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llvm-mirror/lib/Analysis/InlineCost.cpp
Philipp Krones d7917544a3 [Inliner] Make the CallPenalty configurable 
Tests with multiple benchmarks, like Embench [1], showed that the
CallPenalty magic number has the most influence on inlining decisions
when optimizing for size.

On the other hand, there was no good default value for this parameter.
Some benchmarks profited strongly from a reduced call penalty. On
example is the picojpeg benchmark compiled for RISC-V, which got 6%
smaller with a CallPenalty of 10 instead of 12. Other benchmarks
increased in size, like matmult.

This commit makes the compromise of turning the magic number constant of
CallPenalty into a configurable value. This introduces the flag
`--inline-call-penalty`. With that flag users can fine tune the inliner
to their needs.

The CallPenalty constant was also used for loops. This commit replaces
the CallPenalty constant with a new LoopPenalty constant that is now
used instead.

This is a slimmed down version of https://reviews.llvm.org/D30899

[1]: https://github.com/embench/embench-iot

Differential Revision: https://reviews.llvm.org/D105976
2021-07-26 12:07:49 +01:00

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//===- InlineCost.cpp - Cost analysis for inliner -------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// 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/CFG.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/AssemblyAnnotationWriter.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/IR/PatternMatch.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/FormattedStream.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>
DefaultThreshold("inlinedefault-threshold", cl::Hidden, cl::init(225),
cl::ZeroOrMore,
cl::desc("Default amount of inlining to perform"));
static cl::opt<bool> PrintInstructionComments(
"print-instruction-comments", cl::Hidden, cl::init(false),
cl::desc("Prints comments for instruction based on inline cost analysis"));
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::ZeroOrMore,
cl::desc("Threshold for inlining functions with inline hint"));
static cl::opt<int>
ColdCallSiteThreshold("inline-cold-callsite-threshold", cl::Hidden,
cl::init(45), cl::ZeroOrMore,
cl::desc("Threshold for inlining cold callsites"));
static cl::opt<bool> InlineEnableCostBenefitAnalysis(
"inline-enable-cost-benefit-analysis", cl::Hidden, cl::init(false),
cl::desc("Enable the cost-benefit analysis for the inliner"));
static cl::opt<int> InlineSavingsMultiplier(
"inline-savings-multiplier", cl::Hidden, cl::init(8), cl::ZeroOrMore,
cl::desc("Multiplier to multiply cycle savings by during inlining"));
static cl::opt<int>
InlineSizeAllowance("inline-size-allowance", cl::Hidden, cl::init(100),
cl::ZeroOrMore,
cl::desc("The maximum size of a callee that get's "
"inlined without sufficient cycle savings"));
// 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::ZeroOrMore,
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("Maximum 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<int> CallPenalty(
"inline-call-penalty", cl::Hidden, cl::init(25),
cl::desc("Call penalty that is applied per callsite when inlining"));
static cl::opt<bool> OptComputeFullInlineCost(
"inline-cost-full", cl::Hidden, cl::init(false), cl::ZeroOrMore,
cl::desc("Compute the full inline cost of a call site even when the cost "
"exceeds the threshold."));
static cl::opt<bool> InlineCallerSupersetNoBuiltin(
"inline-caller-superset-nobuiltin", cl::Hidden, cl::init(true),
cl::ZeroOrMore,
cl::desc("Allow inlining when caller has a superset of callee's nobuiltin "
"attributes."));
static cl::opt<bool> DisableGEPConstOperand(
"disable-gep-const-evaluation", cl::Hidden, cl::init(false),
cl::desc("Disables evaluation of GetElementPtr with constant operands"));
namespace {
class InlineCostCallAnalyzer;
// This struct is used to store information about inline cost of a
// particular instruction
struct InstructionCostDetail {
int CostBefore = 0;
int CostAfter = 0;
int ThresholdBefore = 0;
int ThresholdAfter = 0;
int getThresholdDelta() const { return ThresholdAfter - ThresholdBefore; }
int getCostDelta() const { return CostAfter - CostBefore; }
bool hasThresholdChanged() const { return ThresholdAfter != ThresholdBefore; }
};
class InlineCostAnnotationWriter : public AssemblyAnnotationWriter {
private:
InlineCostCallAnalyzer *const ICCA;
public:
InlineCostAnnotationWriter(InlineCostCallAnalyzer *ICCA) : ICCA(ICCA) {}
virtual void emitInstructionAnnot(const Instruction *I,
formatted_raw_ostream &OS) override;
};
/// Carry out call site analysis, in order to evaluate inlinability.
/// NOTE: the type is currently used as implementation detail of functions such
/// as llvm::getInlineCost. Note the function_ref constructor parameters - the
/// expectation is that they come from the outer scope, from the wrapper
/// functions. If we want to support constructing CallAnalyzer objects where
/// lambdas are provided inline at construction, or where the object needs to
/// otherwise survive past the scope of the provided functions, we need to
/// revisit the argument types.
class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
typedef InstVisitor<CallAnalyzer, bool> Base;
friend class InstVisitor<CallAnalyzer, bool>;
protected:
virtual ~CallAnalyzer() {}
/// The TargetTransformInfo available for this compilation.
const TargetTransformInfo &TTI;
/// Getter for the cache of @llvm.assume intrinsics.
function_ref<AssumptionCache &(Function &)> GetAssumptionCache;
/// Getter for BlockFrequencyInfo
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.
CallBase &CandidateCall;
/// Extension points for handling callsite features.
// Called before a basic block was analyzed.
virtual void onBlockStart(const BasicBlock *BB) {}
/// Called after a basic block was analyzed.
virtual void onBlockAnalyzed(const BasicBlock *BB) {}
/// Called before an instruction was analyzed
virtual void onInstructionAnalysisStart(const Instruction *I) {}
/// Called after an instruction was analyzed
virtual void onInstructionAnalysisFinish(const Instruction *I) {}
/// Called at the end of the analysis of the callsite. Return the outcome of
/// the analysis, i.e. 'InlineResult(true)' if the inlining may happen, or
/// the reason it can't.
virtual InlineResult finalizeAnalysis() { return InlineResult::success(); }
/// Called when we're about to start processing a basic block, and every time
/// we are done processing an instruction. Return true if there is no point in
/// continuing the analysis (e.g. we've determined already the call site is
/// too expensive to inline)
virtual bool shouldStop() { return false; }
/// Called before the analysis of the callee body starts (with callsite
/// contexts propagated). It checks callsite-specific information. Return a
/// reason analysis can't continue if that's the case, or 'true' if it may
/// continue.
virtual InlineResult onAnalysisStart() { return InlineResult::success(); }
/// Called if the analysis engine decides SROA cannot be done for the given
/// alloca.
virtual void onDisableSROA(AllocaInst *Arg) {}
/// Called the analysis engine determines load elimination won't happen.
virtual void onDisableLoadElimination() {}
/// Called to account for a call.
virtual void onCallPenalty() {}
/// Called to account for the expectation the inlining would result in a load
/// elimination.
virtual void onLoadEliminationOpportunity() {}
/// Called to account for the cost of argument setup for the Call in the
/// callee's body (not the callsite currently under analysis).
virtual void onCallArgumentSetup(const CallBase &Call) {}
/// Called to account for a load relative intrinsic.
virtual void onLoadRelativeIntrinsic() {}
/// Called to account for a lowered call.
virtual void onLoweredCall(Function *F, CallBase &Call, bool IsIndirectCall) {
}
/// Account for a jump table of given size. Return false to stop further
/// processing the switch instruction
virtual bool onJumpTable(unsigned JumpTableSize) { return true; }
/// Account for a case cluster of given size. Return false to stop further
/// processing of the instruction.
virtual bool onCaseCluster(unsigned NumCaseCluster) { return true; }
/// Called at the end of processing a switch instruction, with the given
/// number of case clusters.
virtual void onFinalizeSwitch(unsigned JumpTableSize,
unsigned NumCaseCluster) {}
/// Called to account for any other instruction not specifically accounted
/// for.
virtual void onMissedSimplification() {}
/// Start accounting potential benefits due to SROA for the given alloca.
virtual void onInitializeSROAArg(AllocaInst *Arg) {}
/// Account SROA savings for the AllocaInst value.
virtual void onAggregateSROAUse(AllocaInst *V) {}
bool handleSROA(Value *V, bool DoNotDisable) {
// Check for SROA candidates in comparisons.
if (auto *SROAArg = getSROAArgForValueOrNull(V)) {
if (DoNotDisable) {
onAggregateSROAUse(SROAArg);
return true;
}
disableSROAForArg(SROAArg);
}
return false;
}
bool IsCallerRecursive = false;
bool IsRecursiveCall = false;
bool ExposesReturnsTwice = false;
bool HasDynamicAlloca = false;
bool ContainsNoDuplicateCall = false;
bool HasReturn = false;
bool HasIndirectBr = false;
bool HasUninlineableIntrinsic = false;
bool InitsVargArgs = false;
/// Number of bytes allocated statically by the callee.
uint64_t AllocatedSize = 0;
unsigned NumInstructions = 0;
unsigned NumVectorInstructions = 0;
/// 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 *, AllocaInst *> SROAArgValues;
/// Keep track of Allocas for which we believe we may get SROA optimization.
DenseSet<AllocaInst *> EnabledSROAAllocas;
/// 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;
AllocaInst *getSROAArgForValueOrNull(Value *V) const {
auto It = SROAArgValues.find(V);
if (It == SROAArgValues.end() || EnabledSROAAllocas.count(It->second) == 0)
return nullptr;
return It->second;
}
// Custom simplification helper routines.
bool isAllocaDerivedArg(Value *V);
void disableSROAForArg(AllocaInst *SROAArg);
void disableSROA(Value *V);
void findDeadBlocks(BasicBlock *CurrBB, BasicBlock *NextBB);
void disableLoadElimination();
bool isGEPFree(GetElementPtrInst &GEP);
bool canFoldInboundsGEP(GetElementPtrInst &I);
bool accumulateGEPOffset(GEPOperator &GEP, APInt &Offset);
bool simplifyCallSite(Function *F, CallBase &Call);
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);
/// Return true if size growth is allowed when inlining the callee at \p Call.
bool allowSizeGrowth(CallBase &Call);
// 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 visitCmpInst(CmpInst &I);
bool visitSub(BinaryOperator &I);
bool visitBinaryOperator(BinaryOperator &I);
bool visitFNeg(UnaryOperator &I);
bool visitLoad(LoadInst &I);
bool visitStore(StoreInst &I);
bool visitExtractValue(ExtractValueInst &I);
bool visitInsertValue(InsertValueInst &I);
bool visitCallBase(CallBase &Call);
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(Function &Callee, CallBase &Call, const TargetTransformInfo &TTI,
function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
function_ref<BlockFrequencyInfo &(Function &)> GetBFI = nullptr,
ProfileSummaryInfo *PSI = nullptr,
OptimizationRemarkEmitter *ORE = nullptr)
: TTI(TTI), GetAssumptionCache(GetAssumptionCache), GetBFI(GetBFI),
PSI(PSI), F(Callee), DL(F.getParent()->getDataLayout()), ORE(ORE),
CandidateCall(Call), EnableLoadElimination(true) {}
InlineResult analyze();
Optional<Constant *> getSimplifiedValue(Instruction *I) {
if (SimplifiedValues.find(I) != SimplifiedValues.end())
return SimplifiedValues[I];
return None;
}
// Keep a bunch of stats about the cost savings found so we can print them
// out when debugging.
unsigned NumConstantArgs = 0;
unsigned NumConstantOffsetPtrArgs = 0;
unsigned NumAllocaArgs = 0;
unsigned NumConstantPtrCmps = 0;
unsigned NumConstantPtrDiffs = 0;
unsigned NumInstructionsSimplified = 0;
void dump();
};
// 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
int64_t getExpectedNumberOfCompare(int NumCaseCluster) {
return 3 * static_cast<int64_t>(NumCaseCluster) / 2 - 1;
}
/// FIXME: if it is necessary to derive from InlineCostCallAnalyzer, note
/// the FIXME in onLoweredCall, when instantiating an InlineCostCallAnalyzer
class InlineCostCallAnalyzer final : public CallAnalyzer {
const int CostUpperBound = INT_MAX - InlineConstants::InstrCost - 1;
const bool ComputeFullInlineCost;
int LoadEliminationCost = 0;
/// Bonus to be applied when percentage of vector instructions in callee is
/// high (see more details in updateThreshold).
int VectorBonus = 0;
/// Bonus to be applied when the callee has only one reachable basic block.
int SingleBBBonus = 0;
/// Tunable parameters that control the analysis.
const InlineParams &Params;
// This DenseMap stores the delta change in cost and threshold after
// accounting for the given instruction. The map is filled only with the
// flag PrintInstructionComments on.
DenseMap<const Instruction *, InstructionCostDetail> InstructionCostDetailMap;
/// Upper bound for the inlining cost. Bonuses are being applied to account
/// for speculative "expected profit" of the inlining decision.
int Threshold = 0;
/// Attempt to evaluate indirect calls to boost its inline cost.
const bool BoostIndirectCalls;
/// Ignore the threshold when finalizing analysis.
const bool IgnoreThreshold;
// True if the cost-benefit-analysis-based inliner is enabled.
const bool CostBenefitAnalysisEnabled;
/// Inlining cost measured in abstract units, accounts for all the
/// instructions expected to be executed for a given function invocation.
/// Instructions that are statically proven to be dead based on call-site
/// arguments are not counted here.
int Cost = 0;
// The cumulative cost at the beginning of the basic block being analyzed. At
// the end of analyzing each basic block, "Cost - CostAtBBStart" represents
// the size of that basic block.
int CostAtBBStart = 0;
// The static size of live but cold basic blocks. This is "static" in the
// sense that it's not weighted by profile counts at all.
int ColdSize = 0;
// Whether inlining is decided by cost-benefit analysis.
bool DecidedByCostBenefit = false;
// The cost-benefit pair computed by cost-benefit analysis.
Optional<CostBenefitPair> CostBenefit = None;
bool SingleBB = true;
unsigned SROACostSavings = 0;
unsigned SROACostSavingsLost = 0;
/// 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<AllocaInst *, int> SROAArgCosts;
/// Return true if \p Call is a cold callsite.
bool isColdCallSite(CallBase &Call, BlockFrequencyInfo *CallerBFI);
/// 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(CallBase &Call, Function &Callee);
/// Return a higher threshold if \p Call is a hot callsite.
Optional<int> getHotCallSiteThreshold(CallBase &Call,
BlockFrequencyInfo *CallerBFI);
/// Handle a capped 'int' increment for Cost.
void addCost(int64_t Inc, int64_t UpperBound = INT_MAX) {
assert(UpperBound > 0 && UpperBound <= INT_MAX && "invalid upper bound");
Cost = std::min<int>(UpperBound, Cost + Inc);
}
void onDisableSROA(AllocaInst *Arg) override {
auto CostIt = SROAArgCosts.find(Arg);
if (CostIt == SROAArgCosts.end())
return;
addCost(CostIt->second);
SROACostSavings -= CostIt->second;
SROACostSavingsLost += CostIt->second;
SROAArgCosts.erase(CostIt);
}
void onDisableLoadElimination() override {
addCost(LoadEliminationCost);
LoadEliminationCost = 0;
}
void onCallPenalty() override { addCost(CallPenalty); }
void onCallArgumentSetup(const CallBase &Call) override {
// Pay the price of the argument setup. We account for the average 1
// instruction per call argument setup here.
addCost(Call.arg_size() * InlineConstants::InstrCost);
}
void onLoadRelativeIntrinsic() override {
// This is normally lowered to 4 LLVM instructions.
addCost(3 * InlineConstants::InstrCost);
}
void onLoweredCall(Function *F, CallBase &Call,
bool IsIndirectCall) override {
// We account for the average 1 instruction per call argument setup here.
addCost(Call.arg_size() * InlineConstants::InstrCost);
// 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.
if (IsIndirectCall && BoostIndirectCalls) {
auto IndirectCallParams = Params;
IndirectCallParams.DefaultThreshold =
InlineConstants::IndirectCallThreshold;
/// FIXME: if InlineCostCallAnalyzer is derived from, this may need
/// to instantiate the derived class.
InlineCostCallAnalyzer CA(*F, Call, IndirectCallParams, TTI,
GetAssumptionCache, GetBFI, PSI, ORE, false);
if (CA.analyze().isSuccess()) {
// 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());
}
} else
// Otherwise simply add the cost for merely making the call.
addCost(CallPenalty);
}
void onFinalizeSwitch(unsigned JumpTableSize,
unsigned NumCaseCluster) override {
// If suitable for a jump table, consider the cost for the table size and
// branch to destination.
// Maximum valid cost increased in this function.
if (JumpTableSize) {
int64_t JTCost =
static_cast<int64_t>(JumpTableSize) * InlineConstants::InstrCost +
4 * InlineConstants::InstrCost;
addCost(JTCost, static_cast<int64_t>(CostUpperBound));
return;
}
if (NumCaseCluster <= 3) {
// Suppose a comparison includes one compare and one conditional branch.
addCost(NumCaseCluster * 2 * InlineConstants::InstrCost);
return;
}
int64_t ExpectedNumberOfCompare =
getExpectedNumberOfCompare(NumCaseCluster);
int64_t SwitchCost =
ExpectedNumberOfCompare * 2 * InlineConstants::InstrCost;
addCost(SwitchCost, static_cast<int64_t>(CostUpperBound));
}
void onMissedSimplification() override {
addCost(InlineConstants::InstrCost);
}
void onInitializeSROAArg(AllocaInst *Arg) override {
assert(Arg != nullptr &&
"Should not initialize SROA costs for null value.");
SROAArgCosts[Arg] = 0;
}
void onAggregateSROAUse(AllocaInst *SROAArg) override {
auto CostIt = SROAArgCosts.find(SROAArg);
assert(CostIt != SROAArgCosts.end() &&
"expected this argument to have a cost");
CostIt->second += InlineConstants::InstrCost;
SROACostSavings += InlineConstants::InstrCost;
}
void onBlockStart(const BasicBlock *BB) override { CostAtBBStart = Cost; }
void onBlockAnalyzed(const BasicBlock *BB) override {
if (CostBenefitAnalysisEnabled) {
// Keep track of the static size of live but cold basic blocks. For now,
// we define a cold basic block to be one that's never executed.
assert(GetBFI && "GetBFI must be available");
BlockFrequencyInfo *BFI = &(GetBFI(F));
assert(BFI && "BFI must be available");
auto ProfileCount = BFI->getBlockProfileCount(BB);
assert(ProfileCount.hasValue());
if (ProfileCount.getValue() == 0)
ColdSize += Cost - CostAtBBStart;
}
auto *TI = BB->getTerminator();
// 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;
}
}
void onInstructionAnalysisStart(const Instruction *I) override {
// This function is called to store the initial cost of inlining before
// the given instruction was assessed.
if (!PrintInstructionComments)
return;
InstructionCostDetailMap[I].CostBefore = Cost;
InstructionCostDetailMap[I].ThresholdBefore = Threshold;
}
void onInstructionAnalysisFinish(const Instruction *I) override {
// This function is called to find new values of cost and threshold after
// the instruction has been assessed.
if (!PrintInstructionComments)
return;
InstructionCostDetailMap[I].CostAfter = Cost;
InstructionCostDetailMap[I].ThresholdAfter = Threshold;
}
bool isCostBenefitAnalysisEnabled() {
if (!PSI || !PSI->hasProfileSummary())
return false;
if (!GetBFI)
return false;
if (InlineEnableCostBenefitAnalysis.getNumOccurrences()) {
// Honor the explicit request from the user.
if (!InlineEnableCostBenefitAnalysis)
return false;
} else {
// Otherwise, require instrumentation profile.
if (!PSI->hasInstrumentationProfile())
return false;
}
auto *Caller = CandidateCall.getParent()->getParent();
if (!Caller->getEntryCount())
return false;
BlockFrequencyInfo *CallerBFI = &(GetBFI(*Caller));
if (!CallerBFI)
return false;
// For now, limit to hot call site.
if (!PSI->isHotCallSite(CandidateCall, CallerBFI))
return false;
// Make sure we have a nonzero entry count.
auto EntryCount = F.getEntryCount();
if (!EntryCount || !EntryCount.getCount())
return false;
BlockFrequencyInfo *CalleeBFI = &(GetBFI(F));
if (!CalleeBFI)
return false;
return true;
}
// Determine whether we should inline the given call site, taking into account
// both the size cost and the cycle savings. Return None if we don't have
// suficient profiling information to determine.
Optional<bool> costBenefitAnalysis() {
if (!CostBenefitAnalysisEnabled)
return None;
// buildInlinerPipeline in the pass builder sets HotCallSiteThreshold to 0
// for the prelink phase of the AutoFDO + ThinLTO build. Honor the logic by
// falling back to the cost-based metric.
// TODO: Improve this hacky condition.
if (Threshold == 0)
return None;
assert(GetBFI);
BlockFrequencyInfo *CalleeBFI = &(GetBFI(F));
assert(CalleeBFI);
// The cycle savings expressed as the sum of InlineConstants::InstrCost
// multiplied by the estimated dynamic count of each instruction we can
// avoid. Savings come from the call site cost, such as argument setup and
// the call instruction, as well as the instructions that are folded.
//
// We use 128-bit APInt here to avoid potential overflow. This variable
// should stay well below 10^^24 (or 2^^80) in practice. This "worst" case
// assumes that we can avoid or fold a billion instructions, each with a
// profile count of 10^^15 -- roughly the number of cycles for a 24-hour
// period on a 4GHz machine.
APInt CycleSavings(128, 0);
for (auto &BB : F) {
APInt CurrentSavings(128, 0);
for (auto &I : BB) {
if (BranchInst *BI = dyn_cast<BranchInst>(&I)) {
// Count a conditional branch as savings if it becomes unconditional.
if (BI->isConditional() &&
dyn_cast_or_null<ConstantInt>(
SimplifiedValues.lookup(BI->getCondition()))) {
CurrentSavings += InlineConstants::InstrCost;
}
} else if (Value *V = dyn_cast<Value>(&I)) {
// Count an instruction as savings if we can fold it.
if (SimplifiedValues.count(V)) {
CurrentSavings += InlineConstants::InstrCost;
}
}
}
auto ProfileCount = CalleeBFI->getBlockProfileCount(&BB);
assert(ProfileCount.hasValue());
CurrentSavings *= ProfileCount.getValue();
CycleSavings += CurrentSavings;
}
// Compute the cycle savings per call.
auto EntryProfileCount = F.getEntryCount();
assert(EntryProfileCount.hasValue() && EntryProfileCount.getCount());
auto EntryCount = EntryProfileCount.getCount();
CycleSavings += EntryCount / 2;
CycleSavings = CycleSavings.udiv(EntryCount);
// Compute the total savings for the call site.
auto *CallerBB = CandidateCall.getParent();
BlockFrequencyInfo *CallerBFI = &(GetBFI(*(CallerBB->getParent())));
CycleSavings += getCallsiteCost(this->CandidateCall, DL);
CycleSavings *= CallerBFI->getBlockProfileCount(CallerBB).getValue();
// Remove the cost of the cold basic blocks.
int Size = Cost - ColdSize;
// Allow tiny callees to be inlined regardless of whether they meet the
// savings threshold.
Size = Size > InlineSizeAllowance ? Size - InlineSizeAllowance : 1;
CostBenefit.emplace(APInt(128, Size), CycleSavings);
// Return true if the savings justify the cost of inlining. Specifically,
// we evaluate the following inequality:
//
// CycleSavings PSI->getOrCompHotCountThreshold()
// -------------- >= -----------------------------------
// Size InlineSavingsMultiplier
//
// Note that the left hand side is specific to a call site. The right hand
// side is a constant for the entire executable.
APInt LHS = CycleSavings;
LHS *= InlineSavingsMultiplier;
APInt RHS(128, PSI->getOrCompHotCountThreshold());
RHS *= Size;
return LHS.uge(RHS);
}
InlineResult finalizeAnalysis() override {
// 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).
auto *Caller = CandidateCall.getFunction();
if (Caller->hasMinSize()) {
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++;
}
addCost(NumLoops * InlineConstants::LoopPenalty);
}
// 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;
if (auto Result = costBenefitAnalysis()) {
DecidedByCostBenefit = true;
if (Result.getValue())
return InlineResult::success();
else
return InlineResult::failure("Cost over threshold.");
}
if (IgnoreThreshold || Cost < std::max(1, Threshold))
return InlineResult::success();
return InlineResult::failure("Cost over threshold.");
}
bool shouldStop() override {
// Bail out the moment we cross the threshold. This means we'll under-count
// the cost, but only when undercounting doesn't matter.
return !IgnoreThreshold && Cost >= Threshold && !ComputeFullInlineCost;
}
void onLoadEliminationOpportunity() override {
LoadEliminationCost += InlineConstants::InstrCost;
}
InlineResult onAnalysisStart() override {
// 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(CandidateCall, F);
// While Threshold depends on commandline options that can take negative
// values, we want to enforce the invariant that the computed threshold and
// bonuses are non-negative.
assert(Threshold >= 0);
assert(SingleBBBonus >= 0);
assert(VectorBonus >= 0);
// 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.
addCost(-getCallsiteCost(this->CandidateCall, 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 InlineResult::failure("high cost");
return InlineResult::success();
}
public:
InlineCostCallAnalyzer(
Function &Callee, CallBase &Call, const InlineParams &Params,
const TargetTransformInfo &TTI,
function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
function_ref<BlockFrequencyInfo &(Function &)> GetBFI = nullptr,
ProfileSummaryInfo *PSI = nullptr,
OptimizationRemarkEmitter *ORE = nullptr, bool BoostIndirect = true,
bool IgnoreThreshold = false)
: CallAnalyzer(Callee, Call, TTI, GetAssumptionCache, GetBFI, PSI, ORE),
ComputeFullInlineCost(OptComputeFullInlineCost ||
Params.ComputeFullInlineCost || ORE ||
isCostBenefitAnalysisEnabled()),
Params(Params), Threshold(Params.DefaultThreshold),
BoostIndirectCalls(BoostIndirect), IgnoreThreshold(IgnoreThreshold),
CostBenefitAnalysisEnabled(isCostBenefitAnalysisEnabled()),
Writer(this) {}
/// Annotation Writer for instruction details
InlineCostAnnotationWriter Writer;
void dump();
// Prints the same analysis as dump(), but its definition is not dependent
// on the build.
void print();
Optional<InstructionCostDetail> getCostDetails(const Instruction *I) {
if (InstructionCostDetailMap.find(I) != InstructionCostDetailMap.end())
return InstructionCostDetailMap[I];
return None;
}
virtual ~InlineCostCallAnalyzer() {}
int getThreshold() const { return Threshold; }
int getCost() const { return Cost; }
Optional<CostBenefitPair> getCostBenefitPair() { return CostBenefit; }
bool wasDecidedByCostBenefit() const { return DecidedByCostBenefit; }
};
class InlineCostFeaturesAnalyzer final : public CallAnalyzer {
private:
InlineCostFeatures Cost = {};
// FIXME: These constants are taken from the heuristic-based cost visitor.
// These should be removed entirely in a later revision to avoid reliance on
// heuristics in the ML inliner.
static constexpr int JTCostMultiplier = 4;
static constexpr int CaseClusterCostMultiplier = 2;
static constexpr int SwitchCostMultiplier = 2;
// FIXME: These are taken from the heuristic-based cost visitor: we should
// eventually abstract these to the CallAnalyzer to avoid duplication.
unsigned SROACostSavingOpportunities = 0;
int VectorBonus = 0;
int SingleBBBonus = 0;
int Threshold = 5;
DenseMap<AllocaInst *, unsigned> SROACosts;
void increment(InlineCostFeatureIndex Feature, int64_t Delta = 1) {
Cost[static_cast<size_t>(Feature)] += Delta;
}
void set(InlineCostFeatureIndex Feature, int64_t Value) {
Cost[static_cast<size_t>(Feature)] = Value;
}
void onDisableSROA(AllocaInst *Arg) override {
auto CostIt = SROACosts.find(Arg);
if (CostIt == SROACosts.end())
return;
increment(InlineCostFeatureIndex::SROALosses, CostIt->second);
SROACostSavingOpportunities -= CostIt->second;
SROACosts.erase(CostIt);
}
void onDisableLoadElimination() override {
set(InlineCostFeatureIndex::LoadElimination, 1);
}
void onCallPenalty() override {
increment(InlineCostFeatureIndex::CallPenalty, CallPenalty);
}
void onCallArgumentSetup(const CallBase &Call) override {
increment(InlineCostFeatureIndex::CallArgumentSetup,
Call.arg_size() * InlineConstants::InstrCost);
}
void onLoadRelativeIntrinsic() override {
increment(InlineCostFeatureIndex::LoadRelativeIntrinsic,
3 * InlineConstants::InstrCost);
}
void onLoweredCall(Function *F, CallBase &Call,
bool IsIndirectCall) override {
increment(InlineCostFeatureIndex::LoweredCallArgSetup,
Call.arg_size() * InlineConstants::InstrCost);
if (IsIndirectCall) {
InlineParams IndirectCallParams = {/* DefaultThreshold*/ 0,
/*HintThreshold*/ {},
/*ColdThreshold*/ {},
/*OptSizeThreshold*/ {},
/*OptMinSizeThreshold*/ {},
/*HotCallSiteThreshold*/ {},
/*LocallyHotCallSiteThreshold*/ {},
/*ColdCallSiteThreshold*/ {},
/*ComputeFullInlineCost*/ true,
/*EnableDeferral*/ true};
IndirectCallParams.DefaultThreshold =
InlineConstants::IndirectCallThreshold;
InlineCostCallAnalyzer CA(*F, Call, IndirectCallParams, TTI,
GetAssumptionCache, GetBFI, PSI, ORE, false,
true);
if (CA.analyze().isSuccess()) {
increment(InlineCostFeatureIndex::NestedInlineCostEstimate,
CA.getCost());
increment(InlineCostFeatureIndex::NestedInlines, 1);
}
} else {
onCallPenalty();
}
}
void onFinalizeSwitch(unsigned JumpTableSize,
unsigned NumCaseCluster) override {
if (JumpTableSize) {
int64_t JTCost =
static_cast<int64_t>(JumpTableSize) * InlineConstants::InstrCost +
JTCostMultiplier * InlineConstants::InstrCost;
increment(InlineCostFeatureIndex::JumpTablePenalty, JTCost);
return;
}
if (NumCaseCluster <= 3) {
increment(InlineCostFeatureIndex::CaseClusterPenalty,
NumCaseCluster * CaseClusterCostMultiplier *
InlineConstants::InstrCost);
return;
}
int64_t ExpectedNumberOfCompare =
getExpectedNumberOfCompare(NumCaseCluster);
int64_t SwitchCost = ExpectedNumberOfCompare * SwitchCostMultiplier *
InlineConstants::InstrCost;
increment(InlineCostFeatureIndex::SwitchPenalty, SwitchCost);
}
void onMissedSimplification() override {
increment(InlineCostFeatureIndex::UnsimplifiedCommonInstructions,
InlineConstants::InstrCost);
}
void onInitializeSROAArg(AllocaInst *Arg) override { SROACosts[Arg] = 0; }
void onAggregateSROAUse(AllocaInst *Arg) override {
SROACosts.find(Arg)->second += InlineConstants::InstrCost;
SROACostSavingOpportunities += InlineConstants::InstrCost;
}
void onBlockAnalyzed(const BasicBlock *BB) override {
if (BB->getTerminator()->getNumSuccessors() > 1)
set(InlineCostFeatureIndex::IsMultipleBlocks, 1);
Threshold -= SingleBBBonus;
}
InlineResult finalizeAnalysis() override {
auto *Caller = CandidateCall.getFunction();
if (Caller->hasMinSize()) {
DominatorTree DT(F);
LoopInfo LI(DT);
for (Loop *L : LI) {
// Ignore loops that will not be executed
if (DeadBlocks.count(L->getHeader()))
continue;
increment(InlineCostFeatureIndex::NumLoops,
InlineConstants::LoopPenalty);
}
}
set(InlineCostFeatureIndex::DeadBlocks, DeadBlocks.size());
set(InlineCostFeatureIndex::SimplifiedInstructions,
NumInstructionsSimplified);
set(InlineCostFeatureIndex::ConstantArgs, NumConstantArgs);
set(InlineCostFeatureIndex::ConstantOffsetPtrArgs,
NumConstantOffsetPtrArgs);
set(InlineCostFeatureIndex::SROASavings, SROACostSavingOpportunities);
if (NumVectorInstructions <= NumInstructions / 10)
Threshold -= VectorBonus;
else if (NumVectorInstructions <= NumInstructions / 2)
Threshold -= VectorBonus / 2;
set(InlineCostFeatureIndex::Threshold, Threshold);
return InlineResult::success();
}
bool shouldStop() override { return false; }
void onLoadEliminationOpportunity() override {
increment(InlineCostFeatureIndex::LoadElimination, 1);
}
InlineResult onAnalysisStart() override {
increment(InlineCostFeatureIndex::CallSiteCost,
-1 * getCallsiteCost(this->CandidateCall, DL));
set(InlineCostFeatureIndex::ColdCcPenalty,
(F.getCallingConv() == CallingConv::Cold));
// FIXME: we shouldn't repeat this logic in both the Features and Cost
// analyzer - instead, we should abstract it to a common method in the
// CallAnalyzer
int SingleBBBonusPercent = 50;
int VectorBonusPercent = TTI.getInlinerVectorBonusPercent();
Threshold += TTI.adjustInliningThreshold(&CandidateCall);
Threshold *= TTI.getInliningThresholdMultiplier();
SingleBBBonus = Threshold * SingleBBBonusPercent / 100;
VectorBonus = Threshold * VectorBonusPercent / 100;
Threshold += (SingleBBBonus + VectorBonus);
return InlineResult::success();
}
public:
InlineCostFeaturesAnalyzer(
const TargetTransformInfo &TTI,
function_ref<AssumptionCache &(Function &)> &GetAssumptionCache,
function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE, Function &Callee,
CallBase &Call)
: CallAnalyzer(Callee, Call, TTI, GetAssumptionCache, GetBFI, PSI) {}
const InlineCostFeatures &features() const { return Cost; }
};
} // namespace
/// Test whether the given value is an Alloca-derived function argument.
bool CallAnalyzer::isAllocaDerivedArg(Value *V) {
return SROAArgValues.count(V);
}
void CallAnalyzer::disableSROAForArg(AllocaInst *SROAArg) {
onDisableSROA(SROAArg);
EnabledSROAAllocas.erase(SROAArg);
disableLoadElimination();
}
void InlineCostAnnotationWriter::emitInstructionAnnot(
const Instruction *I, formatted_raw_ostream &OS) {
// The cost of inlining of the given instruction is printed always.
// The threshold delta is printed only when it is non-zero. It happens
// when we decided to give a bonus at a particular instruction.
Optional<InstructionCostDetail> Record = ICCA->getCostDetails(I);
if (!Record)
OS << "; No analysis for the instruction";
else {
OS << "; cost before = " << Record->CostBefore
<< ", cost after = " << Record->CostAfter
<< ", threshold before = " << Record->ThresholdBefore
<< ", threshold after = " << Record->ThresholdAfter << ", ";
OS << "cost delta = " << Record->getCostDelta();
if (Record->hasThresholdChanged())
OS << ", threshold delta = " << Record->getThresholdDelta();
}
auto C = ICCA->getSimplifiedValue(const_cast<Instruction *>(I));
if (C) {
OS << ", simplified to ";
C.getValue()->print(OS, true);
}
OS << "\n";
}
/// If 'V' maps to a SROA candidate, disable SROA for it.
void CallAnalyzer::disableSROA(Value *V) {
if (auto *SROAArg = getSROAArgForValueOrNull(V)) {
disableSROAForArg(SROAArg);
}
}
void CallAnalyzer::disableLoadElimination() {
if (EnableLoadElimination) {
onDisableLoadElimination();
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 (const Use &Op : GEP.indices())
if (Constant *SimpleOp = SimplifiedValues.lookup(Op))
Operands.push_back(SimpleOp);
else
Operands.push_back(Op);
return TTI.getUserCost(&GEP, Operands,
TargetTransformInfo::TCK_SizeAndLatency) ==
TargetTransformInfo::TCC_Free;
}
bool CallAnalyzer::visitAlloca(AllocaInst &I) {
disableSROA(I.getOperand(0));
// 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)) {
// Sometimes a dynamic alloca could be converted into a static alloca
// after this constant prop, and become a huge static alloca on an
// unconditional CFG path. Avoid inlining if this is going to happen above
// a threshold.
// FIXME: If the threshold is removed or lowered too much, we could end up
// being too pessimistic and prevent inlining non-problematic code. This
// could result in unintended perf regressions. A better overall strategy
// is needed to track stack usage during inlining.
Type *Ty = I.getAllocatedType();
AllocatedSize = SaturatingMultiplyAdd(
AllocSize->getLimitedValue(),
DL.getTypeAllocSize(Ty).getKnownMinSize(), AllocatedSize);
if (AllocatedSize > InlineConstants::MaxSimplifiedDynamicAllocaToInline)
HasDynamicAlloca = true;
return false;
}
}
// Accumulate the allocated size.
if (I.isStaticAlloca()) {
Type *Ty = I.getAllocatedType();
AllocatedSize =
SaturatingAdd(DL.getTypeAllocSize(Ty).getKnownMinSize(), AllocatedSize);
}
// 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.
if (!I.isStaticAlloca())
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;
if (auto *SROAArg = getSROAArgForValueOrNull(FirstV))
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) {
auto *SROAArg = getSROAArgForValueOrNull(I.getPointerOperand());
// Lambda to check whether a GEP's indices are all constant.
auto IsGEPOffsetConstant = [&](GetElementPtrInst &GEP) {
for (const Use &Op : GEP.indices())
if (!isa<Constant>(Op) && !SimplifiedValues.lookup(Op))
return false;
return true;
};
if (!DisableGEPConstOperand)
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
SmallVector<Constant *, 2> Indices;
for (unsigned int Index = 1; Index < COps.size(); ++Index)
Indices.push_back(COps[Index]);
return ConstantExpr::getGetElementPtr(
I.getSourceElementType(), COps[0], Indices, I.isInBounds());
}))
return true;
if ((I.isInBounds() && canFoldInboundsGEP(I)) || IsGEPOffsetConstant(I)) {
if (SROAArg)
SROAArgValues[&I] = SROAArg;
// Constant GEPs are modeled as free.
return true;
}
// Variable GEPs will require math and will disable SROA.
if (SROAArg)
disableSROAForArg(SROAArg);
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.
if (auto *SROAArg = getSROAArgForValueOrNull(I.getOperand(0)))
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.
if (auto *SROAArg = getSROAArgForValueOrNull(I.getOperand(0)))
SROAArgValues[&I] = SROAArg;
return TTI.getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency) ==
TargetTransformInfo::TCC_Free;
}
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.
if (auto *SROAArg = getSROAArgForValueOrNull(Op))
SROAArgValues[&I] = SROAArg;
return TTI.getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency) ==
TargetTransformInfo::TCC_Free;
}
bool CallAnalyzer::visitCastInst(CastInst &I) {
// Propagate constants through casts.
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 explicitly list
// 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)
onCallPenalty();
break;
default:
break;
}
return TTI.getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency) ==
TargetTransformInfo::TCC_Free;
}
bool CallAnalyzer::paramHasAttr(Argument *A, Attribute::AttrKind Attr) {
return CandidateCall.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(CallBase &Call) {
// 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().
if (InvokeInst *II = dyn_cast<InvokeInst>(&Call)) {
if (isa<UnreachableInst>(II->getNormalDest()->getTerminator()))
return false;
} else if (isa<UnreachableInst>(Call.getParent()->getTerminator()))
return false;
return true;
}
bool InlineCostCallAnalyzer::isColdCallSite(CallBase &Call,
BlockFrequencyInfo *CallerBFI) {
// If global profile summary is available, then callsite's coldness is
// determined based on that.
if (PSI && PSI->hasProfileSummary())
return PSI->isColdCallSite(Call, 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 = Call.getParent();
auto CallSiteFreq = CallerBFI->getBlockFreq(CallSiteBB);
auto CallerEntryFreq =
CallerBFI->getBlockFreq(&(Call.getCaller()->getEntryBlock()));
return CallSiteFreq < CallerEntryFreq * ColdProb;
}
Optional<int>
InlineCostCallAnalyzer::getHotCallSiteThreshold(CallBase &Call,
BlockFrequencyInfo *CallerBFI) {
// If global profile summary is available, then callsite's hotness is
// determined based on that.
if (PSI && PSI->hasProfileSummary() && PSI->isHotCallSite(Call, 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 = Call.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 InlineCostCallAnalyzer::updateThreshold(CallBase &Call, Function &Callee) {
// If no size growth is allowed for this inlining, set Threshold to 0.
if (!allowSizeGrowth(Call)) {
Threshold = 0;
return;
}
Function *Caller = Call.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.
//
// 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 = TTI.getInlinerVectorBonusPercent();
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->hasMinSize()) {
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->hasOptSize())
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->hasMinSize()) {
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(Call, CallerBFI);
if (!Caller->hasOptSize() && 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(Call, 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);
}
}
}
Threshold += TTI.adjustInliningThreshold(&Call);
// 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 == Call.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;
}
return handleSROA(I.getOperand(0), isa<ConstantPointerNull>(I.getOperand(1)));
}
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 = SimplifyBinOp(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. Unless it's fneg which can be implemented with an xor.
using namespace llvm::PatternMatch;
if (I.getType()->isFloatingPointTy() &&
TTI.getFPOpCost(I.getType()) == TargetTransformInfo::TCC_Expensive &&
!match(&I, m_FNeg(m_Value())))
onCallPenalty();
return false;
}
bool CallAnalyzer::visitFNeg(UnaryOperator &I) {
Value *Op = I.getOperand(0);
Constant *COp = dyn_cast<Constant>(Op);
if (!COp)
COp = SimplifiedValues.lookup(Op);
Value *SimpleV = SimplifyFNegInst(
COp ? COp : Op, cast<FPMathOperator>(I).getFastMathFlags(), 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 fneg.
disableSROA(Op);
return false;
}
bool CallAnalyzer::visitLoad(LoadInst &I) {
if (handleSROA(I.getPointerOperand(), I.isSimple()))
return true;
// 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()) {
onLoadEliminationOpportunity();
return true;
}
return false;
}
bool CallAnalyzer::visitStore(StoreInst &I) {
if (handleSROA(I.getPointerOperand(), I.isSimple()))
return true;
// 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't look through these, but they may be free.
return Base::visitExtractValue(I);
}
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't look through these, but they may be free.
return Base::visitInsertValue(I);
}
/// 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, CallBase &Call) {
// 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(&Call, F))
return false;
// Try to re-map the arguments to constants.
SmallVector<Constant *, 4> ConstantArgs;
ConstantArgs.reserve(Call.arg_size());
for (Value *I : Call.args()) {
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(&Call, F, ConstantArgs)) {
SimplifiedValues[&Call] = C;
return true;
}
return false;
}
bool CallAnalyzer::visitCallBase(CallBase &Call) {
if (Call.hasFnAttr(Attribute::ReturnsTwice) &&
!F.hasFnAttribute(Attribute::ReturnsTwice)) {
// This aborts the entire analysis.
ExposesReturnsTwice = true;
return false;
}
if (isa<CallInst>(Call) && cast<CallInst>(Call).cannotDuplicate())
ContainsNoDuplicateCall = true;
Value *Callee = Call.getCalledOperand();
Function *F = dyn_cast_or_null<Function>(Callee);
bool IsIndirectCall = !F;
if (IsIndirectCall) {
// 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.
F = dyn_cast_or_null<Function>(SimplifiedValues.lookup(Callee));
if (!F) {
onCallArgumentSetup(Call);
if (!Call.onlyReadsMemory())
disableLoadElimination();
return Base::visitCallBase(Call);
}
}
assert(F && "Expected a call to a known function");
// When we have a concrete function, first try to simplify it directly.
if (simplifyCallSite(F, Call))
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>(&Call)) {
switch (II->getIntrinsicID()) {
default:
if (!Call.onlyReadsMemory() && !isAssumeLikeIntrinsic(II))
disableLoadElimination();
return Base::visitCallBase(Call);
case Intrinsic::load_relative:
onLoadRelativeIntrinsic();
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;
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group:
if (auto *SROAArg = getSROAArgForValueOrNull(II->getOperand(0)))
SROAArgValues[II] = SROAArg;
return true;
}
}
if (F == Call.getFunction()) {
// This flag will fully abort the analysis, so don't bother with anything
// else.
IsRecursiveCall = true;
return false;
}
if (TTI.isLoweredToCall(F)) {
onLoweredCall(F, Call, IsIndirectCall);
}
if (!(Call.onlyReadsMemory() || (IsIndirectCall && F->onlyReadsMemory())))
disableLoadElimination();
return Base::visitCallBase(Call);
}
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;
if (auto *SROAArg = getSROAArgForValueOrNull(TrueVal))
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;
if (auto *SROAArg = getSROAArgForValueOrNull(SelectedV))
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 simplifycfg, so this shouldn't prevent
// inlining those. It will prevent inlining in cases where the optimization
// does not (yet) fire.
unsigned JumpTableSize = 0;
BlockFrequencyInfo *BFI = GetBFI ? &(GetBFI(F)) : nullptr;
unsigned NumCaseCluster =
TTI.getEstimatedNumberOfCaseClusters(SI, JumpTableSize, PSI, BFI);
onFinalizeSwitch(JumpTableSize, NumCaseCluster);
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 (TTI.getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency) ==
TargetTransformInfo::TCC_Free)
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 (const Use &Op : I.operands())
disableSROA(Op);
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 (Instruction &I : *BB) {
// 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 pseudo-probes.
if (isa<PseudoProbeInst>(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.
onInstructionAnalysisStart(&I);
if (Base::visit(&I))
++NumInstructionsSimplified;
else
onMissedSimplification();
onInstructionAnalysisFinish(&I);
using namespace ore;
// If the visit this instruction detected an uninlinable pattern, abort.
InlineResult IR = InlineResult::success();
if (IsRecursiveCall)
IR = InlineResult::failure("recursive");
else if (ExposesReturnsTwice)
IR = InlineResult::failure("exposes returns twice");
else if (HasDynamicAlloca)
IR = InlineResult::failure("dynamic alloca");
else if (HasIndirectBr)
IR = InlineResult::failure("indirect branch");
else if (HasUninlineableIntrinsic)
IR = InlineResult::failure("uninlinable intrinsic");
else if (InitsVargArgs)
IR = InlineResult::failure("varargs");
if (!IR.isSuccess()) {
if (ORE)
ORE->emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "NeverInline",
&CandidateCall)
<< NV("Callee", &F) << " has uninlinable pattern ("
<< NV("InlineResult", IR.getFailureReason())
<< ") 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) {
auto IR =
InlineResult::failure("recursive and allocates too much stack space");
if (ORE)
ORE->emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "NeverInline",
&CandidateCall)
<< NV("Callee", &F) << " is "
<< NV("InlineResult", IR.getFailureReason())
<< ". Cost is not fully computed";
});
return IR;
}
if (shouldStop())
return InlineResult::failure(
"Call site analysis is not favorable to inlining.");
}
return InlineResult::success();
}
/// 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 *IdxPtrTy = DL.getIndexType(V->getType());
return cast<ConstantInt>(ConstantInt::get(IdxPtrTy, 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 predecessor 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::analyze() {
++NumCallsAnalyzed;
auto Result = onAnalysisStart();
if (!Result.isSuccess())
return Result;
if (F.empty())
return InlineResult::success();
Function *Caller = CandidateCall.getFunction();
// Check if the caller function is recursive itself.
for (User *U : Caller->users()) {
CallBase *Call = dyn_cast<CallBase>(U);
if (Call && Call->getFunction() == Caller) {
IsCallerRecursive = true;
break;
}
}
// Populate our simplified values by mapping from function arguments to call
// arguments with known important simplifications.
auto CAI = CandidateCall.arg_begin();
for (Argument &FAI : F.args()) {
assert(CAI != CandidateCall.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 (auto *SROAArg = dyn_cast<AllocaInst>(PtrArg)) {
SROAArgValues[&FAI] = SROAArg;
onInitializeSROAArg(SROAArg);
EnabledSROAAllocas.insert(SROAArg);
}
}
++CAI;
}
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());
// Note that we *must not* cache the size, this loop grows the worklist.
for (unsigned Idx = 0; Idx != BBWorklist.size(); ++Idx) {
if (shouldStop())
break;
BasicBlock *BB = BBWorklist[Idx];
if (BB->empty())
continue;
onBlockStart(BB);
// Disallow inlining a blockaddress with uses other than strictly callbr.
// 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.
// FIXME: pr/39560: continue relaxing this overt restriction.
if (BB->hasAddressTaken())
for (User *U : BlockAddress::get(&*BB)->users())
if (!isa<CallBrInst>(*U))
return InlineResult::failure("blockaddress used outside of callbr");
// 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.isSuccess())
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));
onBlockAnalyzed(BB);
}
bool OnlyOneCallAndLocalLinkage = F.hasLocalLinkage() && F.hasOneUse() &&
&F == CandidateCall.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 InlineResult::failure("noduplicate");
return finalizeAnalysis();
}
void InlineCostCallAnalyzer::print() {
#define DEBUG_PRINT_STAT(x) dbgs() << " " #x ": " << x << "\n"
if (PrintInstructionComments)
F.print(dbgs(), &Writer);
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
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// Dump stats about this call's analysis.
LLVM_DUMP_METHOD void InlineCostCallAnalyzer::dump() { print(); }
#endif
/// Test that there are no attribute conflicts between Caller and Callee
/// that prevent inlining.
static bool functionsHaveCompatibleAttributes(
Function *Caller, Function *Callee, TargetTransformInfo &TTI,
function_ref<const TargetLibraryInfo &(Function &)> &GetTLI) {
// Note that CalleeTLI must be a copy not a reference. The legacy pass manager
// caches the most recently created TLI in the TargetLibraryInfoWrapperPass
// object, and always returns the same object (which is overwritten on each
// GetTLI call). Therefore we copy the first result.
auto CalleeTLI = GetTLI(*Callee);
return TTI.areInlineCompatible(Caller, Callee) &&
GetTLI(*Caller).areInlineCompatible(CalleeTLI,
InlineCallerSupersetNoBuiltin) &&
AttributeFuncs::areInlineCompatible(*Caller, *Callee);
}
int llvm::getCallsiteCost(CallBase &Call, const DataLayout &DL) {
int Cost = 0;
for (unsigned I = 0, E = Call.arg_size(); I != E; ++I) {
if (Call.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>(Call.getArgOperand(I)->getType());
unsigned TypeSize = DL.getTypeSizeInBits(Call.getParamByValType(I));
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 + CallPenalty;
return Cost;
}
InlineCost llvm::getInlineCost(
CallBase &Call, const InlineParams &Params, TargetTransformInfo &CalleeTTI,
function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
return getInlineCost(Call, Call.getCalledFunction(), Params, CalleeTTI,
GetAssumptionCache, GetTLI, GetBFI, PSI, ORE);
}
Optional<int> llvm::getInliningCostEstimate(
CallBase &Call, TargetTransformInfo &CalleeTTI,
function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
const InlineParams Params = {/* DefaultThreshold*/ 0,
/*HintThreshold*/ {},
/*ColdThreshold*/ {},
/*OptSizeThreshold*/ {},
/*OptMinSizeThreshold*/ {},
/*HotCallSiteThreshold*/ {},
/*LocallyHotCallSiteThreshold*/ {},
/*ColdCallSiteThreshold*/ {},
/*ComputeFullInlineCost*/ true,
/*EnableDeferral*/ true};
InlineCostCallAnalyzer CA(*Call.getCalledFunction(), Call, Params, CalleeTTI,
GetAssumptionCache, GetBFI, PSI, ORE, true,
/*IgnoreThreshold*/ true);
auto R = CA.analyze();
if (!R.isSuccess())
return None;
return CA.getCost();
}
Optional<InlineCostFeatures> llvm::getInliningCostFeatures(
CallBase &Call, TargetTransformInfo &CalleeTTI,
function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
InlineCostFeaturesAnalyzer CFA(CalleeTTI, GetAssumptionCache, GetBFI, PSI,
ORE, *Call.getCalledFunction(), Call);
auto R = CFA.analyze();
if (!R.isSuccess())
return None;
return CFA.features();
}
Optional<InlineResult> llvm::getAttributeBasedInliningDecision(
CallBase &Call, Function *Callee, TargetTransformInfo &CalleeTTI,
function_ref<const TargetLibraryInfo &(Function &)> GetTLI) {
// Cannot inline indirect calls.
if (!Callee)
return InlineResult::failure("indirect call");
// When callee coroutine function is inlined into caller coroutine function
// before coro-split pass,
// coro-early pass can not handle this quiet well.
// So we won't inline the coroutine function if it have not been unsplited
if (Callee->isPresplitCoroutine())
return InlineResult::failure("unsplited coroutine 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 = Call.arg_size(); I != E; ++I)
if (Call.isByValArgument(I)) {
PointerType *PTy = cast<PointerType>(Call.getArgOperand(I)->getType());
if (PTy->getAddressSpace() != AllocaAS)
return InlineResult::failure("byval arguments without alloca"
" address space");
}
// Calls to functions with always-inline attributes should be inlined
// whenever possible.
if (Call.hasFnAttr(Attribute::AlwaysInline)) {
auto IsViable = isInlineViable(*Callee);
if (IsViable.isSuccess())
return InlineResult::success();
return InlineResult::failure(IsViable.getFailureReason());
}
// Never inline functions with conflicting attributes (unless callee has
// always-inline attribute).
Function *Caller = Call.getCaller();
if (!functionsHaveCompatibleAttributes(Caller, Callee, CalleeTTI, GetTLI))
return InlineResult::failure("conflicting attributes");
// Don't inline this call if the caller has the optnone attribute.
if (Caller->hasOptNone())
return InlineResult::failure("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 InlineResult::failure("nullptr definitions incompatible");
// Don't inline functions which can be interposed at link-time.
if (Callee->isInterposable())
return InlineResult::failure("interposable");
// Don't inline functions marked noinline.
if (Callee->hasFnAttribute(Attribute::NoInline))
return InlineResult::failure("noinline function attribute");
// Don't inline call sites marked noinline.
if (Call.isNoInline())
return InlineResult::failure("noinline call site attribute");
// Don't inline functions if one does not have any stack protector attribute
// but the other does.
if (Caller->hasStackProtectorFnAttr() && !Callee->hasStackProtectorFnAttr())
return InlineResult::failure(
"stack protected caller but callee requested no stack protector");
if (Callee->hasStackProtectorFnAttr() && !Caller->hasStackProtectorFnAttr())
return InlineResult::failure(
"stack protected callee but caller requested no stack protector");
return None;
}
InlineCost llvm::getInlineCost(
CallBase &Call, Function *Callee, const InlineParams &Params,
TargetTransformInfo &CalleeTTI,
function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
function_ref<BlockFrequencyInfo &(Function &)> GetBFI,
ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
auto UserDecision =
llvm::getAttributeBasedInliningDecision(Call, Callee, CalleeTTI, GetTLI);
if (UserDecision.hasValue()) {
if (UserDecision->isSuccess())
return llvm::InlineCost::getAlways("always inline attribute");
return llvm::InlineCost::getNever(UserDecision->getFailureReason());
}
LLVM_DEBUG(llvm::dbgs() << " Analyzing call of " << Callee->getName()
<< "... (caller:" << Call.getCaller()->getName()
<< ")\n");
InlineCostCallAnalyzer CA(*Callee, Call, Params, CalleeTTI,
GetAssumptionCache, GetBFI, PSI, ORE);
InlineResult ShouldInline = CA.analyze();
LLVM_DEBUG(CA.dump());
// Always make cost benefit based decision explicit.
// We use always/never here since threshold is not meaningful,
// as it's not what drives cost-benefit analysis.
if (CA.wasDecidedByCostBenefit()) {
if (ShouldInline.isSuccess())
return InlineCost::getAlways("benefit over cost",
CA.getCostBenefitPair());
else
return InlineCost::getNever("cost over benefit", CA.getCostBenefitPair());
}
// Check if there was a reason to force inlining or no inlining.
if (!ShouldInline.isSuccess() && CA.getCost() < CA.getThreshold())
return InlineCost::getNever(ShouldInline.getFailureReason());
if (ShouldInline.isSuccess() && CA.getCost() >= CA.getThreshold())
return InlineCost::getAlways("empty function");
return llvm::InlineCost::get(CA.getCost(), CA.getThreshold());
}
InlineResult llvm::isInlineViable(Function &F) {
bool ReturnsTwice = F.hasFnAttribute(Attribute::ReturnsTwice);
for (BasicBlock &BB : F) {
// Disallow inlining of functions which contain indirect branches.
if (isa<IndirectBrInst>(BB.getTerminator()))
return InlineResult::failure("contains indirect branches");
// Disallow inlining of blockaddresses which are used by non-callbr
// instructions.
if (BB.hasAddressTaken())
for (User *U : BlockAddress::get(&BB)->users())
if (!isa<CallBrInst>(*U))
return InlineResult::failure("blockaddress used outside of callbr");
for (auto &II : BB) {
CallBase *Call = dyn_cast<CallBase>(&II);
if (!Call)
continue;
// Disallow recursive calls.
Function *Callee = Call->getCalledFunction();
if (&F == Callee)
return InlineResult::failure("recursive call");
// Disallow calls which expose returns-twice to a function not previously
// attributed as such.
if (!ReturnsTwice && isa<CallInst>(Call) &&
cast<CallInst>(Call)->canReturnTwice())
return InlineResult::failure("exposes returns-twice attribute");
if (Callee)
switch (Callee->getIntrinsicID()) {
default:
break;
case llvm::Intrinsic::icall_branch_funnel:
// Disallow inlining of @llvm.icall.branch.funnel because current
// backend can't separate call targets from call arguments.
return InlineResult::failure(
"disallowed inlining of @llvm.icall.branch.funnel");
case llvm::Intrinsic::localescape:
// Disallow inlining functions that call @llvm.localescape. Doing this
// correctly would require major changes to the inliner.
return InlineResult::failure(
"disallowed inlining of @llvm.localescape");
case llvm::Intrinsic::vastart:
// Disallow inlining of functions that initialize VarArgs with
// va_start.
return InlineResult::failure(
"contains VarArgs initialized with va_start");
}
}
}
return InlineResult::success();
}
// 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(DefaultThreshold);
}
// 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 DefaultThreshold;
}
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;
}
PreservedAnalyses
InlineCostAnnotationPrinterPass::run(Function &F,
FunctionAnalysisManager &FAM) {
PrintInstructionComments = true;
std::function<AssumptionCache &(Function &)> GetAssumptionCache =
[&](Function &F) -> AssumptionCache & {
return FAM.getResult<AssumptionAnalysis>(F);
};
Module *M = F.getParent();
ProfileSummaryInfo PSI(*M);
DataLayout DL(M);
TargetTransformInfo TTI(DL);
// FIXME: Redesign the usage of InlineParams to expand the scope of this pass.
// In the current implementation, the type of InlineParams doesn't matter as
// the pass serves only for verification of inliner's decisions.
// We can add a flag which determines InlineParams for this run. Right now,
// the default InlineParams are used.
const InlineParams Params = llvm::getInlineParams();
for (BasicBlock &BB : F) {
for (Instruction &I : BB) {
if (CallInst *CI = dyn_cast<CallInst>(&I)) {
Function *CalledFunction = CI->getCalledFunction();
if (!CalledFunction || CalledFunction->isDeclaration())
continue;
OptimizationRemarkEmitter ORE(CalledFunction);
InlineCostCallAnalyzer ICCA(*CalledFunction, *CI, Params, TTI,
GetAssumptionCache, nullptr, &PSI, &ORE);
ICCA.analyze();
OS << " Analyzing call of " << CalledFunction->getName()
<< "... (caller:" << CI->getCaller()->getName() << ")\n";
ICCA.print();
}
}
}
return PreservedAnalyses::all();
}
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