diff options
Diffstat (limited to 'lib/Analysis/InlineCost.cpp')
| -rw-r--r-- | lib/Analysis/InlineCost.cpp | 1441 |
1 files changed, 898 insertions, 543 deletions
diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp index dedbfebea7..bc6c1687fd 100644 --- a/lib/Analysis/InlineCost.cpp +++ b/lib/Analysis/InlineCost.cpp @@ -11,659 +11,1014 @@ // //===----------------------------------------------------------------------===// +#define DEBUG_TYPE "inline-cost" #include "llvm/Analysis/InlineCost.h" +#include "llvm/Analysis/ConstantFolding.h" +#include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Support/CallSite.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/InstVisitor.h" +#include "llvm/Support/GetElementPtrTypeIterator.h" +#include "llvm/Support/raw_ostream.h" #include "llvm/CallingConv.h" #include "llvm/IntrinsicInst.h" +#include "llvm/Operator.h" +#include "llvm/GlobalAlias.h" #include "llvm/Target/TargetData.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/SmallVector.h" #include "llvm/ADT/SmallPtrSet.h" using namespace llvm; -unsigned InlineCostAnalyzer::FunctionInfo::countCodeReductionForConstant( - const CodeMetrics &Metrics, Value *V) { - unsigned Reduction = 0; - SmallVector<Value *, 4> Worklist; - Worklist.push_back(V); - do { - Value *V = Worklist.pop_back_val(); - for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){ - User *U = *UI; - if (isa<BranchInst>(U) || isa<SwitchInst>(U)) { - // We will be able to eliminate all but one of the successors. - const TerminatorInst &TI = cast<TerminatorInst>(*U); - const unsigned NumSucc = TI.getNumSuccessors(); - unsigned Instrs = 0; - for (unsigned I = 0; I != NumSucc; ++I) - Instrs += Metrics.NumBBInsts.lookup(TI.getSuccessor(I)); - // We don't know which blocks will be eliminated, so use the average size. - Reduction += InlineConstants::InstrCost*Instrs*(NumSucc-1)/NumSucc; - continue; - } +namespace { + +class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> { + typedef InstVisitor<CallAnalyzer, bool> Base; + friend class InstVisitor<CallAnalyzer, bool>; + + // TargetData if available, or null. + const TargetData *const TD; + + // The called function. + Function &F; + + int Threshold; + int Cost; + const bool AlwaysInline; + + bool IsRecursive; + bool ExposesReturnsTwice; + bool HasDynamicAlloca; + unsigned NumInstructions, NumVectorInstructions; + int FiftyPercentVectorBonus, TenPercentVectorBonus; + int VectorBonus; + + // While we walk the potentially-inlined instructions, we build up and + // maintain a mapping of simplified values specific to this callsite. The + // idea is to propagate any special information we have about arguments to + // this call through the inlinable section of the function, and account for + // likely simplifications post-inlining. The most important aspect we track + // is CFG altering simplifications -- when we prove a basic block dead, that + // can cause dramatic shifts in the cost of inlining a function. + DenseMap<Value *, Constant *> SimplifiedValues; + + // Keep track of the values which map back (through function arguments) to + // allocas on the caller stack which could be simplified through SROA. + DenseMap<Value *, Value *> SROAArgValues; + + // The mapping of caller Alloca values to their accumulated cost savings. If + // we have to disable SROA for one of the allocas, this tells us how much + // cost must be added. + DenseMap<Value *, int> SROAArgCosts; + + // Keep track of values which map to a pointer base and constant offset. + DenseMap<Value *, std::pair<Value *, APInt> > ConstantOffsetPtrs; + + // Custom simplification helper routines. + bool isAllocaDerivedArg(Value *V); + bool lookupSROAArgAndCost(Value *V, Value *&Arg, + DenseMap<Value *, int>::iterator &CostIt); + void disableSROA(DenseMap<Value *, int>::iterator CostIt); + void disableSROA(Value *V); + void accumulateSROACost(DenseMap<Value *, int>::iterator CostIt, + int InstructionCost); + bool handleSROACandidate(bool IsSROAValid, + DenseMap<Value *, int>::iterator CostIt, + int InstructionCost); + bool isGEPOffsetConstant(GetElementPtrInst &GEP); + bool accumulateGEPOffset(GEPOperator &GEP, APInt &Offset); + ConstantInt *stripAndComputeInBoundsConstantOffsets(Value *&V); + + // Custom analysis routines. + bool analyzeBlock(BasicBlock *BB); + + // Disable several entry points to the visitor so we don't accidentally use + // them by declaring but not defining them here. + void visit(Module *); void visit(Module &); + void visit(Function *); void visit(Function &); + void visit(BasicBlock *); void visit(BasicBlock &); + + // Provide base case for our instruction visit. + bool visitInstruction(Instruction &I); + + // Our visit overrides. + bool visitAlloca(AllocaInst &I); + bool visitPHI(PHINode &I); + bool visitGetElementPtr(GetElementPtrInst &I); + bool visitBitCast(BitCastInst &I); + bool visitPtrToInt(PtrToIntInst &I); + bool visitIntToPtr(IntToPtrInst &I); + bool visitCastInst(CastInst &I); + bool visitUnaryInstruction(UnaryInstruction &I); + bool visitICmp(ICmpInst &I); + bool visitSub(BinaryOperator &I); + bool visitBinaryOperator(BinaryOperator &I); + bool visitLoad(LoadInst &I); + bool visitStore(StoreInst &I); + bool visitCallSite(CallSite CS); + +public: + CallAnalyzer(const TargetData *TD, Function &Callee, int Threshold) + : TD(TD), F(Callee), Threshold(Threshold), Cost(0), + AlwaysInline(F.hasFnAttr(Attribute::AlwaysInline)), + IsRecursive(false), ExposesReturnsTwice(false), HasDynamicAlloca(false), + NumInstructions(0), NumVectorInstructions(0), + FiftyPercentVectorBonus(0), TenPercentVectorBonus(0), VectorBonus(0), + NumConstantArgs(0), NumConstantOffsetPtrArgs(0), NumAllocaArgs(0), + NumConstantPtrCmps(0), NumConstantPtrDiffs(0), + NumInstructionsSimplified(0), SROACostSavings(0), SROACostSavingsLost(0) { + } - // Figure out if this instruction will be removed due to simple constant - // propagation. - Instruction &Inst = cast<Instruction>(*U); - - // We can't constant propagate instructions which have effects or - // read memory. - // - // FIXME: It would be nice to capture the fact that a load from a - // pointer-to-constant-global is actually a *really* good thing to zap. - // Unfortunately, we don't know the pointer that may get propagated here, - // so we can't make this decision. - if (Inst.mayReadFromMemory() || Inst.mayHaveSideEffects() || - isa<AllocaInst>(Inst)) - continue; + bool analyzeCall(CallSite CS); - bool AllOperandsConstant = true; - for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i) - if (!isa<Constant>(Inst.getOperand(i)) && Inst.getOperand(i) != V) { - AllOperandsConstant = false; - break; - } - if (!AllOperandsConstant) - continue; + int getThreshold() { return Threshold; } + int getCost() { return Cost; } - // We will get to remove this instruction... - Reduction += InlineConstants::InstrCost; + // Keep a bunch of stats about the cost savings found so we can print them + // out when debugging. + unsigned NumConstantArgs; + unsigned NumConstantOffsetPtrArgs; + unsigned NumAllocaArgs; + unsigned NumConstantPtrCmps; + unsigned NumConstantPtrDiffs; + unsigned NumInstructionsSimplified; + unsigned SROACostSavings; + unsigned SROACostSavingsLost; - // And any other instructions that use it which become constants - // themselves. - Worklist.push_back(&Inst); - } - } while (!Worklist.empty()); - return Reduction; -} + void dump(); +}; -static unsigned countCodeReductionForAllocaICmp(const CodeMetrics &Metrics, - ICmpInst *ICI) { - unsigned Reduction = 0; +} // namespace - // Bail if this is comparing against a non-constant; there is nothing we can - // do there. - if (!isa<Constant>(ICI->getOperand(1))) - return Reduction; +/// \brief Test whether the given value is an Alloca-derived function argument. +bool CallAnalyzer::isAllocaDerivedArg(Value *V) { + return SROAArgValues.count(V); +} - // An icmp pred (alloca, C) becomes true if the predicate is true when - // equal and false otherwise. - bool Result = ICI->isTrueWhenEqual(); +/// \brief Lookup the SROA-candidate argument and cost iterator which V maps to. +/// Returns false if V does not map to a SROA-candidate. +bool CallAnalyzer::lookupSROAArgAndCost( + Value *V, Value *&Arg, DenseMap<Value *, int>::iterator &CostIt) { + if (SROAArgValues.empty() || SROAArgCosts.empty()) + return false; - SmallVector<Instruction *, 4> Worklist; - Worklist.push_back(ICI); - do { - Instruction *U = Worklist.pop_back_val(); - Reduction += InlineConstants::InstrCost; - for (Value::use_iterator UI = U->use_begin(), UE = U->use_end(); - UI != UE; ++UI) { - Instruction *I = dyn_cast<Instruction>(*UI); - if (!I || I->mayHaveSideEffects()) continue; - if (I->getNumOperands() == 1) - Worklist.push_back(I); - if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) { - // If BO produces the same value as U, then the other operand is - // irrelevant and we can put it into the Worklist to continue - // deleting dead instructions. If BO produces the same value as the - // other operand, we can delete BO but that's it. - if (Result == true) { - if (BO->getOpcode() == Instruction::Or) - Worklist.push_back(I); - if (BO->getOpcode() == Instruction::And) - Reduction += InlineConstants::InstrCost; - } else { - if (BO->getOpcode() == Instruction::Or || - BO->getOpcode() == Instruction::Xor) - Reduction += InlineConstants::InstrCost; - if (BO->getOpcode() == Instruction::And) - Worklist.push_back(I); - } - } - if (BranchInst *BI = dyn_cast<BranchInst>(I)) { - BasicBlock *BB = BI->getSuccessor(Result ? 0 : 1); - if (BB->getSinglePredecessor()) - Reduction - += InlineConstants::InstrCost * Metrics.NumBBInsts.lookup(BB); - } - } - } while (!Worklist.empty()); + DenseMap<Value *, Value *>::iterator ArgIt = SROAArgValues.find(V); + if (ArgIt == SROAArgValues.end()) + return false; - return Reduction; + Arg = ArgIt->second; + CostIt = SROAArgCosts.find(Arg); + return CostIt != SROAArgCosts.end(); } -/// \brief Compute the reduction possible for a given instruction if we are able -/// to SROA an alloca. +/// \brief Disable SROA for the candidate marked by this cost iterator. /// -/// The reduction for this instruction is added to the SROAReduction output -/// parameter. Returns false if this instruction is expected to defeat SROA in -/// general. -static bool countCodeReductionForSROAInst(Instruction *I, - SmallVectorImpl<Value *> &Worklist, - unsigned &SROAReduction) { - if (LoadInst *LI = dyn_cast<LoadInst>(I)) { - if (!LI->isSimple()) - return false; - SROAReduction += InlineConstants::InstrCost; +/// This markes the candidate as no longer viable for SROA, and adds the cost +/// savings associated with it back into the inline cost measurement. +void CallAnalyzer::disableSROA(DenseMap<Value *, int>::iterator CostIt) { + // If we're no longer able to perform SROA we need to undo its cost savings + // and prevent subsequent analysis. + Cost += CostIt->second; + SROACostSavings -= CostIt->second; + SROACostSavingsLost += CostIt->second; + SROAArgCosts.erase(CostIt); +} + +/// \brief If 'V' maps to a SROA candidate, disable SROA for it. +void CallAnalyzer::disableSROA(Value *V) { + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + if (lookupSROAArgAndCost(V, SROAArg, CostIt)) + disableSROA(CostIt); +} + +/// \brief Accumulate the given cost for a particular SROA candidate. +void CallAnalyzer::accumulateSROACost(DenseMap<Value *, int>::iterator CostIt, + int InstructionCost) { + CostIt->second += InstructionCost; + SROACostSavings += InstructionCost; +} + +/// \brief Helper for the common pattern of handling a SROA candidate. +/// Either accumulates the cost savings if the SROA remains valid, or disables +/// SROA for the candidate. +bool CallAnalyzer::handleSROACandidate(bool IsSROAValid, + DenseMap<Value *, int>::iterator CostIt, + int InstructionCost) { + if (IsSROAValid) { + accumulateSROACost(CostIt, InstructionCost); return true; } - if (StoreInst *SI = dyn_cast<StoreInst>(I)) { - if (!SI->isSimple()) + disableSROA(CostIt); + return false; +} + +/// \brief Check whether a GEP's indices are all constant. +/// +/// Respects any simplified values known during the analysis of this callsite. +bool CallAnalyzer::isGEPOffsetConstant(GetElementPtrInst &GEP) { + for (User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); I != E; ++I) + if (!isa<Constant>(*I) && !SimplifiedValues.lookup(*I)) return false; - SROAReduction += InlineConstants::InstrCost; - return true; - } - if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) { - // If the GEP has variable indices, we won't be able to do much with it. - if (!GEP->hasAllConstantIndices()) + return true; +} + +/// \brief Accumulate a constant GEP offset into an APInt if possible. +/// +/// Returns false if unable to compute the offset for any reason. Respects any +/// simplified values known during the analysis of this callsite. +bool CallAnalyzer::accumulateGEPOffset(GEPOperator &GEP, APInt &Offset) { + if (!TD) + return false; + + unsigned IntPtrWidth = TD->getPointerSizeInBits(); + assert(IntPtrWidth == Offset.getBitWidth()); + + for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP); + GTI != GTE; ++GTI) { + ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand()); + if (!OpC) + if (Constant *SimpleOp = SimplifiedValues.lookup(GTI.getOperand())) + OpC = dyn_cast<ConstantInt>(SimpleOp); + if (!OpC) return false; - // A non-zero GEP will likely become a mask operation after SROA. - if (GEP->hasAllZeroIndices()) - SROAReduction += InlineConstants::InstrCost; - Worklist.push_back(GEP); - return true; - } + if (OpC->isZero()) continue; - if (BitCastInst *BCI = dyn_cast<BitCastInst>(I)) { - // Track pointer through bitcasts. - Worklist.push_back(BCI); - SROAReduction += InlineConstants::InstrCost; - return true; + // Handle a struct index, which adds its field offset to the pointer. + if (StructType *STy = dyn_cast<StructType>(*GTI)) { + unsigned ElementIdx = OpC->getZExtValue(); + const StructLayout *SL = TD->getStructLayout(STy); + Offset += APInt(IntPtrWidth, SL->getElementOffset(ElementIdx)); + continue; + } + + APInt TypeSize(IntPtrWidth, TD->getTypeAllocSize(GTI.getIndexedType())); + Offset += OpC->getValue().sextOrTrunc(IntPtrWidth) * TypeSize; } + return true; +} + +bool CallAnalyzer::visitAlloca(AllocaInst &I) { + // FIXME: Check whether inlining will turn a dynamic alloca into a static + // alloca, and handle that case. - // We just look for non-constant operands to ICmp instructions as those will - // defeat SROA. The actual reduction for these happens even without SROA. - if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) - return isa<Constant>(ICI->getOperand(1)); - - if (SelectInst *SI = dyn_cast<SelectInst>(I)) { - // SROA can handle a select of alloca iff all uses of the alloca are - // loads, and dereferenceable. We assume it's dereferenceable since - // we're told the input is an alloca. - for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end(); - UI != UE; ++UI) { - LoadInst *LI = dyn_cast<LoadInst>(*UI); - if (LI == 0 || !LI->isSimple()) + // We will happily inline tatic alloca instructions or dynamic alloca + // instructions in always-inline situations. + if (AlwaysInline || I.isStaticAlloca()) + return Base::visitAlloca(I); + + // FIXME: This is overly conservative. Dynamic allocas are inefficient for + // a variety of reasons, and so we would like to not inline them into + // functions which don't currently have a dynamic alloca. This simply + // disables inlining altogether in the presence of a dynamic alloca. + HasDynamicAlloca = true; + return false; +} + +bool CallAnalyzer::visitPHI(PHINode &I) { + // FIXME: We should potentially be tracking values through phi nodes, + // especially when they collapse to a single value due to deleted CFG edges + // during inlining. + + // FIXME: We need to propagate SROA *disabling* through phi nodes, even + // though we don't want to propagate it's bonuses. The idea is to disable + // SROA if it *might* be used in an inappropriate manner. + + // Phi nodes are always zero-cost. + return true; +} + +bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) { + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + bool SROACandidate = lookupSROAArgAndCost(I.getPointerOperand(), + SROAArg, CostIt); + + // Try to fold GEPs of constant-offset call site argument pointers. This + // requires target data and inbounds GEPs. + if (TD && I.isInBounds()) { + // Check if we have a base + offset for the pointer. + Value *Ptr = I.getPointerOperand(); + std::pair<Value *, APInt> BaseAndOffset = ConstantOffsetPtrs.lookup(Ptr); + if (BaseAndOffset.first) { + // Check if the offset of this GEP is constant, and if so accumulate it + // into Offset. + if (!accumulateGEPOffset(cast<GEPOperator>(I), BaseAndOffset.second)) { + // Non-constant GEPs aren't folded, and disable SROA. + if (SROACandidate) + disableSROA(CostIt); return false; + } + + // Add the result as a new mapping to Base + Offset. + ConstantOffsetPtrs[&I] = BaseAndOffset; + + // Also handle SROA candidates here, we already know that the GEP is + // all-constant indexed. + if (SROACandidate) + SROAArgValues[&I] = SROAArg; + + return true; } - // We don't know whether we'll be deleting the rest of the chain of - // instructions from the SelectInst on, because we don't know whether - // the other side of the select is also an alloca or not. + } + + if (isGEPOffsetConstant(I)) { + if (SROACandidate) + SROAArgValues[&I] = SROAArg; + + // Constant GEPs are modeled as free. return true; } - if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { - switch (II->getIntrinsicID()) { - default: - return false; - case Intrinsic::memset: - case Intrinsic::memcpy: - case Intrinsic::memmove: - case Intrinsic::lifetime_start: - case Intrinsic::lifetime_end: - // SROA can usually chew through these intrinsics. - SROAReduction += InlineConstants::InstrCost; + // Variable GEPs will require math and will disable SROA. + if (SROACandidate) + disableSROA(CostIt); + return false; +} + +bool CallAnalyzer::visitBitCast(BitCastInst &I) { + // Propagate constants through bitcasts. + if (Constant *COp = dyn_cast<Constant>(I.getOperand(0))) + if (Constant *C = ConstantExpr::getBitCast(COp, I.getType())) { + SimplifiedValues[&I] = C; return true; } + + // Track base/offsets through casts + std::pair<Value *, APInt> BaseAndOffset + = ConstantOffsetPtrs.lookup(I.getOperand(0)); + // Casts don't change the offset, just wrap it up. + if (BaseAndOffset.first) + ConstantOffsetPtrs[&I] = BaseAndOffset; + + // Also look for SROA candidates here. + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) + SROAArgValues[&I] = SROAArg; + + // Bitcasts are always zero cost. + return true; +} + +bool CallAnalyzer::visitPtrToInt(PtrToIntInst &I) { + // Propagate constants through ptrtoint. + if (Constant *COp = dyn_cast<Constant>(I.getOperand(0))) + if (Constant *C = ConstantExpr::getPtrToInt(COp, I.getType())) { + SimplifiedValues[&I] = C; + return true; + } + + // Track base/offset pairs when converted to a plain integer provided the + // integer is large enough to represent the pointer. + unsigned IntegerSize = I.getType()->getScalarSizeInBits(); + if (TD && IntegerSize >= TD->getPointerSizeInBits()) { + std::pair<Value *, APInt> BaseAndOffset + = ConstantOffsetPtrs.lookup(I.getOperand(0)); + if (BaseAndOffset.first) + ConstantOffsetPtrs[&I] = BaseAndOffset; } - // If there is some other strange instruction, we're not going to be - // able to do much if we inline this. - return false; + // This is really weird. Technically, ptrtoint will disable SROA. However, + // unless that ptrtoint is *used* somewhere in the live basic blocks after + // inlining, it will be nuked, and SROA should proceed. All of the uses which + // would block SROA would also block SROA if applied directly to a pointer, + // and so we can just add the integer in here. The only places where SROA is + // preserved either cannot fire on an integer, or won't in-and-of themselves + // disable SROA (ext) w/o some later use that we would see and disable. + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) + SROAArgValues[&I] = SROAArg; + + // A ptrtoint cast is free so long as the result is large enough to store the + // pointer, and a legal integer type. + return TD && TD->isLegalInteger(IntegerSize) && + IntegerSize >= TD->getPointerSizeInBits(); } -unsigned InlineCostAnalyzer::FunctionInfo::countCodeReductionForAlloca( - const CodeMetrics &Metrics, Value *V) { - if (!V->getType()->isPointerTy()) return 0; // Not a pointer - unsigned Reduction = 0; - unsigned SROAReduction = 0; - bool CanSROAAlloca = true; +bool CallAnalyzer::visitIntToPtr(IntToPtrInst &I) { + // Propagate constants through ptrtoint. + if (Constant *COp = dyn_cast<Constant>(I.getOperand(0))) + if (Constant *C = ConstantExpr::getIntToPtr(COp, I.getType())) { + SimplifiedValues[&I] = C; + return true; + } - SmallVector<Value *, 4> Worklist; - Worklist.push_back(V); - do { - Value *V = Worklist.pop_back_val(); - for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); - UI != E; ++UI){ - Instruction *I = cast<Instruction>(*UI); + // Track base/offset pairs when round-tripped through a pointer without + // modifications provided the integer is not too large. + Value *Op = I.getOperand(0); + unsigned IntegerSize = Op->getType()->getScalarSizeInBits(); + if (TD && IntegerSize <= TD->getPointerSizeInBits()) { + std::pair<Value *, APInt> BaseAndOffset = ConstantOffsetPtrs.lookup(Op); + if (BaseAndOffset.first) + ConstantOffsetPtrs[&I] = BaseAndOffset; + } - if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) - Reduction += countCodeReductionForAllocaICmp(Metrics, ICI); + // "Propagate" SROA here in the same manner as we do for ptrtoint above. + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + if (lookupSROAArgAndCost(Op, SROAArg, CostIt)) + SROAArgValues[&I] = SROAArg; - if (CanSROAAlloca) - CanSROAAlloca = countCodeReductionForSROAInst(I, Worklist, - SROAReduction); + // An inttoptr cast is free so long as the input is a legal integer type + // which doesn't contain values outside the range of a pointer. + return TD && TD->isLegalInteger(IntegerSize) && + IntegerSize <= TD->getPointerSizeInBits(); +} + +bool CallAnalyzer::visitCastInst(CastInst &I) { + // Propagate constants through ptrtoint. + if (Constant *COp = dyn_cast<Constant>(I.getOperand(0))) + if (Constant *C = ConstantExpr::getCast(I.getOpcode(), COp, I.getType())) { + SimplifiedValues[&I] = C; + return true; } - } while (!Worklist.empty()); - return Reduction + (CanSROAAlloca ? SROAReduction : 0); + // Disable SROA in the face of arbitrary casts we don't whitelist elsewhere. + disableSROA(I.getOperand(0)); + + // No-op casts don't have any cost. + if (I.isLosslessCast()) + return true; + + // trunc to a native type is free (assuming the target has compare and + // shift-right of the same width). + if (TD && isa<TruncInst>(I) && + TD->isLegalInteger(TD->getTypeSizeInBits(I.getType()))) + return true; + + // Result of a cmp instruction is often extended (to be used by other + // cmp instructions, logical or return instructions). These are usually + // no-ops on most sane targets. + if (isa<CmpInst>(I.getOperand(0))) + return true; + + // Assume the rest of the casts require work. + return false; } -void InlineCostAnalyzer::FunctionInfo::countCodeReductionForPointerPair( - const CodeMetrics &Metrics, DenseMap<Value *, unsigned> &PointerArgs, - Value *V, unsigned ArgIdx) { - SmallVector<Value *, 4> Worklist; - Worklist.push_back(V); - do { - Value *V = Worklist.pop_back_val(); - for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); - UI != E; ++UI){ - Instruction *I = cast<Instruction>(*UI); - - if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) { - // If the GEP has variable indices, we won't be able to do much with it. - if (!GEP->hasAllConstantIndices()) - continue; - // Unless the GEP is in-bounds, some comparisons will be non-constant. - // Fortunately, the real-world cases where this occurs uses in-bounds - // GEPs, and so we restrict the optimization to them here. - if (!GEP->isInBounds()) - continue; +bool CallAnalyzer::visitUnaryInstruction(UnaryInstruction &I) { + Value *Operand = I.getOperand(0); + Constant *Ops[1] = { dyn_cast<Constant>(Operand) }; + if (Ops[0] || (Ops[0] = SimplifiedValues.lookup(Operand))) + if (Constant *C = ConstantFoldInstOperands(I.getOpcode(), I.getType(), + Ops, TD)) { + SimplifiedValues[&I] = C; + return true; + } - // Constant indices just change the constant offset. Add the resulting - // value both to our worklist for this argument, and to the set of - // viable paired values with future arguments. - PointerArgs[GEP] = ArgIdx; - Worklist.push_back(GEP); - continue; + // Disable any SROA on the argument to arbitrary unary operators. + disableSROA(Operand); + + return false; +} + +bool CallAnalyzer::visitICmp(ICmpInst &I) { + Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); + // First try to handle simplified comparisons. + if (!isa<Constant>(LHS)) + if (Constant *SimpleLHS = SimplifiedValues.lookup(LHS)) + LHS = SimpleLHS; + if (!isa<Constant>(RHS)) + if (Constant *SimpleRHS = SimplifiedValues.lookup(RHS)) + RHS = SimpleRHS; + if (Constant *CLHS = dyn_cast<Constant>(LHS)) + if (Constant *CRHS = dyn_cast<Constant>(RHS)) + if (Constant *C = ConstantExpr::getICmp(I.getPredicate(), CLHS, CRHS)) { + SimplifiedValues[&I] = C; + return true; } - // Track pointer through casts. Even when the result is not a pointer, it - // remains a constant relative to constants derived from other constant - // pointers. - if (CastInst *CI = dyn_cast<CastInst>(I)) { - PointerArgs[CI] = ArgIdx; - Worklist.push_back(CI); - continue; + // Otherwise look for a comparison between constant offset pointers with + // a common base. + Value *LHSBase, *RHSBase; + APInt LHSOffset, RHSOffset; + llvm::tie(LHSBase, LHSOffset) = ConstantOffsetPtrs.lookup(LHS); + if (LHSBase) { + llvm::tie(RHSBase, RHSOffset) = ConstantOffsetPtrs.lookup(RHS); + if (RHSBase && LHSBase == RHSBase) { + // We have common bases, fold the icmp to a constant based on the + // offsets. + Constant *CLHS = ConstantInt::get(LHS->getContext(), LHSOffset); + Constant *CRHS = ConstantInt::get(RHS->getContext(), RHSOffset); + if (Constant *C = ConstantExpr::getICmp(I.getPredicate(), CLHS, CRHS)) { + SimplifiedValues[&I] = C; + ++NumConstantPtrCmps; + return true; } + } + } - // There are two instructions which produce a strict constant value when - // applied to two related pointer values. Ignore everything else. - if (!isa<ICmpInst>(I) && I->getOpcode() != Instruction::Sub) - continue; - assert(I->getNumOperands() == 2); - - // Ensure that the two operands are in our set of potentially paired - // pointers (or are derived from them). - Value *OtherArg = I->getOperand(0); - if (OtherArg == V) - OtherArg = I->getOperand(1); - DenseMap<Value *, unsigned>::const_iterator ArgIt - = PointerArgs.find(OtherArg); - if (ArgIt == PointerArgs.end()) - continue; - std::pair<unsigned, unsigned> ArgPair(ArgIt->second, ArgIdx); - if (ArgPair.first > ArgPair.second) - std::swap(ArgPair.first, ArgPair.second); + // If the comparison is an equality comparison with null, we can simplify it + // for any alloca-derived argument. + if (I.isEquality() && isa<ConstantPointerNull>(I.getOperand(1))) + if (isAllocaDerivedArg(I.getOperand(0))) { + // We can actually predict the result of comparisons between an + // alloca-derived value and null. Note that this fires regardless of + // SROA firing. + bool IsNotEqual = I.getPredicate() == CmpInst::ICMP_NE; + SimplifiedValues[&I] = IsNotEqual ? ConstantInt::getTrue(I.getType()) + : ConstantInt::getFalse(I.getType()); + return true; + } - PointerArgPairWeights[ArgPair] - += countCodeReductionForConstant(Metrics, I); + // Finally check for SROA candidates in comparisons. + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) { + if (isa<ConstantPointerNull>(I.getOperand(1))) { + accumulateSROACost(CostIt, InlineConstants::InstrCost); + return true; } - } while (!Worklist.empty()); -} -/// analyzeFunction - Fill in the current structure with information gleaned -/// from the specified function. -void InlineCostAnalyzer::FunctionInfo::analyzeFunction(Function *F, - const TargetData *TD) { - Metrics.analyzeFunction(F, TD); - - // A function with exactly one return has it removed during the inlining - // process (see InlineFunction), so don't count it. - // FIXME: This knowledge should really be encoded outside of FunctionInfo. - if (Metrics.NumRets==1) - --Metrics.NumInsts; - - ArgumentWeights.reserve(F->arg_size()); - DenseMap<Value *, unsigned> PointerArgs; - unsigned ArgIdx = 0; - for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; - ++I, ++ArgIdx) { - // Count how much code can be eliminated if one of the arguments is - // a constant or an alloca. - ArgumentWeights.push_back(ArgInfo(countCodeReductionForConstant(Metrics, I), - countCodeReductionForAlloca(Metrics, I))); - - // If the argument is a pointer, also check for pairs of pointers where - // knowing a fixed offset between them allows simplification. This pattern - // arises mostly due to STL algorithm patterns where pointers are used as - // random access iterators. - if (!I->getType()->isPointerTy()) - continue; - PointerArgs[I] = ArgIdx; - countCodeReductionForPointerPair(Metrics, PointerArgs, I, ArgIdx); + disableSROA(CostIt); } -} -/// NeverInline - returns true if the function should never be inlined into -/// any caller -bool InlineCostAnalyzer::FunctionInfo::NeverInline() { - return (Metrics.exposesReturnsTwice || Metrics.isRecursive || - Metrics.containsIndirectBr); + return false; } -// ConstantFunctionBonus - Figure out how much of a bonus we can get for -// possibly devirtualizing a function. We'll subtract the size of the function -// we may wish to inline from the indirect call bonus providing a limit on -// growth. Leave an upper limit of 0 for the bonus - we don't want to penalize -// inlining because we decide we don't want to give a bonus for -// devirtualizing. -int InlineCostAnalyzer::ConstantFunctionBonus(CallSite CS, Constant *C) { +bool CallAnalyzer::visitSub(BinaryOperator &I) { + // Try to handle a special case: we can fold computing the difference of two + // constant-related pointers. + Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); + Value *LHSBase, *RHSBase; + APInt LHSOffset, RHSOffset; + llvm::tie(LHSBase, LHSOffset) = ConstantOffsetPtrs.lookup(LHS); + if (LHSBase) { + llvm::tie(RHSBase, RHSOffset) = ConstantOffsetPtrs.lookup(RHS); + if (RHSBase && LHSBase == RHSBase) { + // We have common bases, fold the subtract to a constant based on the + // offsets. + Constant *CLHS = ConstantInt::get(LHS->getContext(), LHSOffset); + Constant *CRHS = ConstantInt::get(RHS->getContext(), RHSOffset); + if (Constant *C = ConstantExpr::getSub(CLHS, CRHS)) { + SimplifiedValues[&I] = C; + ++NumConstantPtrDiffs; + return true; + } + } + } - // This could just be NULL. - if (!C) return 0; + // Otherwise, fall back to the generic logic for simplifying and handling + // instructions. + return Base::visitSub(I); +} + +bool CallAnalyzer::visitBinaryOperator(BinaryOperator &I) { + Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); + if (!isa<Constant>(LHS)) + if (Constant *SimpleLHS = SimplifiedValues.lookup(LHS)) + LHS = SimpleLHS; + if (!isa<Constant>(RHS)) + if (Constant *SimpleRHS = SimplifiedValues.lookup(RHS)) + RHS = SimpleRHS; + Value *SimpleV = SimplifyBinOp(I.getOpcode(), LHS, RHS, TD); + if (Constant *C = dyn_cast_or_null<Constant>(SimpleV)) { + SimplifiedValues[&I] = C; + return true; + } - Function *F = dyn_cast<Function>(C); - if (!F) return 0; + // Disable any SROA on arguments to arbitrary, unsimplified binary operators. + disableSROA(LHS); + disableSROA(RHS); - int Bonus = InlineConstants::IndirectCallBonus + getInlineSize(CS, F); - return (Bonus > 0) ? 0 : Bonus; + return false; } -// CountBonusForConstant - Figure out an approximation for how much per-call -// performance boost we can expect if the specified value is constant. -int InlineCostAnalyzer::CountBonusForConstant(Value *V, Constant *C) { - unsigned Bonus = 0; - for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){ - User *U = *UI; - if (CallInst *CI = dyn_cast<CallInst>(U)) { - // Turning an indirect call into a direct call is a BIG win - if (CI->getCalledValue() == V) - Bonus += ConstantFunctionBonus(CallSite(CI), C); - } else if (InvokeInst *II = dyn_cast<InvokeInst>(U)) { - // Turning an indirect call into a direct call is a BIG win - if (II->getCalledValue() == V) - Bonus += ConstantFunctionBonus(CallSite(II), C); +bool CallAnalyzer::visitLoad(LoadInst &I) { + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) { + if (I.isSimple()) { + accumulateSROACost(CostIt, InlineConstants::InstrCost); + return true; } - // FIXME: Eliminating conditional branches and switches should - // also yield a per-call performance boost. - else { - // Figure out the bonuses that wll accrue due to simple constant - // propagation. - Instruction &Inst = cast<Instruction>(*U); - - // We can't constant propagate instructions which have effects or - // read memory. - // - // FIXME: It would be nice to capture the fact that a load from a - // pointer-to-constant-global is actually a *really* good thing to zap. - // Unfortunately, we don't know the pointer that may get propagated here, - // so we can't make this decision. - if (Inst.mayReadFromMemory() || Inst.mayHaveSideEffects() || - isa<AllocaInst>(Inst)) - continue; - bool AllOperandsConstant = true; - for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i) - if (!isa<Constant>(Inst.getOperand(i)) && Inst.getOperand(i) != V) { - AllOperandsConstant = false; - break; - } + disableSROA(CostIt); + } - if (AllOperandsConstant) - Bonus += CountBonusForConstant(&Inst); + return false; +} + +bool CallAnalyzer::visitStore(StoreInst &I) { + Value *SROAArg; + DenseMap<Value *, int>::iterator CostIt; + if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) { + if (I.isSimple()) { + accumulateSROACost(CostIt, InlineConstants::InstrCost); + return true; } + + disableSROA(CostIt); } - return Bonus; + return false; } -int InlineCostAnalyzer::getInlineSize(CallSite CS, Function *Callee) { - // Get information about the callee. - FunctionInfo *CalleeFI = &CachedFunctionInfo[Callee]; - - // If we haven't calculated this information yet, do so now. - if (CalleeFI->Metrics.NumBlocks == 0) - CalleeFI->analyzeFunction(Callee, TD); - - // InlineCost - This value measures how good of an inline candidate this call - // site is to inline. A lower inline cost make is more likely for the call to - // be inlined. This value may go negative. - // - int InlineCost = 0; |