//
// 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()
+//
+// 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
/// \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; }
/// \brief Points to the end of the buffer.
const uint8_t *End;
-};
-
-// Represents the source position in GCC sample profiles.
-struct SourceInfo {
- SourceInfo()
- : FuncName(), DirName(), FileName(), StartLine(0), Line(0),
- Discriminator(0) {}
-
- SourceInfo(StringRef FuncName, StringRef DirName, StringRef FileName,
- uint32_t StartLine, uint32_t Line, uint32_t Discriminator)
- : FuncName(FuncName), DirName(DirName), FileName(FileName),
- StartLine(StartLine), Line(Line), Discriminator(Discriminator) {}
-
- bool operator<(const SourceInfo &p) const;
-
- uint32_t Offset() const { return ((Line - StartLine) << 16) | Discriminator; }
-
- bool Malformed() const { return Line < StartLine; }
- StringRef FuncName;
- StringRef DirName;
- StringRef FileName;
- uint32_t StartLine;
- uint32_t Line;
- uint32_t Discriminator;
+ /// Function name table.
+ std::vector<StringRef> NameTable;
};
typedef SmallVector<FunctionSamples *, 10> InlineCallStack;
projects / oota-llvm.git / blobdiff