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llvm-mirror/lib/Analysis/InlineCost.cpp
David Green 1c51e30a79 [Inliner] Penalise inlining of calls with loops at Oz 
We currently seem to underestimate the size of functions with loops in them,
both in terms of absolute code size and in the difficulties of dealing with
such code. (Calls, for example, can be tail merged to further reduce
codesize). At -Oz, we can then increase code size by inlining small loops
multiple times.

This attempts to penalise functions with loops at -Oz by adding a CallPenalty
for each top level loop in the function. It uses LI (and hence DT) to calculate
the number of loops. As we are dealing with minsize, the inline threshold is
small and functions at this point should be relatively small, making the
construction of these cheap.

Differential Revision: https://reviews.llvm.org/D52716

llvm-svn: 346134
2018-11-05 14:54:34 +00:00

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//===- InlineCost.cpp - Cost analysis for inliner -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements inline cost analysis.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/InlineCost.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "inline-cost"
STATISTIC(NumCallsAnalyzed, "Number of call sites analyzed");
static cl::opt<int> InlineThreshold(
"inline-threshold", cl::Hidden, cl::init(225), cl::ZeroOrMore,
cl::desc("Control the amount of inlining to perform (default = 225)"));
static cl::opt<int> HintThreshold(
"inlinehint-threshold", cl::Hidden, cl::init(325),
cl::desc("Threshold for inlining functions with inline hint"));
static cl::opt<int>
ColdCallSiteThreshold("inline-cold-callsite-threshold", cl::Hidden,
cl::init(45),
cl::desc("Threshold for inlining cold callsites"));
// We introduce this threshold to help performance of instrumentation based
// PGO before we actually hook up inliner with analysis passes such as BPI and
// BFI.
static cl::opt<int> ColdThreshold(
"inlinecold-threshold", cl::Hidden, cl::init(45),
cl::desc("Threshold for inlining functions with cold attribute"));
static cl::opt<int>
HotCallSiteThreshold("hot-callsite-threshold", cl::Hidden, cl::init(3000),
cl::ZeroOrMore,
cl::desc("Threshold for hot callsites "));
static cl::opt<int> LocallyHotCallSiteThreshold(
"locally-hot-callsite-threshold", cl::Hidden, cl::init(525), cl::ZeroOrMore,
cl::desc("Threshold for locally hot callsites "));
static cl::opt<int> ColdCallSiteRelFreq(
"cold-callsite-rel-freq", cl::Hidden, cl::init(2), cl::ZeroOrMore,
cl::desc("Maxmimum block frequency, expressed as a percentage of caller's "
"entry frequency, for a callsite to be cold in the absence of "
"profile information."));
static cl::opt<int> HotCallSiteRelFreq(
"hot-callsite-rel-freq", cl::Hidden, cl::init(60), cl::ZeroOrMore,
cl::desc("Minimum block frequency, expressed as a multiple of caller's "
"entry frequency, for a callsite to be hot in the absence of "
"profile information."));
static cl::opt<bool> OptComputeFullInlineCost(
"inline-cost-full", cl::Hidden, cl::init(false),
cl::desc("Compute the full inline cost of a call site even when the cost "
"exceeds the threshold."));
namespace {
class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
typedef InstVisitor<CallAnalyzer, bool> Base;
friend class InstVisitor<CallAnalyzer, bool>;
/// The TargetTransformInfo available for this compilation.
const TargetTransformInfo &TTI;
/// Getter for the cache of @llvm.assume intrinsics.
std::function<AssumptionCache &(Function &)> &GetAssumptionCache;
/// Getter for BlockFrequencyInfo
Optional<function_ref<BlockFrequencyInfo &(Function &)>> &GetBFI;
/// Profile summary information.
ProfileSummaryInfo *PSI;
/// The called function.
Function &F;
// Cache the DataLayout since we use it a lot.
const DataLayout &DL;
/// The OptimizationRemarkEmitter available for this compilation.
OptimizationRemarkEmitter *ORE;
/// The candidate callsite being analyzed. Please do not use this to do
/// analysis in the caller function; we want the inline cost query to be
/// easily cacheable. Instead, use the cover function paramHasAttr.
CallSite CandidateCS;
/// Tunable parameters that control the analysis.
const InlineParams &Params;
int Threshold;
int Cost;
bool ComputeFullInlineCost;
bool IsCallerRecursive;
bool IsRecursiveCall;
bool ExposesReturnsTwice;
bool HasDynamicAlloca;
bool ContainsNoDuplicateCall;
bool HasReturn;
bool HasIndirectBr;
bool HasUninlineableIntrinsic;
bool InitsVargArgs;
/// Number of bytes allocated statically by the callee.
uint64_t AllocatedSize;
unsigned NumInstructions, NumVectorInstructions;
int VectorBonus, TenPercentVectorBonus;
// Bonus to be applied when the callee has only one reachable basic block.
int SingleBBBonus;
/// 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;
/// Keep track of dead blocks due to the constant arguments.
SetVector<BasicBlock *> DeadBlocks;
/// The mapping of the blocks to their known unique successors due to the
/// constant arguments.
DenseMap<BasicBlock *, BasicBlock *> KnownSuccessors;
/// Model the elimination of repeated loads that is expected to happen
/// whenever we simplify away the stores that would otherwise cause them to be
/// loads.
bool EnableLoadElimination;
SmallPtrSet<Value *, 16> LoadAddrSet;
int LoadEliminationCost;
// 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 findDeadBlocks(BasicBlock *CurrBB, BasicBlock *NextBB);
void accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
int InstructionCost);
void disableLoadElimination();
bool isGEPFree(GetElementPtrInst &GEP);
bool canFoldInboundsGEP(GetElementPtrInst &I);
bool accumulateGEPOffset(GEPOperator &GEP, APInt &Offset);
bool simplifyCallSite(Function *F, CallSite CS);
template <typename Callable>
bool simplifyInstruction(Instruction &I, Callable Evaluate);
ConstantInt *stripAndComputeInBoundsConstantOffsets(Value *&V);
/// Return true if the given argument to the function being considered for
/// inlining has the given attribute set either at the call site or the
/// function declaration. Primarily used to inspect call site specific
/// attributes since these can be more precise than the ones on the callee
/// itself.
bool paramHasAttr(Argument *A, Attribute::AttrKind Attr);
/// Return true if the given value is known non null within the callee if
/// inlined through this particular callsite.
bool isKnownNonNullInCallee(Value *V);
/// Update Threshold based on callsite properties such as callee
/// attributes and callee hotness for PGO builds. The Callee is explicitly
/// passed to support analyzing indirect calls whose target is inferred by
/// analysis.
void updateThreshold(CallSite CS, Function &Callee);
/// Return true if size growth is allowed when inlining the callee at CS.
bool allowSizeGrowth(CallSite CS);
/// Return true if \p CS is a cold callsite.
bool isColdCallSite(CallSite CS, BlockFrequencyInfo *CallerBFI);
/// Return a higher threshold if \p CS is a hot callsite.
Optional<int> getHotCallSiteThreshold(CallSite CS,
BlockFrequencyInfo *CallerBFI);
// Custom analysis routines.
InlineResult analyzeBlock(BasicBlock *BB,
SmallPtrSetImpl<const Value *> &EphValues);
// 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 visitCmpInst(CmpInst &I);
bool visitSub(BinaryOperator &I);
bool visitBinaryOperator(BinaryOperator &I);
bool visitLoad(LoadInst &I);
bool visitStore(StoreInst &I);
bool visitExtractValue(ExtractValueInst &I);
bool visitInsertValue(InsertValueInst &I);
bool visitCallSite(CallSite CS);
bool visitReturnInst(ReturnInst &RI);
bool visitBranchInst(BranchInst &BI);
bool visitSelectInst(SelectInst &SI);
bool visitSwitchInst(SwitchInst &SI);
bool visitIndirectBrInst(IndirectBrInst &IBI);
bool visitResumeInst(ResumeInst &RI);
bool visitCleanupReturnInst(CleanupReturnInst &RI);
bool visitCatchReturnInst(CatchReturnInst &RI);
bool visitUnreachableInst(UnreachableInst &I);
public:
CallAnalyzer(const TargetTransformInfo &TTI,
std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
Optional<function_ref<BlockFrequencyInfo &(Function &)>> &GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE,
Function &Callee, CallSite CSArg, const InlineParams &Params)
: TTI(TTI), GetAssumptionCache(GetAssumptionCache), GetBFI(GetBFI),
PSI(PSI), F(Callee), DL(F.getParent()->getDataLayout()), ORE(ORE),
CandidateCS(CSArg), Params(Params), Threshold(Params.DefaultThreshold),
Cost(0), ComputeFullInlineCost(OptComputeFullInlineCost ||
Params.ComputeFullInlineCost || ORE),
IsCallerRecursive(false), IsRecursiveCall(false),
ExposesReturnsTwice(false), HasDynamicAlloca(false),
ContainsNoDuplicateCall(false), HasReturn(false), HasIndirectBr(false),
HasUninlineableIntrinsic(false), InitsVargArgs(false), AllocatedSize(0),
NumInstructions(0), NumVectorInstructions(0), VectorBonus(0),
SingleBBBonus(0), EnableLoadElimination(true), LoadEliminationCost(0),
NumConstantArgs(0), NumConstantOffsetPtrArgs(0), NumAllocaArgs(0),
NumConstantPtrCmps(0), NumConstantPtrDiffs(0),
NumInstructionsSimplified(0), SROACostSavings(0),
SROACostSavingsLost(0) {}
InlineResult analyzeCall(CallSite CS);
int getThreshold() { return Threshold; }
int getCost() { return Cost; }
// 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;
void dump();
};
} // namespace
/// Test whether the given value is an Alloca-derived function argument.
bool CallAnalyzer::isAllocaDerivedArg(Value *V) {
return SROAArgValues.count(V);
}
/// 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;
DenseMap<Value *, Value *>::iterator ArgIt = SROAArgValues.find(V);
if (ArgIt == SROAArgValues.end())
return false;
Arg = ArgIt->second;
CostIt = SROAArgCosts.find(Arg);
return CostIt != SROAArgCosts.end();
}
/// Disable SROA for the candidate marked by this cost iterator.
///
/// This marks 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);
disableLoadElimination();
}
/// 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);
}
/// Accumulate the given cost for a particular SROA candidate.
void CallAnalyzer::accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
int InstructionCost) {
CostIt->second += InstructionCost;
SROACostSavings += InstructionCost;
}
void CallAnalyzer::disableLoadElimination() {
if (EnableLoadElimination) {
Cost += LoadEliminationCost;
LoadEliminationCost = 0;
EnableLoadElimination = false;
}
}
/// 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) {
unsigned IntPtrWidth = DL.getIndexTypeSizeInBits(GEP.getType());
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 = GTI.getStructTypeOrNull()) {
unsigned ElementIdx = OpC->getZExtValue();
const StructLayout *SL = DL.getStructLayout(STy);
Offset += APInt(IntPtrWidth, SL->getElementOffset(ElementIdx));
continue;
}
APInt TypeSize(IntPtrWidth, DL.getTypeAllocSize(GTI.getIndexedType()));
Offset += OpC->getValue().sextOrTrunc(IntPtrWidth) * TypeSize;
}
return true;
}
/// Use TTI to check whether a GEP is free.
///
/// Respects any simplified values known during the analysis of this callsite.
bool CallAnalyzer::isGEPFree(GetElementPtrInst &GEP) {
SmallVector<Value *, 4> Operands;
Operands.push_back(GEP.getOperand(0));
for (User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); I != E; ++I)
if (Constant *SimpleOp = SimplifiedValues.lookup(*I))
Operands.push_back(SimpleOp);
else
Operands.push_back(*I);
return TargetTransformInfo::TCC_Free == TTI.getUserCost(&GEP, Operands);
}
bool CallAnalyzer::visitAlloca(AllocaInst &I) {
// Check whether inlining will turn a dynamic alloca into a static
// alloca and handle that case.
if (I.isArrayAllocation()) {
Constant *Size = SimplifiedValues.lookup(I.getArraySize());
if (auto *AllocSize = dyn_cast_or_null<ConstantInt>(Size)) {
Type *Ty = I.getAllocatedType();
AllocatedSize = SaturatingMultiplyAdd(
AllocSize->getLimitedValue(), DL.getTypeAllocSize(Ty), AllocatedSize);
return Base::visitAlloca(I);
}
}
// Accumulate the allocated size.
if (I.isStaticAlloca()) {
Type *Ty = I.getAllocatedType();
AllocatedSize = SaturatingAdd(DL.getTypeAllocSize(Ty), AllocatedSize);
}
// We will happily inline static alloca instructions.
if (I.isStaticAlloca())
return Base::visitAlloca(I);
// FIXME: This is overly conservative. Dynamic allocas are inefficient for
// a variety of reasons, and so we would like to not inline them into
// functions which don't currently have a dynamic alloca. This simply
// disables inlining altogether in the presence of a dynamic alloca.
HasDynamicAlloca = true;
return false;
}
bool CallAnalyzer::visitPHI(PHINode &I) {
// FIXME: We need to propagate SROA *disabling* through phi nodes, even
// though we don't want to propagate it's bonuses. The idea is to disable
// SROA if it *might* be used in an inappropriate manner.
// Phi nodes are always zero-cost.
// FIXME: Pointer sizes may differ between different address spaces, so do we
// need to use correct address space in the call to getPointerSizeInBits here?
// Or could we skip the getPointerSizeInBits call completely? As far as I can
// see the ZeroOffset is used as a dummy value, so we can probably use any
// bit width for the ZeroOffset?
APInt ZeroOffset = APInt::getNullValue(DL.getPointerSizeInBits(0));
bool CheckSROA = I.getType()->isPointerTy();
// Track the constant or pointer with constant offset we've seen so far.
Constant *FirstC = nullptr;
std::pair<Value *, APInt> FirstBaseAndOffset = {nullptr, ZeroOffset};
Value *FirstV = nullptr;
for (unsigned i = 0, e = I.getNumIncomingValues(); i != e; ++i) {
BasicBlock *Pred = I.getIncomingBlock(i);
// If the incoming block is dead, skip the incoming block.
if (DeadBlocks.count(Pred))
continue;
// If the parent block of phi is not the known successor of the incoming
// block, skip the incoming block.
BasicBlock *KnownSuccessor = KnownSuccessors[Pred];
if (KnownSuccessor && KnownSuccessor != I.getParent())
continue;
Value *V = I.getIncomingValue(i);
// If the incoming value is this phi itself, skip the incoming value.
if (&I == V)
continue;
Constant *C = dyn_cast<Constant>(V);
if (!C)
C = SimplifiedValues.lookup(V);
std::pair<Value *, APInt> BaseAndOffset = {nullptr, ZeroOffset};
if (!C && CheckSROA)
BaseAndOffset = ConstantOffsetPtrs.lookup(V);
if (!C && !BaseAndOffset.first)
// The incoming value is neither a constant nor a pointer with constant
// offset, exit early.
return true;
if (FirstC) {
if (FirstC == C)
// If we've seen a constant incoming value before and it is the same
// constant we see this time, continue checking the next incoming value.
continue;
// Otherwise early exit because we either see a different constant or saw
// a constant before but we have a pointer with constant offset this time.
return true;
}
if (FirstV) {
// The same logic as above, but check pointer with constant offset here.
if (FirstBaseAndOffset == BaseAndOffset)
continue;
return true;
}
if (C) {
// This is the 1st time we've seen a constant, record it.
FirstC = C;
continue;
}
// The remaining case is that this is the 1st time we've seen a pointer with
// constant offset, record it.
FirstV = V;
FirstBaseAndOffset = BaseAndOffset;
}
// Check if we can map phi to a constant.
if (FirstC) {
SimplifiedValues[&I] = FirstC;
return true;
}
// Check if we can map phi to a pointer with constant offset.
if (FirstBaseAndOffset.first) {
ConstantOffsetPtrs[&I] = FirstBaseAndOffset;
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(FirstV, SROAArg, CostIt))
SROAArgValues[&I] = SROAArg;
}
return true;
}
/// Check we can fold GEPs of constant-offset call site argument pointers.
/// This requires target data and inbounds GEPs.
///
/// \return true if the specified GEP can be folded.
bool CallAnalyzer::canFoldInboundsGEP(GetElementPtrInst &I) {
// Check if we have a base + offset for the pointer.
std::pair<Value *, APInt> BaseAndOffset =
ConstantOffsetPtrs.lookup(I.getPointerOperand());
if (!BaseAndOffset.first)
return false;
// Check if the offset of this GEP is constant, and if so accumulate it
// into Offset.
if (!accumulateGEPOffset(cast<GEPOperator>(I), BaseAndOffset.second))
return false;
// Add the result as a new mapping to Base + Offset.
ConstantOffsetPtrs[&I] = BaseAndOffset;
return true;
}
bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
bool SROACandidate =
lookupSROAArgAndCost(I.getPointerOperand(), SROAArg, CostIt);
// Lambda to check whether a GEP's indices are all constant.
auto 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;
};
if ((I.isInBounds() && canFoldInboundsGEP(I)) || IsGEPOffsetConstant(I)) {
if (SROACandidate)
SROAArgValues[&I] = SROAArg;
// Constant GEPs are modeled as free.
return true;
}
// Variable GEPs will require math and will disable SROA.
if (SROACandidate)
disableSROA(CostIt);
return isGEPFree(I);
}
/// Simplify \p I if its operands are constants and update SimplifiedValues.
/// \p Evaluate is a callable specific to instruction type that evaluates the
/// instruction when all the operands are constants.
template <typename Callable>
bool CallAnalyzer::simplifyInstruction(Instruction &I, Callable Evaluate) {
SmallVector<Constant *, 2> COps;
for (Value *Op : I.operands()) {
Constant *COp = dyn_cast<Constant>(Op);
if (!COp)
COp = SimplifiedValues.lookup(Op);
if (!COp)
return false;
COps.push_back(COp);
}
auto *C = Evaluate(COps);
if (!C)
return false;
SimplifiedValues[&I] = C;
return true;
}
bool CallAnalyzer::visitBitCast(BitCastInst &I) {
// Propagate constants through bitcasts.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getBitCast(COps[0], I.getType());
}))
return true;
// Track base/offsets through casts
std::pair<Value *, APInt> BaseAndOffset =
ConstantOffsetPtrs.lookup(I.getOperand(0));
// Casts don't change the offset, just wrap it up.
if (BaseAndOffset.first)
ConstantOffsetPtrs[&I] = BaseAndOffset;
// Also look for SROA candidates here.
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt))
SROAArgValues[&I] = SROAArg;
// Bitcasts are always zero cost.
return true;
}
bool CallAnalyzer::visitPtrToInt(PtrToIntInst &I) {
// Propagate constants through ptrtoint.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getPtrToInt(COps[0], I.getType());
}))
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();
unsigned AS = I.getOperand(0)->getType()->getPointerAddressSpace();
if (IntegerSize >= DL.getPointerSizeInBits(AS)) {
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;
return TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
}
bool CallAnalyzer::visitIntToPtr(IntToPtrInst &I) {
// Propagate constants through ptrtoint.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getIntToPtr(COps[0], I.getType());
}))
return true;
// 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 (IntegerSize <= DL.getPointerTypeSizeInBits(I.getType())) {
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.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getCast(I.getOpcode(), COps[0], I.getType());
}))
return true;
// Disable SROA in the face of arbitrary casts we don't whitelist elsewhere.
disableSROA(I.getOperand(0));
// If this is a floating-point cast, and the target says this operation
// is expensive, this may eventually become a library call. Treat the cost
// as such.
switch (I.getOpcode()) {
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::UIToFP:
case Instruction::SIToFP:
case Instruction::FPToUI:
case Instruction::FPToSI:
if (TTI.getFPOpCost(I.getType()) == TargetTransformInfo::TCC_Expensive)
Cost += InlineConstants::CallPenalty;
break;
default:
break;
}
return TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
}
bool CallAnalyzer::visitUnaryInstruction(UnaryInstruction &I) {
Value *Operand = I.getOperand(0);
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantFoldInstOperands(&I, COps[0], DL);
}))
return true;
// Disable any SROA on the argument to arbitrary unary operators.
disableSROA(Operand);
return false;
}
bool CallAnalyzer::paramHasAttr(Argument *A, Attribute::AttrKind Attr) {
return CandidateCS.paramHasAttr(A->getArgNo(), 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::allowSizeGrowth(CallSite CS) {
// If the normal destination of the invoke or the parent block of the call
// site is unreachable-terminated, there is little point in inlining this
// unless there is literally zero cost.
// FIXME: Note that it is possible that an unreachable-terminated block has a
// hot entry. For example, in below scenario inlining hot_call_X() may be
// beneficial :
// main() {
// hot_call_1();
// ...
// hot_call_N()
// exit(0);
// }
// For now, we are not handling this corner case here as it is rare in real
// code. In future, we should elaborate this based on BPI and BFI in more
// general threshold adjusting heuristics in updateThreshold().
Instruction *Instr = CS.getInstruction();
if (InvokeInst *II = dyn_cast<InvokeInst>(Instr)) {
if (isa<UnreachableInst>(II->getNormalDest()->getTerminator()))
return false;
} else if (isa<UnreachableInst>(Instr->getParent()->getTerminator()))
return false;
return true;
}
bool CallAnalyzer::isColdCallSite(CallSite CS, BlockFrequencyInfo *CallerBFI) {
// If global profile summary is available, then callsite's coldness is
// determined based on that.
if (PSI && PSI->hasProfileSummary())
return PSI->isColdCallSite(CS, CallerBFI);
// Otherwise we need BFI to be available.
if (!CallerBFI)
return false;
// Determine if the callsite is cold relative to caller's entry. We could
// potentially cache the computation of scaled entry frequency, but the added
// complexity is not worth it unless this scaling shows up high in the
// profiles.
const BranchProbability ColdProb(ColdCallSiteRelFreq, 100);
auto CallSiteBB = CS.getInstruction()->getParent();
auto CallSiteFreq = CallerBFI->getBlockFreq(CallSiteBB);
auto CallerEntryFreq =
CallerBFI->getBlockFreq(&(CS.getCaller()->getEntryBlock()));
return CallSiteFreq < CallerEntryFreq * ColdProb;
}
Optional<int>
CallAnalyzer::getHotCallSiteThreshold(CallSite CS,
BlockFrequencyInfo *CallerBFI) {
// If global profile summary is available, then callsite's hotness is
// determined based on that.
if (PSI && PSI->hasProfileSummary() && PSI->isHotCallSite(CS, CallerBFI))
return Params.HotCallSiteThreshold;
// Otherwise we need BFI to be available and to have a locally hot callsite
// threshold.
if (!CallerBFI || !Params.LocallyHotCallSiteThreshold)
return None;
// Determine if the callsite is hot relative to caller's entry. We could
// potentially cache the computation of scaled entry frequency, but the added
// complexity is not worth it unless this scaling shows up high in the
// profiles.
auto CallSiteBB = CS.getInstruction()->getParent();
auto CallSiteFreq = CallerBFI->getBlockFreq(CallSiteBB).getFrequency();
auto CallerEntryFreq = CallerBFI->getEntryFreq();
if (CallSiteFreq >= CallerEntryFreq * HotCallSiteRelFreq)
return Params.LocallyHotCallSiteThreshold;
// Otherwise treat it normally.
return None;
}
void CallAnalyzer::updateThreshold(CallSite CS, Function &Callee) {
// If no size growth is allowed for this inlining, set Threshold to 0.
if (!allowSizeGrowth(CS)) {
Threshold = 0;
return;
}
Function *Caller = CS.getCaller();
// return min(A, B) if B is valid.
auto MinIfValid = [](int A, Optional<int> B) {
return B ? std::min(A, B.getValue()) : A;
};
// return max(A, B) if B is valid.
auto MaxIfValid = [](int A, Optional<int> B) {
return B ? std::max(A, B.getValue()) : A;
};
// Various bonus percentages. These are multiplied by Threshold to get the
// bonus values.
// SingleBBBonus: This bonus is applied if the callee has a single reachable
// basic block at the given callsite context. This is speculatively applied
// and withdrawn if more than one basic block is seen.
//
// Vector bonuses: We want to more aggressively inline vector-dense kernels
// and apply this bonus based on the percentage of vector instructions. A
// bonus is applied if the vector instructions exceed 50% and half that amount
// is applied if it exceeds 10%. 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 base the bonus values on something more
// scientific.
//
// LstCallToStaticBonus: This large bonus is applied to ensure the inlining
// of the last call to a static function as inlining such functions is
// guaranteed to reduce code size.
//
// These bonus percentages may be set to 0 based on properties of the caller
// and the callsite.
int SingleBBBonusPercent = 50;
int VectorBonusPercent = 150;
int LastCallToStaticBonus = InlineConstants::LastCallToStaticBonus;
// Lambda to set all the above bonus and bonus percentages to 0.
auto DisallowAllBonuses = [&]() {
SingleBBBonusPercent = 0;
VectorBonusPercent = 0;
LastCallToStaticBonus = 0;
};
// Use the OptMinSizeThreshold or OptSizeThreshold knob if they are available
// and reduce the threshold if the caller has the necessary attribute.
if (Caller->optForMinSize()) {
Threshold = MinIfValid(Threshold, Params.OptMinSizeThreshold);
// For minsize, we want to disable the single BB bonus and the vector
// bonuses, but not the last-call-to-static bonus. Inlining the last call to
// a static function will, at the minimum, eliminate the parameter setup and
// call/return instructions.
SingleBBBonusPercent = 0;
VectorBonusPercent = 0;
} else if (Caller->optForSize())
Threshold = MinIfValid(Threshold, Params.OptSizeThreshold);
// Adjust the threshold based on inlinehint attribute and profile based
// hotness information if the caller does not have MinSize attribute.
if (!Caller->optForMinSize()) {
if (Callee.hasFnAttribute(Attribute::InlineHint))
Threshold = MaxIfValid(Threshold, Params.HintThreshold);
// FIXME: After switching to the new passmanager, simplify the logic below
// by checking only the callsite hotness/coldness as we will reliably
// have local profile information.
//
// Callsite hotness and coldness can be determined if sample profile is
// used (which adds hotness metadata to calls) or if caller's
// BlockFrequencyInfo is available.
BlockFrequencyInfo *CallerBFI = GetBFI ? &((*GetBFI)(*Caller)) : nullptr;
auto HotCallSiteThreshold = getHotCallSiteThreshold(CS, CallerBFI);
if (!Caller->optForSize() && HotCallSiteThreshold) {
LLVM_DEBUG(dbgs() << "Hot callsite.\n");
// FIXME: This should update the threshold only if it exceeds the
// current threshold, but AutoFDO + ThinLTO currently relies on this
// behavior to prevent inlining of hot callsites during ThinLTO
// compile phase.
Threshold = HotCallSiteThreshold.getValue();
} else if (isColdCallSite(CS, CallerBFI)) {
LLVM_DEBUG(dbgs() << "Cold callsite.\n");
// Do not apply bonuses for a cold callsite including the
// LastCallToStatic bonus. While this bonus might result in code size
// reduction, it can cause the size of a non-cold caller to increase
// preventing it from being inlined.
DisallowAllBonuses();
Threshold = MinIfValid(Threshold, Params.ColdCallSiteThreshold);
} else if (PSI) {
// Use callee's global profile information only if we have no way of
// determining this via callsite information.
if (PSI->isFunctionEntryHot(&Callee)) {
LLVM_DEBUG(dbgs() << "Hot callee.\n");
// If callsite hotness can not be determined, we may still know
// that the callee is hot and treat it as a weaker hint for threshold
// increase.
Threshold = MaxIfValid(Threshold, Params.HintThreshold);
} else if (PSI->isFunctionEntryCold(&Callee)) {
LLVM_DEBUG(dbgs() << "Cold callee.\n");
// Do not apply bonuses for a cold callee including the
// LastCallToStatic bonus. While this bonus might result in code size
// reduction, it can cause the size of a non-cold caller to increase
// preventing it from being inlined.
DisallowAllBonuses();
Threshold = MinIfValid(Threshold, Params.ColdThreshold);
}
}
}
// Finally, take the target-specific inlining threshold multiplier into
// account.
Threshold *= TTI.getInliningThresholdMultiplier();
SingleBBBonus = Threshold * SingleBBBonusPercent / 100;
VectorBonus = Threshold * VectorBonusPercent / 100;
bool OnlyOneCallAndLocalLinkage =
F.hasLocalLinkage() && F.hasOneUse() && &F == CS.getCalledFunction();
// If there is only one call of the function, and it has internal linkage,
// the cost of inlining it drops dramatically. It may seem odd to update
// Cost in updateThreshold, but the bonus depends on the logic in this method.
if (OnlyOneCallAndLocalLinkage)
Cost -= LastCallToStaticBonus;
}
bool CallAnalyzer::visitCmpInst(CmpInst &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// First try to handle simplified comparisons.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getCompare(I.getPredicate(), COps[0], COps[1]);
}))
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);
Constant *CLHS = dyn_cast<Constant>(LHS);
if (!CLHS)
CLHS = SimplifiedValues.lookup(LHS);
Constant *CRHS = dyn_cast<Constant>(RHS);
if (!CRHS)
CRHS = SimplifiedValues.lookup(RHS);
Value *SimpleV = nullptr;
if (auto FI = dyn_cast<FPMathOperator>(&I))
SimpleV = SimplifyFPBinOp(I.getOpcode(), CLHS ? CLHS : LHS,
CRHS ? CRHS : RHS, FI->getFastMathFlags(), DL);
else
SimpleV =
SimplifyBinOp(I.getOpcode(), CLHS ? CLHS : LHS, CRHS ? CRHS : RHS, DL);
if (Constant *C = dyn_cast_or_null<Constant>(SimpleV))
SimplifiedValues[&I] = C;
if (SimpleV)
return true;
// Disable any SROA on arguments to arbitrary, unsimplified binary operators.
disableSROA(LHS);
disableSROA(RHS);
// If the instruction is floating point, and the target says this operation
// is expensive, this may eventually become a library call. Treat the cost
// as such.
if (I.getType()->isFloatingPointTy() &&
TTI.getFPOpCost(I.getType()) == TargetTransformInfo::TCC_Expensive)
Cost += InlineConstants::CallPenalty;
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);
}
// If the data is already loaded from this address and hasn't been clobbered
// by any stores or calls, this load is likely to be redundant and can be
// eliminated.
if (EnableLoadElimination &&
!LoadAddrSet.insert(I.getPointerOperand()).second && I.isUnordered()) {
LoadEliminationCost += InlineConstants::InstrCost;
return true;
}
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);
}
// The store can potentially clobber loads and prevent repeated loads from
// being eliminated.
// FIXME:
// 1. We can probably keep an initial set of eliminatable loads substracted
// from the cost even when we finally see a store. We just need to disable
// *further* accumulation of elimination savings.
// 2. We should probably at some point thread MemorySSA for the callee into
// this and then use that to actually compute *really* precise savings.
disableLoadElimination();
return false;
}
bool CallAnalyzer::visitExtractValue(ExtractValueInst &I) {
// Constant folding for extract value is trivial.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getExtractValue(COps[0], 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.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getInsertValue(/*AggregateOperand*/ COps[0],
/*InsertedValueOperand*/ COps[1],
I.getIndices());
}))
return true;
// SROA can look through these but give them a cost.
return false;
}
/// 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(CS, 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(CS, 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:
if (!CS.onlyReadsMemory() && !isAssumeLikeIntrinsic(II))
disableLoadElimination();
return Base::visitCallSite(CS);
case Intrinsic::load_relative:
// This is normally lowered to 4 LLVM instructions.
Cost += 3 * InlineConstants::InstrCost;
return false;
case Intrinsic::memset:
case Intrinsic::memcpy:
case Intrinsic::memmove:
disableLoadElimination();
// SROA can usually chew through these intrinsics, but they aren't free.
return false;
case Intrinsic::icall_branch_funnel:
case Intrinsic::localescape:
HasUninlineableIntrinsic = true;
return false;
case Intrinsic::vastart:
InitsVargArgs = true;
return false;
}
}
if (F == CS.getInstruction()->getFunction()) {
// 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;
}
if (!CS.onlyReadsMemory())
disableLoadElimination();
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) {
if (!CS.onlyReadsMemory())
disableLoadElimination();
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.
auto IndirectCallParams = Params;
IndirectCallParams.DefaultThreshold = InlineConstants::IndirectCallThreshold;
CallAnalyzer CA(TTI, GetAssumptionCache, GetBFI, PSI, ORE, *F, CS,
IndirectCallParams);
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());
}
if (!F->onlyReadsMemory())
disableLoadElimination();
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::visitSelectInst(SelectInst &SI) {
bool CheckSROA = SI.getType()->isPointerTy();
Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
Constant *TrueC = dyn_cast<Constant>(TrueVal);
if (!TrueC)
TrueC = SimplifiedValues.lookup(TrueVal);
Constant *FalseC = dyn_cast<Constant>(FalseVal);
if (!FalseC)
FalseC = SimplifiedValues.lookup(FalseVal);
Constant *CondC =
dyn_cast_or_null<Constant>(SimplifiedValues.lookup(SI.getCondition()));
if (!CondC) {
// Select C, X, X => X
if (TrueC == FalseC && TrueC) {
SimplifiedValues[&SI] = TrueC;
return true;
}
if (!CheckSROA)
return Base::visitSelectInst(SI);
std::pair<Value *, APInt> TrueBaseAndOffset =
ConstantOffsetPtrs.lookup(TrueVal);
std::pair<Value *, APInt> FalseBaseAndOffset =
ConstantOffsetPtrs.lookup(FalseVal);
if (TrueBaseAndOffset == FalseBaseAndOffset && TrueBaseAndOffset.first) {
ConstantOffsetPtrs[&SI] = TrueBaseAndOffset;
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(TrueVal, SROAArg, CostIt))
SROAArgValues[&SI] = SROAArg;
return true;
}
return Base::visitSelectInst(SI);
}
// Select condition is a constant.
Value *SelectedV = CondC->isAllOnesValue()
? TrueVal
: (CondC->isNullValue()) ? FalseVal : nullptr;
if (!SelectedV) {
// Condition is a vector constant that is not all 1s or all 0s. If all
// operands are constants, ConstantExpr::getSelect() can handle the cases
// such as select vectors.
if (TrueC && FalseC) {
if (auto *C = ConstantExpr::getSelect(CondC, TrueC, FalseC)) {
SimplifiedValues[&SI] = C;
return true;
}
}
return Base::visitSelectInst(SI);
}
// Condition is either all 1s or all 0s. SI can be simplified.
if (Constant *SelectedC = dyn_cast<Constant>(SelectedV)) {
SimplifiedValues[&SI] = SelectedC;
return true;
}
if (!CheckSROA)
return true;
std::pair<Value *, APInt> BaseAndOffset =
ConstantOffsetPtrs.lookup(SelectedV);
if (BaseAndOffset.first) {
ConstantOffsetPtrs[&SI] = BaseAndOffset;
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(SelectedV, SROAArg, CostIt))
SROAArgValues[&SI] = SROAArg;
}
return true;
}
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;
// Assume the most general case where the switch is lowered into
// either a jump table, bit test, or a balanced binary tree consisting of
// case clusters without merging adjacent clusters with the same
// destination. We do not consider the switches that are lowered with a mix
// of jump table/bit test/binary search tree. The cost of the switch is
// proportional to the size of the tree or the size of jump table range.
//
// 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.
// Maximum valid cost increased in this function.
int CostUpperBound = INT_MAX - InlineConstants::InstrCost - 1;
// Exit early for a large switch, assuming one case needs at least one
// instruction.
// FIXME: This is not true for a bit test, but ignore such case for now to
// save compile-time.
int64_t CostLowerBound =
std::min((int64_t)CostUpperBound,
(int64_t)SI.getNumCases() * InlineConstants::InstrCost + Cost);
if (CostLowerBound > Threshold && !ComputeFullInlineCost) {
Cost = CostLowerBound;
return false;
}
unsigned JumpTableSize = 0;
unsigned NumCaseCluster =
TTI.getEstimatedNumberOfCaseClusters(SI, JumpTableSize);
// If suitable for a jump table, consider the cost for the table size and
// branch to destination.
if (JumpTableSize) {
int64_t JTCost = (int64_t)JumpTableSize * InlineConstants::InstrCost +
4 * InlineConstants::InstrCost;
Cost = std::min((int64_t)CostUpperBound, JTCost + Cost);
return false;
}
// Considering forming a binary search, we should find the number of nodes
// which is same as the number of comparisons when lowered. For a given
// number of clusters, n, we can define a recursive function, f(n), to find
// the number of nodes in the tree. The recursion is :
// f(n) = 1 + f(n/2) + f (n - n/2), when n > 3,
// and f(n) = n, when n <= 3.
// This will lead a binary tree where the leaf should be either f(2) or f(3)
// when n > 3. So, the number of comparisons from leaves should be n, while
// the number of non-leaf should be :
// 2^(log2(n) - 1) - 1
// = 2^log2(n) * 2^-1 - 1
// = n / 2 - 1.
// Considering comparisons from leaf and non-leaf nodes, we can estimate the
// number of comparisons in a simple closed form :
// n + n / 2 - 1 = n * 3 / 2 - 1
if (NumCaseCluster <= 3) {
// Suppose a comparison includes one compare and one conditional branch.
Cost += NumCaseCluster * 2 * InlineConstants::InstrCost;
return false;
}
int64_t ExpectedNumberOfCompare = 3 * (int64_t)NumCaseCluster / 2 - 1;
int64_t SwitchCost =
ExpectedNumberOfCompare * 2 * InlineConstants::InstrCost;
Cost = std::min((int64_t)CostUpperBound, SwitchCost + Cost);
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;
}
/// 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.
InlineResult
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 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;
using namespace ore;
// If the visit this instruction detected an uninlinable pattern, abort.
InlineResult IR;
if (IsRecursiveCall)
IR = "recursive";
else if (ExposesReturnsTwice)
IR = "exposes returns twice";
else if (HasDynamicAlloca)
IR = "dynamic alloca";
else if (HasIndirectBr)
IR = "indirect branch";
else if (HasUninlineableIntrinsic)
IR = "uninlinable intrinsic";
else if (InitsVargArgs)
IR = "varargs";
if (!IR) {
if (ORE)
ORE->emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "NeverInline",
CandidateCS.getInstruction())
<< NV("Callee", &F) << " has uninlinable pattern ("
<< NV("InlineResult", IR.message)
<< ") and cost is not fully computed";
});
return IR;
}
// 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) {
InlineResult IR = "recursive and allocates too much stack space";
if (ORE)
ORE->emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "NeverInline",
CandidateCS.getInstruction())
<< NV("Callee", &F) << " is " << NV("InlineResult", IR.message)
<< ". Cost is not fully computed";
});
return IR;
}
// 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 && !ComputeFullInlineCost)
return false;
}
return true;
}
/// 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;
unsigned AS = V->getType()->getPointerAddressSpace();
unsigned IntPtrWidth = DL.getIndexSizeInBits(AS);
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->isInterposable())
break;
V = GA->getAliasee();
} else {
break;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
} while (Visited.insert(V).second);
Type *IntPtrTy = DL.getIntPtrType(V->getContext(), AS);
return cast<ConstantInt>(ConstantInt::get(IntPtrTy, Offset));
}
/// Find dead blocks due to deleted CFG edges during inlining.
///
/// If we know the successor of the current block, \p CurrBB, has to be \p
/// NextBB, the other successors of \p CurrBB are dead if these successors have
/// no live incoming CFG edges. If one block is found to be dead, we can
/// continue growing the dead block list by checking the successors of the dead
/// blocks to see if all their incoming edges are dead or not.
void CallAnalyzer::findDeadBlocks(BasicBlock *CurrBB, BasicBlock *NextBB) {
auto IsEdgeDead = [&](BasicBlock *Pred, BasicBlock *Succ) {
// A CFG edge is dead if the predecessor is dead or the predessor has a
// known successor which is not the one under exam.
return (DeadBlocks.count(Pred) ||
(KnownSuccessors[Pred] && KnownSuccessors[Pred] != Succ));
};
auto IsNewlyDead = [&](BasicBlock *BB) {
// If all the edges to a block are dead, the block is also dead.
return (!DeadBlocks.count(BB) &&
llvm::all_of(predecessors(BB),
[&](BasicBlock *P) { return IsEdgeDead(P, BB); }));
};
for (BasicBlock *Succ : successors(CurrBB)) {
if (Succ == NextBB || !IsNewlyDead(Succ))
continue;
SmallVector<BasicBlock *, 4> NewDead;
NewDead.push_back(Succ);
while (!NewDead.empty()) {
BasicBlock *Dead = NewDead.pop_back_val();
if (DeadBlocks.insert(Dead))
// Continue growing the dead block lists.
for (BasicBlock *S : successors(Dead))
if (IsNewlyDead(S))
NewDead.push_back(S);
}
}
}
/// 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.
InlineResult 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);
// Update the threshold based on callsite properties
updateThreshold(CS, F);
// 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 + VectorBonus);
// Give out bonuses for the callsite, as the instructions setting them up
// will be gone after inlining.
Cost -= getCallsiteCost(CS, DL);
// 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 && !ComputeFullInlineCost)
return "high cost";
if (F.empty())
return true;
Function *Caller = CS.getInstruction()->getFunction();
// 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->getFunction() == 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, &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());
bool SingleBB = true;
// 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 && !ComputeFullInlineCost)
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 "blockaddress";
// Analyze the cost of this block. If we blow through the threshold, this
// returns false, and we can bail on out.
InlineResult IR = analyzeBlock(BB, EphValues);
if (!IR)
return IR;
Instruction *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))) {
BasicBlock *NextBB = BI->getSuccessor(SimpleCond->isZero() ? 1 : 0);
BBWorklist.insert(NextBB);
KnownSuccessors[BB] = NextBB;
findDeadBlocks(BB, NextBB);
continue;
}
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
Value *Cond = SI->getCondition();
if (ConstantInt *SimpleCond =
dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) {
BasicBlock *NextBB = SI->findCaseValue(SimpleCond)->getCaseSuccessor();
BBWorklist.insert(NextBB);
KnownSuccessors[BB] = NextBB;
findDeadBlocks(BB, NextBB);
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;
}
}
bool OnlyOneCallAndLocalLinkage =
F.hasLocalLinkage() && F.hasOneUse() && &F == CS.getCalledFunction();
// 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 "noduplicate";
// Loops generally act a lot like calls in that they act like barriers to
// movement, require a certain amount of setup, etc. So when optimising for
// size, we penalise any call sites that perform loops. We do this after all
// other costs here, so will likely only be dealing with relatively small
// functions (and hence DT and LI will hopefully be cheap).
if (Caller->optForMinSize()) {
DominatorTree DT(F);
LoopInfo LI(DT);
int NumLoops = 0;
for (Loop *L : LI) {
// Ignore loops that will not be executed
if (DeadBlocks.count(L->getHeader()))
continue;
NumLoops++;
}
Cost += NumLoops * InlineConstants::CallPenalty;
}
// 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 -= VectorBonus;
else if (NumVectorInstructions <= NumInstructions / 2)
Threshold -= VectorBonus/2;
return Cost < std::max(1, Threshold);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// Dump stats about this call's analysis.
LLVM_DUMP_METHOD 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(LoadEliminationCost);
DEBUG_PRINT_STAT(ContainsNoDuplicateCall);
DEBUG_PRINT_STAT(Cost);
DEBUG_PRINT_STAT(Threshold);
#undef DEBUG_PRINT_STAT
}
#endif
/// 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);
}
int llvm::getCallsiteCost(CallSite CS, const DataLayout &DL) {
int Cost = 0;
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 AS = PTy->getAddressSpace();
unsigned PointerSize = DL.getPointerSizeInBits(AS);
// 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;
}
}
// The call instruction also disappears after inlining.
Cost += InlineConstants::InstrCost + InlineConstants::CallPenalty;
return Cost;
}
InlineCost llvm::getInlineCost(
CallSite CS, const InlineParams &Params, TargetTransformInfo &CalleeTTI,
std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
return getInlineCost(CS, CS.getCalledFunction(), Params, CalleeTTI,
GetAssumptionCache, GetBFI, PSI, ORE);
}
InlineCost llvm::getInlineCost(
CallSite CS, Function *Callee, const InlineParams &Params,
TargetTransformInfo &CalleeTTI,
std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
// Cannot inline indirect calls.
if (!Callee)
return llvm::InlineCost::getNever("indirect call");
// Never inline calls with byval arguments that does not have the alloca
// address space. Since byval arguments can be replaced with a copy to an
// alloca, the inlined code would need to be adjusted to handle that the
// argument is in the alloca address space (so it is a little bit complicated
// to solve).
unsigned AllocaAS = Callee->getParent()->getDataLayout().getAllocaAddrSpace();
for (unsigned I = 0, E = CS.arg_size(); I != E; ++I)
if (CS.isByValArgument(I)) {
PointerType *PTy = cast<PointerType>(CS.getArgument(I)->getType());
if (PTy->getAddressSpace() != AllocaAS)
return llvm::InlineCost::getNever("byval arguments without alloca"
" address space");
}
// Calls to functions with always-inline attributes should be inlined
// whenever possible.
if (CS.hasFnAttr(Attribute::AlwaysInline)) {
if (isInlineViable(*Callee))
return llvm::InlineCost::getAlways("always inline attribute");
return llvm::InlineCost::getNever("inapplicable always inline attribute");
}
// Never inline functions with conflicting attributes (unless callee has
// always-inline attribute).
Function *Caller = CS.getCaller();
if (!functionsHaveCompatibleAttributes(Caller, Callee, CalleeTTI))
return llvm::InlineCost::getNever("conflicting attributes");
// Don't inline this call if the caller has the optnone attribute.
if (Caller->hasFnAttribute(Attribute::OptimizeNone))
return llvm::InlineCost::getNever("optnone attribute");
// Don't inline a function that treats null pointer as valid into a caller
// that does not have this attribute.
if (!Caller->nullPointerIsDefined() && Callee->nullPointerIsDefined())
return llvm::InlineCost::getNever("nullptr definitions incompatible");
// Don't inline functions which can be interposed at link-time.
if (Callee->isInterposable())
return llvm::InlineCost::getNever("interposable");
// Don't inline functions marked noinline.
if (Callee->hasFnAttribute(Attribute::NoInline))
return llvm::InlineCost::getNever("noinline function attribute");
// Don't inline call sites marked noinline.
if (CS.isNoInline())
return llvm::InlineCost::getNever("noinline call site attribute");
LLVM_DEBUG(llvm::dbgs() << " Analyzing call of " << Callee->getName()
<< "... (caller:" << Caller->getName() << ")\n");
CallAnalyzer CA(CalleeTTI, GetAssumptionCache, GetBFI, PSI, ORE, *Callee, CS,
Params);
InlineResult ShouldInline = CA.analyzeCall(CS);
LLVM_DEBUG(CA.dump());
// Check if there was a reason to force inlining or no inlining.
if (!ShouldInline && CA.getCost() < CA.getThreshold())
return InlineCost::getNever(ShouldInline.message);
if (ShouldInline && CA.getCost() >= CA.getThreshold())
return InlineCost::getAlways("empty function");
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;
if (CS.getCalledFunction())
switch (CS.getCalledFunction()->getIntrinsicID()) {
default:
break;
// Disallow inlining of @llvm.icall.branch.funnel because current
// backend can't separate call targets from call arguments.
case llvm::Intrinsic::icall_branch_funnel:
// Disallow inlining functions that call @llvm.localescape. Doing this
// correctly would require major changes to the inliner.
case llvm::Intrinsic::localescape:
// Disallow inlining of functions that initialize VarArgs with va_start.
case llvm::Intrinsic::vastart:
return false;
}
}
}
return true;
}
// APIs to create InlineParams based on command line flags and/or other
// parameters.
InlineParams llvm::getInlineParams(int Threshold) {
InlineParams Params;
// This field is the threshold to use for a callee by default. This is
// derived from one or more of:
// * optimization or size-optimization levels,
// * a value passed to createFunctionInliningPass function, or
// * the -inline-threshold flag.
// If the -inline-threshold flag is explicitly specified, that is used
// irrespective of anything else.
if (InlineThreshold.getNumOccurrences() > 0)
Params.DefaultThreshold = InlineThreshold;
else
Params.DefaultThreshold = Threshold;
// Set the HintThreshold knob from the -inlinehint-threshold.
Params.HintThreshold = HintThreshold;
// Set the HotCallSiteThreshold knob from the -hot-callsite-threshold.
Params.HotCallSiteThreshold = HotCallSiteThreshold;
// If the -locally-hot-callsite-threshold is explicitly specified, use it to
// populate LocallyHotCallSiteThreshold. Later, we populate
// Params.LocallyHotCallSiteThreshold from -locally-hot-callsite-threshold if
// we know that optimization level is O3 (in the getInlineParams variant that
// takes the opt and size levels).
// FIXME: Remove this check (and make the assignment unconditional) after
// addressing size regression issues at O2.
if (LocallyHotCallSiteThreshold.getNumOccurrences() > 0)
Params.LocallyHotCallSiteThreshold = LocallyHotCallSiteThreshold;
// Set the ColdCallSiteThreshold knob from the -inline-cold-callsite-threshold.
Params.ColdCallSiteThreshold = ColdCallSiteThreshold;
// Set the OptMinSizeThreshold and OptSizeThreshold params only if the
// -inlinehint-threshold commandline option is not explicitly given. If that
// option is present, then its value applies even for callees with size and
// minsize attributes.
// If the -inline-threshold is not specified, set the ColdThreshold from the
// -inlinecold-threshold even if it is not explicitly passed. If
// -inline-threshold is specified, then -inlinecold-threshold needs to be
// explicitly specified to set the ColdThreshold knob
if (InlineThreshold.getNumOccurrences() == 0) {
Params.OptMinSizeThreshold = InlineConstants::OptMinSizeThreshold;
Params.OptSizeThreshold = InlineConstants::OptSizeThreshold;
Params.ColdThreshold = ColdThreshold;
} else if (ColdThreshold.getNumOccurrences() > 0) {
Params.ColdThreshold = ColdThreshold;
}
return Params;
}
InlineParams llvm::getInlineParams() {
return getInlineParams(InlineThreshold);
}
// Compute the default threshold for inlining based on the opt level and the
// size opt level.
static int computeThresholdFromOptLevels(unsigned OptLevel,
unsigned SizeOptLevel) {
if (OptLevel > 2)
return InlineConstants::OptAggressiveThreshold;
if (SizeOptLevel == 1) // -Os
return InlineConstants::OptSizeThreshold;
if (SizeOptLevel == 2) // -Oz
return InlineConstants::OptMinSizeThreshold;
return InlineThreshold;
}
InlineParams llvm::getInlineParams(unsigned OptLevel, unsigned SizeOptLevel) {
auto Params =
getInlineParams(computeThresholdFromOptLevels(OptLevel, SizeOptLevel));
// At O3, use the value of -locally-hot-callsite-threshold option to populate
// Params.LocallyHotCallSiteThreshold. Below O3, this flag has effect only
// when it is specified explicitly.
if (OptLevel > 2)
Params.LocallyHotCallSiteThreshold = LocallyHotCallSiteThreshold;
return Params;
}
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