//===- SampleProfReader.cpp - Read LLVM sample profile data ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the class that reads LLVM sample profiles. It
// supports two file formats: text and binary. The textual representation
// is useful for debugging and testing purposes. The binary representation
// is more compact, resulting in smaller file sizes. However, they can
// both be used interchangeably.
//
// NOTE: If you are making changes to the file format, please remember
// to document them in the Clang documentation at
// tools/clang/docs/UsersManual.rst.
//
// Text format
// -----------
//
// Sample profiles are written as ASCII text. The file is divided into
// sections, which correspond to each of the functions executed at runtime.
// Each section has the following format
//
// function1:total_samples:total_head_samples
// offset1[.discriminator]: number_of_samples [fn1:num fn2:num ... ]
// offset2[.discriminator]: number_of_samples [fn3:num fn4:num ... ]
// ...
// offsetN[.discriminator]: number_of_samples [fn5:num fn6:num ... ]
//
// The file may contain blank lines between sections and within a
// section. However, the spacing within a single line is fixed. Additional
// spaces will result in an error while reading the file.
//
// Function names must be mangled in order for the profile loader to
// match them in the current translation unit. The two numbers in the
// function header specify how many total samples were accumulated in the
// function (first number), and the total number of samples accumulated
// in the prologue of the function (second number). This head sample
// count provides an indicator of how frequently the function is invoked.
//
// Each sampled line may contain several items. Some are optional (marked
// below):
//
// a. Source line offset. This number represents the line number
// in the function where the sample was collected. The line number is
// always relative to the line where symbol of the function is
// defined. So, if the function has its header at line 280, the offset
// 13 is at line 293 in the file.
//
// Note that this offset should never be a negative number. This could
// happen in cases like macros. The debug machinery will register the
// line number at the point of macro expansion. So, if the macro was
// expanded in a line before the start of the function, the profile
// converter should emit a 0 as the offset (this means that the optimizers
// will not be able to associate a meaningful weight to the instructions
// in the macro).
//
// b. [OPTIONAL] Discriminator. This is used if the sampled program
// was compiled with DWARF discriminator support
// (http://wiki.dwarfstd.org/index.php?title=Path_Discriminators).
// DWARF discriminators are unsigned integer values that allow the
// compiler to distinguish between multiple execution paths on the
// same source line location.
//
// For example, consider the line of code ``if (cond) foo(); else bar();``.
// If the predicate ``cond`` is true 80% of the time, then the edge
// into function ``foo`` should be considered to be taken most of the
// time. But both calls to ``foo`` and ``bar`` are at the same source
// line, so a sample count at that line is not sufficient. The
// compiler needs to know which part of that line is taken more
// frequently.
//
// This is what discriminators provide. In this case, the calls to
// ``foo`` and ``bar`` will be at the same line, but will have
// different discriminator values. This allows the compiler to correctly
// set edge weights into ``foo`` and ``bar``.
//
// c. Number of samples. This is an integer quantity representing the
// number of samples collected by the profiler at this source
// location.
//
// d. [OPTIONAL] Potential call targets and samples. If present, this
// line contains a call instruction. This models both direct and
// number of samples. For example,
//
// 130: 7 foo:3 bar:2 baz:7
//
// The above means that at relative line offset 130 there is a call
// instruction that calls one of ``foo()``, ``bar()`` and ``baz()``,
// with ``baz()`` being the relatively more frequently called target.
//
//===----------------------------------------------------------------------===//
#include "llvm/ProfileData/SampleProfReader.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/LineIterator.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Regex.h"
using namespace llvm::sampleprof;
using namespace llvm;
/// \brief Print the samples collected for a function on stream \p OS.
///
/// \param OS Stream to emit the output to.
void FunctionSamples::print(raw_ostream &OS) {
OS << TotalSamples << ", " << TotalHeadSamples << ", " << BodySamples.size()
<< " sampled lines\n";
for (const auto &SI : BodySamples) {
LineLocation Loc = SI.first;
const SampleRecord &Sample = SI.second;
OS << "\tline offset: " << Loc.LineOffset
<< ", discriminator: " << Loc.Discriminator
<< ", number of samples: " << Sample.getSamples();
if (Sample.hasCalls()) {
OS << ", calls:";
for (const auto &I : Sample.getCallTargets())
OS << " " << I.first() << ":" << I.second;
}
OS << "\n";
}
OS << "\n";
}
/// \brief Dump the function profile for \p FName.
///
/// \param FName Name of the function to print.
/// \param OS Stream to emit the output to.
void SampleProfileReader::dumpFunctionProfile(StringRef FName,
raw_ostream &OS) {
OS << "Function: " << FName << ": ";
Profiles[FName].print(OS);
}
/// \brief Dump all the function profiles found on stream \p OS.
void SampleProfileReader::dump(raw_ostream &OS) {
for (const auto &I : Profiles)
dumpFunctionProfile(I.getKey(), OS);
}
/// \brief Load samples from a text file.
///
/// See the documentation at the top of the file for an explanation of
/// the expected format.
///
/// \returns true if the file was loaded successfully, false otherwise.
std::error_code SampleProfileReaderText::read() {
line_iterator LineIt(*Buffer, /*SkipBlanks=*/true, '#');
// Read the profile of each function. Since each function may be
// mentioned more than once, and we are collecting flat profiles,
// accumulate samples as we parse them.
Regex HeadRE("^([^0-9].*):([0-9]+):([0-9]+)$");
Regex LineSampleRE("^([0-9]+)\\.?([0-9]+)?: ([0-9]+)(.*)$");
Regex CallSampleRE(" +([^0-9 ][^ ]*):([0-9]+)");
while (!LineIt.is_at_eof()) {
// Read the header of each function.
//
// Note that for function identifiers we are actually expecting
// mangled names, but we may not always get them. This happens when
// the compiler decides not to emit the function (e.g., it was inlined
// and removed). In this case, the binary will not have the linkage
// name for the function, so the profiler will emit the function's
// unmangled name, which may contain characters like ':' and '>' in its
// name (member functions, templates, etc).
//
// The only requirement we place on the identifier, then, is that it
// should not begin with a number.
SmallVector<StringRef, 4> Matches;
if (!HeadRE.match(*LineIt, &Matches)) {
reportParseError(LineIt.line_number(),
"Expected 'mangled_name:NUM:NUM', found " + *LineIt);
return sampleprof_error::malformed;
}
assert(Matches.size() == 4);
StringRef FName = Matches[1];
unsigned NumSamples, NumHeadSamples;
Matches[2].getAsInteger(10, NumSamples);
Matches[3].getAsInteger(10, NumHeadSamples);
Profiles[FName] = FunctionSamples();
FunctionSamples &FProfile = Profiles[FName];
FProfile.addTotalSamples(NumSamples);
FProfile.addHeadSamples(NumHeadSamples);
++LineIt;
// Now read the body. The body of the function ends when we reach
// EOF or when we see the start of the next function.
while (!LineIt.is_at_eof() && isdigit((*LineIt)[0])) {
if (!LineSampleRE.match(*LineIt, &Matches)) {
reportParseError(
LineIt.line_number(),
"Expected 'NUM[.NUM]: NUM[ mangled_name:NUM]*', found " + *LineIt);
return sampleprof_error::malformed;
}
assert(Matches.size() == 5);
unsigned LineOffset, NumSamples, Discriminator = 0;
Matches[1].getAsInteger(10, LineOffset);
if (Matches[2] != "")
Matches[2].getAsInteger(10, Discriminator);
Matches[3].getAsInteger(10, NumSamples);
// If there are function calls in this line, generate a call sample
// entry for each call.
std::string CallsLine(Matches[4]);
while (CallsLine != "") {
SmallVector<StringRef, 3> CallSample;
if (!CallSampleRE.match(CallsLine, &CallSample)) {
reportParseError(LineIt.line_number(),
"Expected 'mangled_name:NUM', found " + CallsLine);
return sampleprof_error::malformed;
}
StringRef CalledFunction = CallSample[1];
unsigned CalledFunctionSamples;
CallSample[2].getAsInteger(10, CalledFunctionSamples);
FProfile.addCalledTargetSamples(LineOffset, Discriminator,
CalledFunction, CalledFunctionSamples);
CallsLine = CallSampleRE.sub("", CallsLine);
}
FProfile.addBodySamples(LineOffset, Discriminator, NumSamples);
++LineIt;
}
}
return sampleprof_error::success;
}
template <typename T> ErrorOr<T> SampleProfileReaderBinary::readNumber() {
unsigned NumBytesRead = 0;
std::error_code EC;
uint64_t Val = decodeULEB128(Data, &NumBytesRead);
if (Val > std::numeric_limits<T>::max())
EC = sampleprof_error::malformed;
else if (Data + NumBytesRead > End)
EC = sampleprof_error::truncated;
else
EC = sampleprof_error::success;
if (EC) {
reportParseError(0, EC.message());
return EC;
}
Data += NumBytesRead;
return static_cast<T>(Val);
}
ErrorOr<StringRef> SampleProfileReaderBinary::readString() {
std::error_code EC;
StringRef Str(reinterpret_cast<const char *>(Data));
if (Data + Str.size() + 1 > End) {
EC = sampleprof_error::truncated;
reportParseError(0, EC.message());
return EC;
}
Data += Str.size() + 1;
return Str;
}
std::error_code SampleProfileReaderBinary::read() {
while (!at_eof()) {
auto FName(readString());
if (std::error_code EC = FName.getError())
return EC;
Profiles[*FName] = FunctionSamples();
FunctionSamples &FProfile = Profiles[*FName];
auto Val = readNumber<unsigned>();
if (std::error_code EC = Val.getError())
return EC;
FProfile.addTotalSamples(*Val);
Val = readNumber<unsigned>();
if (std::error_code EC = Val.getError())
return EC;
FProfile.addHeadSamples(*Val);
// Read the samples in the body.
auto NumRecords = readNumber<unsigned>();
if (std::error_code EC = NumRecords.getError())
return EC;
for (unsigned I = 0; I < *NumRecords; ++I) {
auto LineOffset = readNumber<uint64_t>();
if (std::error_code EC = LineOffset.getError())
return EC;
auto Discriminator = readNumber<uint64_t>();
if (std::error_code EC = Discriminator.getError())
return EC;
auto NumSamples = readNumber<uint64_t>();
if (std::error_code EC = NumSamples.getError())
return EC;
auto NumCalls = readNumber<unsigned>();
if (std::error_code EC = NumCalls.getError())
return EC;
for (unsigned J = 0; J < *NumCalls; ++J) {
auto CalledFunction(readString());
if (std::error_code EC = CalledFunction.getError())
return EC;
auto CalledFunctionSamples = readNumber<uint64_t>();
if (std::error_code EC = CalledFunctionSamples.getError())
return EC;
FProfile.addCalledTargetSamples(*LineOffset, *Discriminator,
*CalledFunction,
*CalledFunctionSamples);
}
FProfile.addBodySamples(*LineOffset, *Discriminator, *NumSamples);
}
}
return sampleprof_error::success;
}
std::error_code SampleProfileReaderBinary::readHeader() {
Data = reinterpret_cast<const uint8_t *>(Buffer->getBufferStart());
End = Data + Buffer->getBufferSize();
// Read and check the magic identifier.
auto Magic = readNumber<uint64_t>();
if (std::error_code EC = Magic.getError())
return EC;
else if (*Magic != SPMagic())
return sampleprof_error::bad_magic;
// Read the version number.
auto Version = readNumber<uint64_t>();
if (std::error_code EC = Version.getError())
return EC;
else if (*Version != SPVersion())
return sampleprof_error::unsupported_version;
return sampleprof_error::success;
}
bool SampleProfileReaderBinary::hasFormat(const MemoryBuffer &Buffer) {
const uint8_t *Data =
reinterpret_cast<const uint8_t *>(Buffer.getBufferStart());
uint64_t Magic = decodeULEB128(Data);
return Magic == SPMagic();
}
/// \brief Prepare a memory buffer for the contents of \p Filename.
///
/// \returns an error code indicating the status of the buffer.
static ErrorOr<std::unique_ptr<MemoryBuffer>>
setupMemoryBuffer(std::string Filename) {
auto BufferOrErr = MemoryBuffer::getFileOrSTDIN(Filename);
if (std::error_code EC = BufferOrErr.getError())
return EC;
auto Buffer = std::move(BufferOrErr.get());
// Sanity check the file.
if (Buffer->getBufferSize() > std::numeric_limits<unsigned>::max())
return sampleprof_error::too_large;
return std::move(Buffer);
}
/// \brief Create a sample profile reader based on the format of the input file.
///
/// \param Filename The file to open.
///
/// \param Reader The reader to instantiate according to \p Filename's format.
///
/// \param C The LLVM context to use to emit diagnostics.
///
/// \returns an error code indicating the status of the created reader.
ErrorOr<std::unique_ptr<SampleProfileReader>>
SampleProfileReader::create(StringRef Filename, LLVMContext &C) {
auto BufferOrError = setupMemoryBuffer(Filename);
if (std::error_code EC = BufferOrError.getError())
return EC;
auto Buffer = std::move(BufferOrError.get());
std::unique_ptr<SampleProfileReader> Reader;
if (SampleProfileReaderBinary::hasFormat(*Buffer))
Reader.reset(new SampleProfileReaderBinary(std::move(Buffer), C));
else
Reader.reset(new SampleProfileReaderText(std::move(Buffer), C));
if (std::error_code EC = Reader->readHeader())
return EC;
return std::move(Reader);
}