begin(), UE = From->use_end(); |
| UI != UE; ) { |
| Use &U = *UI++; |
| if (DT.dominates(Root, U)) { |
| U.set(To); |
| DEBUG(dbgs() << "Replace dominated use of '" |
| << From->getName() << "' as " |
| << *To << " in " << *U << "\n"); |
| ++Count; |
| } |
| } |
| return Count; |
| } |