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llvm-mirror/include/llvm/ProfileData/InstrProfWriter.h
Wei Mi 51d4708437 Supplement instr profile with sample profile.
PGO profile is usually more precise than sample profile. However, PGO profile
needs to be collected from loadtest and loadtest may not be representative
enough to the production workload. Sample profile collected from production
can be used as a supplement -- for functions cold in loadtest but warm/hot
in production, we can scale up the related function in PGO profile if the
function is warm or hot in sample profile.

The implementation contains changes in compiler side and llvm-profdata side.
Given an instr profile and a sample profile, for a function cold in PGO
profile but warm/hot in sample profile, llvm-profdata will either mark
all the counters in the profile to be -1 or scale up the max count in the
function to be above hot threshold, depending on the zero counter ratio in
the profile. The assumption is if there are too many counters being zero
in the function profile, the profile is more likely to cause harm than good,
then llvm-profdata will mark all the counters to be -1 indicating the
function is hot but the profile is unaccountable. In compiler side, if a
function profile with all -1 counters is seen, the function entry count will
be set to be above hot threshold but its internal profile will be dropped.

In the long run, it may be useful to let compiler support using PGO profile
and sample profile at the same time, but that requires more careful design
and more substantial changes to make two profiles work seamlessly. The patch
here serves as a simple intermediate solution.

Differential Revision: https://reviews.llvm.org/D81981
2020-07-27 20:17:40 -07:00

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//===- InstrProfWriter.h - Instrumented profiling writer --------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing profiling data for instrumentation
// based PGO and coverage.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_PROFILEDATA_INSTRPROFWRITER_H
#define LLVM_PROFILEDATA_INSTRPROFWRITER_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/MemoryBuffer.h"
#include <cstdint>
#include <memory>
namespace llvm {
/// Writer for instrumentation based profile data.
class InstrProfRecordWriterTrait;
class ProfOStream;
class raw_fd_ostream;
class InstrProfWriter {
public:
using ProfilingData = SmallDenseMap<uint64_t, InstrProfRecord>;
// PF_IRLevelWithCS is the profile from context sensitive IR instrumentation.
enum ProfKind { PF_Unknown = 0, PF_FE, PF_IRLevel, PF_IRLevelWithCS };
private:
bool Sparse;
StringMap<ProfilingData> FunctionData;
ProfKind ProfileKind = PF_Unknown;
bool InstrEntryBBEnabled;
// Use raw pointer here for the incomplete type object.
InstrProfRecordWriterTrait *InfoObj;
public:
InstrProfWriter(bool Sparse = false, bool InstrEntryBBEnabled = false);
~InstrProfWriter();
StringMap<ProfilingData> &getProfileData() { return FunctionData; }
/// Add function counts for the given function. If there are already counts
/// for this function and the hash and number of counts match, each counter is
/// summed. Optionally scale counts by \p Weight.
void addRecord(NamedInstrProfRecord &&I, uint64_t Weight,
function_ref<void(Error)> Warn);
void addRecord(NamedInstrProfRecord &&I, function_ref<void(Error)> Warn) {
addRecord(std::move(I), 1, Warn);
}
/// Merge existing function counts from the given writer.
void mergeRecordsFromWriter(InstrProfWriter &&IPW,
function_ref<void(Error)> Warn);
/// Write the profile to \c OS
void write(raw_fd_ostream &OS);
/// Write the profile in text format to \c OS
Error writeText(raw_fd_ostream &OS);
/// Write \c Record in text format to \c OS
static void writeRecordInText(StringRef Name, uint64_t Hash,
const InstrProfRecord &Counters,
InstrProfSymtab &Symtab, raw_fd_ostream &OS);
/// Write the profile, returning the raw data. For testing.
std::unique_ptr<MemoryBuffer> writeBuffer();
/// Set the ProfileKind. Report error if mixing FE and IR level profiles.
/// \c WithCS indicates if this is for contenxt sensitive instrumentation.
Error setIsIRLevelProfile(bool IsIRLevel, bool WithCS) {
if (ProfileKind == PF_Unknown) {
if (IsIRLevel)
ProfileKind = WithCS ? PF_IRLevelWithCS : PF_IRLevel;
else
ProfileKind = PF_FE;
return Error::success();
}
if (((ProfileKind != PF_FE) && !IsIRLevel) ||
((ProfileKind == PF_FE) && IsIRLevel))
return make_error<InstrProfError>(instrprof_error::unsupported_version);
// When merging a context-sensitive profile (WithCS == true) with an IRLevel
// profile, set the kind to PF_IRLevelWithCS.
if (ProfileKind == PF_IRLevel && WithCS)
ProfileKind = PF_IRLevelWithCS;
return Error::success();
}
void setInstrEntryBBEnabled(bool Enabled) { InstrEntryBBEnabled = Enabled; }
// Internal interface for testing purpose only.
void setValueProfDataEndianness(support::endianness Endianness);
void setOutputSparse(bool Sparse);
// Compute the overlap b/w this object and Other. Program level result is
// stored in Overlap and function level result is stored in FuncLevelOverlap.
void overlapRecord(NamedInstrProfRecord &&Other, OverlapStats &Overlap,
OverlapStats &FuncLevelOverlap,
const OverlapFuncFilters &FuncFilter);
private:
void addRecord(StringRef Name, uint64_t Hash, InstrProfRecord &&I,
uint64_t Weight, function_ref<void(Error)> Warn);
bool shouldEncodeData(const ProfilingData &PD);
void writeImpl(ProfOStream &OS);
};
} // end namespace llvm
#endif // LLVM_PROFILEDATA_INSTRPROFWRITER_H