| //===- 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/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Function.h" |
| #include "llvm/InlineAsm.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Analysis/ProfileInfo.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Target/TargetLowering.h" |
| #include "llvm/Transforms/Utils/AddrModeMatcher.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/Transforms/Utils/BuildLibCalls.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/Assembly/Writer.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/PatternMatch.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Support/IRBuilder.h" |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| namespace { |
| class CodeGenPrepare : public FunctionPass { |
| /// TLI - Keep a pointer of a TargetLowering to consult for determining |
| /// transformation profitability. |
| const TargetLowering *TLI; |
| ProfileInfo *PFI; |
| |
| /// BackEdges - Keep a set of all the loop back edges. |
| /// |
| SmallSet<std::pair<const BasicBlock*, const BasicBlock*>, 8> BackEdges; |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| explicit CodeGenPrepare(const TargetLowering *tli = 0) |
| : FunctionPass(&ID), TLI(tli) {} |
| bool runOnFunction(Function &F); |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addPreserved<ProfileInfo>(); |
| } |
| |
| virtual void releaseMemory() { |
| BackEdges.clear(); |
| } |
| |
| private: |
| bool EliminateMostlyEmptyBlocks(Function &F); |
| bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const; |
| void EliminateMostlyEmptyBlock(BasicBlock *BB); |
| bool OptimizeBlock(BasicBlock &BB); |
| bool OptimizeMemoryInst(Instruction *I, Value *Addr, const Type *AccessTy, |
| DenseMap<Value*,Value*> &SunkAddrs); |
| bool OptimizeInlineAsmInst(Instruction *I, CallSite CS, |
| DenseMap<Value*,Value*> &SunkAddrs); |
| bool OptimizeCallInst(CallInst *CI); |
| bool MoveExtToFormExtLoad(Instruction *I); |
| bool OptimizeExtUses(Instruction *I); |
| void findLoopBackEdges(const Function &F); |
| }; |
| } |
| |
| char CodeGenPrepare::ID = 0; |
| static RegisterPass<CodeGenPrepare> X("codegenprepare", |
| "Optimize for code generation"); |
| |
| FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) { |
| return new CodeGenPrepare(TLI); |
| } |
| |
| /// findLoopBackEdges - Do a DFS walk to find loop back edges. |
| /// |
| void CodeGenPrepare::findLoopBackEdges(const Function &F) { |
| SmallVector<std::pair<const BasicBlock*,const BasicBlock*>, 32> Edges; |
| FindFunctionBackedges(F, Edges); |
| |
| BackEdges.insert(Edges.begin(), Edges.end()); |
| } |
| |
| |
| bool CodeGenPrepare::runOnFunction(Function &F) { |
| bool EverMadeChange = false; |
| |
| PFI = getAnalysisIfAvailable<ProfileInfo>(); |
| // First pass, eliminate blocks that contain only PHI nodes and an |
| // unconditional branch. |
| EverMadeChange |= EliminateMostlyEmptyBlocks(F); |
| |
| // Now find loop back edges. |
| findLoopBackEdges(F); |
| |
| bool MadeChange = true; |
| while (MadeChange) { |
| MadeChange = false; |
| for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) |
| MadeChange |= OptimizeBlock(*BB); |
| EverMadeChange |= MadeChange; |
| } |
| return EverMadeChange; |
| } |
| |
| /// 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 (PFI) { |
| PFI->replaceAllUses(BB, DestBB); |
| PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB)); |
| } |
| BB->eraseFromParent(); |
| |
| DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n"); |
| } |
| |
| /// FindReusablePredBB - Check all of the predecessors of the block DestPHI |
| /// lives in to see if there is a block that we can reuse as a critical edge |
| /// from TIBB. |
| static BasicBlock *FindReusablePredBB(PHINode *DestPHI, BasicBlock *TIBB) { |
| BasicBlock *Dest = DestPHI->getParent(); |
| |
| /// TIPHIValues - This array is lazily computed to determine the values of |
| /// PHIs in Dest that TI would provide. |
| SmallVector<Value*, 32> TIPHIValues; |
| |
| /// TIBBEntryNo - This is a cache to speed up pred queries for TIBB. |
| unsigned TIBBEntryNo = 0; |
| |
| // Check to see if Dest has any blocks that can be used as a split edge for |
| // this terminator. |
| for (unsigned pi = 0, e = DestPHI->getNumIncomingValues(); pi != e; ++pi) { |
| BasicBlock *Pred = DestPHI->getIncomingBlock(pi); |
| // To be usable, the pred has to end with an uncond branch to the dest. |
| BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator()); |
| if (!PredBr || !PredBr->isUnconditional()) |
| continue; |
| // Must be empty other than the branch and debug info. |
| BasicBlock::iterator I = Pred->begin(); |
| while (isa<DbgInfoIntrinsic>(I)) |
| I++; |
| if (&*I != PredBr) |
| continue; |
| // Cannot be the entry block; its label does not get emitted. |
| if (Pred == &Dest->getParent()->getEntryBlock()) |
| continue; |
| |
| // Finally, since we know that Dest has phi nodes in it, we have to make |
| // sure that jumping to Pred will have the same effect as going to Dest in |
| // terms of PHI values. |
| PHINode *PN; |
| unsigned PHINo = 0; |
| unsigned PredEntryNo = pi; |
| |
| bool FoundMatch = true; |
| for (BasicBlock::iterator I = Dest->begin(); |
| (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) { |
| if (PHINo == TIPHIValues.size()) { |
| if (PN->getIncomingBlock(TIBBEntryNo) != TIBB) |
| TIBBEntryNo = PN->getBasicBlockIndex(TIBB); |
| TIPHIValues.push_back(PN->getIncomingValue(TIBBEntryNo)); |
| } |
| |
| // If the PHI entry doesn't work, we can't use this pred. |
| if (PN->getIncomingBlock(PredEntryNo) != Pred) |
| PredEntryNo = PN->getBasicBlockIndex(Pred); |
| |
| if (TIPHIValues[PHINo] != PN->getIncomingValue(PredEntryNo)) { |
| FoundMatch = false; |
| break; |
| } |
| } |
| |
| // If we found a workable predecessor, change TI to branch to Succ. |
| if (FoundMatch) |
| return Pred; |
| } |
| return 0; |
| } |
| |
| |
| /// SplitEdgeNicely - Split the critical edge from TI to its specified |
| /// successor if it will improve codegen. We only do this if the successor has |
| /// phi nodes (otherwise critical edges are ok). If there is already another |
| /// predecessor of the succ that is empty (and thus has no phi nodes), use it |
| /// instead of introducing a new block. |
| static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum, |
| SmallSet<std::pair<const BasicBlock*, |
| const BasicBlock*>, 8> &BackEdges, |
| Pass *P) { |
| BasicBlock *TIBB = TI->getParent(); |
| BasicBlock *Dest = TI->getSuccessor(SuccNum); |
| assert(isa<PHINode>(Dest->begin()) && |
| "This should only be called if Dest has a PHI!"); |
| PHINode *DestPHI = cast<PHINode>(Dest->begin()); |
| |
| // Do not split edges to EH landing pads. |
| if (InvokeInst *Invoke = dyn_cast<InvokeInst>(TI)) |
| if (Invoke->getSuccessor(1) == Dest) |
| return; |
| |
| // As a hack, never split backedges of loops. Even though the copy for any |
| // PHIs inserted on the backedge would be dead for exits from the loop, we |
| // assume that the cost of *splitting* the backedge would be too high. |
| if (BackEdges.count(std::make_pair(TIBB, Dest))) |
| return; |
| |
| if (BasicBlock *ReuseBB = FindReusablePredBB(DestPHI, TIBB)) { |
| ProfileInfo *PFI = P->getAnalysisIfAvailable<ProfileInfo>(); |
| if (PFI) |
| PFI->splitEdge(TIBB, Dest, ReuseBB); |
| Dest->removePredecessor(TIBB); |
| TI->setSuccessor(SuccNum, ReuseBB); |
| return; |
| } |
| |
| SplitCriticalEdge(TI, SuccNum, P, true); |
| } |
| |
| |
| /// 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::Promote) |
| SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT); |
| if (TLI.getTypeAction(CI->getContext(), DstVT) == TargetLowering::Promote) |
| 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->getFirstNonPHI(); |
| |
| 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; |
| } |
| |
| // 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->getFirstNonPHI(); |
| |
| 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; |
| } |
| |
| // 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->getOperand(SizeCIOp))) |
| return SizeCI->isAllOnesValue(); |
| return false; |
| } |
| }; |
| } // end anonymous namespace |
| |
| bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) { |
| // Lower all uses of llvm.objectsize.* |
| IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI); |
| if (II && II->getIntrinsicID() == Intrinsic::objectsize) { |
| bool Min = (cast<ConstantInt>(II->getOperand(2))->getZExtValue() == 1); |
| const Type *ReturnTy = CI->getType(); |
| Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL); |
| CI->replaceAllUsesWith(RetVal); |
| CI->eraseFromParent(); |
| return true; |
| } |
| |
| // From here on out we're working with named functions. |
| if (CI->getCalledFunction() == 0) return false; |
| |
| // We'll need TargetData from here on out. |
| const TargetData *TD = TLI ? TLI->getTargetData() : 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); |
| } |
| //===----------------------------------------------------------------------===// |
| // 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, |
| const Type *AccessTy, |
| DenseMap<Value*,Value*> &SunkAddrs) { |
| // Figure out what addressing mode will be built up for this operation. |
| SmallVector<Instruction*, 16> AddrModeInsts; |
| ExtAddrMode AddrMode = AddressingModeMatcher::Match(Addr, AccessTy,MemoryInst, |
| AddrModeInsts, *TLI); |
| |
| // 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. |
| BasicBlock::iterator InsertPt = 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 = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt); |
| } else { |
| DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for " |
| << *MemoryInst); |
| const Type *IntPtrTy = |
| TLI->getTargetData()->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 = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt); |
| if (V->getType() != IntPtrTy) |
| V = CastInst::CreateIntegerCast(V, IntPtrTy, /*isSigned=*/true, |
| "sunkaddr", InsertPt); |
| Result = V; |
| } |
| |
| // Add the scale value. |
| if (AddrMode.Scale) { |
| Value *V = AddrMode.ScaledReg; |
| if (V->getType() == IntPtrTy) { |
| // done. |
| } else if (V->getType()->isPointerTy()) { |
| V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt); |
| } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() < |
| cast<IntegerType>(V->getType())->getBitWidth()) { |
| V = new TruncInst(V, IntPtrTy, "sunkaddr", InsertPt); |
| } else { |
| V = new SExtInst(V, IntPtrTy, "sunkaddr", InsertPt); |
| } |
| if (AddrMode.Scale != 1) |
| V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy, |
| AddrMode.Scale), |
| "sunkaddr", InsertPt); |
| if (Result) |
| Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt); |
| else |
| Result = V; |
| } |
| |
| // Add in the BaseGV if present. |
| if (AddrMode.BaseGV) { |
| Value *V = new PtrToIntInst(AddrMode.BaseGV, IntPtrTy, "sunkaddr", |
| InsertPt); |
| if (Result) |
| Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt); |
| else |
| Result = V; |
| } |
| |
| // Add in the Base Offset if present. |
| if (AddrMode.BaseOffs) { |
| Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs); |
| if (Result) |
| Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt); |
| else |
| Result = V; |
| } |
| |
| if (Result == 0) |
| SunkAddr = Constant::getNullValue(Addr->getType()); |
| else |
| SunkAddr = new IntToPtrInst(Result, Addr->getType(), "sunkaddr",InsertPt); |
| } |
| |
| MemoryInst->replaceUsesOfWith(Addr, SunkAddr); |
| |
| if (Addr->use_empty()) |
| RecursivelyDeleteTriviallyDeadInstructions(Addr); |
| 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(Instruction *I, CallSite CS, |
| DenseMap<Value*,Value*> &SunkAddrs) { |
| bool MadeChange = false; |
| InlineAsm *IA = cast<InlineAsm>(CS.getCalledValue()); |
| |
| // Do a prepass over the constraints, canonicalizing them, and building up the |
| // ConstraintOperands list. |
| std::vector<InlineAsm::ConstraintInfo> |
| ConstraintInfos = IA->ParseConstraints(); |
| |
| /// ConstraintOperands - Information about all of the constraints. |
| std::vector<TargetLowering::AsmOperandInfo> ConstraintOperands; |
| unsigned ArgNo = 0; // ArgNo - The argument of the CallInst. |
| for (unsigned i = 0, e = ConstraintInfos.size(); i != e; ++i) { |
| ConstraintOperands. |
| push_back(TargetLowering::AsmOperandInfo(ConstraintInfos[i])); |
| TargetLowering::AsmOperandInfo &OpInfo = ConstraintOperands.back(); |
| |
| // Compute the value type for each operand. |
| switch (OpInfo.Type) { |
| case InlineAsm::isOutput: |
| if (OpInfo.isIndirect) |
| OpInfo.CallOperandVal = CS.getArgument(ArgNo++); |
| break; |
| case InlineAsm::isInput: |
| OpInfo.CallOperandVal = CS.getArgument(ArgNo++); |
| break; |
| case InlineAsm::isClobber: |
| // Nothing to do. |
| break; |
| } |
| |
| // Compute the constraint code and ConstraintType to use. |
| TLI->ComputeConstraintToUse(OpInfo, SDValue(), |
| OpInfo.ConstraintType == TargetLowering::C_Memory); |
| |
| if (OpInfo.ConstraintType == TargetLowering::C_Memory && |
| OpInfo.isIndirect) { |
| Value *OpVal = OpInfo.CallOperandVal; |
| MadeChange |= OptimizeMemoryInst(I, OpVal, OpVal->getType(), SunkAddrs); |
| } |
| } |
| |
| 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->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); |
| return true; |
| } |
| |
| bool CodeGenPrepare::OptimizeExtUses(Instruction *I) { |
| BasicBlock *DefBB = I->getParent(); |
| |
| // If both result of the {s|z}xt and its source are 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->getFirstNonPHI(); |
| |
| InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt); |
| } |
| |
| // Replace a use of the {s|z}ext source with a use of the result. |
| TheUse = InsertedTrunc; |
| |
| MadeChange = true; |
| } |
| |
| return MadeChange; |
| } |
| |
| // 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) { |
| bool MadeChange = false; |
| |
| // Split all critical edges where the dest block has a PHI. |
| TerminatorInst *BBTI = BB.getTerminator(); |
| if (BBTI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(BBTI)) { |
| for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) { |
| BasicBlock *SuccBB = BBTI->getSuccessor(i); |
| if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true)) |
| SplitEdgeNicely(BBTI, i, BackEdges, this); |
| } |
| } |
| |
| // Keep track of non-local addresses that have been sunk into this block. |
| // This allows us to avoid inserting duplicate code for blocks with multiple |
| // load/stores of the same address. |
| DenseMap<Value*, Value*> SunkAddrs; |
| |
| for (BasicBlock::iterator BBI = BB.begin(), E = BB.end(); BBI != E; ) { |
| Instruction *I = BBI++; |
| |
| 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))) |
| continue; |
| |
| bool Change = false; |
| if (TLI) { |
| Change = OptimizeNoopCopyExpression(CI, *TLI); |
| MadeChange |= Change; |
| } |
| |
| if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I))) { |
| MadeChange |= MoveExtToFormExtLoad(I); |
| MadeChange |= OptimizeExtUses(I); |
| } |
| } else if (CmpInst *CI = dyn_cast<CmpInst>(I)) { |
| MadeChange |= OptimizeCmpExpression(CI); |
| } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) { |
| if (TLI) |
| MadeChange |= OptimizeMemoryInst(I, I->getOperand(0), LI->getType(), |
| SunkAddrs); |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { |
| if (TLI) |
| MadeChange |= OptimizeMemoryInst(I, SI->getOperand(1), |
| SI->getOperand(0)->getType(), |
| SunkAddrs); |
| } else 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(); |
| MadeChange = true; |
| BBI = NC; |
| } |
| } else if (CallInst *CI = dyn_cast<CallInst>(I)) { |
| // 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)) { |
| BBI = BB.begin(); |
| // Avoid processing instructions out of order, which could cause |
| // reuse before a value is defined. |
| SunkAddrs.clear(); |
| } else |
| // Sink address computing for memory operands into the block. |
| MadeChange |= OptimizeInlineAsmInst(I, &(*CI), SunkAddrs); |
| } else { |
| // Other CallInst optimizations that don't need to muck with the |
| // enclosing iterator here. |
| MadeChange |= OptimizeCallInst(CI); |
| } |
| } |
| } |
| |
| return MadeChange; |
| } |