| //===- 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/Pass.h" |
| #include "llvm/Target/TargetAsmInfo.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Target/TargetLowering.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/PatternMatch.h" |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| static cl::opt<bool> FactorCommonPreds("split-critical-paths-tweak", |
| cl::init(false), cl::Hidden); |
| |
| namespace { |
| class VISIBILITY_HIDDEN CodeGenPrepare : public FunctionPass { |
| /// TLI - Keep a pointer of a TargetLowering to consult for determining |
| /// transformation profitability. |
| const TargetLowering *TLI; |
| |
| /// BackEdges - Keep a set of all the loop back edges. |
| /// |
| SmallSet<std::pair<BasicBlock*,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); |
| |
| 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 OptimizeExtUses(Instruction *I); |
| void findLoopBackEdges(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(Function &F) { |
| SmallPtrSet<BasicBlock*, 8> Visited; |
| SmallVector<std::pair<BasicBlock*, succ_iterator>, 8> VisitStack; |
| SmallPtrSet<BasicBlock*, 8> InStack; |
| |
| BasicBlock *BB = &F.getEntryBlock(); |
| if (succ_begin(BB) == succ_end(BB)) |
| return; |
| Visited.insert(BB); |
| VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); |
| InStack.insert(BB); |
| do { |
| std::pair<BasicBlock*, succ_iterator> &Top = VisitStack.back(); |
| BasicBlock *ParentBB = Top.first; |
| succ_iterator &I = Top.second; |
| |
| bool FoundNew = false; |
| while (I != succ_end(ParentBB)) { |
| BB = *I++; |
| if (Visited.insert(BB)) { |
| FoundNew = true; |
| break; |
| } |
| // Successor is in VisitStack, it's a back edge. |
| if (InStack.count(BB)) |
| BackEdges.insert(std::make_pair(ParentBB, BB)); |
| } |
| |
| if (FoundNew) { |
| // Go down one level if there is a unvisited successor. |
| InStack.insert(BB); |
| VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); |
| } else { |
| // Go up one level. |
| std::pair<BasicBlock*, succ_iterator> &Pop = VisitStack.back(); |
| InStack.erase(Pop.first); |
| VisitStack.pop_back(); |
| } |
| } while (!VisitStack.empty()); |
| } |
| |
| |
| bool CodeGenPrepare::runOnFunction(Function &F) { |
| bool EverMadeChange = false; |
| |
| // 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 |
| /// 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 isn't a phi node, then other stuff |
| // is happening here. |
| BasicBlock::iterator BBI = BI; |
| if (BBI != BB->begin()) { |
| --BBI; |
| if (!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::use_const_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); |
| |
| DOUT << "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); |
| |
| if (isEntry && BB != &BB->getParent()->getEntryBlock()) |
| BB->moveBefore(&BB->getParent()->getEntryBlock()); |
| |
| DOUT << "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); |
| BB->eraseFromParent(); |
| |
| DOUT << "AFTER:\n" << *DestBB << "\n\n\n"; |
| } |
| |
| |
| /// 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<BasicBlock*,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!"); |
| |
| // 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 (!FactorCommonPreds) { |
| /// TIPHIValues - This array is lazily computed to determine the values of |
| /// PHIs in Dest that TI would provide. |
| SmallVector<Value*, 32> TIPHIValues; |
| |
| // Check to see if Dest has any blocks that can be used as a split edge for |
| // this terminator. |
| for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) { |
| BasicBlock *Pred = *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() || |
| // Must be empty other than the branch. |
| &Pred->front() != PredBr || |
| // Cannot be the entry block; its label does not get emitted. |
| 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 affect as going to Dest in |
| // terms of PHI values. |
| PHINode *PN; |
| unsigned PHINo = 0; |
| bool FoundMatch = true; |
| for (BasicBlock::iterator I = Dest->begin(); |
| (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) { |
| if (PHINo == TIPHIValues.size()) |
| TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB)); |
| |
| // If the PHI entry doesn't work, we can't use this pred. |
| if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) { |
| FoundMatch = false; |
| break; |
| } |
| } |
| |
| // If we found a workable predecessor, change TI to branch to Succ. |
| if (FoundMatch) { |
| Dest->removePredecessor(TIBB); |
| TI->setSuccessor(SuccNum, Pred); |
| return; |
| } |
| } |
| |
| SplitCriticalEdge(TI, SuccNum, P, true); |
| return; |
| } |
| |
| PHINode *PN; |
| SmallVector<Value*, 8> TIPHIValues; |
| for (BasicBlock::iterator I = Dest->begin(); |
| (PN = dyn_cast<PHINode>(I)); ++I) |
| TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB)); |
| |
| SmallVector<BasicBlock*, 8> IdenticalPreds; |
| for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) { |
| BasicBlock *Pred = *PI; |
| if (BackEdges.count(std::make_pair(Pred, Dest))) |
| continue; |
| if (PI == TIBB) |
| IdenticalPreds.push_back(Pred); |
| else { |
| bool Identical = true; |
| unsigned PHINo = 0; |
| for (BasicBlock::iterator I = Dest->begin(); |
| (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) |
| if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) { |
| Identical = false; |
| break; |
| } |
| if (Identical) |
| IdenticalPreds.push_back(Pred); |
| } |
| } |
| |
| assert(!IdenticalPreds.empty()); |
| SplitBlockPredecessors(Dest, &IdenticalPreds[0], IdenticalPreds.size(), |
| ".critedge", P); |
| } |
| |
| |
| /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop |
| /// copy (e.g. it's casting from one pointer type to another, int->uint, or |
| /// int->sbyte 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, |
| MVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType()); |
| MVT 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(SrcVT) == TargetLowering::Promote) |
| SrcVT = TLI.getTypeToTransformTo(SrcVT); |
| if (TLI.getTypeAction(DstVT) == TargetLowering::Promote) |
| DstVT = TLI.getTypeToTransformTo(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; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Addressing Mode Analysis and Optimization |
| //===----------------------------------------------------------------------===// |
| |
| namespace { |
| /// ExtAddrMode - This is an extended version of TargetLowering::AddrMode |
| /// which holds actual Value*'s for register values. |
| struct ExtAddrMode : public TargetLowering::AddrMode { |
| Value *BaseReg; |
| Value *ScaledReg; |
| ExtAddrMode() : BaseReg(0), ScaledReg(0) {} |
| void print(OStream &OS) const; |
| void dump() const { |
| print(cerr); |
| cerr << '\n'; |
| } |
| }; |
| } // end anonymous namespace |
| |
| static inline OStream &operator<<(OStream &OS, const ExtAddrMode &AM) { |
| AM.print(OS); |
| return OS; |
| } |
| |
| void ExtAddrMode::print(OStream &OS) const { |
| bool NeedPlus = false; |
| OS << "["; |
| if (BaseGV) |
| OS << (NeedPlus ? " + " : "") |
| << "GV:%" << BaseGV->getName(), NeedPlus = true; |
| |
| if (BaseOffs) |
| OS << (NeedPlus ? " + " : "") << BaseOffs, NeedPlus = true; |
| |
| if (BaseReg) |
| OS << (NeedPlus ? " + " : "") |
| << "Base:%" << BaseReg->getName(), NeedPlus = true; |
| if (Scale) |
| OS << (NeedPlus ? " + " : "") |
| << Scale << "*%" << ScaledReg->getName(), NeedPlus = true; |
| |
| OS << ']'; |
| } |
| |
| namespace { |
| /// AddressingModeMatcher - This class exposes a single public method, which is |
| /// used to construct a "maximal munch" of the addressing mode for the target |
| /// specified by TLI for an access to "V" with an access type of AccessTy. This |
| /// returns the addressing mode that is actually matched by value, but also |
| /// returns the list of instructions involved in that addressing computation in |
| /// AddrModeInsts. |
| class AddressingModeMatcher { |
| SmallVectorImpl<Instruction*> &AddrModeInsts; |
| const TargetLowering &TLI; |
| |
| /// AccessTy/MemoryInst - This is the type for the access (e.g. double) and |
| /// the memory instruction that we're computing this address for. |
| const Type *AccessTy; |
| Instruction *MemoryInst; |
| |
| /// AddrMode - This is the addressing mode that we're building up. This is |
| /// part of the return value of this addressing mode matching stuff. |
| ExtAddrMode &AddrMode; |
| |
| /// IgnoreProfitability - This is set to true when we should not do |
| /// profitability checks. When true, IsProfitableToFoldIntoAddressingMode |
| /// always returns true. |
| bool IgnoreProfitability; |
| |
| AddressingModeMatcher(SmallVectorImpl<Instruction*> &AMI, |
| const TargetLowering &T, const Type *AT, |
| Instruction *MI, ExtAddrMode &AM) |
| : AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM) { |
| IgnoreProfitability = false; |
| } |
| public: |
| |
| /// Match - Find the maximal addressing mode that a load/store of V can fold, |
| /// give an access type of AccessTy. This returns a list of involved |
| /// instructions in AddrModeInsts. |
| static ExtAddrMode Match(Value *V, const Type *AccessTy, |
| Instruction *MemoryInst, |
| SmallVectorImpl<Instruction*> &AddrModeInsts, |
| const TargetLowering &TLI) { |
| ExtAddrMode Result; |
| |
| bool Success = |
| AddressingModeMatcher(AddrModeInsts, TLI, AccessTy, |
| MemoryInst, Result).MatchAddr(V, 0); |
| Success = Success; assert(Success && "Couldn't select *anything*?"); |
| return Result; |
| } |
| private: |
| bool MatchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth); |
| bool MatchAddr(Value *V, unsigned Depth); |
| bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth); |
| bool IsProfitableToFoldIntoAddressingMode(Instruction *I, |
| ExtAddrMode &AMBefore, |
| ExtAddrMode &AMAfter); |
| bool ValueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2); |
| }; |
| } // end anonymous namespace |
| |
| /// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode. |
| /// Return true and update AddrMode if this addr mode is legal for the target, |
| /// false if not. |
| bool AddressingModeMatcher::MatchScaledValue(Value *ScaleReg, int64_t Scale, |
| unsigned Depth) { |
| // If Scale is 1, then this is the same as adding ScaleReg to the addressing |
| // mode. Just process that directly. |
| if (Scale == 1) |
| return MatchAddr(ScaleReg, Depth); |
| |
| // If the scale is 0, it takes nothing to add this. |
| if (Scale == 0) |
| return true; |
| |
| // If we already have a scale of this value, we can add to it, otherwise, we |
| // need an available scale field. |
| if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg) |
| return false; |
| |
| ExtAddrMode TestAddrMode = AddrMode; |
| |
| // Add scale to turn X*4+X*3 -> X*7. This could also do things like |
| // [A+B + A*7] -> [B+A*8]. |
| TestAddrMode.Scale += Scale; |
| TestAddrMode.ScaledReg = ScaleReg; |
| |
| // If the new address isn't legal, bail out. |
| if (!TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) |
| return false; |
| |
| // It was legal, so commit it. |
| AddrMode = TestAddrMode; |
| |
| // Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now |
| // to see if ScaleReg is actually X+C. If so, we can turn this into adding |
| // X*Scale + C*Scale to addr mode. |
| ConstantInt *CI; Value *AddLHS; |
| if (isa<Instruction>(ScaleReg) && // not a constant expr. |
| match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) { |
| TestAddrMode.ScaledReg = AddLHS; |
| TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale; |
| |
| // If this addressing mode is legal, commit it and remember that we folded |
| // this instruction. |
| if (TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) { |
| AddrModeInsts.push_back(cast<Instruction>(ScaleReg)); |
| AddrMode = TestAddrMode; |
| return true; |
| } |
| } |
| |
| // Otherwise, not (x+c)*scale, just return what we have. |
| return true; |
| } |
| |
| /// MightBeFoldableInst - This is a little filter, which returns true if an |
| /// addressing computation involving I might be folded into a load/store |
| /// accessing it. This doesn't need to be perfect, but needs to accept at least |
| /// the set of instructions that MatchOperationAddr can. |
| static bool MightBeFoldableInst(Instruction *I) { |
| switch (I->getOpcode()) { |
| case Instruction::BitCast: |
| // Don't touch identity bitcasts. |
| if (I->getType() == I->getOperand(0)->getType()) |
| return false; |
| return isa<PointerType>(I->getType()) || isa<IntegerType>(I->getType()); |
| case Instruction::PtrToInt: |
| // PtrToInt is always a noop, as we know that the int type is pointer sized. |
| return true; |
| case Instruction::IntToPtr: |
| // We know the input is intptr_t, so this is foldable. |
| return true; |
| case Instruction::Add: |
| return true; |
| case Instruction::Mul: |
| case Instruction::Shl: |
| // Can only handle X*C and X << C. |
| return isa<ConstantInt>(I->getOperand(1)); |
| case Instruction::GetElementPtr: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| |
| /// MatchOperationAddr - Given an instruction or constant expr, see if we can |
| /// fold the operation into the addressing mode. If so, update the addressing |
| /// mode and return true, otherwise return false without modifying AddrMode. |
| bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode, |
| unsigned Depth) { |
| // Avoid exponential behavior on extremely deep expression trees. |
| if (Depth >= 5) return false; |
| |
| switch (Opcode) { |
| case Instruction::PtrToInt: |
| // PtrToInt is always a noop, as we know that the int type is pointer sized. |
| return MatchAddr(AddrInst->getOperand(0), Depth); |
| case Instruction::IntToPtr: |
| // This inttoptr is a no-op if the integer type is pointer sized. |
| if (TLI.getValueType(AddrInst->getOperand(0)->getType()) == |
| TLI.getPointerTy()) |
| return MatchAddr(AddrInst->getOperand(0), Depth); |
| return false; |
| case Instruction::BitCast: |
| // BitCast is always a noop, and we can handle it as long as it is |
| // int->int or pointer->pointer (we don't want int<->fp or something). |
| if ((isa<PointerType>(AddrInst->getOperand(0)->getType()) || |
| isa<IntegerType>(AddrInst->getOperand(0)->getType())) && |
| // Don't touch identity bitcasts. These were probably put here by LSR, |
| // and we don't want to mess around with them. Assume it knows what it |
| // is doing. |
| AddrInst->getOperand(0)->getType() != AddrInst->getType()) |
| return MatchAddr(AddrInst->getOperand(0), Depth); |
| return false; |
| case Instruction::Add: { |
| // Check to see if we can merge in the RHS then the LHS. If so, we win. |
| ExtAddrMode BackupAddrMode = AddrMode; |
| unsigned OldSize = AddrModeInsts.size(); |
| if (MatchAddr(AddrInst->getOperand(1), Depth+1) && |
| MatchAddr(AddrInst->getOperand(0), Depth+1)) |
| return true; |
| |
| // Restore the old addr mode info. |
| AddrMode = BackupAddrMode; |
| AddrModeInsts.resize(OldSize); |
| |
| // Otherwise this was over-aggressive. Try merging in the LHS then the RHS. |
| if (MatchAddr(AddrInst->getOperand(0), Depth+1) && |
| MatchAddr(AddrInst->getOperand(1), Depth+1)) |
| return true; |
| |
| // Otherwise we definitely can't merge the ADD in. |
| AddrMode = BackupAddrMode; |
| AddrModeInsts.resize(OldSize); |
| break; |
| } |
| //case Instruction::Or: |
| // TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD. |
| //break; |
| case Instruction::Mul: |
| case Instruction::Shl: { |
| // Can only handle X*C and X << C. |
| ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1)); |
| if (!RHS) return false; |
| int64_t Scale = RHS->getSExtValue(); |
| if (Opcode == Instruction::Shl) |
| Scale = 1 << Scale; |
| |
| return MatchScaledValue(AddrInst->getOperand(0), Scale, Depth); |
| } |
| case Instruction::GetElementPtr: { |
| // Scan the GEP. We check it if it contains constant offsets and at most |
| // one variable offset. |
| int VariableOperand = -1; |
| unsigned VariableScale = 0; |
| |
| int64_t ConstantOffset = 0; |
| const TargetData *TD = TLI.getTargetData(); |
| gep_type_iterator GTI = gep_type_begin(AddrInst); |
| for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) { |
| if (const StructType *STy = dyn_cast<StructType>(*GTI)) { |
| const StructLayout *SL = TD->getStructLayout(STy); |
| unsigned Idx = |
| cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue(); |
| ConstantOffset += SL->getElementOffset(Idx); |
| } else { |
| uint64_t TypeSize = TD->getTypePaddedSize(GTI.getIndexedType()); |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) { |
| ConstantOffset += CI->getSExtValue()*TypeSize; |
| } else if (TypeSize) { // Scales of zero don't do anything. |
| // We only allow one variable index at the moment. |
| if (VariableOperand != -1) |
| return false; |
| |
| // Remember the variable index. |
| VariableOperand = i; |
| VariableScale = TypeSize; |
| } |
| } |
| } |
| |
| // A common case is for the GEP to only do a constant offset. In this case, |
| // just add it to the disp field and check validity. |
| if (VariableOperand == -1) { |
| AddrMode.BaseOffs += ConstantOffset; |
| if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){ |
| // Check to see if we can fold the base pointer in too. |
| if (MatchAddr(AddrInst->getOperand(0), Depth+1)) |
| return true; |
| } |
| AddrMode.BaseOffs -= ConstantOffset; |
| return false; |
| } |
| |
| // Save the valid addressing mode in case we can't match. |
| ExtAddrMode BackupAddrMode = AddrMode; |
| |
| // Check that this has no base reg yet. If so, we won't have a place to |
| // put the base of the GEP (assuming it is not a null ptr). |
| bool SetBaseReg = true; |
| if (isa<ConstantPointerNull>(AddrInst->getOperand(0))) |
| SetBaseReg = false; // null pointer base doesn't need representation. |
| else if (AddrMode.HasBaseReg) |
| return false; // Base register already specified, can't match GEP. |
| else { |
| // Otherwise, we'll use the GEP base as the BaseReg. |
| AddrMode.HasBaseReg = true; |
| AddrMode.BaseReg = AddrInst->getOperand(0); |
| } |
| |
| // See if the scale and offset amount is valid for this target. |
| AddrMode.BaseOffs += ConstantOffset; |
| |
| if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale, |
| Depth)) { |
| AddrMode = BackupAddrMode; |
| return false; |
| } |
| |
| // If we have a null as the base of the GEP, folding in the constant offset |
| // plus variable scale is all we can do. |
| if (!SetBaseReg) return true; |
| |
| // If this match succeeded, we know that we can form an address with the |
| // GepBase as the basereg. Match the base pointer of the GEP more |
| // aggressively by zeroing out BaseReg and rematching. If the base is |
| // (for example) another GEP, this allows merging in that other GEP into |
| // the addressing mode we're forming. |
| AddrMode.HasBaseReg = false; |
| AddrMode.BaseReg = 0; |
| bool Success = MatchAddr(AddrInst->getOperand(0), Depth+1); |
| assert(Success && "MatchAddr should be able to fill in BaseReg!"); |
| Success=Success; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /// MatchAddr - If we can, try to add the value of 'Addr' into the current |
| /// addressing mode. If Addr can't be added to AddrMode this returns false and |
| /// leaves AddrMode unmodified. This assumes that Addr is either a pointer type |
| /// or intptr_t for the target. |
| /// |
| bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) { |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) { |
| // Fold in immediates if legal for the target. |
| AddrMode.BaseOffs += CI->getSExtValue(); |
| if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) |
| return true; |
| AddrMode.BaseOffs -= CI->getSExtValue(); |
| } else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) { |
| // If this is a global variable, try to fold it into the addressing mode. |
| if (AddrMode.BaseGV == 0) { |
| AddrMode.BaseGV = GV; |
| if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) |
| return true; |
| AddrMode.BaseGV = 0; |
| } |
| } else if (Instruction *I = dyn_cast<Instruction>(Addr)) { |
| ExtAddrMode BackupAddrMode = AddrMode; |
| unsigned OldSize = AddrModeInsts.size(); |
| |
| // Check to see if it is possible to fold this operation. |
| if (MatchOperationAddr(I, I->getOpcode(), Depth)) { |
| // Okay, it's possible to fold this. Check to see if it is actually |
| // *profitable* to do so. We use a simple cost model to avoid increasing |
| // register pressure too much. |
| if (I->hasOneUse() || |
| IsProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) { |
| AddrModeInsts.push_back(I); |
| return true; |
| } |
| |
| // It isn't profitable to do this, roll back. |
| //cerr << "NOT FOLDING: " << *I; |
| AddrMode = BackupAddrMode; |
| AddrModeInsts.resize(OldSize); |
| } |
| } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) { |
| if (MatchOperationAddr(CE, CE->getOpcode(), Depth)) |
| return true; |
| } else if (isa<ConstantPointerNull>(Addr)) { |
| // Null pointer gets folded without affecting the addressing mode. |
| return true; |
| } |
| |
| // Worse case, the target should support [reg] addressing modes. :) |
| if (!AddrMode.HasBaseReg) { |
| AddrMode.HasBaseReg = true; |
| AddrMode.BaseReg = Addr; |
| // Still check for legality in case the target supports [imm] but not [i+r]. |
| if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) |
| return true; |
| AddrMode.HasBaseReg = false; |
| AddrMode.BaseReg = 0; |
| } |
| |
| // If the base register is already taken, see if we can do [r+r]. |
| if (AddrMode.Scale == 0) { |
| AddrMode.Scale = 1; |
| AddrMode.ScaledReg = Addr; |
| if (TLI.isLegalAddressingMode(AddrMode, AccessTy)) |
| return true; |
| AddrMode.Scale = 0; |
| AddrMode.ScaledReg = 0; |
| } |
| // Couldn't match. |
| return false; |
| } |
| |
| |
| /// IsOperandAMemoryOperand - Check to see if all uses of OpVal by the specified |
| /// inline asm call are due to memory operands. If so, return true, otherwise |
| /// return false. |
| static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal, |
| const TargetLowering &TLI) { |
| std::vector<InlineAsm::ConstraintInfo> |
| Constraints = IA->ParseConstraints(); |
| |
| unsigned ArgNo = 1; // ArgNo - The operand of the CallInst. |
| for (unsigned i = 0, e = Constraints.size(); i != e; ++i) { |
| TargetLowering::AsmOperandInfo OpInfo(Constraints[i]); |
| |
| // Compute the value type for each operand. |
| switch (OpInfo.Type) { |
| case InlineAsm::isOutput: |
| if (OpInfo.isIndirect) |
| OpInfo.CallOperandVal = CI->getOperand(ArgNo++); |
| break; |
| case InlineAsm::isInput: |
| OpInfo.CallOperandVal = CI->getOperand(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 this asm operand is our Value*, and if it isn't an indirect memory |
| // operand, we can't fold it! |
| if (OpInfo.CallOperandVal == OpVal && |
| (OpInfo.ConstraintType != TargetLowering::C_Memory || |
| !OpInfo.isIndirect)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| |
| /// FindAllMemoryUses - Recursively walk all the uses of I until we find a |
| /// memory use. If we find an obviously non-foldable instruction, return true. |
| /// Add the ultimately found memory instructions to MemoryUses. |
| static bool FindAllMemoryUses(Instruction *I, |
| SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses, |
| SmallPtrSet<Instruction*, 16> &ConsideredInsts, |
| const TargetLowering &TLI) { |
| // If we already considered this instruction, we're done. |
| if (!ConsideredInsts.insert(I)) |
| return false; |
| |
| // If this is an obviously unfoldable instruction, bail out. |
| if (!MightBeFoldableInst(I)) |
| return true; |
| |
| // Loop over all the uses, recursively processing them. |
| for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); |
| UI != E; ++UI) { |
| if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { |
| MemoryUses.push_back(std::make_pair(LI, UI.getOperandNo())); |
| continue; |
| } |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { |
| if (UI.getOperandNo() == 0) return true; // Storing addr, not into addr. |
| MemoryUses.push_back(std::make_pair(SI, UI.getOperandNo())); |
| continue; |
| } |
| |
| if (CallInst *CI = dyn_cast<CallInst>(*UI)) { |
| InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue()); |
| if (IA == 0) return true; |
| |
| // If this is a memory operand, we're cool, otherwise bail out. |
| if (!IsOperandAMemoryOperand(CI, IA, I, TLI)) |
| return true; |
| continue; |
| } |
| |
| if (FindAllMemoryUses(cast<Instruction>(*UI), MemoryUses, ConsideredInsts, |
| TLI)) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| |
| /// ValueAlreadyLiveAtInst - Retrn true if Val is already known to be live at |
| /// the use site that we're folding it into. If so, there is no cost to |
| /// include it in the addressing mode. KnownLive1 and KnownLive2 are two values |
| /// that we know are live at the instruction already. |
| bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1, |
| Value *KnownLive2) { |
| // If Val is either of the known-live values, we know it is live! |
| if (Val == 0 || Val == KnownLive1 || Val == KnownLive2) |
| return true; |
| |
| // All values other than instructions and arguments (e.g. constants) are live. |
| if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true; |
| |
| // If Val is a constant sized alloca in the entry block, it is live, this is |
| // true because it is just a reference to the stack/frame pointer, which is |
| // live for the whole function. |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(Val)) |
| if (AI->isStaticAlloca()) |
| return true; |
| |
| // Check to see if this value is already used in the memory instruction's |
| // block. If so, it's already live into the block at the very least, so we |
| // can reasonably fold it. |
| BasicBlock *MemBB = MemoryInst->getParent(); |
| for (Value::use_iterator UI = Val->use_begin(), E = Val->use_end(); |
| UI != E; ++UI) |
| // We know that uses of arguments and instructions have to be instructions. |
| if (cast<Instruction>(*UI)->getParent() == MemBB) |
| return true; |
| |
| return false; |
| } |
| |
| |
| |
| /// IsProfitableToFoldIntoAddressingMode - It is possible for the addressing |
| /// mode of the machine to fold the specified instruction into a load or store |
| /// that ultimately uses it. However, the specified instruction has multiple |
| /// uses. Given this, it may actually increase register pressure to fold it |
| /// into the load. For example, consider this code: |
| /// |
| /// X = ... |
| /// Y = X+1 |
| /// use(Y) -> nonload/store |
| /// Z = Y+1 |
| /// load Z |
| /// |
| /// In this case, Y has multiple uses, and can be folded into the load of Z |
| /// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to |
| /// be live at the use(Y) line. If we don't fold Y into load Z, we use one |
| /// fewer register. Since Y can't be folded into "use(Y)" we don't increase the |
| /// number of computations either. |
| /// |
| /// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If |
| /// X was live across 'load Z' for other reasons, we actually *would* want to |
| /// fold the addressing mode in the Z case. This would make Y die earlier. |
| bool AddressingModeMatcher:: |
| IsProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore, |
| ExtAddrMode &AMAfter) { |
| if (IgnoreProfitability) return true; |
| |
| // AMBefore is the addressing mode before this instruction was folded into it, |
| // and AMAfter is the addressing mode after the instruction was folded. Get |
| // the set of registers referenced by AMAfter and subtract out those |
| // referenced by AMBefore: this is the set of values which folding in this |
| // address extends the lifetime of. |
| // |
| // Note that there are only two potential values being referenced here, |
| // BaseReg and ScaleReg (global addresses are always available, as are any |
| // folded immediates). |
| Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg; |
| |
| // If the BaseReg or ScaledReg was referenced by the previous addrmode, their |
| // lifetime wasn't extended by adding this instruction. |
| if (ValueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg)) |
| BaseReg = 0; |
| if (ValueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg)) |
| ScaledReg = 0; |
| |
| // If folding this instruction (and it's subexprs) didn't extend any live |
| // ranges, we're ok with it. |
| if (BaseReg == 0 && ScaledReg == 0) |
| return true; |
| |
| // If all uses of this instruction are ultimately load/store/inlineasm's, |
| // check to see if their addressing modes will include this instruction. If |
| // so, we can fold it into all uses, so it doesn't matter if it has multiple |
| // uses. |
| SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses; |
| SmallPtrSet<Instruction*, 16> ConsideredInsts; |
| if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI)) |
| return false; // Has a non-memory, non-foldable use! |
| |
| // Now that we know that all uses of this instruction are part of a chain of |
| // computation involving only operations that could theoretically be folded |
| // into a memory use, loop over each of these uses and see if they could |
| // *actually* fold the instruction. |
| SmallVector<Instruction*, 32> MatchedAddrModeInsts; |
| for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) { |
| Instruction *User = MemoryUses[i].first; |
| unsigned OpNo = MemoryUses[i].second; |
| |
| // Get the access type of this use. If the use isn't a pointer, we don't |
| // know what it accesses. |
| Value *Address = User->getOperand(OpNo); |
| if (!isa<PointerType>(Address->getType())) |
| return false; |
| const Type *AddressAccessTy = |
| cast<PointerType>(Address->getType())->getElementType(); |
| |
| // Do a match against the root of this address, ignoring profitability. This |
| // will tell us if the addressing mode for the memory operation will |
| // *actually* cover the shared instruction. |
| ExtAddrMode Result; |
| AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy, |
| MemoryInst, Result); |
| Matcher.IgnoreProfitability = true; |
| bool Success = Matcher.MatchAddr(Address, 0); |
| Success = Success; assert(Success && "Couldn't select *anything*?"); |
| |
| // If the match didn't cover I, then it won't be shared by it. |
| if (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(), |
| I) == MatchedAddrModeInsts.end()) |
| return false; |
| |
| MatchedAddrModeInsts.clear(); |
| } |
| |
| return true; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // 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 have 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(cerr << "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(cerr << "CGP: Reusing nonlocal addrmode: " << AddrMode << "\n"); |
| if (SunkAddr->getType() != Addr->getType()) |
| SunkAddr = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt); |
| } else { |
| DEBUG(cerr << "CGP: SINKING nonlocal addrmode: " << AddrMode << "\n"); |
| const Type *IntPtrTy = TLI->getTargetData()->getIntPtrType(); |
| |
| Value *Result = 0; |
| // Start with the scale value. |
| if (AddrMode.Scale) { |
| Value *V = AddrMode.ScaledReg; |
| if (V->getType() == IntPtrTy) { |
| // done. |
| } else if (isa<PointerType>(V->getType())) { |
| 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); |
| Result = V; |
| } |
| |
| // Add in the base register. |
| if (AddrMode.BaseReg) { |
| Value *V = AddrMode.BaseReg; |
| if (V->getType() != IntPtrTy) |
| V = new PtrToIntInst(V, IntPtrTy, "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; |
| } |
| |
| 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) { |
| 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 |= 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 (const TargetAsmInfo *TAI = |
| TLI->getTargetMachine().getTargetAsmInfo()) { |
| if (TAI->ExpandInlineAsm(CI)) |
| BBI = BB.begin(); |
| else |
| // Sink address computing for memory operands into the block. |
| MadeChange |= OptimizeInlineAsmInst(I, &(*CI), SunkAddrs); |
| } |
| } |
| } |
| |
| return MadeChange; |
| } |