//===- SampleProfReader.h - Read LLVM sample profile data -------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains definitions needed for reading sample profiles.
//
// NOTE: If you are making changes to this 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 ... ]
// offsetA[.discriminator]: fnA:num_of_total_samples
// offsetA1[.discriminator]: number_of_samples [fn7:num fn8:num ... ]
// ...
//
// This is a nested tree in which the identation represents the nesting level
// of the inline stack. There are no blank lines in the file. And the spacing
// within a single line is fixed. Additional spaces will result in an error
// while reading the file.
//
// Any line starting with the '#' character is completely ignored.
//
// Inlined calls are represented with indentation. The Inline stack is a
// stack of source locations in which the top of the stack represents the
// leaf function, and the bottom of the stack represents the actual
// symbol to which the instruction belongs.
//
// 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.
//
// There are two types of lines in the function body.
//
// * Sampled line represents the profile information of a source location.
// * Callsite line represents the profile information of a callsite.
//
// 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.
//
// Each callsite line may contain several items. Some are optional.
//
// a. Source line offset. This number represents the line number of the
// callsite that is inlined in the profiled binary.
//
// b. [OPTIONAL] Discriminator. Same as the discriminator for sampled line.
//
// c. Number of samples. This is an integer quantity representing the
// total number of samples collected for the inlined instance at this
// callsite
//
//
// Binary format
// -------------
//
// This is a more compact encoding. Numbers are encoded as ULEB128 values
// and all strings are encoded in a name table. The file is organized in
// the following sections:
//
// MAGIC (uint64_t)
// File identifier computed by function SPMagic() (0x5350524f463432ff)
//
// VERSION (uint32_t)
// File format version number computed by SPVersion()
//
// SUMMARY
// TOTAL_COUNT (uint64_t)
// Total number of samples in the profile.
// MAX_COUNT (uint64_t)
// Maximum value of samples on a line.
// MAX_FUNCTION_COUNT (uint64_t)
// Maximum number of samples at function entry (head samples).
// NUM_COUNTS (uint64_t)
// Number of lines with samples.
// NUM_FUNCTIONS (uint64_t)
// Number of functions with samples.
// NUM_DETAILED_SUMMARY_ENTRIES (size_t)
// Number of entries in detailed summary
// DETAILED_SUMMARY
// A list of detailed summary entry. Each entry consists of
// CUTOFF (uint32_t)
// Required percentile of total sample count expressed as a fraction
// multiplied by 1000000.
// MIN_COUNT (uint64_t)
// The minimum number of samples required to reach the target
// CUTOFF.
// NUM_COUNTS (uint64_t)
// Number of samples to get to the desrired percentile.
//
// NAME TABLE
// SIZE (uint32_t)
// Number of entries in the name table.
// NAMES
// A NUL-separated list of SIZE strings.
//
// FUNCTION BODY (one for each uninlined function body present in the profile)
// HEAD_SAMPLES (uint64_t) [only for top-level functions]
// Total number of samples collected at the head (prologue) of the
// function.
// NOTE: This field should only be present for top-level functions
// (i.e., not inlined into any caller). Inlined function calls
// have no prologue, so they don't need this.
// NAME_IDX (uint32_t)
// Index into the name table indicating the function name.
// SAMPLES (uint64_t)
// Total number of samples collected in this function.
// NRECS (uint32_t)
// Total number of sampling records this function's profile.
// BODY RECORDS
// A list of NRECS entries. Each entry contains:
// OFFSET (uint32_t)
// Line offset from the start of the function.
// DISCRIMINATOR (uint32_t)
// Discriminator value (see description of discriminators
// in the text format documentation above).
// SAMPLES (uint64_t)
// Number of samples collected at this location.
// NUM_CALLS (uint32_t)
// Number of non-inlined function calls made at this location. In the
// case of direct calls, this number will always be 1. For indirect
// calls (virtual functions and function pointers) this will
// represent all the actual functions called at runtime.
// CALL_TARGETS
// A list of NUM_CALLS entries for each called function:
// NAME_IDX (uint32_t)
// Index into the name table with the callee name.
// SAMPLES (uint64_t)
// Number of samples collected at the call site.
// NUM_INLINED_FUNCTIONS (uint32_t)
// Number of callees inlined into this function.
// INLINED FUNCTION RECORDS
// A list of NUM_INLINED_FUNCTIONS entries describing each of the inlined
// callees.
// OFFSET (uint32_t)
// Line offset from the start of the function.
// DISCRIMINATOR (uint32_t)
// Discriminator value (see description of discriminators
// in the text format documentation above).
// FUNCTION BODY
// A FUNCTION BODY entry describing the inlined function.
//===----------------------------------------------------------------------===//
#ifndef LLVM_PROFILEDATA_SAMPLEPROFREADER_H
#define LLVM_PROFILEDATA_SAMPLEPROFREADER_H
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/ProfileSummary.h"
#include "llvm/ProfileData/SampleProf.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/GCOV.h"
#include "llvm/Support/MemoryBuffer.h"
#include <algorithm>
#include <cstdint>
#include <memory>
#include <string>
#include <system_error>
#include <vector>
namespace llvm {
class raw_ostream;
namespace sampleprof {
/// \brief Sample-based profile reader.
///
/// Each profile contains sample counts for all the functions
/// executed. Inside each function, statements are annotated with the
/// collected samples on all the instructions associated with that
/// statement.
///
/// For this to produce meaningful data, the program needs to be
/// compiled with some debug information (at minimum, line numbers:
/// -gline-tables-only). Otherwise, it will be impossible to match IR
/// instructions to the line numbers collected by the profiler.
///
/// From the profile file, we are interested in collecting the
/// following information:
///
/// * A list of functions included in the profile (mangled names).
///
/// * For each function F:
/// 1. The total number of samples collected in F.
///
/// 2. The samples collected at each line in F. To provide some
/// protection against source code shuffling, line numbers should
/// be relative to the start of the function.
///
/// The reader supports two file formats: text and binary. The text format
/// is useful for debugging and testing, while the binary format is more
/// compact and I/O efficient. They can both be used interchangeably.
class SampleProfileReader {
public:
SampleProfileReader(std::unique_ptr<MemoryBuffer> B, LLVMContext &C)
: Profiles(0), Ctx(C), Buffer(std::move(B)) {}
virtual ~SampleProfileReader() = default;
/// \brief Read and validate the file header.
virtual std::error_code readHeader() = 0;
/// \brief Read sample profiles from the associated file.
virtual std::error_code read() = 0;
/// \brief Print the profile for \p FName on stream \p OS.
void dumpFunctionProfile(StringRef FName, raw_ostream &OS = dbgs());
/// \brief Print all the profiles on stream \p OS.
void dump(raw_ostream &OS = dbgs());
/// \brief Return the samples collected for function \p F.
FunctionSamples *getSamplesFor(const Function &F) {
// The function name may have been updated by adding suffix. In sample
// profile, the function names are all stripped, so we need to strip
// the function name suffix before matching with profile.
if (Profiles.count(F.getName().split('.').first))
return &Profiles[(F.getName().split('.').first)];
return nullptr;
}
/// \brief Return all the profiles.
StringMap<FunctionSamples> &getProfiles() { return Profiles; }
/// \brief Report a parse error message.
void reportError(int64_t LineNumber, Twine Msg) const {
Ctx.diagnose(DiagnosticInfoSampleProfile(Buffer->getBufferIdentifier(),
LineNumber, Msg));
}
/// \brief Create a sample profile reader appropriate to the file format.
static ErrorOr<std::unique_ptr<SampleProfileReader>>
create(const Twine &Filename, LLVMContext &C);
/// \brief Create a sample profile reader from the supplied memory buffer.
static ErrorOr<std::unique_ptr<SampleProfileReader>>
create(std::unique_ptr<MemoryBuffer> &B, LLVMContext &C);
/// \brief Return the profile summary.
ProfileSummary &getSummary() { return *(Summary.get()); }
protected:
/// \brief Map every function to its associated profile.
///
/// The profile of every function executed at runtime is collected
/// in the structure FunctionSamples. This maps function objects
/// to their corresponding profiles.
StringMap<FunctionSamples> Profiles;
/// \brief LLVM context used to emit diagnostics.
LLVMContext &Ctx;
/// \brief Memory buffer holding the profile file.
std::unique_ptr<MemoryBuffer> Buffer;
/// \brief Profile summary information.
std::unique_ptr<ProfileSummary> Summary;
/// \brief Compute summary for this profile.
void computeSummary();
};
class SampleProfileReaderText : public SampleProfileReader {
public:
SampleProfileReaderText(std::unique_ptr<MemoryBuffer> B, LLVMContext &C)
: SampleProfileReader(std::move(B), C) {}
/// \brief Read and validate the file header.
std::error_code readHeader() override { return sampleprof_error::success; }
/// \brief Read sample profiles from the associated file.
std::error_code read() override;
/// \brief Return true if \p Buffer is in the format supported by this class.
static bool hasFormat(const MemoryBuffer &Buffer);
};
class SampleProfileReaderBinary : public SampleProfileReader {
public:
SampleProfileReaderBinary(std::unique_ptr<MemoryBuffer> B, LLVMContext &C)
: SampleProfileReader(std::move(B), C) {}
/// \brief Read and validate the file header.
std::error_code readHeader() override;
/// \brief Read sample profiles from the associated file.
std::error_code read() override;
/// \brief Return true if \p Buffer is in the format supported by this class.
static bool hasFormat(const MemoryBuffer &Buffer);
protected:
/// \brief Read a numeric value of type T from the profile.
///
/// If an error occurs during decoding, a diagnostic message is emitted and
/// EC is set.
///
/// \returns the read value.
template <typename T> ErrorOr<T> readNumber();
/// \brief Read a string from the profile.
///
/// If an error occurs during decoding, a diagnostic message is emitted and
/// EC is set.
///
/// \returns the read value.
ErrorOr<StringRef> readString();
/// Read a string indirectly via the name table.
ErrorOr<StringRef> readStringFromTable();
/// \brief Return true if we've reached the end of file.
bool at_eof() const { return Data >= End; }
/// Read the contents of the given profile instance.
std::error_code readProfile(FunctionSamples &FProfile);
/// \brief Points to the current location in the buffer.
const uint8_t *Data = nullptr;
/// \brief Points to the end of the buffer.
const uint8_t *End = nullptr;
/// Function name table.
std::vector<StringRef> NameTable;
private:
std::error_code readSummaryEntry(std::vector<ProfileSummaryEntry> &Entries);
/// \brief Read profile summary.
std::error_code readSummary();
};
using InlineCallStack = SmallVector<FunctionSamples *, 10>;
// Supported histogram types in GCC. Currently, we only need support for
// call target histograms.
enum HistType {
HIST_TYPE_INTERVAL,
HIST_TYPE_POW2,
HIST_TYPE_SINGLE_VALUE,
HIST_TYPE_CONST_DELTA,
HIST_TYPE_INDIR_CALL,
HIST_TYPE_AVERAGE,
HIST_TYPE_IOR,
HIST_TYPE_INDIR_CALL_TOPN
};
class SampleProfileReaderGCC : public SampleProfileReader {
public:
SampleProfileReaderGCC(std::unique_ptr<MemoryBuffer> B, LLVMContext &C)
: SampleProfileReader(std::move(B), C), GcovBuffer(Buffer.get()) {}
/// \brief Read and validate the file header.
std::error_code readHeader() override;
/// \brief Read sample profiles from the associated file.
std::error_code read() override;
/// \brief Return true if \p Buffer is in the format supported by this class.
static bool hasFormat(const MemoryBuffer &Buffer);
protected:
std::error_code readNameTable();
std::error_code readOneFunctionProfile(const InlineCallStack &InlineStack,
bool Update, uint32_t Offset);
std::error_code readFunctionProfiles();
std::error_code skipNextWord();
template <typename T> ErrorOr<T> readNumber();
ErrorOr<StringRef> readString();
/// \brief Read the section tag and check that it's the same as \p Expected.
std::error_code readSectionTag(uint32_t Expected);
/// GCOV buffer containing the profile.
GCOVBuffer GcovBuffer;
/// Function names in this profile.
std::vector<std::string> Names;
/// GCOV tags used to separate sections in the profile file.
static const uint32_t GCOVTagAFDOFileNames = 0xaa000000;
static const uint32_t GCOVTagAFDOFunction = 0xac000000;
};
} // end namespace sampleprof
} // end namespace llvm
#endif // LLVM_PROFILEDATA_SAMPLEPROFREADER_H