llvm/llvm/lib/Analysis/IndirectCallPromotionAnalysis.cpp

//===-- 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/IR/Instruction.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include <memory>

usingnamespacellvm;

#define DEBUG_TYPE …

// 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::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::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::desc("Max number of promotions for a single indirect "
                              "call callsite"));

cl::opt<unsigned> MaxNumVTableAnnotations(
    "icp-max-num-vtables", cl::init(6), cl::Hidden,
    cl::desc("Max number of vtables annotated for a vtable load instruction."));

bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
                                                   uint64_t TotalCount,
                                                   uint64_t RemainingCount) { … }

// 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, uint64_t TotalCount) { … }

MutableArrayRef<InstrProfValueData>
ICallPromotionAnalysis::getPromotionCandidatesForInstruction(
    const Instruction *I, uint64_t &TotalCount, uint32_t &NumCandidates) { … }