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It isn't always useful to skip blank lines, as evidenced by the somewhat awkward use of line_iterator in llvm-cov. This adds a knob to control whether or not to skip blanks. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217960 91177308-0d34-0410-b5e6-96231b3b80d8
239 lines
9.8 KiB
C++
239 lines
9.8 KiB
C++
//===- SampleProfReader.cpp - Read LLVM sample profile data ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the class that reads LLVM sample profiles. It
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// supports two file formats: text and bitcode. The textual representation
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// is useful for debugging and testing purposes. The bitcode representation
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// is more compact, resulting in smaller file sizes. However, they can
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// both be used interchangeably.
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//
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// NOTE: If you are making changes to the file format, please remember
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// to document them in the Clang documentation at
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// tools/clang/docs/UsersManual.rst.
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//
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// Text format
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// -----------
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//
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// Sample profiles are written as ASCII text. The file is divided into
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// sections, which correspond to each of the functions executed at runtime.
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// Each section has the following format
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//
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// function1:total_samples:total_head_samples
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// offset1[.discriminator]: number_of_samples [fn1:num fn2:num ... ]
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// offset2[.discriminator]: number_of_samples [fn3:num fn4:num ... ]
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// ...
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// offsetN[.discriminator]: number_of_samples [fn5:num fn6:num ... ]
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//
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// The file may contain blank lines between sections and within a
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// section. However, the spacing within a single line is fixed. Additional
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// spaces will result in an error while reading the file.
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//
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// Function names must be mangled in order for the profile loader to
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// match them in the current translation unit. The two numbers in the
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// function header specify how many total samples were accumulated in the
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// function (first number), and the total number of samples accumulated
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// in the prologue of the function (second number). This head sample
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// count provides an indicator of how frequently the function is invoked.
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//
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// Each sampled line may contain several items. Some are optional (marked
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// below):
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//
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// a. Source line offset. This number represents the line number
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// in the function where the sample was collected. The line number is
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// always relative to the line where symbol of the function is
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// defined. So, if the function has its header at line 280, the offset
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// 13 is at line 293 in the file.
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//
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// Note that this offset should never be a negative number. This could
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// happen in cases like macros. The debug machinery will register the
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// line number at the point of macro expansion. So, if the macro was
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// expanded in a line before the start of the function, the profile
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// converter should emit a 0 as the offset (this means that the optimizers
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// will not be able to associate a meaningful weight to the instructions
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// in the macro).
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//
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// b. [OPTIONAL] Discriminator. This is used if the sampled program
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// was compiled with DWARF discriminator support
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// (http://wiki.dwarfstd.org/index.php?title=Path_Discriminators).
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// DWARF discriminators are unsigned integer values that allow the
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// compiler to distinguish between multiple execution paths on the
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// same source line location.
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//
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// For example, consider the line of code ``if (cond) foo(); else bar();``.
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// If the predicate ``cond`` is true 80% of the time, then the edge
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// into function ``foo`` should be considered to be taken most of the
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// time. But both calls to ``foo`` and ``bar`` are at the same source
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// line, so a sample count at that line is not sufficient. The
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// compiler needs to know which part of that line is taken more
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// frequently.
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//
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// This is what discriminators provide. In this case, the calls to
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// ``foo`` and ``bar`` will be at the same line, but will have
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// different discriminator values. This allows the compiler to correctly
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// set edge weights into ``foo`` and ``bar``.
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//
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// c. Number of samples. This is an integer quantity representing the
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// number of samples collected by the profiler at this source
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// location.
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//
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// d. [OPTIONAL] Potential call targets and samples. If present, this
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// line contains a call instruction. This models both direct and
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// number of samples. For example,
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//
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// 130: 7 foo:3 bar:2 baz:7
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//
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// The above means that at relative line offset 130 there is a call
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// instruction that calls one of ``foo()``, ``bar()`` and ``baz()``,
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// with ``baz()`` being the relatively more frequently called target.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ProfileData/SampleProfReader.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorOr.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/LineIterator.h"
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#include "llvm/Support/Regex.h"
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using namespace sampleprof;
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using namespace llvm;
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/// \brief Print the samples collected for a function on stream \p OS.
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///
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/// \param OS Stream to emit the output to.
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void FunctionSamples::print(raw_ostream &OS) {
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OS << TotalSamples << ", " << TotalHeadSamples << ", " << BodySamples.size()
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<< " sampled lines\n";
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for (BodySampleMap::const_iterator SI = BodySamples.begin(),
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SE = BodySamples.end();
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SI != SE; ++SI)
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OS << "\tline offset: " << SI->first.LineOffset
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<< ", discriminator: " << SI->first.Discriminator
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<< ", number of samples: " << SI->second << "\n";
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OS << "\n";
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}
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/// \brief Print the function profile for \p FName on stream \p OS.
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///
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/// \param OS Stream to emit the output to.
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/// \param FName Name of the function to print.
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void SampleProfileReader::printFunctionProfile(raw_ostream &OS,
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StringRef FName) {
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OS << "Function: " << FName << ":\n";
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Profiles[FName].print(OS);
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}
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/// \brief Dump the function profile for \p FName.
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///
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/// \param FName Name of the function to print.
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void SampleProfileReader::dumpFunctionProfile(StringRef FName) {
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printFunctionProfile(dbgs(), FName);
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}
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/// \brief Dump all the function profiles found.
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void SampleProfileReader::dump() {
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for (StringMap<FunctionSamples>::const_iterator I = Profiles.begin(),
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E = Profiles.end();
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I != E; ++I)
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dumpFunctionProfile(I->getKey());
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}
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/// \brief Load samples from a text file.
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///
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/// See the documentation at the top of the file for an explanation of
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/// the expected format.
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///
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/// \returns true if the file was loaded successfully, false otherwise.
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bool SampleProfileReader::loadText() {
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ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
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MemoryBuffer::getFile(Filename);
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if (std::error_code EC = BufferOrErr.getError()) {
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std::string Msg(EC.message());
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M.getContext().diagnose(DiagnosticInfoSampleProfile(Filename.data(), Msg));
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return false;
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}
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MemoryBuffer &Buffer = *BufferOrErr.get();
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line_iterator LineIt(Buffer, /*SkipBlanks=*/true, '#');
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// Read the profile of each function. Since each function may be
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// mentioned more than once, and we are collecting flat profiles,
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// accumulate samples as we parse them.
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Regex HeadRE("^([^0-9].*):([0-9]+):([0-9]+)$");
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Regex LineSample("^([0-9]+)\\.?([0-9]+)?: ([0-9]+)(.*)$");
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while (!LineIt.is_at_eof()) {
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// Read the header of each function.
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//
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// Note that for function identifiers we are actually expecting
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// mangled names, but we may not always get them. This happens when
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// the compiler decides not to emit the function (e.g., it was inlined
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// and removed). In this case, the binary will not have the linkage
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// name for the function, so the profiler will emit the function's
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// unmangled name, which may contain characters like ':' and '>' in its
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// name (member functions, templates, etc).
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//
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// The only requirement we place on the identifier, then, is that it
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// should not begin with a number.
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SmallVector<StringRef, 3> Matches;
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if (!HeadRE.match(*LineIt, &Matches)) {
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reportParseError(LineIt.line_number(),
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"Expected 'mangled_name:NUM:NUM', found " + *LineIt);
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return false;
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}
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assert(Matches.size() == 4);
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StringRef FName = Matches[1];
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unsigned NumSamples, NumHeadSamples;
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Matches[2].getAsInteger(10, NumSamples);
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Matches[3].getAsInteger(10, NumHeadSamples);
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Profiles[FName] = FunctionSamples();
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FunctionSamples &FProfile = Profiles[FName];
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FProfile.addTotalSamples(NumSamples);
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FProfile.addHeadSamples(NumHeadSamples);
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++LineIt;
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// Now read the body. The body of the function ends when we reach
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// EOF or when we see the start of the next function.
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while (!LineIt.is_at_eof() && isdigit((*LineIt)[0])) {
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if (!LineSample.match(*LineIt, &Matches)) {
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reportParseError(
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LineIt.line_number(),
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"Expected 'NUM[.NUM]: NUM[ mangled_name:NUM]*', found " + *LineIt);
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return false;
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}
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assert(Matches.size() == 5);
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unsigned LineOffset, NumSamples, Discriminator = 0;
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Matches[1].getAsInteger(10, LineOffset);
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if (Matches[2] != "")
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Matches[2].getAsInteger(10, Discriminator);
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Matches[3].getAsInteger(10, NumSamples);
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// FIXME: Handle called targets (in Matches[4]).
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// When dealing with instruction weights, we use the value
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// zero to indicate the absence of a sample. If we read an
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// actual zero from the profile file, return it as 1 to
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// avoid the confusion later on.
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if (NumSamples == 0)
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NumSamples = 1;
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FProfile.addBodySamples(LineOffset, Discriminator, NumSamples);
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++LineIt;
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}
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}
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return true;
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}
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/// \brief Load execution samples from a file.
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///
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/// This function examines the header of the given file to determine
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/// whether to use the text or the bitcode loader.
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bool SampleProfileReader::load() {
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// TODO Actually detect the file format.
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return loadText();
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}
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