1426 lines
53 KiB
C++
1426 lines
53 KiB
C++
//===- InlineCost.cpp - Cost analysis for inliner -------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements inline cost analysis.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/InlineCost.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/Analysis/CodeMetrics.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/TargetTransformInfo.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/CallingConv.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/GetElementPtrTypeIterator.h"
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#include "llvm/IR/GlobalAlias.h"
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#include "llvm/IR/InstVisitor.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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#define DEBUG_TYPE "inline-cost"
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STATISTIC(NumCallsAnalyzed, "Number of call sites analyzed");
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namespace {
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class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
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typedef InstVisitor<CallAnalyzer, bool> Base;
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friend class InstVisitor<CallAnalyzer, bool>;
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/// The TargetTransformInfo available for this compilation.
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const TargetTransformInfo &TTI;
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/// The cache of @llvm.assume intrinsics.
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AssumptionCacheTracker *ACT;
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// The called function.
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Function &F;
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// The candidate callsite being analyzed. Please do not use this to do
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// analysis in the caller function; we want the inline cost query to be
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// easily cacheable. Instead, use the cover function paramHasAttr.
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CallSite CandidateCS;
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int Threshold;
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int Cost;
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bool IsCallerRecursive;
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bool IsRecursiveCall;
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bool ExposesReturnsTwice;
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bool HasDynamicAlloca;
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bool ContainsNoDuplicateCall;
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bool HasReturn;
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bool HasIndirectBr;
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bool HasFrameEscape;
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/// Number of bytes allocated statically by the callee.
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uint64_t AllocatedSize;
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unsigned NumInstructions, NumVectorInstructions;
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int FiftyPercentVectorBonus, TenPercentVectorBonus;
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int VectorBonus;
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// While we walk the potentially-inlined instructions, we build up and
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// maintain a mapping of simplified values specific to this callsite. The
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// idea is to propagate any special information we have about arguments to
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// this call through the inlinable section of the function, and account for
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// likely simplifications post-inlining. The most important aspect we track
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// is CFG altering simplifications -- when we prove a basic block dead, that
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// can cause dramatic shifts in the cost of inlining a function.
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DenseMap<Value *, Constant *> SimplifiedValues;
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// Keep track of the values which map back (through function arguments) to
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// allocas on the caller stack which could be simplified through SROA.
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DenseMap<Value *, Value *> SROAArgValues;
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// The mapping of caller Alloca values to their accumulated cost savings. If
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// we have to disable SROA for one of the allocas, this tells us how much
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// cost must be added.
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DenseMap<Value *, int> SROAArgCosts;
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// Keep track of values which map to a pointer base and constant offset.
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DenseMap<Value *, std::pair<Value *, APInt> > ConstantOffsetPtrs;
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// Custom simplification helper routines.
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bool isAllocaDerivedArg(Value *V);
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bool lookupSROAArgAndCost(Value *V, Value *&Arg,
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DenseMap<Value *, int>::iterator &CostIt);
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void disableSROA(DenseMap<Value *, int>::iterator CostIt);
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void disableSROA(Value *V);
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void accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
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int InstructionCost);
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bool isGEPOffsetConstant(GetElementPtrInst &GEP);
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bool accumulateGEPOffset(GEPOperator &GEP, APInt &Offset);
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bool simplifyCallSite(Function *F, CallSite CS);
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ConstantInt *stripAndComputeInBoundsConstantOffsets(Value *&V);
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/// Return true if the given argument to the function being considered for
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/// inlining has the given attribute set either at the call site or the
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/// function declaration. Primarily used to inspect call site specific
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/// attributes since these can be more precise than the ones on the callee
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/// itself.
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bool paramHasAttr(Argument *A, Attribute::AttrKind Attr);
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/// Return true if the given value is known non null within the callee if
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/// inlined through this particular callsite.
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bool isKnownNonNullInCallee(Value *V);
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// Custom analysis routines.
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bool analyzeBlock(BasicBlock *BB, SmallPtrSetImpl<const Value *> &EphValues);
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// Disable several entry points to the visitor so we don't accidentally use
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// them by declaring but not defining them here.
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void visit(Module *); void visit(Module &);
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void visit(Function *); void visit(Function &);
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void visit(BasicBlock *); void visit(BasicBlock &);
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// Provide base case for our instruction visit.
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bool visitInstruction(Instruction &I);
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// Our visit overrides.
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bool visitAlloca(AllocaInst &I);
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bool visitPHI(PHINode &I);
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bool visitGetElementPtr(GetElementPtrInst &I);
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bool visitBitCast(BitCastInst &I);
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bool visitPtrToInt(PtrToIntInst &I);
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bool visitIntToPtr(IntToPtrInst &I);
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bool visitCastInst(CastInst &I);
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bool visitUnaryInstruction(UnaryInstruction &I);
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bool visitCmpInst(CmpInst &I);
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bool visitSub(BinaryOperator &I);
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bool visitBinaryOperator(BinaryOperator &I);
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bool visitLoad(LoadInst &I);
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bool visitStore(StoreInst &I);
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bool visitExtractValue(ExtractValueInst &I);
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bool visitInsertValue(InsertValueInst &I);
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bool visitCallSite(CallSite CS);
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bool visitReturnInst(ReturnInst &RI);
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bool visitBranchInst(BranchInst &BI);
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bool visitSwitchInst(SwitchInst &SI);
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bool visitIndirectBrInst(IndirectBrInst &IBI);
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bool visitResumeInst(ResumeInst &RI);
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bool visitCleanupReturnInst(CleanupReturnInst &RI);
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bool visitCatchReturnInst(CatchReturnInst &RI);
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bool visitUnreachableInst(UnreachableInst &I);
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public:
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CallAnalyzer(const TargetTransformInfo &TTI, AssumptionCacheTracker *ACT,
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Function &Callee, int Threshold, CallSite CSArg)
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: TTI(TTI), ACT(ACT), F(Callee), CandidateCS(CSArg), Threshold(Threshold),
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Cost(0), IsCallerRecursive(false), IsRecursiveCall(false),
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ExposesReturnsTwice(false), HasDynamicAlloca(false),
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ContainsNoDuplicateCall(false), HasReturn(false), HasIndirectBr(false),
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HasFrameEscape(false), AllocatedSize(0), NumInstructions(0),
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NumVectorInstructions(0), FiftyPercentVectorBonus(0),
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TenPercentVectorBonus(0), VectorBonus(0), NumConstantArgs(0),
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NumConstantOffsetPtrArgs(0), NumAllocaArgs(0), NumConstantPtrCmps(0),
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NumConstantPtrDiffs(0), NumInstructionsSimplified(0),
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SROACostSavings(0), SROACostSavingsLost(0) {}
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bool analyzeCall(CallSite CS);
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int getThreshold() { return Threshold; }
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int getCost() { return Cost; }
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// Keep a bunch of stats about the cost savings found so we can print them
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// out when debugging.
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unsigned NumConstantArgs;
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unsigned NumConstantOffsetPtrArgs;
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unsigned NumAllocaArgs;
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unsigned NumConstantPtrCmps;
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unsigned NumConstantPtrDiffs;
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unsigned NumInstructionsSimplified;
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unsigned SROACostSavings;
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unsigned SROACostSavingsLost;
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void dump();
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};
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} // namespace
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/// \brief Test whether the given value is an Alloca-derived function argument.
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bool CallAnalyzer::isAllocaDerivedArg(Value *V) {
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return SROAArgValues.count(V);
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}
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/// \brief Lookup the SROA-candidate argument and cost iterator which V maps to.
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/// Returns false if V does not map to a SROA-candidate.
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bool CallAnalyzer::lookupSROAArgAndCost(
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Value *V, Value *&Arg, DenseMap<Value *, int>::iterator &CostIt) {
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if (SROAArgValues.empty() || SROAArgCosts.empty())
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return false;
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DenseMap<Value *, Value *>::iterator ArgIt = SROAArgValues.find(V);
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if (ArgIt == SROAArgValues.end())
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return false;
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Arg = ArgIt->second;
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CostIt = SROAArgCosts.find(Arg);
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return CostIt != SROAArgCosts.end();
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}
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/// \brief Disable SROA for the candidate marked by this cost iterator.
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///
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/// This marks the candidate as no longer viable for SROA, and adds the cost
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/// savings associated with it back into the inline cost measurement.
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void CallAnalyzer::disableSROA(DenseMap<Value *, int>::iterator CostIt) {
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// If we're no longer able to perform SROA we need to undo its cost savings
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// and prevent subsequent analysis.
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Cost += CostIt->second;
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SROACostSavings -= CostIt->second;
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SROACostSavingsLost += CostIt->second;
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SROAArgCosts.erase(CostIt);
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}
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/// \brief If 'V' maps to a SROA candidate, disable SROA for it.
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void CallAnalyzer::disableSROA(Value *V) {
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Value *SROAArg;
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DenseMap<Value *, int>::iterator CostIt;
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if (lookupSROAArgAndCost(V, SROAArg, CostIt))
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disableSROA(CostIt);
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}
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/// \brief Accumulate the given cost for a particular SROA candidate.
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void CallAnalyzer::accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
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int InstructionCost) {
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CostIt->second += InstructionCost;
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SROACostSavings += InstructionCost;
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}
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/// \brief Check whether a GEP's indices are all constant.
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///
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/// Respects any simplified values known during the analysis of this callsite.
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bool CallAnalyzer::isGEPOffsetConstant(GetElementPtrInst &GEP) {
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for (User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); I != E; ++I)
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if (!isa<Constant>(*I) && !SimplifiedValues.lookup(*I))
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return false;
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return true;
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}
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/// \brief Accumulate a constant GEP offset into an APInt if possible.
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///
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/// Returns false if unable to compute the offset for any reason. Respects any
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/// simplified values known during the analysis of this callsite.
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bool CallAnalyzer::accumulateGEPOffset(GEPOperator &GEP, APInt &Offset) {
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const DataLayout &DL = F.getParent()->getDataLayout();
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unsigned IntPtrWidth = DL.getPointerSizeInBits();
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assert(IntPtrWidth == Offset.getBitWidth());
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for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
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GTI != GTE; ++GTI) {
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ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
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if (!OpC)
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if (Constant *SimpleOp = SimplifiedValues.lookup(GTI.getOperand()))
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OpC = dyn_cast<ConstantInt>(SimpleOp);
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if (!OpC)
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return false;
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if (OpC->isZero()) continue;
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// Handle a struct index, which adds its field offset to the pointer.
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if (StructType *STy = dyn_cast<StructType>(*GTI)) {
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unsigned ElementIdx = OpC->getZExtValue();
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const StructLayout *SL = DL.getStructLayout(STy);
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Offset += APInt(IntPtrWidth, SL->getElementOffset(ElementIdx));
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continue;
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}
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APInt TypeSize(IntPtrWidth, DL.getTypeAllocSize(GTI.getIndexedType()));
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Offset += OpC->getValue().sextOrTrunc(IntPtrWidth) * TypeSize;
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}
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return true;
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}
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bool CallAnalyzer::visitAlloca(AllocaInst &I) {
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// Check whether inlining will turn a dynamic alloca into a static
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// alloca, and handle that case.
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if (I.isArrayAllocation()) {
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if (Constant *Size = SimplifiedValues.lookup(I.getArraySize())) {
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ConstantInt *AllocSize = dyn_cast<ConstantInt>(Size);
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assert(AllocSize && "Allocation size not a constant int?");
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Type *Ty = I.getAllocatedType();
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AllocatedSize += Ty->getPrimitiveSizeInBits() * AllocSize->getZExtValue();
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return Base::visitAlloca(I);
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}
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}
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// Accumulate the allocated size.
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if (I.isStaticAlloca()) {
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const DataLayout &DL = F.getParent()->getDataLayout();
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Type *Ty = I.getAllocatedType();
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AllocatedSize += DL.getTypeAllocSize(Ty);
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}
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// We will happily inline static alloca instructions.
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if (I.isStaticAlloca())
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return Base::visitAlloca(I);
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// FIXME: This is overly conservative. Dynamic allocas are inefficient for
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// a variety of reasons, and so we would like to not inline them into
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// functions which don't currently have a dynamic alloca. This simply
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// disables inlining altogether in the presence of a dynamic alloca.
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HasDynamicAlloca = true;
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return false;
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}
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bool CallAnalyzer::visitPHI(PHINode &I) {
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// FIXME: We should potentially be tracking values through phi nodes,
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// especially when they collapse to a single value due to deleted CFG edges
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// during inlining.
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// FIXME: We need to propagate SROA *disabling* through phi nodes, even
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// though we don't want to propagate it's bonuses. The idea is to disable
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// SROA if it *might* be used in an inappropriate manner.
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// Phi nodes are always zero-cost.
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return true;
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}
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bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
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Value *SROAArg;
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DenseMap<Value *, int>::iterator CostIt;
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bool SROACandidate = lookupSROAArgAndCost(I.getPointerOperand(),
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SROAArg, CostIt);
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// Try to fold GEPs of constant-offset call site argument pointers. This
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// requires target data and inbounds GEPs.
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if (I.isInBounds()) {
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// Check if we have a base + offset for the pointer.
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Value *Ptr = I.getPointerOperand();
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std::pair<Value *, APInt> BaseAndOffset = ConstantOffsetPtrs.lookup(Ptr);
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if (BaseAndOffset.first) {
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// Check if the offset of this GEP is constant, and if so accumulate it
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// into Offset.
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if (!accumulateGEPOffset(cast<GEPOperator>(I), BaseAndOffset.second)) {
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// Non-constant GEPs aren't folded, and disable SROA.
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if (SROACandidate)
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disableSROA(CostIt);
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return false;
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}
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// Add the result as a new mapping to Base + Offset.
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ConstantOffsetPtrs[&I] = BaseAndOffset;
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// Also handle SROA candidates here, we already know that the GEP is
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// all-constant indexed.
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if (SROACandidate)
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SROAArgValues[&I] = SROAArg;
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return true;
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}
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}
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if (isGEPOffsetConstant(I)) {
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if (SROACandidate)
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SROAArgValues[&I] = SROAArg;
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// Constant GEPs are modeled as free.
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return true;
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}
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// Variable GEPs will require math and will disable SROA.
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if (SROACandidate)
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disableSROA(CostIt);
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return false;
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}
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bool CallAnalyzer::visitBitCast(BitCastInst &I) {
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// Propagate constants through bitcasts.
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Constant *COp = dyn_cast<Constant>(I.getOperand(0));
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if (!COp)
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COp = SimplifiedValues.lookup(I.getOperand(0));
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if (COp)
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if (Constant *C = ConstantExpr::getBitCast(COp, I.getType())) {
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SimplifiedValues[&I] = C;
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return true;
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}
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// Track base/offsets through casts
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std::pair<Value *, APInt> BaseAndOffset
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= ConstantOffsetPtrs.lookup(I.getOperand(0));
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// Casts don't change the offset, just wrap it up.
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if (BaseAndOffset.first)
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ConstantOffsetPtrs[&I] = BaseAndOffset;
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// Also look for SROA candidates here.
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Value *SROAArg;
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DenseMap<Value *, int>::iterator CostIt;
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if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt))
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SROAArgValues[&I] = SROAArg;
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// Bitcasts are always zero cost.
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return true;
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}
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bool CallAnalyzer::visitPtrToInt(PtrToIntInst &I) {
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// Propagate constants through ptrtoint.
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Constant *COp = dyn_cast<Constant>(I.getOperand(0));
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if (!COp)
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COp = SimplifiedValues.lookup(I.getOperand(0));
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if (COp)
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if (Constant *C = ConstantExpr::getPtrToInt(COp, I.getType())) {
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SimplifiedValues[&I] = C;
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return true;
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}
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// Track base/offset pairs when converted to a plain integer provided the
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// integer is large enough to represent the pointer.
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unsigned IntegerSize = I.getType()->getScalarSizeInBits();
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const DataLayout &DL = F.getParent()->getDataLayout();
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if (IntegerSize >= DL.getPointerSizeInBits()) {
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std::pair<Value *, APInt> BaseAndOffset
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= ConstantOffsetPtrs.lookup(I.getOperand(0));
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if (BaseAndOffset.first)
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ConstantOffsetPtrs[&I] = BaseAndOffset;
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}
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// This is really weird. Technically, ptrtoint will disable SROA. However,
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// unless that ptrtoint is *used* somewhere in the live basic blocks after
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// inlining, it will be nuked, and SROA should proceed. All of the uses which
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// would block SROA would also block SROA if applied directly to a pointer,
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// and so we can just add the integer in here. The only places where SROA is
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// preserved either cannot fire on an integer, or won't in-and-of themselves
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// disable SROA (ext) w/o some later use that we would see and disable.
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Value *SROAArg;
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DenseMap<Value *, int>::iterator CostIt;
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if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt))
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SROAArgValues[&I] = SROAArg;
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return TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
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}
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bool CallAnalyzer::visitIntToPtr(IntToPtrInst &I) {
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// Propagate constants through ptrtoint.
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Constant *COp = dyn_cast<Constant>(I.getOperand(0));
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if (!COp)
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COp = SimplifiedValues.lookup(I.getOperand(0));
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if (COp)
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if (Constant *C = ConstantExpr::getIntToPtr(COp, I.getType())) {
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SimplifiedValues[&I] = C;
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return true;
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}
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// Track base/offset pairs when round-tripped through a pointer without
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// modifications provided the integer is not too large.
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Value *Op = I.getOperand(0);
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unsigned IntegerSize = Op->getType()->getScalarSizeInBits();
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const DataLayout &DL = F.getParent()->getDataLayout();
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if (IntegerSize <= DL.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 TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
|
|
}
|
|
|
|
bool CallAnalyzer::visitCastInst(CastInst &I) {
|
|
// Propagate constants through ptrtoint.
|
|
Constant *COp = dyn_cast<Constant>(I.getOperand(0));
|
|
if (!COp)
|
|
COp = SimplifiedValues.lookup(I.getOperand(0));
|
|
if (COp)
|
|
if (Constant *C = ConstantExpr::getCast(I.getOpcode(), COp, I.getType())) {
|
|
SimplifiedValues[&I] = C;
|
|
return true;
|
|
}
|
|
|
|
// Disable SROA in the face of arbitrary casts we don't whitelist elsewhere.
|
|
disableSROA(I.getOperand(0));
|
|
|
|
return TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
|
|
}
|
|
|
|
bool CallAnalyzer::visitUnaryInstruction(UnaryInstruction &I) {
|
|
Value *Operand = I.getOperand(0);
|
|
Constant *COp = dyn_cast<Constant>(Operand);
|
|
if (!COp)
|
|
COp = SimplifiedValues.lookup(Operand);
|
|
if (COp) {
|
|
const DataLayout &DL = F.getParent()->getDataLayout();
|
|
if (Constant *C = ConstantFoldInstOperands(I.getOpcode(), I.getType(),
|
|
COp, DL)) {
|
|
SimplifiedValues[&I] = C;
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// Disable any SROA on the argument to arbitrary unary operators.
|
|
disableSROA(Operand);
|
|
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::paramHasAttr(Argument *A, Attribute::AttrKind Attr) {
|
|
unsigned ArgNo = A->getArgNo();
|
|
return CandidateCS.paramHasAttr(ArgNo+1, Attr);
|
|
}
|
|
|
|
bool CallAnalyzer::isKnownNonNullInCallee(Value *V) {
|
|
// Does the *call site* have the NonNull attribute set on an argument? We
|
|
// use the attribute on the call site to memoize any analysis done in the
|
|
// caller. This will also trip if the callee function has a non-null
|
|
// parameter attribute, but that's a less interesting case because hopefully
|
|
// the callee would already have been simplified based on that.
|
|
if (Argument *A = dyn_cast<Argument>(V))
|
|
if (paramHasAttr(A, Attribute::NonNull))
|
|
return true;
|
|
|
|
// Is this an alloca in the caller? This is distinct from the attribute case
|
|
// above because attributes aren't updated within the inliner itself and we
|
|
// always want to catch the alloca derived case.
|
|
if (isAllocaDerivedArg(V))
|
|
// We can actually predict the result of comparisons between an
|
|
// alloca-derived value and null. Note that this fires regardless of
|
|
// SROA firing.
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitCmpInst(CmpInst &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::getCompare(I.getPredicate(), CLHS, CRHS)) {
|
|
SimplifiedValues[&I] = C;
|
|
return true;
|
|
}
|
|
}
|
|
|
|
if (I.getOpcode() == Instruction::FCmp)
|
|
return false;
|
|
|
|
// Otherwise look for a comparison between constant offset pointers with
|
|
// a common base.
|
|
Value *LHSBase, *RHSBase;
|
|
APInt LHSOffset, RHSOffset;
|
|
std::tie(LHSBase, LHSOffset) = ConstantOffsetPtrs.lookup(LHS);
|
|
if (LHSBase) {
|
|
std::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;
|
|
}
|
|
}
|
|
}
|
|
|
|
// If the comparison is an equality comparison with null, we can simplify it
|
|
// if we know the value (argument) can't be null
|
|
if (I.isEquality() && isa<ConstantPointerNull>(I.getOperand(1)) &&
|
|
isKnownNonNullInCallee(I.getOperand(0))) {
|
|
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;
|
|
}
|
|
|
|
disableSROA(CostIt);
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
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;
|
|
std::tie(LHSBase, LHSOffset) = ConstantOffsetPtrs.lookup(LHS);
|
|
if (LHSBase) {
|
|
std::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;
|
|
}
|
|
}
|
|
}
|
|
|
|
// 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);
|
|
const DataLayout &DL = F.getParent()->getDataLayout();
|
|
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 = nullptr;
|
|
if (auto FI = dyn_cast<FPMathOperator>(&I))
|
|
SimpleV =
|
|
SimplifyFPBinOp(I.getOpcode(), LHS, RHS, FI->getFastMathFlags(), DL);
|
|
else
|
|
SimpleV = SimplifyBinOp(I.getOpcode(), LHS, RHS, DL);
|
|
|
|
if (Constant *C = dyn_cast_or_null<Constant>(SimpleV)) {
|
|
SimplifiedValues[&I] = C;
|
|
return true;
|
|
}
|
|
|
|
// Disable any SROA on arguments to arbitrary, unsimplified binary operators.
|
|
disableSROA(LHS);
|
|
disableSROA(RHS);
|
|
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitLoad(LoadInst &I) {
|
|
Value *SROAArg;
|
|
DenseMap<Value *, int>::iterator CostIt;
|
|
if (lookupSROAArgAndCost(I.getPointerOperand(), SROAArg, CostIt)) {
|
|
if (I.isSimple()) {
|
|
accumulateSROACost(CostIt, InlineConstants::InstrCost);
|
|
return true;
|
|
}
|
|
|
|
disableSROA(CostIt);
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitStore(StoreInst &I) {
|
|
Value *SROAArg;
|
|
DenseMap<Value *, int>::iterator CostIt;
|
|
if (lookupSROAArgAndCost(I.getPointerOperand(), SROAArg, CostIt)) {
|
|
if (I.isSimple()) {
|
|
accumulateSROACost(CostIt, InlineConstants::InstrCost);
|
|
return true;
|
|
}
|
|
|
|
disableSROA(CostIt);
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitExtractValue(ExtractValueInst &I) {
|
|
// Constant folding for extract value is trivial.
|
|
Constant *C = dyn_cast<Constant>(I.getAggregateOperand());
|
|
if (!C)
|
|
C = SimplifiedValues.lookup(I.getAggregateOperand());
|
|
if (C) {
|
|
SimplifiedValues[&I] = ConstantExpr::getExtractValue(C, I.getIndices());
|
|
return true;
|
|
}
|
|
|
|
// SROA can look through these but give them a cost.
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitInsertValue(InsertValueInst &I) {
|
|
// Constant folding for insert value is trivial.
|
|
Constant *AggC = dyn_cast<Constant>(I.getAggregateOperand());
|
|
if (!AggC)
|
|
AggC = SimplifiedValues.lookup(I.getAggregateOperand());
|
|
Constant *InsertedC = dyn_cast<Constant>(I.getInsertedValueOperand());
|
|
if (!InsertedC)
|
|
InsertedC = SimplifiedValues.lookup(I.getInsertedValueOperand());
|
|
if (AggC && InsertedC) {
|
|
SimplifiedValues[&I] = ConstantExpr::getInsertValue(AggC, InsertedC,
|
|
I.getIndices());
|
|
return true;
|
|
}
|
|
|
|
// SROA can look through these but give them a cost.
|
|
return false;
|
|
}
|
|
|
|
/// \brief Try to simplify a call site.
|
|
///
|
|
/// Takes a concrete function and callsite and tries to actually simplify it by
|
|
/// analyzing the arguments and call itself with instsimplify. Returns true if
|
|
/// it has simplified the callsite to some other entity (a constant), making it
|
|
/// free.
|
|
bool CallAnalyzer::simplifyCallSite(Function *F, CallSite CS) {
|
|
// FIXME: Using the instsimplify logic directly for this is inefficient
|
|
// because we have to continually rebuild the argument list even when no
|
|
// simplifications can be performed. Until that is fixed with remapping
|
|
// inside of instsimplify, directly constant fold calls here.
|
|
if (!canConstantFoldCallTo(F))
|
|
return false;
|
|
|
|
// Try to re-map the arguments to constants.
|
|
SmallVector<Constant *, 4> ConstantArgs;
|
|
ConstantArgs.reserve(CS.arg_size());
|
|
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
|
|
I != E; ++I) {
|
|
Constant *C = dyn_cast<Constant>(*I);
|
|
if (!C)
|
|
C = dyn_cast_or_null<Constant>(SimplifiedValues.lookup(*I));
|
|
if (!C)
|
|
return false; // This argument doesn't map to a constant.
|
|
|
|
ConstantArgs.push_back(C);
|
|
}
|
|
if (Constant *C = ConstantFoldCall(F, ConstantArgs)) {
|
|
SimplifiedValues[CS.getInstruction()] = C;
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitCallSite(CallSite CS) {
|
|
if (CS.hasFnAttr(Attribute::ReturnsTwice) &&
|
|
!F.hasFnAttribute(Attribute::ReturnsTwice)) {
|
|
// This aborts the entire analysis.
|
|
ExposesReturnsTwice = true;
|
|
return false;
|
|
}
|
|
if (CS.isCall() &&
|
|
cast<CallInst>(CS.getInstruction())->cannotDuplicate())
|
|
ContainsNoDuplicateCall = true;
|
|
|
|
if (Function *F = CS.getCalledFunction()) {
|
|
// When we have a concrete function, first try to simplify it directly.
|
|
if (simplifyCallSite(F, CS))
|
|
return true;
|
|
|
|
// Next check if it is an intrinsic we know about.
|
|
// FIXME: Lift this into part of the InstVisitor.
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
|
|
switch (II->getIntrinsicID()) {
|
|
default:
|
|
return Base::visitCallSite(CS);
|
|
|
|
case Intrinsic::memset:
|
|
case Intrinsic::memcpy:
|
|
case Intrinsic::memmove:
|
|
// SROA can usually chew through these intrinsics, but they aren't free.
|
|
return false;
|
|
case Intrinsic::localescape:
|
|
HasFrameEscape = true;
|
|
return false;
|
|
}
|
|
}
|
|
|
|
if (F == CS.getInstruction()->getParent()->getParent()) {
|
|
// This flag will fully abort the analysis, so don't bother with anything
|
|
// else.
|
|
IsRecursiveCall = true;
|
|
return false;
|
|
}
|
|
|
|
if (TTI.isLoweredToCall(F)) {
|
|
// We account for the average 1 instruction per call argument setup
|
|
// here.
|
|
Cost += CS.arg_size() * InlineConstants::InstrCost;
|
|
|
|
// Everything other than inline ASM will also have a significant cost
|
|
// merely from making the call.
|
|
if (!isa<InlineAsm>(CS.getCalledValue()))
|
|
Cost += InlineConstants::CallPenalty;
|
|
}
|
|
|
|
return Base::visitCallSite(CS);
|
|
}
|
|
|
|
// 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(TTI, ACT, *F, InlineConstants::IndirectCallThreshold, CS);
|
|
if (CA.analyzeCall(CS)) {
|
|
// We were able to inline the indirect call! Subtract the cost from the
|
|
// threshold to get the bonus we want to apply, but don't go below zero.
|
|
Cost -= std::max(0, CA.getThreshold() - CA.getCost());
|
|
}
|
|
|
|
return Base::visitCallSite(CS);
|
|
}
|
|
|
|
bool CallAnalyzer::visitReturnInst(ReturnInst &RI) {
|
|
// At least one return instruction will be free after inlining.
|
|
bool Free = !HasReturn;
|
|
HasReturn = true;
|
|
return Free;
|
|
}
|
|
|
|
bool CallAnalyzer::visitBranchInst(BranchInst &BI) {
|
|
// We model unconditional branches as essentially free -- they really
|
|
// shouldn't exist at all, but handling them makes the behavior of the
|
|
// inliner more regular and predictable. Interestingly, conditional branches
|
|
// which will fold away are also free.
|
|
return BI.isUnconditional() || isa<ConstantInt>(BI.getCondition()) ||
|
|
dyn_cast_or_null<ConstantInt>(
|
|
SimplifiedValues.lookup(BI.getCondition()));
|
|
}
|
|
|
|
bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
|
|
// We model unconditional switches as free, see the comments on handling
|
|
// branches.
|
|
if (isa<ConstantInt>(SI.getCondition()))
|
|
return true;
|
|
if (Value *V = SimplifiedValues.lookup(SI.getCondition()))
|
|
if (isa<ConstantInt>(V))
|
|
return true;
|
|
|
|
// Otherwise, we need to accumulate a cost proportional to the number of
|
|
// distinct successor blocks. This fan-out in the CFG cannot be represented
|
|
// for free even if we can represent the core switch as a jumptable that
|
|
// takes a single instruction.
|
|
//
|
|
// NB: We convert large switches which are just used to initialize large phi
|
|
// nodes to lookup tables instead in simplify-cfg, so this shouldn't prevent
|
|
// inlining those. It will prevent inlining in cases where the optimization
|
|
// does not (yet) fire.
|
|
SmallPtrSet<BasicBlock *, 8> SuccessorBlocks;
|
|
SuccessorBlocks.insert(SI.getDefaultDest());
|
|
for (auto I = SI.case_begin(), E = SI.case_end(); I != E; ++I)
|
|
SuccessorBlocks.insert(I.getCaseSuccessor());
|
|
// Add cost corresponding to the number of distinct destinations. The first
|
|
// we model as free because of fallthrough.
|
|
Cost += (SuccessorBlocks.size() - 1) * InlineConstants::InstrCost;
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitIndirectBrInst(IndirectBrInst &IBI) {
|
|
// 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.
|
|
HasIndirectBr = true;
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitResumeInst(ResumeInst &RI) {
|
|
// FIXME: It's not clear that a single instruction is an accurate model for
|
|
// the inline cost of a resume instruction.
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitCleanupReturnInst(CleanupReturnInst &CRI) {
|
|
// FIXME: It's not clear that a single instruction is an accurate model for
|
|
// the inline cost of a cleanupret instruction.
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitCatchReturnInst(CatchReturnInst &CRI) {
|
|
// FIXME: It's not clear that a single instruction is an accurate model for
|
|
// the inline cost of a catchret instruction.
|
|
return false;
|
|
}
|
|
|
|
bool CallAnalyzer::visitUnreachableInst(UnreachableInst &I) {
|
|
// FIXME: It might be reasonably to discount the cost of instructions leading
|
|
// to unreachable as they have the lowest possible impact on both runtime and
|
|
// code size.
|
|
return true; // No actual code is needed for unreachable.
|
|
}
|
|
|
|
bool CallAnalyzer::visitInstruction(Instruction &I) {
|
|
// Some instructions are free. All of the free intrinsics can also be
|
|
// handled by SROA, etc.
|
|
if (TargetTransformInfo::TCC_Free == TTI.getUserCost(&I))
|
|
return true;
|
|
|
|
// 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;
|
|
}
|
|
|
|
|
|
/// \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,
|
|
SmallPtrSetImpl<const Value *> &EphValues) {
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
|
|
// FIXME: Currently, the number of instructions in a function regardless of
|
|
// our ability to simplify them during inline to constants or dead code,
|
|
// are actually used by the vector bonus heuristic. As long as that's true,
|
|
// we have to special case debug intrinsics here to prevent differences in
|
|
// inlining due to debug symbols. Eventually, the number of unsimplified
|
|
// instructions shouldn't factor into the cost computation, but until then,
|
|
// hack around it here.
|
|
if (isa<DbgInfoIntrinsic>(I))
|
|
continue;
|
|
|
|
// Skip ephemeral values.
|
|
if (EphValues.count(&*I))
|
|
continue;
|
|
|
|
++NumInstructions;
|
|
if (isa<ExtractElementInst>(I) || I->getType()->isVectorTy())
|
|
++NumVectorInstructions;
|
|
|
|
// If the instruction is floating point, and the target says this operation
|
|
// is expensive or the function has the "use-soft-float" attribute, this may
|
|
// eventually become a library call. Treat the cost as such.
|
|
if (I->getType()->isFloatingPointTy()) {
|
|
bool hasSoftFloatAttr = false;
|
|
|
|
// If the function has the "use-soft-float" attribute, mark it as
|
|
// expensive.
|
|
if (F.hasFnAttribute("use-soft-float")) {
|
|
Attribute Attr = F.getFnAttribute("use-soft-float");
|
|
StringRef Val = Attr.getValueAsString();
|
|
if (Val == "true")
|
|
hasSoftFloatAttr = true;
|
|
}
|
|
|
|
if (TTI.getFPOpCost(I->getType()) == TargetTransformInfo::TCC_Expensive ||
|
|
hasSoftFloatAttr)
|
|
Cost += InlineConstants::CallPenalty;
|
|
}
|
|
|
|
// 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 (IsRecursiveCall || ExposesReturnsTwice || HasDynamicAlloca ||
|
|
HasIndirectBr || HasFrameEscape)
|
|
return false;
|
|
|
|
// If the caller is a recursive function then we don't want to inline
|
|
// functions which allocate a lot of stack space because it would increase
|
|
// the caller stack usage dramatically.
|
|
if (IsCallerRecursive &&
|
|
AllocatedSize > InlineConstants::TotalAllocaSizeRecursiveCaller)
|
|
return false;
|
|
|
|
// Check if we've past the maximum possible threshold so we don't spin in
|
|
// huge basic blocks that will never inline.
|
|
if (Cost > Threshold)
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// \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 (!V->getType()->isPointerTy())
|
|
return nullptr;
|
|
|
|
const DataLayout &DL = F.getParent()->getDataLayout();
|
|
unsigned IntPtrWidth = DL.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 nullptr;
|
|
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).second);
|
|
|
|
Type *IntPtrTy = DL.getIntPtrType(V->getContext());
|
|
return cast<ConstantInt>(ConstantInt::get(IntPtrTy, Offset));
|
|
}
|
|
|
|
/// \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 routine.
|
|
bool CallAnalyzer::analyzeCall(CallSite CS) {
|
|
++NumCallsAnalyzed;
|
|
|
|
// Perform some tweaks to the cost and threshold based on the direct
|
|
// callsite information.
|
|
|
|
// 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. Note that these bonuses are some what arbitrary and evolved over time
|
|
// by accident as much as because they are principled bonuses.
|
|
//
|
|
// FIXME: It would be nice to remove all such bonuses. At least it would be
|
|
// nice to base the bonus values on something more scientific.
|
|
assert(NumInstructions == 0);
|
|
assert(NumVectorInstructions == 0);
|
|
FiftyPercentVectorBonus = 3 * Threshold / 2;
|
|
TenPercentVectorBonus = 3 * Threshold / 4;
|
|
const DataLayout &DL = F.getParent()->getDataLayout();
|
|
|
|
// 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;
|
|
|
|
// Speculatively apply all possible bonuses to Threshold. If cost exceeds
|
|
// this Threshold any time, and cost cannot decrease, we can stop processing
|
|
// the rest of the function body.
|
|
Threshold += (SingleBBBonus + FiftyPercentVectorBonus);
|
|
|
|
// Give out bonuses per argument, as the instructions setting them up will
|
|
// be gone after inlining.
|
|
for (unsigned I = 0, E = CS.arg_size(); I != E; ++I) {
|
|
if (CS.isByValArgument(I)) {
|
|
// We approximate the number of loads and stores needed by dividing the
|
|
// size of the byval type by the target's pointer size.
|
|
PointerType *PTy = cast<PointerType>(CS.getArgument(I)->getType());
|
|
unsigned TypeSize = DL.getTypeSizeInBits(PTy->getElementType());
|
|
unsigned PointerSize = DL.getPointerSizeInBits();
|
|
// Ceiling division.
|
|
unsigned NumStores = (TypeSize + PointerSize - 1) / PointerSize;
|
|
|
|
// If it generates more than 8 stores it is likely to be expanded as an
|
|
// inline memcpy so we take that as an upper bound. Otherwise we assume
|
|
// one load and one store per word copied.
|
|
// FIXME: The maxStoresPerMemcpy setting from the target should be used
|
|
// here instead of a magic number of 8, but it's not available via
|
|
// DataLayout.
|
|
NumStores = std::min(NumStores, 8U);
|
|
|
|
Cost -= 2 * NumStores * InlineConstants::InstrCost;
|
|
} else {
|
|
// For non-byval arguments subtract off one instruction per call
|
|
// argument.
|
|
Cost -= InlineConstants::InstrCost;
|
|
}
|
|
}
|
|
|
|
// If there is only one call of the function, and it has internal linkage,
|
|
// the cost of inlining it drops dramatically.
|
|
bool OnlyOneCallAndLocalLinkage = F.hasLocalLinkage() && F.hasOneUse() &&
|
|
&F == CS.getCalledFunction();
|
|
if (OnlyOneCallAndLocalLinkage)
|
|
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.
|
|
Instruction *Instr = CS.getInstruction();
|
|
if (InvokeInst *II = dyn_cast<InvokeInst>(Instr)) {
|
|
if (isa<UnreachableInst>(II->getNormalDest()->begin()))
|
|
Threshold = 0;
|
|
} else if (isa<UnreachableInst>(++BasicBlock::iterator(Instr)))
|
|
Threshold = 0;
|
|
|
|
// 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;
|
|
|
|
if (F.empty())
|
|
return true;
|
|
|
|
Function *Caller = CS.getInstruction()->getParent()->getParent();
|
|
// Check if the caller function is recursive itself.
|
|
for (User *U : Caller->users()) {
|
|
CallSite Site(U);
|
|
if (!Site)
|
|
continue;
|
|
Instruction *I = Site.getInstruction();
|
|
if (I->getParent()->getParent() == Caller) {
|
|
IsCallerRecursive = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// 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();
|
|
|
|
// FIXME: If a caller has multiple calls to a callee, we end up recomputing
|
|
// the ephemeral values multiple times (and they're completely determined by
|
|
// the callee, so this is purely duplicate work).
|
|
SmallPtrSet<const Value *, 32> EphValues;
|
|
CodeMetrics::collectEphemeralValues(&F, &ACT->getAssumptionCache(F), EphValues);
|
|
|
|
// 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 (Cost > Threshold)
|
|
break;
|
|
|
|
BasicBlock *BB = BBWorklist[Idx];
|
|
if (BB->empty())
|
|
continue;
|
|
|
|
// Disallow inlining a blockaddress. A blockaddress only has defined
|
|
// behavior for an indirect branch in the same function, and we do not
|
|
// currently support inlining indirect branches. But, the inliner may not
|
|
// see an indirect branch that ends up being dead code at a particular call
|
|
// site. If the blockaddress escapes the function, e.g., via a global
|
|
// variable, inlining may lead to an invalid cross-function reference.
|
|
if (BB->hasAddressTaken())
|
|
return false;
|
|
|
|
// Analyze the cost of this block. If we blow through the threshold, this
|
|
// returns false, and we can bail on out.
|
|
if (!analyzeBlock(BB, EphValues)) {
|
|
if (IsRecursiveCall || ExposesReturnsTwice || HasDynamicAlloca ||
|
|
HasIndirectBr || HasFrameEscape)
|
|
return false;
|
|
|
|
// If the caller is a recursive function then we don't want to inline
|
|
// functions which allocate a lot of stack space because it would increase
|
|
// the caller stack usage dramatically.
|
|
if (IsCallerRecursive &&
|
|
AllocatedSize > InlineConstants::TotalAllocaSizeRecursiveCaller)
|
|
return false;
|
|
|
|
break;
|
|
}
|
|
|
|
TerminatorInst *TI = BB->getTerminator();
|
|
|
|
// 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 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;
|
|
}
|
|
}
|
|
|
|
// If this is a noduplicate call, we can still inline as long as
|
|
// inlining this would cause the removal of the caller (so the instruction
|
|
// is not actually duplicated, just moved).
|
|
if (!OnlyOneCallAndLocalLinkage && ContainsNoDuplicateCall)
|
|
return false;
|
|
|
|
// We applied the maximum possible vector bonus at the beginning. Now,
|
|
// subtract the excess bonus, if any, from the Threshold before
|
|
// comparing against Cost.
|
|
if (NumVectorInstructions <= NumInstructions / 10)
|
|
Threshold -= FiftyPercentVectorBonus;
|
|
else if (NumVectorInstructions <= NumInstructions / 2)
|
|
Threshold -= (FiftyPercentVectorBonus - TenPercentVectorBonus);
|
|
|
|
return Cost <= std::max(0, Threshold);
|
|
}
|
|
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
/// \brief Dump stats about this call's analysis.
|
|
void CallAnalyzer::dump() {
|
|
#define DEBUG_PRINT_STAT(x) 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(NumInstructions);
|
|
DEBUG_PRINT_STAT(SROACostSavings);
|
|
DEBUG_PRINT_STAT(SROACostSavingsLost);
|
|
DEBUG_PRINT_STAT(ContainsNoDuplicateCall);
|
|
DEBUG_PRINT_STAT(Cost);
|
|
DEBUG_PRINT_STAT(Threshold);
|
|
#undef DEBUG_PRINT_STAT
|
|
}
|
|
#endif
|
|
|
|
/// \brief Test that two functions either have or have not the given attribute
|
|
/// at the same time.
|
|
template<typename AttrKind>
|
|
static bool attributeMatches(Function *F1, Function *F2, AttrKind Attr) {
|
|
return F1->getFnAttribute(Attr) == F2->getFnAttribute(Attr);
|
|
}
|
|
|
|
/// \brief Test that there are no attribute conflicts between Caller and Callee
|
|
/// that prevent inlining.
|
|
static bool functionsHaveCompatibleAttributes(Function *Caller,
|
|
Function *Callee,
|
|
TargetTransformInfo &TTI) {
|
|
return TTI.areInlineCompatible(Caller, Callee) &&
|
|
AttributeFuncs::areInlineCompatible(*Caller, *Callee);
|
|
}
|
|
|
|
InlineCost llvm::getInlineCost(CallSite CS, int Threshold,
|
|
TargetTransformInfo &CalleeTTI,
|
|
AssumptionCacheTracker *ACT) {
|
|
return getInlineCost(CS, CS.getCalledFunction(), Threshold, CalleeTTI, ACT);
|
|
}
|
|
|
|
InlineCost llvm::getInlineCost(CallSite CS, Function *Callee, int Threshold,
|
|
TargetTransformInfo &CalleeTTI,
|
|
AssumptionCacheTracker *ACT) {
|
|
// Cannot inline indirect calls.
|
|
if (!Callee)
|
|
return llvm::InlineCost::getNever();
|
|
|
|
// Calls to functions with always-inline attributes should be inlined
|
|
// whenever possible.
|
|
if (CS.hasFnAttr(Attribute::AlwaysInline)) {
|
|
if (isInlineViable(*Callee))
|
|
return llvm::InlineCost::getAlways();
|
|
return llvm::InlineCost::getNever();
|
|
}
|
|
|
|
// Never inline functions with conflicting attributes (unless callee has
|
|
// always-inline attribute).
|
|
if (!functionsHaveCompatibleAttributes(CS.getCaller(), Callee, CalleeTTI))
|
|
return llvm::InlineCost::getNever();
|
|
|
|
// Don't inline this call if the caller has the optnone attribute.
|
|
if (CS.getCaller()->hasFnAttribute(Attribute::OptimizeNone))
|
|
return llvm::InlineCost::getNever();
|
|
|
|
// 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->hasFnAttribute(Attribute::NoInline) || CS.isNoInline())
|
|
return llvm::InlineCost::getNever();
|
|
|
|
DEBUG(llvm::dbgs() << " Analyzing call of " << Callee->getName()
|
|
<< "...\n");
|
|
|
|
CallAnalyzer CA(CalleeTTI, ACT, *Callee, Threshold, CS);
|
|
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());
|
|
}
|
|
|
|
bool llvm::isInlineViable(Function &F) {
|
|
bool ReturnsTwice = F.hasFnAttribute(Attribute::ReturnsTwice);
|
|
for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
|
|
// Disallow inlining of functions which contain indirect branches or
|
|
// blockaddresses.
|
|
if (isa<IndirectBrInst>(BI->getTerminator()) || BI->hasAddressTaken())
|
|
return false;
|
|
|
|
for (auto &II : *BI) {
|
|
CallSite CS(&II);
|
|
if (!CS)
|
|
continue;
|
|
|
|
// Disallow recursive calls.
|
|
if (&F == CS.getCalledFunction())
|
|
return false;
|
|
|
|
// Disallow calls which expose returns-twice to a function not previously
|
|
// attributed as such.
|
|
if (!ReturnsTwice && CS.isCall() &&
|
|
cast<CallInst>(CS.getInstruction())->canReturnTwice())
|
|
return false;
|
|
|
|
// Disallow inlining functions that call @llvm.localescape. Doing this
|
|
// correctly would require major changes to the inliner.
|
|
if (CS.getCalledFunction() &&
|
|
CS.getCalledFunction()->getIntrinsicID() ==
|
|
llvm::Intrinsic::localescape)
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|