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107 lines
4.3 KiB
C++
107 lines
4.3 KiB
C++
//===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Helper methods for identifying profitable indirect call promotion
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// candidates for an instruction when the indirect-call value profile metadata
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// is available.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/IndirectCallPromotionAnalysis.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Analysis/IndirectCallVisitor.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/InstVisitor.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/ProfileData/InstrProf.h"
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#include "llvm/Support/Debug.h"
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#include <string>
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#include <utility>
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#include <vector>
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using namespace llvm;
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#define DEBUG_TYPE "pgo-icall-prom-analysis"
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// The percent threshold for the direct-call target (this call site vs the
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// remaining call count) for it to be considered as the promotion target.
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static cl::opt<unsigned> ICPRemainingPercentThreshold(
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"icp-remaining-percent-threshold", cl::init(30), cl::Hidden, cl::ZeroOrMore,
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cl::desc("The percentage threshold against remaining unpromoted indirect "
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"call count for the promotion"));
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// The percent threshold for the direct-call target (this call site vs the
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// total call count) for it to be considered as the promotion target.
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static cl::opt<unsigned>
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ICPTotalPercentThreshold("icp-total-percent-threshold", cl::init(5),
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cl::Hidden, cl::ZeroOrMore,
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cl::desc("The percentage threshold against total "
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"count for the promotion"));
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// Set the maximum number of targets to promote for a single indirect-call
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// callsite.
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static cl::opt<unsigned>
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MaxNumPromotions("icp-max-prom", cl::init(3), cl::Hidden, cl::ZeroOrMore,
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cl::desc("Max number of promotions for a single indirect "
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"call callsite"));
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ICallPromotionAnalysis::ICallPromotionAnalysis() {
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ValueDataArray = llvm::make_unique<InstrProfValueData[]>(MaxNumPromotions);
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}
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bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
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uint64_t TotalCount,
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uint64_t RemainingCount) {
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return Count * 100 >= ICPRemainingPercentThreshold * RemainingCount &&
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Count * 100 >= ICPTotalPercentThreshold * TotalCount;
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}
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// Indirect-call promotion heuristic. The direct targets are sorted based on
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// the count. Stop at the first target that is not promoted. Returns the
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// number of candidates deemed profitable.
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uint32_t ICallPromotionAnalysis::getProfitablePromotionCandidates(
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const Instruction *Inst, uint32_t NumVals, uint64_t TotalCount) {
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ArrayRef<InstrProfValueData> ValueDataRef(ValueDataArray.get(), NumVals);
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LLVM_DEBUG(dbgs() << " \nWork on callsite " << *Inst
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<< " Num_targets: " << NumVals << "\n");
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uint32_t I = 0;
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uint64_t RemainingCount = TotalCount;
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for (; I < MaxNumPromotions && I < NumVals; I++) {
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uint64_t Count = ValueDataRef[I].Count;
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assert(Count <= RemainingCount);
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LLVM_DEBUG(dbgs() << " Candidate " << I << " Count=" << Count
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<< " Target_func: " << ValueDataRef[I].Value << "\n");
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if (!isPromotionProfitable(Count, TotalCount, RemainingCount)) {
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LLVM_DEBUG(dbgs() << " Not promote: Cold target.\n");
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return I;
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}
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RemainingCount -= Count;
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}
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return I;
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}
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ArrayRef<InstrProfValueData>
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ICallPromotionAnalysis::getPromotionCandidatesForInstruction(
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const Instruction *I, uint32_t &NumVals, uint64_t &TotalCount,
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uint32_t &NumCandidates) {
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bool Res =
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getValueProfDataFromInst(*I, IPVK_IndirectCallTarget, MaxNumPromotions,
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ValueDataArray.get(), NumVals, TotalCount);
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if (!Res) {
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NumCandidates = 0;
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return ArrayRef<InstrProfValueData>();
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}
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NumCandidates = getProfitablePromotionCandidates(I, NumVals, TotalCount);
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return ArrayRef<InstrProfValueData>(ValueDataArray.get(), NumVals);
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}
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