| //===- CodeGenPrepare.cpp - Prepare a function for code generation --------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass munges the code in the input function to better prepare it for |
| // SelectionDAG-based code generation. This works around limitations in it's |
| // basic-block-at-a-time approach. It should eventually be removed. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "codegenprepare" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/Analysis/DominatorInternals.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/ProfileInfo.h" |
| #include "llvm/Assembly/Writer.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DataLayout.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Function.h" |
| #include "llvm/IRBuilder.h" |
| #include "llvm/InlineAsm.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/PatternMatch.h" |
| #include "llvm/Support/ValueHandle.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetLibraryInfo.h" |
| #include "llvm/Target/TargetLowering.h" |
| #include "llvm/Transforms/Utils/AddrModeMatcher.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/BuildLibCalls.h" |
| #include "llvm/Transforms/Utils/BypassSlowDivision.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| STATISTIC(NumBlocksElim, "Number of blocks eliminated"); |
| STATISTIC(NumPHIsElim, "Number of trivial PHIs eliminated"); |
| STATISTIC(NumGEPsElim, "Number of GEPs converted to casts"); |
| STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of " |
| "sunken Cmps"); |
| STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses " |
| "of sunken Casts"); |
| STATISTIC(NumMemoryInsts, "Number of memory instructions whose address " |
| "computations were sunk"); |
| STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads"); |
| STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized"); |
| STATISTIC(NumRetsDup, "Number of return instructions duplicated"); |
| STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved"); |
| STATISTIC(NumSelectsExpanded, "Number of selects turned into branches"); |
| |
| static cl::opt<bool> DisableBranchOpts( |
| "disable-cgp-branch-opts", cl::Hidden, cl::init(false), |
| cl::desc("Disable branch optimizations in CodeGenPrepare")); |
| |
| static cl::opt<bool> DisableSelectToBranch( |
| "disable-cgp-select2branch", cl::Hidden, cl::init(false), |
| cl::desc("Disable select to branch conversion.")); |
| |
| namespace { |
| class CodeGenPrepare : public FunctionPass { |
| /// TLI - Keep a pointer of a TargetLowering to consult for determining |
| /// transformation profitability. |
| const TargetLowering *TLI; |
| const TargetLibraryInfo *TLInfo; |
| DominatorTree *DT; |
| ProfileInfo *PFI; |
| |
| /// CurInstIterator - As we scan instructions optimizing them, this is the |
| /// next instruction to optimize. Xforms that can invalidate this should |
| /// update it. |
| BasicBlock::iterator CurInstIterator; |
| |
| /// Keeps track of non-local addresses that have been sunk into a block. |
| /// This allows us to avoid inserting duplicate code for blocks with |
| /// multiple load/stores of the same address. |
| DenseMap<Value*, Value*> SunkAddrs; |
| |
| /// ModifiedDT - If CFG is modified in anyway, dominator tree may need to |
| /// be updated. |
| bool ModifiedDT; |
| |
| /// OptSize - True if optimizing for size. |
| bool OptSize; |
| |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| explicit CodeGenPrepare(const TargetLowering *tli = 0) |
| : FunctionPass(ID), TLI(tli) { |
| initializeCodeGenPreparePass(*PassRegistry::getPassRegistry()); |
| } |
| bool runOnFunction(Function &F); |
| |
| const char *getPassName() const { return "CodeGen Prepare"; } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addPreserved<DominatorTree>(); |
| AU.addPreserved<ProfileInfo>(); |
| AU.addRequired<TargetLibraryInfo>(); |
| } |
| |
| private: |
| bool EliminateFallThrough(Function &F); |
| bool EliminateMostlyEmptyBlocks(Function &F); |
| bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const; |
| void EliminateMostlyEmptyBlock(BasicBlock *BB); |
| bool OptimizeBlock(BasicBlock &BB); |
| bool OptimizeInst(Instruction *I); |
| bool OptimizeMemoryInst(Instruction *I, Value *Addr, Type *AccessTy); |
| bool OptimizeInlineAsmInst(CallInst *CS); |
| bool OptimizeCallInst(CallInst *CI); |
| bool MoveExtToFormExtLoad(Instruction *I); |
| bool OptimizeExtUses(Instruction *I); |
| bool OptimizeSelectInst(SelectInst *SI); |
| bool DupRetToEnableTailCallOpts(BasicBlock *BB); |
| bool PlaceDbgValues(Function &F); |
| }; |
| } |
| |
| char CodeGenPrepare::ID = 0; |
| INITIALIZE_PASS_BEGIN(CodeGenPrepare, "codegenprepare", |
| "Optimize for code generation", false, false) |
| INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) |
| INITIALIZE_PASS_END(CodeGenPrepare, "codegenprepare", |
| "Optimize for code generation", false, false) |
| |
| FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) { |
| return new CodeGenPrepare(TLI); |
| } |
| |
| bool CodeGenPrepare::runOnFunction(Function &F) { |
| bool EverMadeChange = false; |
| |
| ModifiedDT = false; |
| TLInfo = &getAnalysis<TargetLibraryInfo>(); |
| DT = getAnalysisIfAvailable<DominatorTree>(); |
| PFI = getAnalysisIfAvailable<ProfileInfo>(); |
| OptSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex, |
| Attribute::OptimizeForSize); |
| |
| /// This optimization identifies DIV instructions that can be |
| /// profitably bypassed and carried out with a shorter, faster divide. |
| if (TLI && TLI->isSlowDivBypassed()) { |
| const DenseMap<unsigned int, unsigned int> &BypassWidths = |
| TLI->getBypassSlowDivWidths(); |
| for (Function::iterator I = F.begin(); I != F.end(); I++) |
| EverMadeChange |= bypassSlowDivision(F, I, BypassWidths); |
| } |
| |
| // Eliminate blocks that contain only PHI nodes and an |
| // unconditional branch. |
| EverMadeChange |= EliminateMostlyEmptyBlocks(F); |
| |
| // llvm.dbg.value is far away from the value then iSel may not be able |
| // handle it properly. iSel will drop llvm.dbg.value if it can not |
| // find a node corresponding to the value. |
| EverMadeChange |= PlaceDbgValues(F); |
| |
| bool MadeChange = true; |
| while (MadeChange) { |
| MadeChange = false; |
| for (Function::iterator I = F.begin(); I != F.end(); ) { |
| BasicBlock *BB = I++; |
| MadeChange |= OptimizeBlock(*BB); |
| } |
| EverMadeChange |= MadeChange; |
| } |
| |
| SunkAddrs.clear(); |
| |
| if (!DisableBranchOpts) { |
| MadeChange = false; |
| SmallPtrSet<BasicBlock*, 8> WorkList; |
| for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { |
| SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB)); |
| MadeChange |= ConstantFoldTerminator(BB, true); |
| if (!MadeChange) continue; |
| |
| for (SmallVectorImpl<BasicBlock*>::iterator |
| II = Successors.begin(), IE = Successors.end(); II != IE; ++II) |
| if (pred_begin(*II) == pred_end(*II)) |
| WorkList.insert(*II); |
| } |
| |
| // Delete the dead blocks and any of their dead successors. |
| MadeChange |= !WorkList.empty(); |
| while (!WorkList.empty()) { |
| BasicBlock *BB = *WorkList.begin(); |
| WorkList.erase(BB); |
| SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB)); |
| |
| DeleteDeadBlock(BB); |
| |
| for (SmallVectorImpl<BasicBlock*>::iterator |
| II = Successors.begin(), IE = Successors.end(); II != IE; ++II) |
| if (pred_begin(*II) == pred_end(*II)) |
| WorkList.insert(*II); |
| } |
| |
| // Merge pairs of basic blocks with unconditional branches, connected by |
| // a single edge. |
| if (EverMadeChange || MadeChange) |
| MadeChange |= EliminateFallThrough(F); |
| |
| if (MadeChange) |
| ModifiedDT = true; |
| EverMadeChange |= MadeChange; |
| } |
| |
| if (ModifiedDT && DT) |
| DT->DT->recalculate(F); |
| |
| return EverMadeChange; |
| } |
| |
| /// EliminateFallThrough - Merge basic blocks which are connected |
| /// by a single edge, where one of the basic blocks has a single successor |
| /// pointing to the other basic block, which has a single predecessor. |
| bool CodeGenPrepare::EliminateFallThrough(Function &F) { |
| bool Changed = false; |
| // Scan all of the blocks in the function, except for the entry block. |
| for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) { |
| BasicBlock *BB = I++; |
| // If the destination block has a single pred, then this is a trivial |
| // edge, just collapse it. |
| BasicBlock *SinglePred = BB->getSinglePredecessor(); |
| |
| // Don't merge if BB's address is taken. |
| if (!SinglePred || SinglePred == BB || BB->hasAddressTaken()) continue; |
| |
| BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator()); |
| if (Term && !Term->isConditional()) { |
| Changed = true; |
| DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n"); |
| // Remember if SinglePred was the entry block of the function. |
| // If so, we will need to move BB back to the entry position. |
| bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock(); |
| MergeBasicBlockIntoOnlyPred(BB, this); |
| |
| if (isEntry && BB != &BB->getParent()->getEntryBlock()) |
| BB->moveBefore(&BB->getParent()->getEntryBlock()); |
| |
| // We have erased a block. Update the iterator. |
| I = BB; |
| } |
| } |
| return Changed; |
| } |
| |
| /// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes, |
| /// debug info directives, and an unconditional branch. Passes before isel |
| /// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for |
| /// isel. Start by eliminating these blocks so we can split them the way we |
| /// want them. |
| bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) { |
| bool MadeChange = false; |
| // Note that this intentionally skips the entry block. |
| for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) { |
| BasicBlock *BB = I++; |
| |
| // If this block doesn't end with an uncond branch, ignore it. |
| BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()); |
| if (!BI || !BI->isUnconditional()) |
| continue; |
| |
| // If the instruction before the branch (skipping debug info) isn't a phi |
| // node, then other stuff is happening here. |
| BasicBlock::iterator BBI = BI; |
| if (BBI != BB->begin()) { |
| --BBI; |
| while (isa<DbgInfoIntrinsic>(BBI)) { |
| if (BBI == BB->begin()) |
| break; |
| --BBI; |
| } |
| if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI)) |
| continue; |
| } |
| |
| // Do not break infinite loops. |
| BasicBlock *DestBB = BI->getSuccessor(0); |
| if (DestBB == BB) |
| continue; |
| |
| if (!CanMergeBlocks(BB, DestBB)) |
| continue; |
| |
| EliminateMostlyEmptyBlock(BB); |
| MadeChange = true; |
| } |
| return MadeChange; |
| } |
| |
| /// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a |
| /// single uncond branch between them, and BB contains no other non-phi |
| /// instructions. |
| bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB, |
| const BasicBlock *DestBB) const { |
| // We only want to eliminate blocks whose phi nodes are used by phi nodes in |
| // the successor. If there are more complex condition (e.g. preheaders), |
| // don't mess around with them. |
| BasicBlock::const_iterator BBI = BB->begin(); |
| while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) { |
| for (Value::const_use_iterator UI = PN->use_begin(), E = PN->use_end(); |
| UI != E; ++UI) { |
| const Instruction *User = cast<Instruction>(*UI); |
| if (User->getParent() != DestBB || !isa<PHINode>(User)) |
| return false; |
| // If User is inside DestBB block and it is a PHINode then check |
| // incoming value. If incoming value is not from BB then this is |
| // a complex condition (e.g. preheaders) we want to avoid here. |
| if (User->getParent() == DestBB) { |
| if (const PHINode *UPN = dyn_cast<PHINode>(User)) |
| for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) { |
| Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I)); |
| if (Insn && Insn->getParent() == BB && |
| Insn->getParent() != UPN->getIncomingBlock(I)) |
| return false; |
| } |
| } |
| } |
| } |
| |
| // If BB and DestBB contain any common predecessors, then the phi nodes in BB |
| // and DestBB may have conflicting incoming values for the block. If so, we |
| // can't merge the block. |
| const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin()); |
| if (!DestBBPN) return true; // no conflict. |
| |
| // Collect the preds of BB. |
| SmallPtrSet<const BasicBlock*, 16> BBPreds; |
| if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) { |
| // It is faster to get preds from a PHI than with pred_iterator. |
| for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i) |
| BBPreds.insert(BBPN->getIncomingBlock(i)); |
| } else { |
| BBPreds.insert(pred_begin(BB), pred_end(BB)); |
| } |
| |
| // Walk the preds of DestBB. |
| for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) { |
| BasicBlock *Pred = DestBBPN->getIncomingBlock(i); |
| if (BBPreds.count(Pred)) { // Common predecessor? |
| BBI = DestBB->begin(); |
| while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) { |
| const Value *V1 = PN->getIncomingValueForBlock(Pred); |
| const Value *V2 = PN->getIncomingValueForBlock(BB); |
| |
| // If V2 is a phi node in BB, look up what the mapped value will be. |
| if (const PHINode *V2PN = dyn_cast<PHINode>(V2)) |
| if (V2PN->getParent() == BB) |
| V2 = V2PN->getIncomingValueForBlock(Pred); |
| |
| // If there is a conflict, bail out. |
| if (V1 != V2) return false; |
| } |
| } |
| } |
| |
| return true; |
| } |
| |
| |
| /// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and |
| /// an unconditional branch in it. |
| void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) { |
| BranchInst *BI = cast<BranchInst>(BB->getTerminator()); |
| BasicBlock *DestBB = BI->getSuccessor(0); |
| |
| DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB); |
| |
| // If the destination block has a single pred, then this is a trivial edge, |
| // just collapse it. |
| if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) { |
| if (SinglePred != DestBB) { |
| // Remember if SinglePred was the entry block of the function. If so, we |
| // will need to move BB back to the entry position. |
| bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock(); |
| MergeBasicBlockIntoOnlyPred(DestBB, this); |
| |
| if (isEntry && BB != &BB->getParent()->getEntryBlock()) |
| BB->moveBefore(&BB->getParent()->getEntryBlock()); |
| |
| DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n"); |
| return; |
| } |
| } |
| |
| // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB |
| // to handle the new incoming edges it is about to have. |
| PHINode *PN; |
| for (BasicBlock::iterator BBI = DestBB->begin(); |
| (PN = dyn_cast<PHINode>(BBI)); ++BBI) { |
| // Remove the incoming value for BB, and remember it. |
| Value *InVal = PN->removeIncomingValue(BB, false); |
| |
| // Two options: either the InVal is a phi node defined in BB or it is some |
| // value that dominates BB. |
| PHINode *InValPhi = dyn_cast<PHINode>(InVal); |
| if (InValPhi && InValPhi->getParent() == BB) { |
| // Add all of the input values of the input PHI as inputs of this phi. |
| for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i) |
| PN->addIncoming(InValPhi->getIncomingValue(i), |
| InValPhi->getIncomingBlock(i)); |
| } else { |
| // Otherwise, add one instance of the dominating value for each edge that |
| // we will be adding. |
| if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) { |
| for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i) |
| PN->addIncoming(InVal, BBPN->getIncomingBlock(i)); |
| } else { |
| for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) |
| PN->addIncoming(InVal, *PI); |
| } |
| } |
| } |
| |
| // The PHIs are now updated, change everything that refers to BB to use |
| // DestBB and remove BB. |
| BB->replaceAllUsesWith(DestBB); |
| if (DT && !ModifiedDT) { |
| BasicBlock *BBIDom = DT->getNode(BB)->getIDom()->getBlock(); |
| BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock(); |
| BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom); |
| DT->changeImmediateDominator(DestBB, NewIDom); |
| DT->eraseNode(BB); |
| } |
| if (PFI) { |
| PFI->replaceAllUses(BB, DestBB); |
| PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB)); |
| } |
| BB->eraseFromParent(); |
| ++NumBlocksElim; |
| |
| DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n"); |
| } |
| |
| /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop |
| /// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC), |
| /// sink it into user blocks to reduce the number of virtual |
| /// registers that must be created and coalesced. |
| /// |
| /// Return true if any changes are made. |
| /// |
| static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){ |
| // If this is a noop copy, |
| EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType()); |
| EVT DstVT = TLI.getValueType(CI->getType()); |
| |
| // This is an fp<->int conversion? |
| if (SrcVT.isInteger() != DstVT.isInteger()) |
| return false; |
| |
| // If this is an extension, it will be a zero or sign extension, which |
| // isn't a noop. |
| if (SrcVT.bitsLT(DstVT)) return false; |
| |
| // If these values will be promoted, find out what they will be promoted |
| // to. This helps us consider truncates on PPC as noop copies when they |
| // are. |
| if (TLI.getTypeAction(CI->getContext(), SrcVT) == |
| TargetLowering::TypePromoteInteger) |
| SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT); |
| if (TLI.getTypeAction(CI->getContext(), DstVT) == |
| TargetLowering::TypePromoteInteger) |
| DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT); |
| |
| // If, after promotion, these are the same types, this is a noop copy. |
| if (SrcVT != DstVT) |
| return false; |
| |
| BasicBlock *DefBB = CI->getParent(); |
| |
| /// InsertedCasts - Only insert a cast in each block once. |
| DenseMap<BasicBlock*, CastInst*> InsertedCasts; |
| |
| bool MadeChange = false; |
| for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end(); |
| UI != E; ) { |
| Use &TheUse = UI.getUse(); |
| Instruction *User = cast<Instruction>(*UI); |
| |
| // Figure out which BB this cast is used in. For PHI's this is the |
| // appropriate predecessor block. |
| BasicBlock *UserBB = User->getParent(); |
| if (PHINode *PN = dyn_cast<PHINode>(User)) { |
| UserBB = PN->getIncomingBlock(UI); |
| } |
| |
| // Preincrement use iterator so we don't invalidate it. |
| ++UI; |
| |
| // If this user is in the same block as the cast, don't change the cast. |
| if (UserBB == DefBB) continue; |
| |
| // If we have already inserted a cast into this block, use it. |
| CastInst *&InsertedCast = InsertedCasts[UserBB]; |
| |
| if (!InsertedCast) { |
| BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); |
| InsertedCast = |
| CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "", |
| InsertPt); |
| MadeChange = true; |
| } |
| |
| // Replace a use of the cast with a use of the new cast. |
| TheUse = InsertedCast; |
| ++NumCastUses; |
| } |
| |
| // If we removed all uses, nuke the cast. |
| if (CI->use_empty()) { |
| CI->eraseFromParent(); |
| MadeChange = true; |
| } |
| |
| return MadeChange; |
| } |
| |
| /// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce |
| /// the number of virtual registers that must be created and coalesced. This is |
| /// a clear win except on targets with multiple condition code registers |
| /// (PowerPC), where it might lose; some adjustment may be wanted there. |
| /// |
| /// Return true if any changes are made. |
| static bool OptimizeCmpExpression(CmpInst *CI) { |
| BasicBlock *DefBB = CI->getParent(); |
| |
| /// InsertedCmp - Only insert a cmp in each block once. |
| DenseMap<BasicBlock*, CmpInst*> InsertedCmps; |
| |
| bool MadeChange = false; |
| for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end(); |
| UI != E; ) { |
| Use &TheUse = UI.getUse(); |
| Instruction *User = cast<Instruction>(*UI); |
| |
| // Preincrement use iterator so we don't invalidate it. |
| ++UI; |
| |
| // Don't bother for PHI nodes. |
| if (isa<PHINode>(User)) |
| continue; |
| |
| // Figure out which BB this cmp is used in. |
| BasicBlock *UserBB = User->getParent(); |
| |
| // If this user is in the same block as the cmp, don't change the cmp. |
| if (UserBB == DefBB) continue; |
| |
| // If we have already inserted a cmp into this block, use it. |
| CmpInst *&InsertedCmp = InsertedCmps[UserBB]; |
| |
| if (!InsertedCmp) { |
| BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); |
| InsertedCmp = |
| CmpInst::Create(CI->getOpcode(), |
| CI->getPredicate(), CI->getOperand(0), |
| CI->getOperand(1), "", InsertPt); |
| MadeChange = true; |
| } |
| |
| // Replace a use of the cmp with a use of the new cmp. |
| TheUse = InsertedCmp; |
| ++NumCmpUses; |
| } |
| |
| // If we removed all uses, nuke the cmp. |
| if (CI->use_empty()) |
| CI->eraseFromParent(); |
| |
| return MadeChange; |
| } |
| |
| namespace { |
| class CodeGenPrepareFortifiedLibCalls : public SimplifyFortifiedLibCalls { |
| protected: |
| void replaceCall(Value *With) { |
| CI->replaceAllUsesWith(With); |
| CI->eraseFromParent(); |
| } |
| bool isFoldable(unsigned SizeCIOp, unsigned, bool) const { |
| if (ConstantInt *SizeCI = |
| dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp))) |
| return SizeCI->isAllOnesValue(); |
| return false; |
| } |
| }; |
| } // end anonymous namespace |
| |
| bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) { |
| BasicBlock *BB = CI->getParent(); |
| |
| // Lower inline assembly if we can. |
| // If we found an inline asm expession, and if the target knows how to |
| // lower it to normal LLVM code, do so now. |
| if (TLI && isa<InlineAsm>(CI->getCalledValue())) { |
| if (TLI->ExpandInlineAsm(CI)) { |
| // Avoid invalidating the iterator. |
| CurInstIterator = BB->begin(); |
| // Avoid processing instructions out of order, which could cause |
| // reuse before a value is defined. |
| SunkAddrs.clear(); |
| return true; |
| } |
| // Sink address computing for memory operands into the block. |
| if (OptimizeInlineAsmInst(CI)) |
| return true; |
| } |
| |
| // Lower all uses of llvm.objectsize.* |
| IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI); |
| if (II && II->getIntrinsicID() == Intrinsic::objectsize) { |
| bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1); |
| Type *ReturnTy = CI->getType(); |
| Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL); |
| |
| // Substituting this can cause recursive simplifications, which can |
| // invalidate our iterator. Use a WeakVH to hold onto it in case this |
| // happens. |
| WeakVH IterHandle(CurInstIterator); |
| |
| replaceAndRecursivelySimplify(CI, RetVal, TLI ? TLI->getDataLayout() : 0, |
| TLInfo, ModifiedDT ? 0 : DT); |
| |
| // If the iterator instruction was recursively deleted, start over at the |
| // start of the block. |
| if (IterHandle != CurInstIterator) { |
| CurInstIterator = BB->begin(); |
| SunkAddrs.clear(); |
| } |
| return true; |
| } |
| |
| if (II && TLI) { |
| SmallVector<Value*, 2> PtrOps; |
| Type *AccessTy; |
| if (TLI->GetAddrModeArguments(II, PtrOps, AccessTy)) |
| while (!PtrOps.empty()) |
| if (OptimizeMemoryInst(II, PtrOps.pop_back_val(), AccessTy)) |
| return true; |
| } |
| |
| // From here on out we're working with named functions. |
| if (CI->getCalledFunction() == 0) return false; |
| |
| // We'll need DataLayout from here on out. |
| const DataLayout *TD = TLI ? TLI->getDataLayout() : 0; |
| if (!TD) return false; |
| |
| // Lower all default uses of _chk calls. This is very similar |
| // to what InstCombineCalls does, but here we are only lowering calls |
| // that have the default "don't know" as the objectsize. Anything else |
| // should be left alone. |
| CodeGenPrepareFortifiedLibCalls Simplifier; |
| return Simplifier.fold(CI, TD, TLInfo); |
| } |
| |
| /// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return |
| /// instructions to the predecessor to enable tail call optimizations. The |
| /// case it is currently looking for is: |
| /// @code |
| /// bb0: |
| /// %tmp0 = tail call i32 @f0() |
| /// br label %return |
| /// bb1: |
| /// %tmp1 = tail call i32 @f1() |
| /// br label %return |
| /// bb2: |
| /// %tmp2 = tail call i32 @f2() |
| /// br label %return |
| /// return: |
| /// %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ] |
| /// ret i32 %retval |
| /// @endcode |
| /// |
| /// => |
| /// |
| /// @code |
| /// bb0: |
| /// %tmp0 = tail call i32 @f0() |
| /// ret i32 %tmp0 |
| /// bb1: |
| /// %tmp1 = tail call i32 @f1() |
| /// ret i32 %tmp1 |
| /// bb2: |
| /// %tmp2 = tail call i32 @f2() |
| /// ret i32 %tmp2 |
| /// @endcode |
| bool CodeGenPrepare::DupRetToEnableTailCallOpts(BasicBlock *BB) { |
| if (!TLI) |
| return false; |
| |
| ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()); |
| if (!RI) |
| return false; |
| |
| PHINode *PN = 0; |
| BitCastInst *BCI = 0; |
| Value *V = RI->getReturnValue(); |
| if (V) { |
| BCI = dyn_cast<BitCastInst>(V); |
| if (BCI) |
| V = BCI->getOperand(0); |
| |
| PN = dyn_cast<PHINode>(V); |
| if (!PN) |
| return false; |
| } |
| |
| if (PN && PN->getParent() != BB) |
| return false; |
| |
| // It's not safe to eliminate the sign / zero extension of the return value. |
| // See llvm::isInTailCallPosition(). |
| const Function *F = BB->getParent(); |
| Attribute CallerRetAttr = F->getAttributes().getRetAttributes(); |
| if (CallerRetAttr.hasAttribute(Attribute::ZExt) || |
| CallerRetAttr.hasAttribute(Attribute::SExt)) |
| return false; |
| |
| // Make sure there are no instructions between the PHI and return, or that the |
| // return is the first instruction in the block. |
| if (PN) { |
| BasicBlock::iterator BI = BB->begin(); |
| do { ++BI; } while (isa<DbgInfoIntrinsic>(BI)); |
| if (&*BI == BCI) |
| // Also skip over the bitcast. |
| ++BI; |
| if (&*BI != RI) |
| return false; |
| } else { |
| BasicBlock::iterator BI = BB->begin(); |
| while (isa<DbgInfoIntrinsic>(BI)) ++BI; |
| if (&*BI != RI) |
| return false; |
| } |
| |
| /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail |
| /// call. |
| SmallVector<CallInst*, 4> TailCalls; |
| if (PN) { |
| for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) { |
| CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I)); |
| // Make sure the phi value is indeed produced by the tail call. |
| if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) && |
| TLI->mayBeEmittedAsTailCall(CI)) |
| TailCalls.push_back(CI); |
| } |
| } else { |
| SmallPtrSet<BasicBlock*, 4> VisitedBBs; |
| for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) { |
| if (!VisitedBBs.insert(*PI)) |
| continue; |
| |
| BasicBlock::InstListType &InstList = (*PI)->getInstList(); |
| BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin(); |
| BasicBlock::InstListType::reverse_iterator RE = InstList.rend(); |
| do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI)); |
| if (RI == RE) |
| continue; |
| |
| CallInst *CI = dyn_cast<CallInst>(&*RI); |
| if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI)) |
| TailCalls.push_back(CI); |
| } |
| } |
| |
| bool Changed = false; |
| for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) { |
| CallInst *CI = TailCalls[i]; |
| CallSite CS(CI); |
| |
| // Conservatively require the attributes of the call to match those of the |
| // return. Ignore noalias because it doesn't affect the call sequence. |
| Attribute CalleeRetAttr = CS.getAttributes().getRetAttributes(); |
| if (AttrBuilder(CalleeRetAttr). |
| removeAttribute(Attribute::NoAlias) != |
| AttrBuilder(CallerRetAttr). |
| removeAttribute(Attribute::NoAlias)) |
| continue; |
| |
| // Make sure the call instruction is followed by an unconditional branch to |
| // the return block. |
| BasicBlock *CallBB = CI->getParent(); |
| BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator()); |
| if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB) |
| continue; |
| |
| // Duplicate the return into CallBB. |
| (void)FoldReturnIntoUncondBranch(RI, BB, CallBB); |
| ModifiedDT = Changed = true; |
| ++NumRetsDup; |
| } |
| |
| // If we eliminated all predecessors of the block, delete the block now. |
| if (Changed && !BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB)) |
| BB->eraseFromParent(); |
| |
| return Changed; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Memory Optimization |
| //===----------------------------------------------------------------------===// |
| |
| /// IsNonLocalValue - Return true if the specified values are defined in a |
| /// different basic block than BB. |
| static bool IsNonLocalValue(Value *V, BasicBlock *BB) { |
| if (Instruction *I = dyn_cast<Instruction>(V)) |
| return I->getParent() != BB; |
| return false; |
| } |
| |
| /// OptimizeMemoryInst - Load and Store Instructions often have |
| /// addressing modes that can do significant amounts of computation. As such, |
| /// instruction selection will try to get the load or store to do as much |
| /// computation as possible for the program. The problem is that isel can only |
| /// see within a single block. As such, we sink as much legal addressing mode |
| /// stuff into the block as possible. |
| /// |
| /// This method is used to optimize both load/store and inline asms with memory |
| /// operands. |
| bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr, |
| Type *AccessTy) { |
| Value *Repl = Addr; |
| |
| // Try to collapse single-value PHI nodes. This is necessary to undo |
| // unprofitable PRE transformations. |
| SmallVector<Value*, 8> worklist; |
| SmallPtrSet<Value*, 16> Visited; |
| worklist.push_back(Addr); |
| |
| // Use a worklist to iteratively look through PHI nodes, and ensure that |
| // the addressing mode obtained from the non-PHI roots of the graph |
| // are equivalent. |
| Value *Consensus = 0; |
| unsigned NumUsesConsensus = 0; |
| bool IsNumUsesConsensusValid = false; |
| SmallVector<Instruction*, 16> AddrModeInsts; |
| ExtAddrMode AddrMode; |
| while (!worklist.empty()) { |
| Value *V = worklist.back(); |
| worklist.pop_back(); |
| |
| // Break use-def graph loops. |
| if (!Visited.insert(V)) { |
| Consensus = 0; |
| break; |
| } |
| |
| // For a PHI node, push all of its incoming values. |
| if (PHINode *P = dyn_cast<PHINode>(V)) { |
| for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) |
| worklist.push_back(P->getIncomingValue(i)); |
| continue; |
| } |
| |
| // For non-PHIs, determine the addressing mode being computed. |
| SmallVector<Instruction*, 16> NewAddrModeInsts; |
| ExtAddrMode NewAddrMode = |
| AddressingModeMatcher::Match(V, AccessTy, MemoryInst, |
| NewAddrModeInsts, *TLI); |
| |
| // This check is broken into two cases with very similar code to avoid using |
| // getNumUses() as much as possible. Some values have a lot of uses, so |
| // calling getNumUses() unconditionally caused a significant compile-time |
| // regression. |
| if (!Consensus) { |
| Consensus = V; |
| AddrMode = NewAddrMode; |
| AddrModeInsts = NewAddrModeInsts; |
| continue; |
| } else if (NewAddrMode == AddrMode) { |
| if (!IsNumUsesConsensusValid) { |
| NumUsesConsensus = Consensus->getNumUses(); |
| IsNumUsesConsensusValid = true; |
| } |
| |
| // Ensure that the obtained addressing mode is equivalent to that obtained |
| // for all other roots of the PHI traversal. Also, when choosing one |
| // such root as representative, select the one with the most uses in order |
| // to keep the cost modeling heuristics in AddressingModeMatcher |
| // applicable. |
| unsigned NumUses = V->getNumUses(); |
| if (NumUses > NumUsesConsensus) { |
| Consensus = V; |
| NumUsesConsensus = NumUses; |
| AddrModeInsts = NewAddrModeInsts; |
| } |
| continue; |
| } |
| |
| Consensus = 0; |
| break; |
| } |
| |
| // If the addressing mode couldn't be determined, or if multiple different |
| // ones were determined, bail out now. |
| if (!Consensus) return false; |
| |
| // Check to see if any of the instructions supersumed by this addr mode are |
| // non-local to I's BB. |
| bool AnyNonLocal = false; |
| for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) { |
| if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) { |
| AnyNonLocal = true; |
| break; |
| } |
| } |
| |
| // If all the instructions matched are already in this BB, don't do anything. |
| if (!AnyNonLocal) { |
| DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n"); |
| return false; |
| } |
| |
| // Insert this computation right after this user. Since our caller is |
| // scanning from the top of the BB to the bottom, reuse of the expr are |
| // guaranteed to happen later. |
| IRBuilder<> Builder(MemoryInst); |
| |
| // Now that we determined the addressing expression we want to use and know |
| // that we have to sink it into this block. Check to see if we have already |
| // done this for some other load/store instr in this block. If so, reuse the |
| // computation. |
| Value *&SunkAddr = SunkAddrs[Addr]; |
| if (SunkAddr) { |
| DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for " |
| << *MemoryInst); |
| if (SunkAddr->getType() != Addr->getType()) |
| SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType()); |
| } else { |
| DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for " |
| << *MemoryInst); |
| Type *IntPtrTy = |
| TLI->getDataLayout()->getIntPtrType(AccessTy->getContext()); |
| |
| Value *Result = 0; |
| |
| // Start with the base register. Do this first so that subsequent address |
| // matching finds it last, which will prevent it from trying to match it |
| // as the scaled value in case it happens to be a mul. That would be |
| // problematic if we've sunk a different mul for the scale, because then |
| // we'd end up sinking both muls. |
| if (AddrMode.BaseReg) { |
| Value *V = AddrMode.BaseReg; |
| if (V->getType()->isPointerTy()) |
| V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr"); |
| if (V->getType() != IntPtrTy) |
| V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr"); |
| Result = V; |
| } |
| |
| // Add the scale value. |
| if (AddrMode.Scale) { |
| Value *V = AddrMode.ScaledReg; |
| if (V->getType() == IntPtrTy) { |
| // done. |
| } else if (V->getType()->isPointerTy()) { |
| V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr"); |
| } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() < |
| cast<IntegerType>(V->getType())->getBitWidth()) { |
| V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr"); |
| } else { |
| V = Builder.CreateSExt(V, IntPtrTy, "sunkaddr"); |
| } |
| if (AddrMode.Scale != 1) |
| V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale), |
| "sunkaddr"); |
| if (Result) |
| Result = Builder.CreateAdd(Result, V, "sunkaddr"); |
| else |
| Result = V; |
| } |
| |
| // Add in the BaseGV if present. |
| if (AddrMode.BaseGV) { |
| Value *V = Builder.CreatePtrToInt(AddrMode.BaseGV, IntPtrTy, "sunkaddr"); |
| if (Result) |
| Result = Builder.CreateAdd(Result, V, "sunkaddr"); |
| else |
| Result = V; |
| } |
| |
| // Add in the Base Offset if present. |
| if (AddrMode.BaseOffs) { |
| Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs); |
| if (Result) |
| Result = Builder.CreateAdd(Result, V, "sunkaddr"); |
| else |
| Result = V; |
| } |
| |
| if (Result == 0) |
| SunkAddr = Constant::getNullValue(Addr->getType()); |
| else |
| SunkAddr = Builder.CreateIntToPtr(Result, Addr->getType(), "sunkaddr"); |
| } |
| |
| MemoryInst->replaceUsesOfWith(Repl, SunkAddr); |
| |
| // If we have no uses, recursively delete the value and all dead instructions |
| // using it. |
| if (Repl->use_empty()) { |
| // This can cause recursive deletion, which can invalidate our iterator. |
| // Use a WeakVH to hold onto it in case this happens. |
| WeakVH IterHandle(CurInstIterator); |
| BasicBlock *BB = CurInstIterator->getParent(); |
| |
| RecursivelyDeleteTriviallyDeadInstructions(Repl, TLInfo); |
| |
| if (IterHandle != CurInstIterator) { |
| // If the iterator instruction was recursively deleted, start over at the |
| // start of the block. |
| CurInstIterator = BB->begin(); |
| SunkAddrs.clear(); |
| } else { |
| // This address is now available for reassignment, so erase the table |
| // entry; we don't want to match some completely different instruction. |
| SunkAddrs[Addr] = 0; |
| } |
| } |
| ++NumMemoryInsts; |
| return true; |
| } |
| |
| /// OptimizeInlineAsmInst - If there are any memory operands, use |
| /// OptimizeMemoryInst to sink their address computing into the block when |
| /// possible / profitable. |
| bool CodeGenPrepare::OptimizeInlineAsmInst(CallInst *CS) { |
| bool MadeChange = false; |
| |
| TargetLowering::AsmOperandInfoVector |
| TargetConstraints = TLI->ParseConstraints(CS); |
| unsigned ArgNo = 0; |
| for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) { |
| TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i]; |
| |
| // Compute the constraint code and ConstraintType to use. |
| TLI->ComputeConstraintToUse(OpInfo, SDValue()); |
| |
| if (OpInfo.ConstraintType == TargetLowering::C_Memory && |
| OpInfo.isIndirect) { |
| Value *OpVal = CS->getArgOperand(ArgNo++); |
| MadeChange |= OptimizeMemoryInst(CS, OpVal, OpVal->getType()); |
| } else if (OpInfo.Type == InlineAsm::isInput) |
| ArgNo++; |
| } |
| |
| return MadeChange; |
| } |
| |
| /// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same |
| /// basic block as the load, unless conditions are unfavorable. This allows |
| /// SelectionDAG to fold the extend into the load. |
| /// |
| bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) { |
| // Look for a load being extended. |
| LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0)); |
| if (!LI) return false; |
| |
| // If they're already in the same block, there's nothing to do. |
| if (LI->getParent() == I->getParent()) |
| return false; |
| |
| // If the load has other users and the truncate is not free, this probably |
| // isn't worthwhile. |
| if (!LI->hasOneUse() && |
| TLI && (TLI->isTypeLegal(TLI->getValueType(LI->getType())) || |
| !TLI->isTypeLegal(TLI->getValueType(I->getType()))) && |
| !TLI->isTruncateFree(I->getType(), LI->getType())) |
| return false; |
| |
| // Check whether the target supports casts folded into loads. |
| unsigned LType; |
| if (isa<ZExtInst>(I)) |
| LType = ISD::ZEXTLOAD; |
| else { |
| assert(isa<SExtInst>(I) && "Unexpected ext type!"); |
| LType = ISD::SEXTLOAD; |
| } |
| if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType()))) |
| return false; |
| |
| // Move the extend into the same block as the load, so that SelectionDAG |
| // can fold it. |
| I->removeFromParent(); |
| I->insertAfter(LI); |
| ++NumExtsMoved; |
| return true; |
| } |
| |
| bool CodeGenPrepare::OptimizeExtUses(Instruction *I) { |
| BasicBlock *DefBB = I->getParent(); |
| |
| // If the result of a {s|z}ext and its source are both live out, rewrite all |
| // other uses of the source with result of extension. |
| Value *Src = I->getOperand(0); |
| if (Src->hasOneUse()) |
| return false; |
| |
| // Only do this xform if truncating is free. |
| if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType())) |
| return false; |
| |
| // Only safe to perform the optimization if the source is also defined in |
| // this block. |
| if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent()) |
| return false; |
| |
| bool DefIsLiveOut = false; |
| for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); |
| UI != E; ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| |
| // Figure out which BB this ext is used in. |
| BasicBlock *UserBB = User->getParent(); |
| if (UserBB == DefBB) continue; |
| DefIsLiveOut = true; |
| break; |
| } |
| if (!DefIsLiveOut) |
| return false; |
| |
| // Make sure non of the uses are PHI nodes. |
| for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); |
| UI != E; ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| BasicBlock *UserBB = User->getParent(); |
| if (UserBB == DefBB) continue; |
| // Be conservative. We don't want this xform to end up introducing |
| // reloads just before load / store instructions. |
| if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User)) |
| return false; |
| } |
| |
| // InsertedTruncs - Only insert one trunc in each block once. |
| DenseMap<BasicBlock*, Instruction*> InsertedTruncs; |
| |
| bool MadeChange = false; |
| for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); |
| UI != E; ++UI) { |
| Use &TheUse = UI.getUse(); |
| Instruction *User = cast<Instruction>(*UI); |
| |
| // Figure out which BB this ext is used in. |
| BasicBlock *UserBB = User->getParent(); |
| if (UserBB == DefBB) continue; |
| |
| // Both src and def are live in this block. Rewrite the use. |
| Instruction *&InsertedTrunc = InsertedTruncs[UserBB]; |
| |
| if (!InsertedTrunc) { |
| BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt(); |
| InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt); |
| } |
| |
| // Replace a use of the {s|z}ext source with a use of the result. |
| TheUse = InsertedTrunc; |
| ++NumExtUses; |
| MadeChange = true; |
| } |
| |
| return MadeChange; |
| } |
| |
| /// isFormingBranchFromSelectProfitable - Returns true if a SelectInst should be |
| /// turned into an explicit branch. |
| static bool isFormingBranchFromSelectProfitable(SelectInst *SI) { |
| // FIXME: This should use the same heuristics as IfConversion to determine |
| // whether a select is better represented as a branch. This requires that |
| // branch probability metadata is preserved for the select, which is not the |
| // case currently. |
| |
| CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition()); |
| |
| // If the branch is predicted right, an out of order CPU can avoid blocking on |
| // the compare. Emit cmovs on compares with a memory operand as branches to |
| // avoid stalls on the load from memory. If the compare has more than one use |
| // there's probably another cmov or setcc around so it's not worth emitting a |
| // branch. |
| if (!Cmp) |
| return false; |
| |
| Value *CmpOp0 = Cmp->getOperand(0); |
| Value *CmpOp1 = Cmp->getOperand(1); |
| |
| // We check that the memory operand has one use to avoid uses of the loaded |
| // value directly after the compare, making branches unprofitable. |
| return Cmp->hasOneUse() && |
| ((isa<LoadInst>(CmpOp0) && CmpOp0->hasOneUse()) || |
| (isa<LoadInst>(CmpOp1) && CmpOp1->hasOneUse())); |
| } |
| |
| |
| /// If we have a SelectInst that will likely profit from branch prediction, |
| /// turn it into a branch. |
| bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) { |
| bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1); |
| |
| // Can we convert the 'select' to CF ? |
| if (DisableSelectToBranch || OptSize || !TLI || VectorCond) |
| return false; |
| |
| TargetLowering::SelectSupportKind SelectKind; |
| if (VectorCond) |
| SelectKind = TargetLowering::VectorMaskSelect; |
| else if (SI->getType()->isVectorTy()) |
| SelectKind = TargetLowering::ScalarCondVectorVal; |
| else |
| SelectKind = TargetLowering::ScalarValSelect; |
| |
| // Do we have efficient codegen support for this kind of 'selects' ? |
| if (TLI->isSelectSupported(SelectKind)) { |
| // We have efficient codegen support for the select instruction. |
| // Check if it is profitable to keep this 'select'. |
| if (!TLI->isPredictableSelectExpensive() || |
| !isFormingBranchFromSelectProfitable(SI)) |
| return false; |
| } |
| |
| ModifiedDT = true; |
| |
| // First, we split the block containing the select into 2 blocks. |
| BasicBlock *StartBlock = SI->getParent(); |
| BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(SI)); |
| BasicBlock *NextBlock = StartBlock->splitBasicBlock(SplitPt, "select.end"); |
| |
| // Create a new block serving as the landing pad for the branch. |
| BasicBlock *SmallBlock = BasicBlock::Create(SI->getContext(), "select.mid", |
| NextBlock->getParent(), NextBlock); |
| |
| // Move the unconditional branch from the block with the select in it into our |
| // landing pad block. |
| StartBlock->getTerminator()->eraseFromParent(); |
| BranchInst::Create(NextBlock, SmallBlock); |
| |
| // Insert the real conditional branch based on the original condition. |
| BranchInst::Create(NextBlock, SmallBlock, SI->getCondition(), SI); |
| |
| // The select itself is replaced with a PHI Node. |
| PHINode *PN = PHINode::Create(SI->getType(), 2, "", NextBlock->begin()); |
| PN->takeName(SI); |
| PN->addIncoming(SI->getTrueValue(), StartBlock); |
| PN->addIncoming(SI->getFalseValue(), SmallBlock); |
| SI->replaceAllUsesWith(PN); |
| SI->eraseFromParent(); |
| |
| // Instruct OptimizeBlock to skip to the next block. |
| CurInstIterator = StartBlock->end(); |
| ++NumSelectsExpanded; |
| return true; |
| } |
| |
| bool CodeGenPrepare::OptimizeInst(Instruction *I) { |
| if (PHINode *P = dyn_cast<PHINode>(I)) { |
| // It is possible for very late stage optimizations (such as SimplifyCFG) |
| // to introduce PHI nodes too late to be cleaned up. If we detect such a |
| // trivial PHI, go ahead and zap it here. |
| if (Value *V = SimplifyInstruction(P)) { |
| P->replaceAllUsesWith(V); |
| P->eraseFromParent(); |
| ++NumPHIsElim; |
| return true; |
| } |
| return false; |
| } |
| |
| if (CastInst *CI = dyn_cast<CastInst>(I)) { |
| // If the source of the cast is a constant, then this should have |
| // already been constant folded. The only reason NOT to constant fold |
| // it is if something (e.g. LSR) was careful to place the constant |
| // evaluation in a block other than then one that uses it (e.g. to hoist |
| // the address of globals out of a loop). If this is the case, we don't |
| // want to forward-subst the cast. |
| if (isa<Constant>(CI->getOperand(0))) |
| return false; |
| |
| if (TLI && OptimizeNoopCopyExpression(CI, *TLI)) |
| return true; |
| |
| if (isa<ZExtInst>(I) || isa<SExtInst>(I)) { |
| bool MadeChange = MoveExtToFormExtLoad(I); |
| return MadeChange | OptimizeExtUses(I); |
| } |
| return false; |
| } |
| |
| if (CmpInst *CI = dyn_cast<CmpInst>(I)) |
| return OptimizeCmpExpression(CI); |
| |
| if (LoadInst *LI = dyn_cast<LoadInst>(I)) { |
| if (TLI) |
| return OptimizeMemoryInst(I, I->getOperand(0), LI->getType()); |
| return false; |
| } |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(I)) { |
| if (TLI) |
| return OptimizeMemoryInst(I, SI->getOperand(1), |
| SI->getOperand(0)->getType()); |
| return false; |
| } |
| |
| if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { |
| if (GEPI->hasAllZeroIndices()) { |
| /// The GEP operand must be a pointer, so must its result -> BitCast |
| Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(), |
| GEPI->getName(), GEPI); |
| GEPI->replaceAllUsesWith(NC); |
| GEPI->eraseFromParent(); |
| ++NumGEPsElim; |
| OptimizeInst(NC); |
| return true; |
| } |
| return false; |
| } |
| |
| if (CallInst *CI = dyn_cast<CallInst>(I)) |
| return OptimizeCallInst(CI); |
| |
| if (SelectInst *SI = dyn_cast<SelectInst>(I)) |
| return OptimizeSelectInst(SI); |
| |
| return false; |
| } |
| |
| // In this pass we look for GEP and cast instructions that are used |
| // across basic blocks and rewrite them to improve basic-block-at-a-time |
| // selection. |
| bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) { |
| SunkAddrs.clear(); |
| bool MadeChange = false; |
| |
| CurInstIterator = BB.begin(); |
| while (CurInstIterator != BB.end()) |
| MadeChange |= OptimizeInst(CurInstIterator++); |
| |
| MadeChange |= DupRetToEnableTailCallOpts(&BB); |
| |
| return MadeChange; |
| } |
| |
| // llvm.dbg.value is far away from the value then iSel may not be able |
| // handle it properly. iSel will drop llvm.dbg.value if it can not |
| // find a node corresponding to the value. |
| bool CodeGenPrepare::PlaceDbgValues(Function &F) { |
| bool MadeChange = false; |
| for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { |
| Instruction *PrevNonDbgInst = NULL; |
| for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) { |
| Instruction *Insn = BI; ++BI; |
| DbgValueInst *DVI = dyn_cast<DbgValueInst>(Insn); |
| if (!DVI) { |
| PrevNonDbgInst = Insn; |
| continue; |
| } |
| |
| Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue()); |
| if (VI && VI != PrevNonDbgInst && !VI->isTerminator()) { |
| DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI); |
| DVI->removeFromParent(); |
| if (isa<PHINode>(VI)) |
| DVI->insertBefore(VI->getParent()->getFirstInsertionPt()); |
| else |
| DVI->insertAfter(VI); |
| MadeChange = true; |
| ++NumDbgValueMoved; |
| } |
| } |
| } |
| return MadeChange; |
| } |