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Diffstat (limited to 'lib/Analysis/InlineCost.cpp')
| -rw-r--r-- | lib/Analysis/InlineCost.cpp | 1439 |
1 files changed, 903 insertions, 536 deletions
diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp index e12e322..3e3d2ab 100644 --- a/lib/Analysis/InlineCost.cpp +++ b/lib/Analysis/InlineCost.cpp @@ -11,645 +11,1012 @@ // //===----------------------------------------------------------------------===// +#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" +#include "llvm/ADT/Statistic.h" using namespace llvm; -/// callIsSmall - If a call is likely to lower to a single target instruction, -/// or is otherwise deemed small return true. -/// TODO: Perhaps calls like memcpy, strcpy, etc? -bool llvm::callIsSmall(const Function *F) { - if (!F) return false; +STATISTIC(NumCallsAnalyzed, "Number of call sites analyzed"); + +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) { + } - if (F->hasLocalLinkage()) return false; + bool analyzeCall(CallSite CS); - if (!F->hasName()) return false; + int getThreshold() { return Threshold; } + int getCost() { return Cost; } - StringRef Name = F->getName(); + // 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; - // These will all likely lower to a single selection DAG node. - if (Name == "copysign" || Name == "copysignf" || Name == "copysignl" || - Name == "fabs" || Name == "fabsf" || Name == "fabsl" || - Name == "sin" || Name == "sinf" || Name == "sinl" || - Name == "cos" || Name == "cosf" || Name == "cosl" || - Name == "sqrt" || Name == "sqrtf" || Name == "sqrtl" ) - return true; + void dump(); +}; - // These are all likely to be optimized into something smaller. - if (Name == "pow" || Name == "powf" || Name == "powl" || - Name == "exp2" || Name == "exp2l" || Name == "exp2f" || - Name == "floor" || Name == "floorf" || Name == "ceil" || - Name == "round" || Name == "ffs" || Name == "ffsl" || - Name == "abs" || Name == "labs" || Name == "llabs") - return true; +} // namespace - return false; +/// \brief Test whether the given value is an Alloca-derived function argument. +bool CallAnalyzer::isAllocaDerivedArg(Value *V) { + return SROAArgValues.count(V); } -/// analyzeBasicBlock - Fill in the current structure with information gleaned -/// from the specified block. -void CodeMetrics::analyzeBasicBlock(const BasicBlock *BB, - const TargetData *TD) { - ++NumBlocks; - unsigned NumInstsBeforeThisBB = NumInsts; - for (BasicBlock::const_iterator II = BB->begin(), E = BB->end(); - II != E; ++II) { - if (isa<PHINode>(II)) continue; // PHI nodes don't count. - - // Special handling for calls. - if (isa<CallInst>(II) || isa<InvokeInst>(II)) { - if (isa<DbgInfoIntrinsic>(II)) - continue; // Debug intrinsics don't count as size. - - ImmutableCallSite CS(cast<Instruction>(II)); - - if (const Function *F = CS.getCalledFunction()) { - // If a function is both internal and has a single use, then it is - // extremely likely to get inlined in the future (it was probably - // exposed by an interleaved devirtualization pass). - if (F->hasInternalLinkage() && F->hasOneUse()) - ++NumInlineCandidates; - - // If this call is to function itself, then the function is recursive. - // Inlining it into other functions is a bad idea, because this is - // basically just a form of loop peeling, and our metrics aren't useful - // for that case. - if (F == BB->getParent()) - isRecursive = true; - } +/// \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; - if (!isa<IntrinsicInst>(II) && !callIsSmall(CS.getCalledFunction())) { - // Each argument to a call takes on average one instruction to set up. - NumInsts += CS.arg_size(); + DenseMap<Value *, Value *>::iterator ArgIt = SROAArgValues.find(V); + if (ArgIt == SROAArgValues.end()) + return false; - // We don't want inline asm to count as a call - that would prevent loop - // unrolling. The argument setup cost is still real, though. - if (!isa<InlineAsm>(CS.getCalledValue())) - ++NumCalls; - } - } + Arg = ArgIt->second; + CostIt = SROAArgCosts.find(Arg); + return CostIt != SROAArgCosts.end(); +} - if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { - if (!AI->isStaticAlloca()) - this->usesDynamicAlloca = true; - } +/// \brief Disable SROA for the candidate marked by this cost iterator. +/// +/// 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); +} - if (isa<ExtractElementInst>(II) || II->getType()->isVectorTy()) - ++NumVectorInsts; +/// \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); +} - if (const CastInst *CI = dyn_cast<CastInst>(II)) { - // Noop casts, including ptr <-> int, don't count. - if (CI->isLosslessCast() || isa<IntToPtrInst>(CI) || - isa<PtrToIntInst>(CI)) - continue; - // trunc to a native type is free (assuming the target has compare and - // shift-right of the same width). - if (isa<TruncInst>(CI) && TD && - TD->isLegalInteger(TD->getTypeSizeInBits(CI->getType()))) - continue; - // Result of a cmp instruction is often extended (to be used by other - // cmp instructions, logical or return instructions). These are usually - // nop on most sane targets. - if (isa<CmpInst>(CI->getOperand(0))) - continue; - } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(II)){ - // If a GEP has all constant indices, it will probably be folded with - // a load/store. - if (GEPI->hasAllConstantIndices()) - continue; +/// \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; + } + + 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; + + 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; + if (OpC->isZero()) continue; + + // 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; } - ++NumInsts; + APInt TypeSize(IntPtrWidth, TD->getTypeAllocSize(GTI.getIndexedType())); + Offset += OpC->getValue().sextOrTrunc(IntPtrWidth) * TypeSize; } + return true; +} - if (isa<ReturnInst>(BB->getTerminator())) - ++NumRets; +bool CallAnalyzer::visitAlloca(AllocaInst &I) { + // FIXME: Check whether inlining will turn a dynamic alloca into a static + // alloca, and handle that case. - // We never want to inline functions that contain an indirectbr. This is - // incorrect because all the blockaddress's (in static global initializers - // for example) would be referring to the original function, and this indirect - // jump would jump from the inlined copy of the function into the original - // function which is extremely undefined behavior. - if (isa<IndirectBrInst>(BB->getTerminator())) - containsIndirectBr = true; + // We will happily inline static alloca instructions or dynamic alloca + // instructions in always-inline situations. + if (AlwaysInline || I.isStaticAlloca()) + return Base::visitAlloca(I); - // Remember NumInsts for this BB. - NumBBInsts[BB] = NumInsts - NumInstsBeforeThisBB; + // 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; } -// CountCodeReductionForConstant - Figure out an approximation for how many -// instructions will be constant folded if the specified value is constant. -// -unsigned CodeMetrics::CountCodeReductionForConstant(Value *V) { - unsigned Reduction = 0; - 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 += NumBBInsts[TI.getSuccessor(I)]; - // We don't know which blocks will be eliminated, so use the average size. - Reduction += InlineConstants::InstrCost*Instrs*(NumSucc-1)/NumSucc; - } else { - // 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 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. - 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; - } + // 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. - if (AllOperandsConstant) { - // We will get to remove this instruction... - Reduction += InlineConstants::InstrCost; + // Phi nodes are always zero-cost. + return true; +} - // And any other instructions that use it which become constants - // themselves. - Reduction += CountCodeReductionForConstant(&Inst); +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; } } - return Reduction; -} -// CountCodeReductionForAlloca - Figure out an approximation of how much smaller -// the function will be if it is inlined into a context where an argument -// becomes an alloca. -// -unsigned CodeMetrics::CountCodeReductionForAlloca(Value *V) { - if (!V->getType()->isPointerTy()) return 0; // Not a pointer - unsigned Reduction = 0; - for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){ - Instruction *I = cast<Instruction>(*UI); - if (isa<LoadInst>(I) || isa<StoreInst>(I)) - Reduction += InlineConstants::InstrCost; - else 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()) - Reduction += CountCodeReductionForAlloca(GEP); - } else if (BitCastInst *BCI = dyn_cast<BitCastInst>(I)) { - // Track pointer through bitcasts. - Reduction += CountCodeReductionForAlloca(BCI); - } else { - // If there is some other strange instruction, we're not going to be able - // to do much if we inline this. - return 0; - } + if (isGEPOffsetConstant(I)) { + if (SROACandidate) + SROAArgValues[&I] = SROAArg; + + // Constant GEPs are modeled as free. + return true; } - return Reduction; + // Variable GEPs will require math and will disable SROA. + if (SROACandidate) + disableSROA(CostIt); + return false; } -/// analyzeFunction - Fill in the current structure with information gleaned -/// from the specified function. -void CodeMetrics::analyzeFunction(Function *F, const TargetData *TD) { - // If this function contains a call to setjmp or _setjmp, never inline - // it. This is a hack because we depend on the user marking their local - // variables as volatile if they are live across a setjmp call, and they - // probably won't do this in callers. - if (F->callsFunctionThatReturnsTwice()) - callsSetJmp = true; - - // Look at the size of the callee. - for (Function::const_iterator BB = F->begin(), E = F->end(); BB != E; ++BB) - analyzeBasicBlock(&*BB, TD); -} +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; + } -/// 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; - - // Check out all of the arguments to the function, figuring out how much - // code can be eliminated if one of the arguments is a constant. - ArgumentWeights.reserve(F->arg_size()); - for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I) - ArgumentWeights.push_back(ArgInfo(Metrics.CountCodeReductionForConstant(I), - Metrics.CountCodeReductionForAlloca(I))); + // 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; } -/// NeverInline - returns true if the function should never be inlined into -/// any caller -bool InlineCostAnalyzer::FunctionInfo::NeverInline() { - return (Metrics.callsSetJmp || Metrics.isRecursive || - Metrics.containsIndirectBr); +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; + } + + // 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(); } -// getSpecializationBonus - The heuristic used to determine the per-call -// performance boost for using a specialization of Callee with argument -// specializedArgNo replaced by a constant. -int InlineCostAnalyzer::getSpecializationBonus(Function *Callee, - SmallVectorImpl<unsigned> &SpecializedArgNos) -{ - if (Callee->mayBeOverridden()) - return 0; - int Bonus = 0; - // If this function uses the coldcc calling convention, prefer not to - // specialize it. - if (Callee->getCallingConv() == CallingConv::Cold) - Bonus -= InlineConstants::ColdccPenalty; - - // 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); - - unsigned ArgNo = 0; - unsigned i = 0; - for (Function::arg_iterator I = Callee->arg_begin(), E = Callee->arg_end(); - I != E; ++I, ++ArgNo) - if (ArgNo == SpecializedArgNos[i]) { - ++i; - Bonus += CountBonusForConstant(I); +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; } - // Calls usually take a long time, so they make the specialization gain - // smaller. - Bonus -= CalleeFI->Metrics.NumCalls * InlineConstants::CallPenalty; + // 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; + } + + // "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; - return Bonus; + // 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(); } -// 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::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; + } - // This could just be NULL. - if (!C) return 0; + // Disable SROA in the face of arbitrary casts we don't whitelist elsewhere. + disableSROA(I.getOperand(0)); - Function *F = dyn_cast<Function>(C); - if (!F) return 0; + // No-op casts don't have any cost. + if (I.isLosslessCast()) + return true; - int Bonus = InlineConstants::IndirectCallBonus + getInlineSize(CS, F); - return (Bonus > 0) ? 0 : Bonus; + // 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; } -// 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::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; } - // 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; - } + // Disable any SROA on the argument to arbitrary unary operators. + disableSROA(Operand); - if (AllOperandsConstant) - Bonus += CountBonusForConstant(&Inst); + 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; + } + + // 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; + } } } - return Bonus; -} + // 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; + } + + // 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; + } -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; - - // Compute any size reductions we can expect due to arguments being passed into - // the function. - // - unsigned ArgNo = 0; - CallSite::arg_iterator I = CS.arg_begin(); - for (Function::arg_iterator FI = Callee->arg_begin(), FE = Callee->arg_end(); - FI != FE; ++I, ++FI, ++ArgNo) { - - // If an alloca is passed in, inlining this function is likely to allow - // significant future optimization possibilities (like scalar promotion, and - // scalarization), so encourage the inlining of the function. - // - if (isa<AllocaInst>(I)) - InlineCost -= CalleeFI->ArgumentWeights[ArgNo].AllocaWeight; - - // If this is a constant being passed into the function, use the argument - // weights calculated for the callee to determine how much will be folded - // away with this information. - else if (isa<Constant>(I)) - InlineCost -= CalleeFI->ArgumentWeights[ArgNo].ConstantWeight; + disableSROA(CostIt); } - // Each argument passed in has a cost at both the caller and the callee - // sides. Measurements show that each argument costs about the same as an - // instruction. - InlineCost -= (CS.arg_size() * InlineConstants::InstrCost); + return false; +} - // Now that we have considered all of the factors that make the call site more - // likely to be inlined, look at factors that make us not want to inline it. +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; + } + } + } - // Calls usually take a long time, so they make the inlining gain smaller. - InlineCost += CalleeFI->Metrics.NumCalls * InlineConstants::CallPenalty; + // Otherwise, fall back to the generic logic for simplifying and handling + // instructions. + return Base::visitSub(I); +} - // Look at the size of the callee. Each instruction counts as 5. - InlineCost += CalleeFI->Metrics.NumInsts*InlineConstants::InstrCost; +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; + } - return InlineCost; -} + // Disable any SROA on arguments to arbitrary, unsimplified binary operators. + disableSROA(LHS); + disableSROA(RHS); -int InlineCostAnalyzer::getInlineBonuses(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); - - bool isDirectCall = CS.getCalledFunction() == Callee; - Instruction *TheCall = CS.getInstruction(); - int Bonus = 0; - - // If there is only one call of the function, and it has internal linkage, - // make it almost guaranteed to be inlined. - // - if (Callee->hasLocalLinkage() && Callee->hasOneUse() && isDirectCall) - Bonus += InlineConstants::LastCallToStaticBonus; - - // If the instruction after the call, or if the normal destination of the - // invoke is an unreachable instruction, the function is noreturn. As such, - // there is little point in inlining this. - if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { - if (isa<UnreachableInst>(II->getNormalDest()->begin())) - Bonus += InlineConstants::NoreturnPenalty; - } else if (isa<UnreachableInst>(++BasicBlock::iterator(TheCall))) - Bonus += InlineConstants::NoreturnPenalty; - - // If this function uses the coldcc calling convention, prefer not to inline - // it. - if (Callee->getCallingConv() == CallingConv::Cold) - Bonus += InlineConstants::ColdccPenalty; - - // Add to the inline quality for properties that make the call valuable to - // inline. This includes factors that indicate that the result of inlining - // the function will be optimizable. Currently this just looks at arguments - // passed into the function. - // - CallSite::arg_iterator I = CS.arg_begin(); - for (Function::arg_iterator FI = Callee->arg_begin(), FE = Callee->arg_end(); - FI != FE; ++I, ++FI) - // Compute any constant bonus due to inlining we want to give here. - if (isa<Constant>(I)) - Bonus += CountBonusForConstant(FI, cast<Constant>(I)); - - return Bonus; + return false; } -// getInlineCost - The heuristic used to determine if we should inline the -// function call or not. -// -InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS, - SmallPtrSet<const Function*, 16> &NeverInline) { - return getInlineCost(CS, CS.getCalledFunction(), NeverInline); -} +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; + } -InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS, - Function *Callee, - SmallPtrSet<const Function*, 16> &NeverInline) { - Instruction *TheCall = CS.getInstruction(); - Function *Caller = TheCall->getParent()->getParent(); + disableSROA(CostIt); + } - // Don't inline functions which can be redefined at link-time to mean - // something else. Don't inline functions marked noinline or call sites - // marked noinline. - if (Callee->mayBeOverridden() || - Callee->hasFnAttr(Attribute::NoInline) || NeverInline.count(Callee) || - CS.isNoInline()) - return llvm::InlineCost::getNever(); + return false; +} - // Get information about the callee. - FunctionInfo *CalleeFI = &CachedFunctionInfo[Callee]; +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; + } - // If we haven't calculated this information yet, do so now. - if (CalleeFI->Metrics.NumBlocks == 0) - CalleeFI->analyzeFunction(Callee, TD); + disableSROA(CostIt); + } - // If we should never inline this, return a huge cost. - if (CalleeFI->NeverInline()) - return InlineCost::getNever(); + return false; +} - // FIXME: It would be nice to kill off CalleeFI->NeverInline. Then we - // could move this up and avoid computing the FunctionInfo for - // things we are going to just return always inline for. This - // requires handling setjmp somewhere else, however. - if (!Callee->isDeclaration() && Callee->hasFnAttr(Attribute::AlwaysInline)) - return InlineCost::getAlways(); +bool CallAnalyzer::visitCallSite(CallSite CS) { + if (CS.isCall() && cast<CallInst>(CS.getInstruction())->canReturnTwice() && + !F.hasFnAttr(Attribute::ReturnsTwice)) { + // This aborts the entire analysis. + ExposesReturnsTwice = true; + return false; + } - if (CalleeFI->Metrics.usesDynamicAlloca) { - // Get information about the caller. - FunctionInfo &CallerFI = CachedFunctionInfo[Caller]; + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) { + switch (II->getIntrinsicID()) { + default: + return Base::visitCallSite(CS); + + case Intrinsic::dbg_declare: + case Intrinsic::dbg_value: + case Intrinsic::invariant_start: + case Intrinsic::invariant_end: + case Intrinsic::lifetime_start: + case Intrinsic::lifetime_end: + case Intrinsic::memset: + case Intrinsic::memcpy: + case Intrinsic::memmove: + case Intrinsic::objectsize: + case Intrinsic::ptr_annotation: + case Intrinsic::var_annotation: + // SROA can usually chew through these intrinsics and they have no cost + // so don't pay the price of analyzing them in detail. + return true; + } + } + + if (Function *F = CS.getCalledFunction()) { + if (F == CS.getInstruction()->getParent()->getParent()) { + // This flag will fully abort the analysis, so don't bother with anything + // else. + IsRecursive = true; + return false; + } - // If we haven't calculated this information yet, do so now. - if (CallerFI.Metrics.NumBlocks == 0) { - CallerFI.analyzeFunction(Caller, TD); + if (!callIsSmall(F)) { + // We account for the average 1 instruction per call argument setup + // here. + Cost += CS.arg_size() * InlineConstants::InstrCost; - // Recompute the CalleeFI pointer, getting Caller could have invalidated - // it. - CalleeFI = &CachedFunctionInfo[Callee]; + // Everything other than inline ASM will also have a significant cost + // merely from making the call. + if (!isa<InlineAsm>(CS.getCalledValue())) + Cost += InlineConstants::CallPenalty; } - // Don't inline a callee with dynamic alloca into a caller without them. - // Functions containing dynamic alloca's are inefficient in various ways; - // don't create more inefficiency. - if (!CallerFI.Metrics.usesDynamicAlloca) - return InlineCost::getNever(); + return Base::visitCallSite(CS); } - // 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 due to the fact that bonuses - // are negative numbers. - // - int InlineCost = getInlineSize(CS, Callee) + getInlineBonuses(CS, Callee); - return llvm::InlineCost::get(InlineCost); + // Otherwise we're in a very special case -- an indirect function call. See + // if we can be particularly clever about this. + Value *Callee = CS.getCalledValue(); + + // First, pay the price of the argument setup. We account for the average + // 1 instruction per call argument setup here. + Cost += CS.arg_size() * InlineConstants::InstrCost; + + // Next, check if this happens to be an indirect function call to a known + // function in this inline context. If not, we've done all we can. + Function *F = dyn_cast_or_null<Function>(SimplifiedValues.lookup(Callee)); + if (!F) + return Base::visitCallSite(CS); + + // If we have a constant that we are calling as a function, we can peer + // through it and see the function target. This happens not infrequently + // during devirtualization and so we want to give it a hefty bonus for + // inlining, but cap that bonus in the event that inlining wouldn't pan + // out. Pretend to inline the function, with a custom threshold. + CallAnalyzer CA(TD, *F, InlineConstants::IndirectCallThreshold); + if (CA.analyzeCall(CS)) { + // We were able to inline the indirect call! Subtract the cost from the + // bonus we want to apply, but don't go below zero. + Cost -= std::max(0, InlineConstants::IndirectCallThreshold - CA.getCost()); + } + + return Base::visitCallSite(CS); } -// getSpecializationCost - The heuristic used to determine the code-size -// impact of creating a specialized version of Callee with argument -// SpecializedArgNo replaced by a constant. -InlineCost InlineCostAnalyzer::getSpecializationCost(Function *Callee, - SmallVectorImpl<unsigned> &SpecializedArgNos) -{ - // Don't specialize functions which can be redefined at link-time to mean - // something else. - if (Callee->mayBeOverridden()) - return llvm::InlineCost::getNever(); +bool CallAnalyzer::visitInstruction(Instruction &I) { + // We found something we don't understand or can't handle. Mark any SROA-able + // values in the operand list as no longer viable. + for (User::op_iterator OI = I.op_begin(), OE = I.op_end(); OI != OE; ++OI) + disableSROA(*OI); + + return false; +} - // 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); +/// \brief Analyze a basic block for its contribution to the inline cost. +/// +/// This method walks the analyzer over every instruction in the given basic +/// block and accounts for their cost during inlining at this callsite. It +/// aborts early if the threshold has been exceeded or an impossible to inline +/// construct has been detected. It returns false if inlining is no longer +/// viable, and true if inlining remains viable. +bool CallAnalyzer::analyzeBlock(BasicBlock *BB) { + for (BasicBlock::iterator I = BB->begin(), E = llvm::prior(BB->end()); + I != E; ++I) { + ++NumInstructions; + if (isa<ExtractElementInst>(I) || I->getType()->isVectorTy()) + ++NumVectorInstructions; + + // If the instruction simplified to a constant, there is no cost to this + // instruction. Visit the instructions using our InstVisitor to account for + // all of the per-instruction logic. The visit tree returns true if we + // consumed the instruction in any way, and false if the instruction's base + // cost should count against inlining. + if (Base::visit(I)) + ++NumInstructionsSimplified; + else + Cost += InlineConstants::InstrCost; + + // If the visit this instruction detected an uninlinable pattern, abort. + if (IsRecursive || ExposesReturnsTwice || HasDynamicAlloca) + return false; + + if (NumVectorInstructions > NumInstructions/2) + VectorBonus = FiftyPercentVectorBonus; + else if (NumVectorInstructions > NumInstructions/10) + VectorBonus = TenPercentVectorBonus; + else + VectorBonus = 0; + + // Check if we've past the threshold so we don't spin in huge basic + // blocks that will never inline. + if (!AlwaysInline && Cost > (Threshold + VectorBonus)) + return false; + } - int Cost = 0; + return true; +} - // Look at the original size of the callee. Each instruction counts as 5. - Cost += CalleeFI->Metrics.NumInsts * InlineConstants::InstrCost; +/// \brief Compute the base pointer and cumulative constant offsets for V. +/// +/// This strips all constant offsets off of V, leaving it the base pointer, and +/// accumulates the total constant offset applied in the returned constant. It +/// returns 0 if V is not a pointer, and returns the constant '0' if there are +/// no constant offsets applied. +ConstantInt *CallAnalyzer::stripAndComputeInBoundsConstantOffsets(Value *&V) { + if (!TD || !V->getType()->isPointerTy()) + return 0; - // Offset that with the amount of code that can be constant-folded - // away with the given arguments replaced by constants. - for (SmallVectorImpl<unsigned>::iterator an = SpecializedArgNos.begin(), - ae = SpecializedArgNos.end(); an != ae; ++an) - Cost -= CalleeFI->ArgumentWeights[*an].ConstantWeight; + unsigned IntPtrWidth = TD->getPointerSizeInBits(); + APInt Offset = APInt::getNullValue(IntPtrWidth); + + // Even though we don't look through PHI nodes, we could be called on an + // instruction in an unreachable block, which may be on a cycle. + SmallPtrSet<Value *, 4> Visited; + Visited.insert(V); + do { + if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { + if (!GEP->isInBounds() || !accumulateGEPOffset(*GEP, Offset)) + return 0; + V = GEP->getPointerOperand(); + } else if (Operator::getOpcode(V) == Instruction::BitCast) { + V = cast<Operator>(V)->getOperand(0); + } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) { + if (GA->mayBeOverridden()) + break; + V = GA->getAliasee(); + } else { + break; + } + assert(V->getType()->isPointerTy() && "Unexpected operand type!"); + } while (Visited.insert(V)); - return llvm::InlineCost::get(Cost); + Type *IntPtrTy = TD->getIntPtrType(V->getContext()); + return cast<ConstantInt>(ConstantInt::get(IntPtrTy, Offset)); } -// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a -// higher threshold to determine if the function call should be inlined. -float InlineCostAnalyzer::getInlineFudgeFactor(CallSite CS) { - Function *Callee = CS.getCalledFunction(); - - // 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); - - float Factor = 1.0f; - // Single BB functions are often written to be inlined. - if (CalleeFI.Metrics.NumBlocks == 1) - Factor += 0.5f; - - // Be more aggressive if the function contains a good chunk (if it mades up - // at least 10% of the instructions) of vector instructions. - if (CalleeFI.Metrics.NumVectorInsts > CalleeFI.Metrics.NumInsts/2) - Factor += 2.0f; - else if (CalleeFI.Metrics.NumVectorInsts > CalleeFI.Metrics.NumInsts/10) - Factor += 1.5f; - return Factor; -} +/// \brief Analyze a call site for potential inlining. +/// +/// Returns true if inlining this call is viable, and false if it is not +/// viable. It computes the cost and adjusts the threshold based on numerous +/// factors and heuristics. If this method returns false but the computed cost +/// is below the computed threshold, then inlining was forcibly disabled by +/// some artifact of the rountine. +bool CallAnalyzer::analyzeCall(CallSite CS) { + ++NumCallsAnalyzed; + + // Track whether the post-inlining function would have more than one basic + // block. A single basic block is often intended for inlining. Balloon the + // threshold by 50% until we pass the single-BB phase. + bool SingleBB = true; + int SingleBBBonus = Threshold / 2; + Threshold += SingleBBBonus; + + // Unless we are always-inlining, perform some tweaks to the cost and + // threshold based on the direct callsite information. + if (!AlwaysInline) { + // We want to more aggressively inline vector-dense kernels, so up the + // threshold, and we'll lower it if the % of vector instructions gets too + // low. + assert(NumInstructions == 0); + assert(NumVectorInstructions == 0); + FiftyPercentVectorBonus = Threshold; + TenPercentVectorBonus = Threshold / 2; + + // Subtract off one instruction per call argument as those will be free after + // inlining. + Cost -= CS.arg_size() * InlineConstants::InstrCost; + + // If there is only one call of the function, and it has internal linkage, + // the cost of inlining it drops dramatically. + if (F.hasLocalLinkage() && F.hasOneUse() && &F == CS.getCalledFunction()) + Cost += InlineConstants::LastCallToStaticBonus; + + // If the instruction after the call, or if the normal destination of the + // invoke is an unreachable instruction, the function is noreturn. As such, + // there is little point in inlining this unless there is literally zero cost. + if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) { + if (isa<UnreachableInst>(II->getNormalDest()->begin())) + Threshold = 1; + } else if (isa<UnreachableInst>(++BasicBlock::iterator(CS.getInstruction()))) + Threshold = 1; + + // If this function uses the coldcc calling convention, prefer not to inline + // it. + if (F.getCallingConv() == CallingConv::Cold) + Cost += InlineConstants::ColdccPenalty; + + // Check if we're done. This can happen due to bonuses and penalties. + if (Cost > Threshold) + return false; + } -/// growCachedCostInfo - update the cached cost info for Caller after Callee has -/// been inlined. -void -InlineCostAnalyzer::growCachedCostInfo(Function *Caller, Function *Callee) { - CodeMetrics &CallerMetrics = CachedFunctionInfo[Caller].Metrics; + if (F.empty()) + return true; - // For small functions we prefer to recalculate the cost for better accuracy. - if (CallerMetrics.NumBlocks < 10 && CallerMetrics.NumInsts < 1000) { - resetCachedCostInfo(Caller); - return; + // Track whether we've seen a return instruction. The first return + // instruction is free, as at least one will usually disappear in inlining. + bool HasReturn = false; + + // Populate our simplified values by mapping from function arguments to call + // arguments with known important simplifications. + CallSite::arg_iterator CAI = CS.arg_begin(); + for (Function::arg_iterator FAI = F.arg_begin(), FAE = F.arg_end(); + FAI != FAE; ++FAI, ++CAI) { + assert(CAI != CS.arg_end()); + if (Constant *C = dyn_cast<Constant>(CAI)) + SimplifiedValues[FAI] = C; + + Value *PtrArg = *CAI; + if (ConstantInt *C = stripAndComputeInBoundsConstantOffsets(PtrArg)) { + ConstantOffsetPtrs[FAI] = std::make_pair(PtrArg, C->getValue()); + + // We can SROA any pointer arguments derived from alloca instructions. + if (isa<AllocaInst>(PtrArg)) { + SROAArgValues[FAI] = PtrArg; + SROAArgCosts[PtrArg] = 0; + } + } } + NumConstantArgs = SimplifiedValues.size(); + NumConstantOffsetPtrArgs = ConstantOffsetPtrs.size(); + NumAllocaArgs = SROAArgValues.size(); + + // The worklist of live basic blocks in the callee *after* inlining. We avoid + // adding basic blocks of the callee which can be proven to be dead for this + // particular call site in order to get more accurate cost estimates. This + // requires a somewhat heavyweight iteration pattern: we need to walk the + // basic blocks in a breadth-first order as we insert live successors. To + // accomplish this, prioritizing for small iterations because we exit after + // crossing our threshold, we use a small-size optimized SetVector. + typedef SetVector<BasicBlock *, SmallVector<BasicBlock *, 16>, + SmallPtrSet<BasicBlock *, 16> > BBSetVector; + BBSetVector BBWorklist; + BBWorklist.insert(&F.getEntryBlock()); + // Note that we *must not* cache the size, this loop grows the worklist. + for (unsigned Idx = 0; Idx != BBWorklist.size(); ++Idx) { + // Bail out the moment we cross the threshold. This means we'll under-count + // the cost, but only when undercounting doesn't matter. + if (!AlwaysInline && Cost > (Threshold + VectorBonus)) + break; + + BasicBlock *BB = BBWorklist[Idx]; + if (BB->empty()) + continue; + + // Handle the terminator cost here where we can track returns and other + // function-wide constructs. + TerminatorInst *TI = BB->getTerminator(); + + // We never want to inline functions that contain an indirectbr. This is + // incorrect because all the blockaddress's (in static global initializers + // for example) would be referring to the original function, and this indirect + // jump would jump from the inlined copy of the function into the original + // function which is extremely undefined behavior. + // FIXME: This logic isn't really right; we can safely inline functions + // with indirectbr's as long as no other function or global references the + // blockaddress of a block within the current function. And as a QOI issue, + // if someone is using a blockaddress without an indirectbr, and that + // reference somehow ends up in another function or global, we probably + // don't want to inline this function. + if (isa<IndirectBrInst>(TI)) + return false; + + if (!HasReturn && isa<ReturnInst>(TI)) + HasReturn = true; + else + Cost += InlineConstants::InstrCost; + + // Analyze the cost of this block. If we blow through the threshold, this + // returns false, and we can bail on out. + if (!analyzeBlock(BB)) { + if (IsRecursive || ExposesReturnsTwice || HasDynamicAlloca) + return false; + break; + } - // For large functions, we can save a lot of computation time by skipping - // recalculations. - if (CallerMetrics.NumCalls > 0) - --CallerMetrics.NumCalls; + // Add in the live successors by first checking whether we have terminator + // that may be simplified based on the values simplified by this call. + if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { + if (BI->isConditional()) { + Value *Cond = BI->getCondition(); + if (ConstantInt *SimpleCond + = dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) { + BBWorklist.insert(BI->getSuccessor(SimpleCond->isZero() ? 1 : 0)); + continue; + } + } + } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { + Value *Cond = SI->getCondition(); + if (ConstantInt *SimpleCond + = dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) { + BBWorklist.insert(SI->findCaseValue(SimpleCond).getCaseSuccessor()); + continue; + } + } - if (Callee == 0) return; + // If we're unable to select a particular successor, just count all of + // them. + for (unsigned TIdx = 0, TSize = TI->getNumSuccessors(); TIdx != TSize; ++TIdx) + BBWorklist.insert(TI->getSuccessor(TIdx)); + + // If we had any successors at this point, than post-inlining is likely to + // have them as well. Note that we assume any basic blocks which existed + // due to branches or switches which folded above will also fold after + // inlining. + if (SingleBB && TI->getNumSuccessors() > 1) { + // Take off the bonus we applied to the threshold. + Threshold -= SingleBBBonus; + SingleBB = false; + } + } - CodeMetrics &CalleeMetrics = CachedFunctionInfo[Callee].Metrics; + Threshold += VectorBonus; - // If we don't have metrics for the callee, don't recalculate them just to - // update an approximation in the caller. Instead, just recalculate the - // caller info from scratch. - if (CalleeMetrics.NumBlocks == 0) { - resetCachedCostInfo(Caller); - return; - } + return AlwaysInline || Cost < Threshold; +} - // Since CalleeMetrics were already calculated, we know that the CallerMetrics - // reference isn't invalidated: both were in the DenseMap. - CallerMetrics.usesDynamicAlloca |= CalleeMetrics.usesDynamicAlloca; - - // FIXME: If any of these three are true for the callee, the callee was - // not inlined into the caller, so I think they're redundant here. - CallerMetrics.callsSetJmp |= CalleeMetrics.callsSetJmp; - CallerMetrics.isRecursive |= CalleeMetrics.isRecursive; - CallerMetrics.containsIndirectBr |= CalleeMetrics.containsIndirectBr; - - CallerMetrics.NumInsts += CalleeMetrics.NumInsts; - CallerMetrics.NumBlocks += CalleeMetrics.NumBlocks; - CallerMetrics.NumCalls += CalleeMetrics.NumCalls; - CallerMetrics.NumVectorInsts += CalleeMetrics.NumVectorInsts; - CallerMetrics.NumRets += CalleeMetrics.NumRets; - - // analyzeBasicBlock counts each function argument as an inst. - if (CallerMetrics.NumInsts >= Callee->arg_size()) - CallerMetrics.NumInsts -= Callee->arg_size(); - else - CallerMetrics.NumInsts = 0; - - // We are not updating the argument weights. We have already determined that - // Caller is a fairly large function, so we accept the loss of precision. +/// \brief Dump stats about this call's analysis. +void CallAnalyzer::dump() { +#define DEBUG_PRINT_STAT(x) llvm::dbgs() << " " #x ": " << x << "\n" + DEBUG_PRINT_STAT(NumConstantArgs); + DEBUG_PRINT_STAT(NumConstantOffsetPtrArgs); + DEBUG_PRINT_STAT(NumAllocaArgs); + DEBUG_PRINT_STAT(NumConstantPtrCmps); + DEBUG_PRINT_STAT(NumConstantPtrDiffs); + DEBUG_PRINT_STAT(NumInstructionsSimplified); + DEBUG_PRINT_STAT(SROACostSavings); + DEBUG_PRINT_STAT(SROACostSavingsLost); +#undef DEBUG_PRINT_STAT } -/// clear - empty the cache of inline costs -void InlineCostAnalyzer::clear() { - CachedFunctionInfo.clear(); +InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS, int Threshold) { + return getInlineCost(CS, CS.getCalledFunction(), Threshold); +} + +InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS, Function *Callee, + int Threshold) { + // Don't inline functions which can be redefined at link-time to mean + // something else. Don't inline functions marked noinline or call sites + // marked noinline. + if (!Callee || Callee->mayBeOverridden() || + Callee->hasFnAttr(Attribute::NoInline) || CS.isNoInline()) + return llvm::InlineCost::getNever(); + + DEBUG(llvm::dbgs() << " Analyzing call of " << Callee->getName() << "...\n"); + + CallAnalyzer CA(TD, *Callee, Threshold); + bool ShouldInline = CA.analyzeCall(CS); + + DEBUG(CA.dump()); + + // Check if there was a reason to force inlining or no inlining. + if (!ShouldInline && CA.getCost() < CA.getThreshold()) + return InlineCost::getNever(); + if (ShouldInline && CA.getCost() >= CA.getThreshold()) + return InlineCost::getAlways(); + + return llvm::InlineCost::get(CA.getCost(), CA.getThreshold()); } |
