freebsd-nq/contrib/llvm/lib/Analysis/IndirectCallPromotionAnalysis.cpp
2017-06-03 18:18:34 +00:00

110 lines
4.1 KiB
C++

//===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/IndirectCallSiteVisitor.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DiagnosticInfo.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/Debug.h"
#include <string>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "pgo-icall-prom-analysis"
// The minimum call count for the direct-call target to be considered as the
// promotion candidate.
static cl::opt<unsigned>
ICPCountThreshold("icp-count-threshold", cl::Hidden, cl::ZeroOrMore,
cl::init(1000),
cl::desc("The minimum count to the direct call target "
"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>
ICPPercentThreshold("icp-percent-threshold", cl::init(30), cl::Hidden,
cl::ZeroOrMore,
cl::desc("The percentage threshold 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(2), cl::Hidden, cl::ZeroOrMore,
cl::desc("Max number of promotions for a single indirect "
"call callsite"));
ICallPromotionAnalysis::ICallPromotionAnalysis() {
ValueDataArray = llvm::make_unique<InstrProfValueData[]>(MaxNumPromotions);
}
bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
uint64_t TotalCount) {
if (Count < ICPCountThreshold)
return false;
unsigned Percentage = (Count * 100) / TotalCount;
return (Percentage >= ICPPercentThreshold);
}
// 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);
DEBUG(dbgs() << " \nWork on callsite " << *Inst << " Num_targets: " << NumVals
<< "\n");
uint32_t I = 0;
for (; I < MaxNumPromotions && I < NumVals; I++) {
uint64_t Count = ValueDataRef[I].Count;
assert(Count <= TotalCount);
DEBUG(dbgs() << " Candidate " << I << " Count=" << Count
<< " Target_func: " << ValueDataRef[I].Value << "\n");
if (!isPromotionProfitable(Count, TotalCount)) {
DEBUG(dbgs() << " Not promote: Cold target.\n");
return I;
}
TotalCount -= 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);
}