1 //===- SampleProfReader.h - Read LLVM sample profile data -------*- C++ -*-===// 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 contains definitions needed for reading sample profiles. 11 // 12 // NOTE: If you are making changes to this file format, please remember 13 // to document them in the Clang documentation at 14 // tools/clang/docs/UsersManual.rst. 15 // 16 // Text format 17 // ----------- 18 // 19 // Sample profiles are written as ASCII text. The file is divided into 20 // sections, which correspond to each of the functions executed at runtime. 21 // Each section has the following format 22 // 23 // function1:total_samples:total_head_samples 24 // offset1[.discriminator]: number_of_samples [fn1:num fn2:num ... ] 25 // offset2[.discriminator]: number_of_samples [fn3:num fn4:num ... ] 26 // ... 27 // offsetN[.discriminator]: number_of_samples [fn5:num fn6:num ... ] 28 // offsetA[.discriminator]: fnA:num_of_total_samples 29 // offsetA1[.discriminator]: number_of_samples [fn7:num fn8:num ... ] 30 // ... 31 // 32 // This is a nested tree in which the identation represents the nesting level 33 // of the inline stack. There are no blank lines in the file. And the spacing 34 // within a single line is fixed. Additional spaces will result in an error 35 // while reading the file. 36 // 37 // Any line starting with the '#' character is completely ignored. 38 // 39 // Inlined calls are represented with indentation. The Inline stack is a 40 // stack of source locations in which the top of the stack represents the 41 // leaf function, and the bottom of the stack represents the actual 42 // symbol to which the instruction belongs. 43 // 44 // Function names must be mangled in order for the profile loader to 45 // match them in the current translation unit. The two numbers in the 46 // function header specify how many total samples were accumulated in the 47 // function (first number), and the total number of samples accumulated 48 // in the prologue of the function (second number). This head sample 49 // count provides an indicator of how frequently the function is invoked. 50 // 51 // There are two types of lines in the function body. 52 // 53 // * Sampled line represents the profile information of a source location. 54 // * Callsite line represents the profile information of a callsite. 55 // 56 // Each sampled line may contain several items. Some are optional (marked 57 // below): 58 // 59 // a. Source line offset. This number represents the line number 60 // in the function where the sample was collected. The line number is 61 // always relative to the line where symbol of the function is 62 // defined. So, if the function has its header at line 280, the offset 63 // 13 is at line 293 in the file. 64 // 65 // Note that this offset should never be a negative number. This could 66 // happen in cases like macros. The debug machinery will register the 67 // line number at the point of macro expansion. So, if the macro was 68 // expanded in a line before the start of the function, the profile 69 // converter should emit a 0 as the offset (this means that the optimizers 70 // will not be able to associate a meaningful weight to the instructions 71 // in the macro). 72 // 73 // b. [OPTIONAL] Discriminator. This is used if the sampled program 74 // was compiled with DWARF discriminator support 75 // (http://wiki.dwarfstd.org/index.php?title=Path_Discriminators). 76 // DWARF discriminators are unsigned integer values that allow the 77 // compiler to distinguish between multiple execution paths on the 78 // same source line location. 79 // 80 // For example, consider the line of code ``if (cond) foo(); else bar();``. 81 // If the predicate ``cond`` is true 80% of the time, then the edge 82 // into function ``foo`` should be considered to be taken most of the 83 // time. But both calls to ``foo`` and ``bar`` are at the same source 84 // line, so a sample count at that line is not sufficient. The 85 // compiler needs to know which part of that line is taken more 86 // frequently. 87 // 88 // This is what discriminators provide. In this case, the calls to 89 // ``foo`` and ``bar`` will be at the same line, but will have 90 // different discriminator values. This allows the compiler to correctly 91 // set edge weights into ``foo`` and ``bar``. 92 // 93 // c. Number of samples. This is an integer quantity representing the 94 // number of samples collected by the profiler at this source 95 // location. 96 // 97 // d. [OPTIONAL] Potential call targets and samples. If present, this 98 // line contains a call instruction. This models both direct and 99 // number of samples. For example, 100 // 101 // 130: 7 foo:3 bar:2 baz:7 102 // 103 // The above means that at relative line offset 130 there is a call 104 // instruction that calls one of ``foo()``, ``bar()`` and ``baz()``, 105 // with ``baz()`` being the relatively more frequently called target. 106 // 107 // Each callsite line may contain several items. Some are optional. 108 // 109 // a. Source line offset. This number represents the line number of the 110 // callsite that is inlined in the profiled binary. 111 // 112 // b. [OPTIONAL] Discriminator. Same as the discriminator for sampled line. 113 // 114 // c. Number of samples. This is an integer quantity representing the 115 // total number of samples collected for the inlined instance at this 116 // callsite 117 // 118 // 119 // Binary format 120 // ------------- 121 // 122 // This is a more compact encoding. Numbers are encoded as ULEB128 values 123 // and all strings are encoded in a name table. The file is organized in 124 // the following sections: 125 // 126 // MAGIC (uint64_t) 127 // File identifier computed by function SPMagic() (0x5350524f463432ff) 128 // 129 // VERSION (uint32_t) 130 // File format version number computed by SPVersion() 131 // 132 // SUMMARY 133 // TOTAL_COUNT (uint64_t) 134 // Total number of samples in the profile. 135 // MAX_COUNT (uint64_t) 136 // Maximum value of samples on a line. 137 // MAX_FUNCTION_COUNT (uint64_t) 138 // Maximum number of samples at function entry (head samples). 139 // NUM_COUNTS (uint64_t) 140 // Number of lines with samples. 141 // NUM_FUNCTIONS (uint64_t) 142 // Number of functions with samples. 143 // NUM_DETAILED_SUMMARY_ENTRIES (size_t) 144 // Number of entries in detailed summary 145 // DETAILED_SUMMARY 146 // A list of detailed summary entry. Each entry consists of 147 // CUTOFF (uint32_t) 148 // Required percentile of total sample count expressed as a fraction 149 // multiplied by 1000000. 150 // MIN_COUNT (uint64_t) 151 // The minimum number of samples required to reach the target 152 // CUTOFF. 153 // NUM_COUNTS (uint64_t) 154 // Number of samples to get to the desrired percentile. 155 // 156 // NAME TABLE 157 // SIZE (uint32_t) 158 // Number of entries in the name table. 159 // NAMES 160 // A NUL-separated list of SIZE strings. 161 // 162 // FUNCTION BODY (one for each uninlined function body present in the profile) 163 // HEAD_SAMPLES (uint64_t) [only for top-level functions] 164 // Total number of samples collected at the head (prologue) of the 165 // function. 166 // NOTE: This field should only be present for top-level functions 167 // (i.e., not inlined into any caller). Inlined function calls 168 // have no prologue, so they don't need this. 169 // NAME_IDX (uint32_t) 170 // Index into the name table indicating the function name. 171 // SAMPLES (uint64_t) 172 // Total number of samples collected in this function. 173 // NRECS (uint32_t) 174 // Total number of sampling records this function's profile. 175 // BODY RECORDS 176 // A list of NRECS entries. Each entry contains: 177 // OFFSET (uint32_t) 178 // Line offset from the start of the function. 179 // DISCRIMINATOR (uint32_t) 180 // Discriminator value (see description of discriminators 181 // in the text format documentation above). 182 // SAMPLES (uint64_t) 183 // Number of samples collected at this location. 184 // NUM_CALLS (uint32_t) 185 // Number of non-inlined function calls made at this location. In the 186 // case of direct calls, this number will always be 1. For indirect 187 // calls (virtual functions and function pointers) this will 188 // represent all the actual functions called at runtime. 189 // CALL_TARGETS 190 // A list of NUM_CALLS entries for each called function: 191 // NAME_IDX (uint32_t) 192 // Index into the name table with the callee name. 193 // SAMPLES (uint64_t) 194 // Number of samples collected at the call site. 195 // NUM_INLINED_FUNCTIONS (uint32_t) 196 // Number of callees inlined into this function. 197 // INLINED FUNCTION RECORDS 198 // A list of NUM_INLINED_FUNCTIONS entries describing each of the inlined 199 // callees. 200 // OFFSET (uint32_t) 201 // Line offset from the start of the function. 202 // DISCRIMINATOR (uint32_t) 203 // Discriminator value (see description of discriminators 204 // in the text format documentation above). 205 // FUNCTION BODY 206 // A FUNCTION BODY entry describing the inlined function. 207 //===----------------------------------------------------------------------===// 208 209 #ifndef LLVM_PROFILEDATA_SAMPLEPROFREADER_H 210 #define LLVM_PROFILEDATA_SAMPLEPROFREADER_H 211 212 #include "llvm/ADT/SmallVector.h" 213 #include "llvm/ADT/StringMap.h" 214 #include "llvm/ADT/StringRef.h" 215 #include "llvm/ADT/Twine.h" 216 #include "llvm/IR/DiagnosticInfo.h" 217 #include "llvm/IR/Function.h" 218 #include "llvm/IR/LLVMContext.h" 219 #include "llvm/IR/ProfileSummary.h" 220 #include "llvm/ProfileData/SampleProf.h" 221 #include "llvm/Support/Debug.h" 222 #include "llvm/Support/ErrorOr.h" 223 #include "llvm/Support/GCOV.h" 224 #include "llvm/Support/MemoryBuffer.h" 225 #include <algorithm> 226 #include <cstdint> 227 #include <memory> 228 #include <string> 229 #include <system_error> 230 #include <vector> 231 232 namespace llvm { 233 234 class raw_ostream; 235 236 namespace sampleprof { 237 238 /// \brief Sample-based profile reader. 239 /// 240 /// Each profile contains sample counts for all the functions 241 /// executed. Inside each function, statements are annotated with the 242 /// collected samples on all the instructions associated with that 243 /// statement. 244 /// 245 /// For this to produce meaningful data, the program needs to be 246 /// compiled with some debug information (at minimum, line numbers: 247 /// -gline-tables-only). Otherwise, it will be impossible to match IR 248 /// instructions to the line numbers collected by the profiler. 249 /// 250 /// From the profile file, we are interested in collecting the 251 /// following information: 252 /// 253 /// * A list of functions included in the profile (mangled names). 254 /// 255 /// * For each function F: 256 /// 1. The total number of samples collected in F. 257 /// 258 /// 2. The samples collected at each line in F. To provide some 259 /// protection against source code shuffling, line numbers should 260 /// be relative to the start of the function. 261 /// 262 /// The reader supports two file formats: text and binary. The text format 263 /// is useful for debugging and testing, while the binary format is more 264 /// compact and I/O efficient. They can both be used interchangeably. 265 class SampleProfileReader { 266 public: 267 SampleProfileReader(std::unique_ptr<MemoryBuffer> B, LLVMContext &C) 268 : Profiles(0), Ctx(C), Buffer(std::move(B)) {} 269 270 virtual ~SampleProfileReader() = default; 271 272 /// \brief Read and validate the file header. 273 virtual std::error_code readHeader() = 0; 274 275 /// \brief Read sample profiles from the associated file. 276 virtual std::error_code read() = 0; 277 278 /// \brief Print the profile for \p FName on stream \p OS. 279 void dumpFunctionProfile(StringRef FName, raw_ostream &OS = dbgs()); 280 281 /// \brief Print all the profiles on stream \p OS. 282 void dump(raw_ostream &OS = dbgs()); 283 284 /// \brief Return the samples collected for function \p F. 285 FunctionSamples *getSamplesFor(const Function &F) { 286 // The function name may have been updated by adding suffix. In sample 287 // profile, the function names are all stripped, so we need to strip 288 // the function name suffix before matching with profile. 289 if (Profiles.count(F.getName().split('.').first)) 290 return &Profiles[(F.getName().split('.').first)]; 291 return nullptr; 292 } 293 294 /// \brief Return all the profiles. 295 StringMap<FunctionSamples> &getProfiles() { return Profiles; } 296 297 /// \brief Report a parse error message. 298 void reportError(int64_t LineNumber, Twine Msg) const { 299 Ctx.diagnose(DiagnosticInfoSampleProfile(Buffer->getBufferIdentifier(), 300 LineNumber, Msg)); 301 } 302 303 /// \brief Create a sample profile reader appropriate to the file format. 304 static ErrorOr<std::unique_ptr<SampleProfileReader>> 305 create(const Twine &Filename, LLVMContext &C); 306 307 /// \brief Create a sample profile reader from the supplied memory buffer. 308 static ErrorOr<std::unique_ptr<SampleProfileReader>> 309 create(std::unique_ptr<MemoryBuffer> &B, LLVMContext &C); 310 311 /// \brief Return the profile summary. 312 ProfileSummary &getSummary() { return *(Summary.get()); } 313 314 protected: 315 /// \brief Map every function to its associated profile. 316 /// 317 /// The profile of every function executed at runtime is collected 318 /// in the structure FunctionSamples. This maps function objects 319 /// to their corresponding profiles. 320 StringMap<FunctionSamples> Profiles; 321 322 /// \brief LLVM context used to emit diagnostics. 323 LLVMContext &Ctx; 324 325 /// \brief Memory buffer holding the profile file. 326 std::unique_ptr<MemoryBuffer> Buffer; 327 328 /// \brief Profile summary information. 329 std::unique_ptr<ProfileSummary> Summary; 330 331 /// \brief Compute summary for this profile. 332 void computeSummary(); 333 }; 334 335 class SampleProfileReaderText : public SampleProfileReader { 336 public: 337 SampleProfileReaderText(std::unique_ptr<MemoryBuffer> B, LLVMContext &C) 338 : SampleProfileReader(std::move(B), C) {} 339 340 /// \brief Read and validate the file header. 341 std::error_code readHeader() override { return sampleprof_error::success; } 342 343 /// \brief Read sample profiles from the associated file. 344 std::error_code read() override; 345 346 /// \brief Return true if \p Buffer is in the format supported by this class. 347 static bool hasFormat(const MemoryBuffer &Buffer); 348 }; 349 350 class SampleProfileReaderBinary : public SampleProfileReader { 351 public: 352 SampleProfileReaderBinary(std::unique_ptr<MemoryBuffer> B, LLVMContext &C) 353 : SampleProfileReader(std::move(B), C) {} 354 355 /// \brief Read and validate the file header. 356 std::error_code readHeader() override; 357 358 /// \brief Read sample profiles from the associated file. 359 std::error_code read() override; 360 361 /// \brief Return true if \p Buffer is in the format supported by this class. 362 static bool hasFormat(const MemoryBuffer &Buffer); 363 364 protected: 365 /// \brief Read a numeric value of type T from the profile. 366 /// 367 /// If an error occurs during decoding, a diagnostic message is emitted and 368 /// EC is set. 369 /// 370 /// \returns the read value. 371 template <typename T> ErrorOr<T> readNumber(); 372 373 /// \brief Read a string from the profile. 374 /// 375 /// If an error occurs during decoding, a diagnostic message is emitted and 376 /// EC is set. 377 /// 378 /// \returns the read value. 379 ErrorOr<StringRef> readString(); 380 381 /// Read a string indirectly via the name table. 382 ErrorOr<StringRef> readStringFromTable(); 383 384 /// \brief Return true if we've reached the end of file. 385 bool at_eof() const { return Data >= End; } 386 387 /// Read the contents of the given profile instance. 388 std::error_code readProfile(FunctionSamples &FProfile); 389 390 /// \brief Points to the current location in the buffer. 391 const uint8_t *Data = nullptr; 392 393 /// \brief Points to the end of the buffer. 394 const uint8_t *End = nullptr; 395 396 /// Function name table. 397 std::vector<StringRef> NameTable; 398 399 private: 400 std::error_code readSummaryEntry(std::vector<ProfileSummaryEntry> &Entries); 401 402 /// \brief Read profile summary. 403 std::error_code readSummary(); 404 }; 405 406 using InlineCallStack = SmallVector<FunctionSamples *, 10>; 407 408 // Supported histogram types in GCC. Currently, we only need support for 409 // call target histograms. 410 enum HistType { 411 HIST_TYPE_INTERVAL, 412 HIST_TYPE_POW2, 413 HIST_TYPE_SINGLE_VALUE, 414 HIST_TYPE_CONST_DELTA, 415 HIST_TYPE_INDIR_CALL, 416 HIST_TYPE_AVERAGE, 417 HIST_TYPE_IOR, 418 HIST_TYPE_INDIR_CALL_TOPN 419 }; 420 421 class SampleProfileReaderGCC : public SampleProfileReader { 422 public: 423 SampleProfileReaderGCC(std::unique_ptr<MemoryBuffer> B, LLVMContext &C) 424 : SampleProfileReader(std::move(B), C), GcovBuffer(Buffer.get()) {} 425 426 /// \brief Read and validate the file header. 427 std::error_code readHeader() override; 428 429 /// \brief Read sample profiles from the associated file. 430 std::error_code read() override; 431 432 /// \brief Return true if \p Buffer is in the format supported by this class. 433 static bool hasFormat(const MemoryBuffer &Buffer); 434 435 protected: 436 std::error_code readNameTable(); 437 std::error_code readOneFunctionProfile(const InlineCallStack &InlineStack, 438 bool Update, uint32_t Offset); 439 std::error_code readFunctionProfiles(); 440 std::error_code skipNextWord(); 441 template <typename T> ErrorOr<T> readNumber(); 442 ErrorOr<StringRef> readString(); 443 444 /// \brief Read the section tag and check that it's the same as \p Expected. 445 std::error_code readSectionTag(uint32_t Expected); 446 447 /// GCOV buffer containing the profile. 448 GCOVBuffer GcovBuffer; 449 450 /// Function names in this profile. 451 std::vector<std::string> Names; 452 453 /// GCOV tags used to separate sections in the profile file. 454 static const uint32_t GCOVTagAFDOFileNames = 0xaa000000; 455 static const uint32_t GCOVTagAFDOFunction = 0xac000000; 456 }; 457 458 } // end namespace sampleprof 459 460 } // end namespace llvm 461 462 #endif // LLVM_PROFILEDATA_SAMPLEPROFREADER_H 463