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