1 //===- SampleProfReader.cpp - Read LLVM sample profile data ---------------===//
2 //
3 //                      The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the class that reads LLVM sample profiles. It
11 // supports two file formats: text and binary. The textual representation
12 // is useful for debugging and testing purposes. The binary representation
13 // is more compact, resulting in smaller file sizes. However, they can
14 // both be used interchangeably.
15 //
16 // NOTE: If you are making changes to the file format, please remember
17 //       to document them in the Clang documentation at
18 //       tools/clang/docs/UsersManual.rst.
19 //
20 // Text format
21 // -----------
22 //
23 // Sample profiles are written as ASCII text. The file is divided into
24 // sections, which correspond to each of the functions executed at runtime.
25 // Each section has the following format
26 //
27 //     function1:total_samples:total_head_samples
28 //     offset1[.discriminator]: number_of_samples [fn1:num fn2:num ... ]
29 //     offset2[.discriminator]: number_of_samples [fn3:num fn4:num ... ]
30 //     ...
31 //     offsetN[.discriminator]: number_of_samples [fn5:num fn6:num ... ]
32 //
33 // The file may contain blank lines between sections and within a
34 // section. However, the spacing within a single line is fixed. Additional
35 // spaces will result in an error while reading the file.
36 //
37 // Function names must be mangled in order for the profile loader to
38 // match them in the current translation unit. The two numbers in the
39 // function header specify how many total samples were accumulated in the
40 // function (first number), and the total number of samples accumulated
41 // in the prologue of the function (second number). This head sample
42 // count provides an indicator of how frequently the function is invoked.
43 //
44 // Each sampled line may contain several items. Some are optional (marked
45 // below):
46 //
47 // a. Source line offset. This number represents the line number
48 //    in the function where the sample was collected. The line number is
49 //    always relative to the line where symbol of the function is
50 //    defined. So, if the function has its header at line 280, the offset
51 //    13 is at line 293 in the file.
52 //
53 //    Note that this offset should never be a negative number. This could
54 //    happen in cases like macros. The debug machinery will register the
55 //    line number at the point of macro expansion. So, if the macro was
56 //    expanded in a line before the start of the function, the profile
57 //    converter should emit a 0 as the offset (this means that the optimizers
58 //    will not be able to associate a meaningful weight to the instructions
59 //    in the macro).
60 //
61 // b. [OPTIONAL] Discriminator. This is used if the sampled program
62 //    was compiled with DWARF discriminator support
63 //    (http://wiki.dwarfstd.org/index.php?title=Path_Discriminators).
64 //    DWARF discriminators are unsigned integer values that allow the
65 //    compiler to distinguish between multiple execution paths on the
66 //    same source line location.
67 //
68 //    For example, consider the line of code ``if (cond) foo(); else bar();``.
69 //    If the predicate ``cond`` is true 80% of the time, then the edge
70 //    into function ``foo`` should be considered to be taken most of the
71 //    time. But both calls to ``foo`` and ``bar`` are at the same source
72 //    line, so a sample count at that line is not sufficient. The
73 //    compiler needs to know which part of that line is taken more
74 //    frequently.
75 //
76 //    This is what discriminators provide. In this case, the calls to
77 //    ``foo`` and ``bar`` will be at the same line, but will have
78 //    different discriminator values. This allows the compiler to correctly
79 //    set edge weights into ``foo`` and ``bar``.
80 //
81 // c. Number of samples. This is an integer quantity representing the
82 //    number of samples collected by the profiler at this source
83 //    location.
84 //
85 // d. [OPTIONAL] Potential call targets and samples. If present, this
86 //    line contains a call instruction. This models both direct and
87 //    number of samples. For example,
88 //
89 //      130: 7  foo:3  bar:2  baz:7
90 //
91 //    The above means that at relative line offset 130 there is a call
92 //    instruction that calls one of ``foo()``, ``bar()`` and ``baz()``,
93 //    with ``baz()`` being the relatively more frequently called target.
94 //
95 //===----------------------------------------------------------------------===//
96 
97 #include "llvm/ProfileData/SampleProfReader.h"
98 #include "llvm/Support/Debug.h"
99 #include "llvm/Support/ErrorOr.h"
100 #include "llvm/Support/LEB128.h"
101 #include "llvm/Support/LineIterator.h"
102 #include "llvm/Support/MemoryBuffer.h"
103 #include "llvm/Support/Regex.h"
104 
105 using namespace llvm::sampleprof;
106 using namespace llvm;
107 
108 /// \brief Print the samples collected for a function on stream \p OS.
109 ///
110 /// \param OS Stream to emit the output to.
print(raw_ostream & OS)111 void FunctionSamples::print(raw_ostream &OS) {
112   OS << TotalSamples << ", " << TotalHeadSamples << ", " << BodySamples.size()
113      << " sampled lines\n";
114   for (const auto &SI : BodySamples) {
115     LineLocation Loc = SI.first;
116     const SampleRecord &Sample = SI.second;
117     OS << "\tline offset: " << Loc.LineOffset
118        << ", discriminator: " << Loc.Discriminator
119        << ", number of samples: " << Sample.getSamples();
120     if (Sample.hasCalls()) {
121       OS << ", calls:";
122       for (const auto &I : Sample.getCallTargets())
123         OS << " " << I.first() << ":" << I.second;
124     }
125     OS << "\n";
126   }
127   OS << "\n";
128 }
129 
130 /// \brief Dump the function profile for \p FName.
131 ///
132 /// \param FName Name of the function to print.
133 /// \param OS Stream to emit the output to.
dumpFunctionProfile(StringRef FName,raw_ostream & OS)134 void SampleProfileReader::dumpFunctionProfile(StringRef FName,
135                                               raw_ostream &OS) {
136   OS << "Function: " << FName << ": ";
137   Profiles[FName].print(OS);
138 }
139 
140 /// \brief Dump all the function profiles found on stream \p OS.
dump(raw_ostream & OS)141 void SampleProfileReader::dump(raw_ostream &OS) {
142   for (const auto &I : Profiles)
143     dumpFunctionProfile(I.getKey(), OS);
144 }
145 
146 /// \brief Load samples from a text file.
147 ///
148 /// See the documentation at the top of the file for an explanation of
149 /// the expected format.
150 ///
151 /// \returns true if the file was loaded successfully, false otherwise.
read()152 std::error_code SampleProfileReaderText::read() {
153   line_iterator LineIt(*Buffer, /*SkipBlanks=*/true, '#');
154 
155   // Read the profile of each function. Since each function may be
156   // mentioned more than once, and we are collecting flat profiles,
157   // accumulate samples as we parse them.
158   Regex HeadRE("^([^0-9].*):([0-9]+):([0-9]+)$");
159   Regex LineSampleRE("^([0-9]+)\\.?([0-9]+)?: ([0-9]+)(.*)$");
160   Regex CallSampleRE(" +([^0-9 ][^ ]*):([0-9]+)");
161   while (!LineIt.is_at_eof()) {
162     // Read the header of each function.
163     //
164     // Note that for function identifiers we are actually expecting
165     // mangled names, but we may not always get them. This happens when
166     // the compiler decides not to emit the function (e.g., it was inlined
167     // and removed). In this case, the binary will not have the linkage
168     // name for the function, so the profiler will emit the function's
169     // unmangled name, which may contain characters like ':' and '>' in its
170     // name (member functions, templates, etc).
171     //
172     // The only requirement we place on the identifier, then, is that it
173     // should not begin with a number.
174     SmallVector<StringRef, 4> Matches;
175     if (!HeadRE.match(*LineIt, &Matches)) {
176       reportParseError(LineIt.line_number(),
177                        "Expected 'mangled_name:NUM:NUM', found " + *LineIt);
178       return sampleprof_error::malformed;
179     }
180     assert(Matches.size() == 4);
181     StringRef FName = Matches[1];
182     unsigned NumSamples, NumHeadSamples;
183     Matches[2].getAsInteger(10, NumSamples);
184     Matches[3].getAsInteger(10, NumHeadSamples);
185     Profiles[FName] = FunctionSamples();
186     FunctionSamples &FProfile = Profiles[FName];
187     FProfile.addTotalSamples(NumSamples);
188     FProfile.addHeadSamples(NumHeadSamples);
189     ++LineIt;
190 
191     // Now read the body. The body of the function ends when we reach
192     // EOF or when we see the start of the next function.
193     while (!LineIt.is_at_eof() && isdigit((*LineIt)[0])) {
194       if (!LineSampleRE.match(*LineIt, &Matches)) {
195         reportParseError(
196             LineIt.line_number(),
197             "Expected 'NUM[.NUM]: NUM[ mangled_name:NUM]*', found " + *LineIt);
198         return sampleprof_error::malformed;
199       }
200       assert(Matches.size() == 5);
201       unsigned LineOffset, NumSamples, Discriminator = 0;
202       Matches[1].getAsInteger(10, LineOffset);
203       if (Matches[2] != "")
204         Matches[2].getAsInteger(10, Discriminator);
205       Matches[3].getAsInteger(10, NumSamples);
206 
207       // If there are function calls in this line, generate a call sample
208       // entry for each call.
209       std::string CallsLine(Matches[4]);
210       while (CallsLine != "") {
211         SmallVector<StringRef, 3> CallSample;
212         if (!CallSampleRE.match(CallsLine, &CallSample)) {
213           reportParseError(LineIt.line_number(),
214                            "Expected 'mangled_name:NUM', found " + CallsLine);
215           return sampleprof_error::malformed;
216         }
217         StringRef CalledFunction = CallSample[1];
218         unsigned CalledFunctionSamples;
219         CallSample[2].getAsInteger(10, CalledFunctionSamples);
220         FProfile.addCalledTargetSamples(LineOffset, Discriminator,
221                                         CalledFunction, CalledFunctionSamples);
222         CallsLine = CallSampleRE.sub("", CallsLine);
223       }
224 
225       FProfile.addBodySamples(LineOffset, Discriminator, NumSamples);
226       ++LineIt;
227     }
228   }
229 
230   return sampleprof_error::success;
231 }
232 
readNumber()233 template <typename T> ErrorOr<T> SampleProfileReaderBinary::readNumber() {
234   unsigned NumBytesRead = 0;
235   std::error_code EC;
236   uint64_t Val = decodeULEB128(Data, &NumBytesRead);
237 
238   if (Val > std::numeric_limits<T>::max())
239     EC = sampleprof_error::malformed;
240   else if (Data + NumBytesRead > End)
241     EC = sampleprof_error::truncated;
242   else
243     EC = sampleprof_error::success;
244 
245   if (EC) {
246     reportParseError(0, EC.message());
247     return EC;
248   }
249 
250   Data += NumBytesRead;
251   return static_cast<T>(Val);
252 }
253 
readString()254 ErrorOr<StringRef> SampleProfileReaderBinary::readString() {
255   std::error_code EC;
256   StringRef Str(reinterpret_cast<const char *>(Data));
257   if (Data + Str.size() + 1 > End) {
258     EC = sampleprof_error::truncated;
259     reportParseError(0, EC.message());
260     return EC;
261   }
262 
263   Data += Str.size() + 1;
264   return Str;
265 }
266 
read()267 std::error_code SampleProfileReaderBinary::read() {
268   while (!at_eof()) {
269     auto FName(readString());
270     if (std::error_code EC = FName.getError())
271       return EC;
272 
273     Profiles[*FName] = FunctionSamples();
274     FunctionSamples &FProfile = Profiles[*FName];
275 
276     auto Val = readNumber<unsigned>();
277     if (std::error_code EC = Val.getError())
278       return EC;
279     FProfile.addTotalSamples(*Val);
280 
281     Val = readNumber<unsigned>();
282     if (std::error_code EC = Val.getError())
283       return EC;
284     FProfile.addHeadSamples(*Val);
285 
286     // Read the samples in the body.
287     auto NumRecords = readNumber<unsigned>();
288     if (std::error_code EC = NumRecords.getError())
289       return EC;
290     for (unsigned I = 0; I < *NumRecords; ++I) {
291       auto LineOffset = readNumber<uint64_t>();
292       if (std::error_code EC = LineOffset.getError())
293         return EC;
294 
295       auto Discriminator = readNumber<uint64_t>();
296       if (std::error_code EC = Discriminator.getError())
297         return EC;
298 
299       auto NumSamples = readNumber<uint64_t>();
300       if (std::error_code EC = NumSamples.getError())
301         return EC;
302 
303       auto NumCalls = readNumber<unsigned>();
304       if (std::error_code EC = NumCalls.getError())
305         return EC;
306 
307       for (unsigned J = 0; J < *NumCalls; ++J) {
308         auto CalledFunction(readString());
309         if (std::error_code EC = CalledFunction.getError())
310           return EC;
311 
312         auto CalledFunctionSamples = readNumber<uint64_t>();
313         if (std::error_code EC = CalledFunctionSamples.getError())
314           return EC;
315 
316         FProfile.addCalledTargetSamples(*LineOffset, *Discriminator,
317                                         *CalledFunction,
318                                         *CalledFunctionSamples);
319       }
320 
321       FProfile.addBodySamples(*LineOffset, *Discriminator, *NumSamples);
322     }
323   }
324 
325   return sampleprof_error::success;
326 }
327 
readHeader()328 std::error_code SampleProfileReaderBinary::readHeader() {
329   Data = reinterpret_cast<const uint8_t *>(Buffer->getBufferStart());
330   End = Data + Buffer->getBufferSize();
331 
332   // Read and check the magic identifier.
333   auto Magic = readNumber<uint64_t>();
334   if (std::error_code EC = Magic.getError())
335     return EC;
336   else if (*Magic != SPMagic())
337     return sampleprof_error::bad_magic;
338 
339   // Read the version number.
340   auto Version = readNumber<uint64_t>();
341   if (std::error_code EC = Version.getError())
342     return EC;
343   else if (*Version != SPVersion())
344     return sampleprof_error::unsupported_version;
345 
346   return sampleprof_error::success;
347 }
348 
hasFormat(const MemoryBuffer & Buffer)349 bool SampleProfileReaderBinary::hasFormat(const MemoryBuffer &Buffer) {
350   const uint8_t *Data =
351       reinterpret_cast<const uint8_t *>(Buffer.getBufferStart());
352   uint64_t Magic = decodeULEB128(Data);
353   return Magic == SPMagic();
354 }
355 
356 /// \brief Prepare a memory buffer for the contents of \p Filename.
357 ///
358 /// \returns an error code indicating the status of the buffer.
359 static ErrorOr<std::unique_ptr<MemoryBuffer>>
setupMemoryBuffer(std::string Filename)360 setupMemoryBuffer(std::string Filename) {
361   auto BufferOrErr = MemoryBuffer::getFileOrSTDIN(Filename);
362   if (std::error_code EC = BufferOrErr.getError())
363     return EC;
364   auto Buffer = std::move(BufferOrErr.get());
365 
366   // Sanity check the file.
367   if (Buffer->getBufferSize() > std::numeric_limits<unsigned>::max())
368     return sampleprof_error::too_large;
369 
370   return std::move(Buffer);
371 }
372 
373 /// \brief Create a sample profile reader based on the format of the input file.
374 ///
375 /// \param Filename The file to open.
376 ///
377 /// \param Reader The reader to instantiate according to \p Filename's format.
378 ///
379 /// \param C The LLVM context to use to emit diagnostics.
380 ///
381 /// \returns an error code indicating the status of the created reader.
382 ErrorOr<std::unique_ptr<SampleProfileReader>>
create(StringRef Filename,LLVMContext & C)383 SampleProfileReader::create(StringRef Filename, LLVMContext &C) {
384   auto BufferOrError = setupMemoryBuffer(Filename);
385   if (std::error_code EC = BufferOrError.getError())
386     return EC;
387 
388   auto Buffer = std::move(BufferOrError.get());
389   std::unique_ptr<SampleProfileReader> Reader;
390   if (SampleProfileReaderBinary::hasFormat(*Buffer))
391     Reader.reset(new SampleProfileReaderBinary(std::move(Buffer), C));
392   else
393     Reader.reset(new SampleProfileReaderText(std::move(Buffer), C));
394 
395   if (std::error_code EC = Reader->readHeader())
396     return EC;
397 
398   return std::move(Reader);
399 }
400