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//===- ProfileSummaryInfo.cpp - Global profile summary information --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains a pass that provides access to the global profile summary
// information.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/ProfileSummary.h"
using namespace llvm;
// The following two parameters determine the threshold for a count to be
// considered hot/cold. These two parameters are percentile values (multiplied
// by 10000). If the counts are sorted in descending order, the minimum count to
// reach ProfileSummaryCutoffHot gives the threshold to determine a hot count.
// Similarly, the minimum count to reach ProfileSummaryCutoffCold gives the
// threshold for determining cold count (everything <= this threshold is
// considered cold).
static cl::opt<int> ProfileSummaryCutoffHot(
"profile-summary-cutoff-hot", cl::Hidden, cl::init(999000), cl::ZeroOrMore,
cl::desc("A count is hot if it exceeds the minimum count to"
" reach this percentile of total counts."));
static cl::opt<int> ProfileSummaryCutoffCold(
"profile-summary-cutoff-cold", cl::Hidden, cl::init(999999), cl::ZeroOrMore,
cl::desc("A count is cold if it is below the minimum count"
" to reach this percentile of total counts."));
// Find the minimum count to reach a desired percentile of counts.
static uint64_t getMinCountForPercentile(SummaryEntryVector &DS,
uint64_t Percentile) {
auto Compare = [](const ProfileSummaryEntry &Entry, uint64_t Percentile) {
return Entry.Cutoff < Percentile;
};
auto It = std::lower_bound(DS.begin(), DS.end(), Percentile, Compare);
// The required percentile has to be <= one of the percentiles in the
// detailed summary.
if (It == DS.end())
report_fatal_error("Desired percentile exceeds the maximum cutoff");
return It->MinCount;
}
// The profile summary metadata may be attached either by the frontend or by
// any backend passes (IR level instrumentation, for example). This method
// checks if the Summary is null and if so checks if the summary metadata is now
// available in the module and parses it to get the Summary object.
void ProfileSummaryInfo::computeSummary() {
if (Summary)
return;
auto *SummaryMD = M.getProfileSummary();
if (!SummaryMD)
return;
Summary.reset(ProfileSummary::getFromMD(SummaryMD));
}
/// Returns true if the function's entry is hot. If it returns false, it
/// either means it is not hot or it is unknown whether it is hot or not (for
/// example, no profile data is available).
bool ProfileSummaryInfo::isFunctionEntryHot(const Function *F) {
computeSummary();
if (!F || !Summary)
return false;
auto FunctionCount = F->getEntryCount();
// FIXME: The heuristic used below for determining hotness is based on
// preliminary SPEC tuning for inliner. This will eventually be a
// convenience method that calls isHotCount.
return FunctionCount && isHotCount(FunctionCount.getValue());
}
/// Returns true if the function's entry is a cold. If it returns false, it
/// either means it is not cold or it is unknown whether it is cold or not (for
/// example, no profile data is available).
bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) {
computeSummary();
if (!F)
return false;
if (F->hasFnAttribute(Attribute::Cold)) {
return true;
}
if (!Summary)
return false;
auto FunctionCount = F->getEntryCount();
// FIXME: The heuristic used below for determining coldness is based on
// preliminary SPEC tuning for inliner. This will eventually be a
// convenience method that calls isHotCount.
return FunctionCount && isColdCount(FunctionCount.getValue());
}
/// Compute the hot and cold thresholds.
void ProfileSummaryInfo::computeThresholds() {
if (!Summary)
computeSummary();
if (!Summary)
return;
auto &DetailedSummary = Summary->getDetailedSummary();
HotCountThreshold =
getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
ColdCountThreshold =
getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
}
bool ProfileSummaryInfo::isHotCount(uint64_t C) {
if (!HotCountThreshold)
computeThresholds();
return HotCountThreshold && C >= HotCountThreshold.getValue();
}
bool ProfileSummaryInfo::isColdCount(uint64_t C) {
if (!ColdCountThreshold)
computeThresholds();
return ColdCountThreshold && C <= ColdCountThreshold.getValue();
}
bool ProfileSummaryInfo::isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI) {
auto Count = BFI->getBlockProfileCount(B);
if (Count && isHotCount(*Count))
return true;
// Use extractProfTotalWeight to get BB count.
// For Sample PGO, BFI may not provide accurate BB count due to errors
// magnified during sample count propagation. This serves as a backup plan
// to ensure all hot BB will not be missed.
// The query currently has false positives as branch instruction cloning does
// not update/scale branch weights. Unlike false negatives, this will not cause
// performance problem.
uint64_t TotalCount;
if (B->getTerminator()->extractProfTotalWeight(TotalCount) &&
isHotCount(TotalCount))
return true;
return false;
}
INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
"Profile summary info", false, true)
ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
: ImmutablePass(ID) {
initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
}
bool ProfileSummaryInfoWrapperPass::doInitialization(Module &M) {
PSI.reset(new ProfileSummaryInfo(M));
return false;
}
bool ProfileSummaryInfoWrapperPass::doFinalization(Module &M) {
PSI.reset();
return false;
}
AnalysisKey ProfileSummaryAnalysis::Key;
ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
ModuleAnalysisManager &) {
return ProfileSummaryInfo(M);
}
PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
ModuleAnalysisManager &AM) {
ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
for (auto &F : M) {
OS << F.getName();
if (PSI.isFunctionEntryHot(&F))
OS << " :hot entry ";
else if (PSI.isFunctionEntryCold(&F))
OS << " :cold entry ";
OS << "\n";
}
return PreservedAnalyses::all();
}
char ProfileSummaryInfoWrapperPass::ID = 0;
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