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//===- SampleProfWriter.h - Write LLVM sample profile data ------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file contains definitions needed for writing sample profiles.
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/IR/ProfileSummary.h"
#include "llvm/ProfileData/SampleProf.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/raw_ostream.h"
#include <cstdint>
#include <memory>
#include <set>
#include <system_error>
namespace llvm {
namespace sampleprof {
enum SectionLayout {
// The layout splits profile with context information from profile without
// context information. When Thinlto is enabled, ThinLTO postlink phase only
// has to load profile with context information and can skip the other part.
/// When writing a profile with size limit, user may want to use a different
/// strategy to reduce function count other than dropping functions with fewest
/// samples first. In this case a class implementing the same interfaces should
/// be provided to SampleProfileWriter::writeWithSizeLimit().
class FunctionPruningStrategy {
SampleProfileMap &ProfileMap;
size_t OutputSizeLimit;
/// \p ProfileMap A reference to the original profile map. It will be modified
/// by Erase().
/// \p OutputSizeLimit Size limit in bytes of the output profile. This is
/// necessary to estimate how many functions to remove.
FunctionPruningStrategy(SampleProfileMap &ProfileMap, size_t OutputSizeLimit)
: ProfileMap(ProfileMap), OutputSizeLimit(OutputSizeLimit) {}
virtual ~FunctionPruningStrategy() = default;
/// SampleProfileWriter::writeWithSizeLimit() calls this after every write
/// iteration if the output size still exceeds the limit. This function
/// should erase some functions from the profile map so that the writer tries
/// to write the profile again with fewer functions. At least 1 entry from the
/// profile map must be erased.
/// \p CurrentOutputSize Number of bytes in the output if current profile map
/// is written.
virtual void Erase(size_t CurrentOutputSize) = 0;
class DefaultFunctionPruningStrategy : public FunctionPruningStrategy {
std::vector<NameFunctionSamples> SortedFunctions;
DefaultFunctionPruningStrategy(SampleProfileMap &ProfileMap,
size_t OutputSizeLimit);
/// In this default implementation, functions with fewest samples are dropped
/// first. Since the exact size of the output cannot be easily calculated due
/// to compression, we use a heuristic to remove as many functions as
/// necessary but not too many, aiming to minimize the number of write
/// iterations.
/// Empirically, functions with larger total sample count contain linearly
/// more sample entries, meaning it takes linearly more space to write them.
/// The cumulative length is therefore quadratic if all functions are sorted
/// by total sample count.
/// TODO: Find better heuristic.
void Erase(size_t CurrentOutputSize) override;
/// Sample-based profile writer. Base class.
class SampleProfileWriter {
virtual ~SampleProfileWriter() = default;
/// Write sample profiles in \p S.
/// \returns status code of the file update operation.
virtual std::error_code writeSample(const FunctionSamples &S) = 0;
/// Write all the sample profiles in the given map of samples.
/// \returns status code of the file update operation.
virtual std::error_code write(const SampleProfileMap &ProfileMap);
/// Write sample profiles up to given size limit, using the pruning strategy
/// to drop some functions if necessary.
/// \returns status code of the file update operation.
template <typename FunctionPruningStrategy = DefaultFunctionPruningStrategy>
std::error_code writeWithSizeLimit(SampleProfileMap &ProfileMap,
size_t OutputSizeLimit) {
FunctionPruningStrategy Strategy(ProfileMap, OutputSizeLimit);
return writeWithSizeLimitInternal(ProfileMap, OutputSizeLimit, &Strategy);
raw_ostream &getOutputStream() { return *OutputStream; }
/// Profile writer factory.
/// Create a new file writer based on the value of \p Format.
static ErrorOr<std::unique_ptr<SampleProfileWriter>>
create(StringRef Filename, SampleProfileFormat Format);
/// Create a new stream writer based on the value of \p Format.
/// For testing.
static ErrorOr<std::unique_ptr<SampleProfileWriter>>
create(std::unique_ptr<raw_ostream> &OS, SampleProfileFormat Format);
virtual void setProfileSymbolList(ProfileSymbolList *PSL) {}
virtual void setToCompressAllSections() {}
virtual void setUseMD5() {}
virtual void setPartialProfile() {}
virtual void resetSecLayout(SectionLayout SL) {}
SampleProfileWriter(std::unique_ptr<raw_ostream> &OS)
: OutputStream(std::move(OS)) {}
/// Write a file header for the profile file.
virtual std::error_code writeHeader(const SampleProfileMap &ProfileMap) = 0;
// Write function profiles to the profile file.
virtual std::error_code writeFuncProfiles(const SampleProfileMap &ProfileMap);
std::error_code writeWithSizeLimitInternal(SampleProfileMap &ProfileMap,
size_t OutputSizeLimit,
FunctionPruningStrategy *Strategy);
/// For writeWithSizeLimit in text mode, each newline takes 1 additional byte
/// on Windows when actually written to the file, but not written to a memory
/// buffer. This needs to be accounted for when rewriting the profile.
size_t LineCount;
/// Output stream where to emit the profile to.
std::unique_ptr<raw_ostream> OutputStream;
/// Profile summary.
std::unique_ptr<ProfileSummary> Summary;
/// Compute summary for this profile.
void computeSummary(const SampleProfileMap &ProfileMap);
/// Profile format.
SampleProfileFormat Format = SPF_None;
/// Sample-based profile writer (text format).
class SampleProfileWriterText : public SampleProfileWriter {
std::error_code writeSample(const FunctionSamples &S) override;
SampleProfileWriterText(std::unique_ptr<raw_ostream> &OS)
: SampleProfileWriter(OS), Indent(0) {}
std::error_code writeHeader(const SampleProfileMap &ProfileMap) override {
LineCount = 0;
return sampleprof_error::success;
/// Indent level to use when writing.
/// This is used when printing inlined callees.
unsigned Indent;
friend ErrorOr<std::unique_ptr<SampleProfileWriter>>
SampleProfileWriter::create(std::unique_ptr<raw_ostream> &OS,
SampleProfileFormat Format);
/// Sample-based profile writer (binary format).
class SampleProfileWriterBinary : public SampleProfileWriter {
SampleProfileWriterBinary(std::unique_ptr<raw_ostream> &OS)
: SampleProfileWriter(OS) {}
std::error_code writeSample(const FunctionSamples &S) override;
virtual MapVector<StringRef, uint32_t> &getNameTable() { return NameTable; }
virtual std::error_code writeMagicIdent(SampleProfileFormat Format);
virtual std::error_code writeNameTable();
std::error_code writeHeader(const SampleProfileMap &ProfileMap) override;
std::error_code writeSummary();
virtual std::error_code writeContextIdx(const SampleContext &Context);
std::error_code writeNameIdx(StringRef FName);
std::error_code writeBody(const FunctionSamples &S);
inline void stablizeNameTable(MapVector<StringRef, uint32_t> &NameTable,
std::set<StringRef> &V);
MapVector<StringRef, uint32_t> NameTable;
void addName(StringRef FName);
virtual void addContext(const SampleContext &Context);
void addNames(const FunctionSamples &S);
friend ErrorOr<std::unique_ptr<SampleProfileWriter>>
SampleProfileWriter::create(std::unique_ptr<raw_ostream> &OS,
SampleProfileFormat Format);
class SampleProfileWriterRawBinary : public SampleProfileWriterBinary {
using SampleProfileWriterBinary::SampleProfileWriterBinary;
const std::array<SmallVector<SecHdrTableEntry, 8>, NumOfLayout>
ExtBinaryHdrLayoutTable = {
// Note that SecFuncOffsetTable section is written after SecLBRProfile
// in the profile, but is put before SecLBRProfile in SectionHdrLayout.
// This is because sample reader follows the order in SectionHdrLayout
// to read each section. To read function profiles on demand, sample
// reader need to get the offset of each function profile first.
// DefaultLayout
SmallVector<SecHdrTableEntry, 8>({{SecProfSummary, 0, 0, 0, 0},
{SecNameTable, 0, 0, 0, 0},
{SecCSNameTable, 0, 0, 0, 0},
{SecFuncOffsetTable, 0, 0, 0, 0},
{SecLBRProfile, 0, 0, 0, 0},
{SecProfileSymbolList, 0, 0, 0, 0},
{SecFuncMetadata, 0, 0, 0, 0}}),
// CtxSplitLayout
SmallVector<SecHdrTableEntry, 8>({{SecProfSummary, 0, 0, 0, 0},
{SecNameTable, 0, 0, 0, 0},
// profile with context
// for next two sections
{SecFuncOffsetTable, 0, 0, 0, 0},
{SecLBRProfile, 0, 0, 0, 0},
// profile without context
// for next two sections
{SecFuncOffsetTable, 0, 0, 0, 0},
{SecLBRProfile, 0, 0, 0, 0},
{SecProfileSymbolList, 0, 0, 0, 0},
{SecFuncMetadata, 0, 0, 0, 0}}),
class SampleProfileWriterExtBinaryBase : public SampleProfileWriterBinary {
using SampleProfileWriterBinary::SampleProfileWriterBinary;
std::error_code write(const SampleProfileMap &ProfileMap) override;
void setToCompressAllSections() override;
void setToCompressSection(SecType Type);
std::error_code writeSample(const FunctionSamples &S) override;
// Set to use MD5 to represent string in NameTable.
void setUseMD5() override {
UseMD5 = true;
addSectionFlag(SecNameTable, SecNameTableFlags::SecFlagMD5Name);
// MD5 will be stored as plain uint64_t instead of variable-length
// quantity format in NameTable section.
addSectionFlag(SecNameTable, SecNameTableFlags::SecFlagFixedLengthMD5);
// Set the profile to be partial. It means the profile is for
// common/shared code. The common profile is usually merged from
// profiles collected from running other targets.
void setPartialProfile() override {
addSectionFlag(SecProfSummary, SecProfSummaryFlags::SecFlagPartial);
void setProfileSymbolList(ProfileSymbolList *PSL) override {
ProfSymList = PSL;
void resetSecLayout(SectionLayout SL) override {
#ifndef NDEBUG
// Make sure resetSecLayout is called before any flag setting.
for (auto &Entry : SectionHdrLayout) {
assert(Entry.Flags == 0 &&
"resetSecLayout has to be called before any flag setting");
SecLayout = SL;
SectionHdrLayout = ExtBinaryHdrLayoutTable[SL];
uint64_t markSectionStart(SecType Type, uint32_t LayoutIdx);
std::error_code addNewSection(SecType Sec, uint32_t LayoutIdx,
uint64_t SectionStart);
template <class SecFlagType>
void addSectionFlag(SecType Type, SecFlagType Flag) {
for (auto &Entry : SectionHdrLayout) {
if (Entry.Type == Type)
addSecFlag(Entry, Flag);
template <class SecFlagType>
void addSectionFlag(uint32_t SectionIdx, SecFlagType Flag) {
addSecFlag(SectionHdrLayout[SectionIdx], Flag);
void addContext(const SampleContext &Context) override;
// placeholder for subclasses to dispatch their own section writers.
virtual std::error_code writeCustomSection(SecType Type) = 0;
// Verify the SecLayout is supported by the format.
virtual void verifySecLayout(SectionLayout SL) = 0;
// specify the order to write sections.
virtual std::error_code writeSections(const SampleProfileMap &ProfileMap) = 0;
// Dispatch section writer for each section. \p LayoutIdx is the sequence
// number indicating where the section is located in SectionHdrLayout.
virtual std::error_code writeOneSection(SecType Type, uint32_t LayoutIdx,
const SampleProfileMap &ProfileMap);
// Helper function to write name table.
std::error_code writeNameTable() override;
std::error_code writeContextIdx(const SampleContext &Context) override;
std::error_code writeCSNameIdx(const SampleContext &Context);
std::error_code writeCSNameTableSection();
std::error_code writeFuncMetadata(const SampleProfileMap &Profiles);
std::error_code writeFuncMetadata(const FunctionSamples &Profile);
// Functions to write various kinds of sections.
std::error_code writeNameTableSection(const SampleProfileMap &ProfileMap);
std::error_code writeFuncOffsetTable();
std::error_code writeProfileSymbolListSection();
SectionLayout SecLayout = DefaultLayout;
// Specifiy the order of sections in section header table. Note
// the order of sections in SecHdrTable may be different that the
// order in SectionHdrLayout. sample Reader will follow the order
// in SectionHdrLayout to read each section.
SmallVector<SecHdrTableEntry, 8> SectionHdrLayout =
// Save the start of SecLBRProfile so we can compute the offset to the
// start of SecLBRProfile for each Function's Profile and will keep it
// in FuncOffsetTable.
uint64_t SecLBRProfileStart = 0;
void allocSecHdrTable();
std::error_code writeSecHdrTable();
std::error_code writeHeader(const SampleProfileMap &ProfileMap) override;
std::error_code compressAndOutput();
// We will swap the raw_ostream held by LocalBufStream and that
// held by OutputStream if we try to add a section which needs
// compression. After the swap, all the data written to output
// will be temporarily buffered into the underlying raw_string_ostream
// originally held by LocalBufStream. After the data writing for the
// section is completed, compress the data in the local buffer,
// swap the raw_ostream back and write the compressed data to the
// real output.
std::unique_ptr<raw_ostream> LocalBufStream;
// The location where the output stream starts.
uint64_t FileStart;
// The location in the output stream where the SecHdrTable should be
// written to.
uint64_t SecHdrTableOffset;
// The table contains SecHdrTableEntry entries in order of how they are
// populated in the writer. It may be different from the order in
// SectionHdrLayout which specifies the sequence in which sections will
// be read.
std::vector<SecHdrTableEntry> SecHdrTable;
// FuncOffsetTable maps function context to its profile offset in
// SecLBRProfile section. It is used to load function profile on demand.
MapVector<SampleContext, uint64_t> FuncOffsetTable;
// Whether to use MD5 to represent string.
bool UseMD5 = false;
/// CSNameTable maps function context to its offset in SecCSNameTable section.
/// The offset will be used everywhere where the context is referenced.
MapVector<SampleContext, uint32_t> CSNameTable;
ProfileSymbolList *ProfSymList = nullptr;
class SampleProfileWriterExtBinary : public SampleProfileWriterExtBinaryBase {
SampleProfileWriterExtBinary(std::unique_ptr<raw_ostream> &OS)
: SampleProfileWriterExtBinaryBase(OS) {}
std::error_code writeDefaultLayout(const SampleProfileMap &ProfileMap);
std::error_code writeCtxSplitLayout(const SampleProfileMap &ProfileMap);
std::error_code writeSections(const SampleProfileMap &ProfileMap) override;
std::error_code writeCustomSection(SecType Type) override {
return sampleprof_error::success;
void verifySecLayout(SectionLayout SL) override {
assert((SL == DefaultLayout || SL == CtxSplitLayout) &&
"Unsupported layout");
} // end namespace sampleprof
} // end namespace llvm