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-rw-r--r--llvm/lib/Transforms/Scalar/SampleProfile.cpp201
1 files changed, 95 insertions, 106 deletions
diff --git a/llvm/lib/Transforms/Scalar/SampleProfile.cpp b/llvm/lib/Transforms/Scalar/SampleProfile.cpp
index e3d290194cf..47da32a5f28 100644
--- a/llvm/lib/Transforms/Scalar/SampleProfile.cpp
+++ b/llvm/lib/Transforms/Scalar/SampleProfile.cpp
@@ -45,6 +45,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/InstIterator.h"
+#include "llvm/Support/LineIterator.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Regex.h"
#include "llvm/Support/raw_ostream.h"
@@ -115,6 +116,7 @@ protected:
unsigned TotalSamples;
/// \brief Total number of samples collected at the head of the function.
+ /// FIXME: Use head samples to estimate a cold/hot attribute for the function.
unsigned TotalHeadSamples;
/// \brief Line number for the function header. Used to compute relative
@@ -204,6 +206,11 @@ public:
return Profiles[F.getName()];
}
+ /// \brief Report a parse error message and stop compilation.
+ void reportParseError(int64_t LineNumber, Twine Msg) const {
+ report_fatal_error(Filename + ":" + Twine(LineNumber) + ": " + Msg + "\n");
+ }
+
protected:
/// \brief Map every function to its associated profile.
///
@@ -221,63 +228,6 @@ protected:
StringRef Filename;
};
-/// \brief Loader class for text-based profiles.
-///
-/// This class defines a simple interface to read text files containing
-/// profiles. It keeps track of line number information and location of
-/// the file pointer. Users of this class are responsible for actually
-/// parsing the lines returned by the readLine function.
-///
-/// TODO - This does not really belong here. It is a generic text file
-/// reader. It should be moved to the Support library and made more general.
-class ExternalProfileTextLoader {
-public:
- ExternalProfileTextLoader(StringRef F) : Filename(F) {
- error_code EC;
- EC = MemoryBuffer::getFile(Filename, Buffer);
- if (EC)
- report_fatal_error("Could not open profile file " + Filename + ": " +
- EC.message());
- FP = Buffer->getBufferStart();
- Lineno = 0;
- }
-
- /// \brief Read a line from the mapped file.
- StringRef readLine() {
- size_t Length = 0;
- const char *start = FP;
- while (FP != Buffer->getBufferEnd() && *FP != '\n') {
- Length++;
- FP++;
- }
- if (FP != Buffer->getBufferEnd())
- FP++;
- Lineno++;
- return StringRef(start, Length);
- }
-
- /// \brief Return true, if we've reached EOF.
- bool atEOF() const { return FP == Buffer->getBufferEnd(); }
-
- /// \brief Report a parse error message and stop compilation.
- void reportParseError(Twine Msg) const {
- report_fatal_error(Filename + ":" + Twine(Lineno) + ": " + Msg + "\n");
- }
-
-private:
- /// \brief Memory buffer holding the text file.
- OwningPtr<MemoryBuffer> Buffer;
-
- /// \brief Current position into the memory buffer.
- const char *FP;
-
- /// \brief Current line number.
- int64_t Lineno;
-
- /// \brief Path name where to the profile file.
- StringRef Filename;
-};
-
/// \brief Sample profile pass.
///
/// This pass reads profile data from the file specified by
@@ -386,77 +336,118 @@ void SampleModuleProfile::dump() {
/// \brief Load samples from a text file.
///
-/// The file is divided in two segments:
+/// The file contains a list of samples for every function executed at
+/// runtime. Each function profile has the following format:
///
-/// Symbol table (represented with the string "symbol table")
-/// Number of symbols in the table
-/// symbol 1
-/// symbol 2
+/// function1:total_samples:total_head_samples
+/// offset1[.discriminator]: number_of_samples [fn1:num fn2:num ... ]
+/// offset2[.discriminator]: number_of_samples [fn3:num fn4:num ... ]
/// ...
-/// symbol N
-///
-/// Function body profiles
-/// function1:total_samples:total_head_samples:number_of_locations
-/// location_offset_1: number_of_samples
-/// location_offset_2: number_of_samples
-/// ...
-/// location_offset_N: number_of_samples
+/// offsetN[.discriminator]: number_of_samples [fn5:num fn6:num ... ]
///
/// Function names must be mangled in order for the profile loader to
-/// match them in the current translation unit.
+/// 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
+/// at the prologue of the function (second number). This head sample
+/// count provides an indicator of how frequent is the function 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.
+///
+/// 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)
+/// This is currently only emitted by GCC and we just ignore it.
+///
+/// FIXME: Handle discriminators, since they are needed to distinguish
+/// multiple control flow within a single source LOC.
+///
+/// c- Number of samples. This is 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
+/// indirect calls. Each called target is listed together with the
+/// 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 frequent call target.
+///
+/// FIXME: This is currently unhandled, but it has a lot of
+/// potential for aiding the inliner.
+///
///
/// Since this is a flat profile, a function that shows up more than
/// once gets all its samples aggregated across all its instances.
-/// TODO - flat profiles are too imprecise to provide good optimization
-/// opportunities. Convert them to context-sensitive profile.
+///
+/// FIXME: flat profiles are too imprecise to provide good optimization
+/// opportunities. Convert them to context-sensitive profile.
///
/// This textual representation is useful to generate unit tests and
/// for debugging purposes, but it should not be used to generate
/// profiles for large programs, as the representation is extremely
/// inefficient.
void SampleModuleProfile::loadText() {
- ExternalProfileTextLoader Loader(Filename);
-
- // Read the symbol table.
- StringRef Line = Loader.readLine();
- if (Line != "symbol table")
- Loader.reportParseError("Expected 'symbol table', found " + Line);
- int NumSymbols;
- Line = Loader.readLine();
- if (Line.getAsInteger(10, NumSymbols))
- Loader.reportParseError("Expected a number, found " + Line);
- for (int I = 0; I < NumSymbols; I++)
- Profiles[Loader.readLine()] = SampleFunctionProfile();
+ OwningPtr<MemoryBuffer> Buffer;
+ error_code EC = MemoryBuffer::getFile(Filename, Buffer);
+ if (EC)
+ report_fatal_error("Could not open file " + Filename + ": " + EC.message());
+ line_iterator LineIt(*Buffer, '#');
// 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]+)$");
- Regex LineSample("^([0-9]+): ([0-9]+)$");
- while (!Loader.atEOF()) {
- SmallVector<StringRef, 4> Matches;
- Line = Loader.readLine();
- if (!HeadRE.match(Line, &Matches))
- Loader.reportParseError("Expected 'mangled_name:NUM:NUM:NUM', found " +
- Line);
- assert(Matches.size() == 5);
+ Regex HeadRE("^([^:]+):([0-9]+):([0-9]+)$");
+ Regex LineSample("^([0-9]+)(\\.[0-9]+)?: ([0-9]+)(.*)$");
+ while (!LineIt.is_at_eof()) {
+ // Read the header of each function. The function header should
+ // have this format:
+ //
+ // function_name:total_samples:total_head_samples
+ //
+ // See above for an explanation of each field.
+ SmallVector<StringRef, 3> Matches;
+ if (!HeadRE.match(*LineIt, &Matches))
+ reportParseError(LineIt.line_number(),
+ "Expected 'mangled_name:NUM:NUM', found " + *LineIt);
+ assert(Matches.size() == 4);
StringRef FName = Matches[1];
- unsigned NumSamples, NumHeadSamples, NumSampledLines;
+ unsigned NumSamples, NumHeadSamples;
Matches[2].getAsInteger(10, NumSamples);
Matches[3].getAsInteger(10, NumHeadSamples);
- Matches[4].getAsInteger(10, NumSampledLines);
+ Profiles[FName] = SampleFunctionProfile();
SampleFunctionProfile &FProfile = Profiles[FName];
FProfile.addTotalSamples(NumSamples);
FProfile.addHeadSamples(NumHeadSamples);
- unsigned I;
- for (I = 0; I < NumSampledLines && !Loader.atEOF(); I++) {
- Line = Loader.readLine();
- if (!LineSample.match(Line, &Matches))
- Loader.reportParseError("Expected 'NUM: NUM', found " + Line);
- assert(Matches.size() == 3);
+ ++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 (!LineSample.match(*LineIt, &Matches))
+ reportParseError(
+ LineIt.line_number(),
+ "Expected 'NUM[.NUM]: NUM[ mangled_name:NUM]*', found " + *LineIt);
+ assert(Matches.size() == 5);
unsigned LineOffset, NumSamples;
Matches[1].getAsInteger(10, LineOffset);
- Matches[2].getAsInteger(10, NumSamples);
+
+ // FIXME: Handle discriminator information (in Matches[2]).
+
+ Matches[3].getAsInteger(10, NumSamples);
+
+ // FIXME: Handle called targets (in Matches[4]).
+
// When dealing with instruction weights, we use the value
// zero to indicate the absence of a sample. If we read an
// actual zero from the profile file, return it as 1 to
@@ -464,10 +455,8 @@ void SampleModuleProfile::loadText() {
if (NumSamples == 0)
NumSamples = 1;
FProfile.addBodySamples(LineOffset, NumSamples);
+ ++LineIt;
}
-
- if (I < NumSampledLines)
- Loader.reportParseError("Unexpected end of file");
}
}
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