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Summary: Currently, ICP checks the count against a fixed value to see if it is hot enough to be promoted. This does not work for SamplePGO because sampled count may be much smaller. This patch uses PSI to check if the count is hot enough to be promoted. Reviewers: davidxl, tejohnson, eraman Reviewed By: davidxl Subscribers: sanjoy, llvm-commits, mehdi_amini Differential Revision: https://reviews.llvm.org/D36341 llvm-svn: 310416
109 lines
4.3 KiB
C++
109 lines
4.3 KiB
C++
//===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// 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/IndirectCallSiteVisitor.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/DiagnosticInfo.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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DEBUG(dbgs() << " \nWork on callsite " << *Inst << " Num_targets: " << NumVals
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<< "\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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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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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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