WinCodeViewLineTables.cpp revision 280031
1//===-- llvm/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp --*- 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 support for writing line tables info into COFF files. 11// 12//===----------------------------------------------------------------------===// 13 14#include "WinCodeViewLineTables.h" 15#include "llvm/MC/MCExpr.h" 16#include "llvm/MC/MCSymbol.h" 17#include "llvm/Support/COFF.h" 18 19namespace llvm { 20 21StringRef WinCodeViewLineTables::getFullFilepath(const MDNode *S) { 22 assert(S); 23 DIDescriptor D(S); 24 assert((D.isCompileUnit() || D.isFile() || D.isSubprogram() || 25 D.isLexicalBlockFile() || D.isLexicalBlock()) && 26 "Unexpected scope info"); 27 28 DIScope Scope(S); 29 StringRef Dir = Scope.getDirectory(), 30 Filename = Scope.getFilename(); 31 char *&Result = DirAndFilenameToFilepathMap[std::make_pair(Dir, Filename)]; 32 if (Result) 33 return Result; 34 35 // Clang emits directory and relative filename info into the IR, but CodeView 36 // operates on full paths. We could change Clang to emit full paths too, but 37 // that would increase the IR size and probably not needed for other users. 38 // For now, just concatenate and canonicalize the path here. 39 std::string Filepath; 40 if (Filename.find(':') == 1) 41 Filepath = Filename; 42 else 43 Filepath = (Dir + Twine("\\") + Filename).str(); 44 45 // Canonicalize the path. We have to do it textually because we may no longer 46 // have access the file in the filesystem. 47 // First, replace all slashes with backslashes. 48 std::replace(Filepath.begin(), Filepath.end(), '/', '\\'); 49 50 // Remove all "\.\" with "\". 51 size_t Cursor = 0; 52 while ((Cursor = Filepath.find("\\.\\", Cursor)) != std::string::npos) 53 Filepath.erase(Cursor, 2); 54 55 // Replace all "\XXX\..\" with "\". Don't try too hard though as the original 56 // path should be well-formatted, e.g. start with a drive letter, etc. 57 Cursor = 0; 58 while ((Cursor = Filepath.find("\\..\\", Cursor)) != std::string::npos) { 59 // Something's wrong if the path starts with "\..\", abort. 60 if (Cursor == 0) 61 break; 62 63 size_t PrevSlash = Filepath.rfind('\\', Cursor - 1); 64 if (PrevSlash == std::string::npos) 65 // Something's wrong, abort. 66 break; 67 68 Filepath.erase(PrevSlash, Cursor + 3 - PrevSlash); 69 // The next ".." might be following the one we've just erased. 70 Cursor = PrevSlash; 71 } 72 73 // Remove all duplicate backslashes. 74 Cursor = 0; 75 while ((Cursor = Filepath.find("\\\\", Cursor)) != std::string::npos) 76 Filepath.erase(Cursor, 1); 77 78 Result = strdup(Filepath.c_str()); 79 return StringRef(Result); 80} 81 82void WinCodeViewLineTables::maybeRecordLocation(DebugLoc DL, 83 const MachineFunction *MF) { 84 const MDNode *Scope = DL.getScope(MF->getFunction()->getContext()); 85 if (!Scope) 86 return; 87 StringRef Filename = getFullFilepath(Scope); 88 89 // Skip this instruction if it has the same file:line as the previous one. 90 assert(CurFn); 91 if (!CurFn->Instrs.empty()) { 92 const InstrInfoTy &LastInstr = InstrInfo[CurFn->Instrs.back()]; 93 if (LastInstr.Filename == Filename && LastInstr.LineNumber == DL.getLine()) 94 return; 95 } 96 FileNameRegistry.add(Filename); 97 98 MCSymbol *MCL = Asm->MMI->getContext().CreateTempSymbol(); 99 Asm->OutStreamer.EmitLabel(MCL); 100 CurFn->Instrs.push_back(MCL); 101 InstrInfo[MCL] = InstrInfoTy(Filename, DL.getLine()); 102} 103 104WinCodeViewLineTables::WinCodeViewLineTables(AsmPrinter *AP) 105 : Asm(nullptr), CurFn(nullptr) { 106 MachineModuleInfo *MMI = AP->MMI; 107 108 // If module doesn't have named metadata anchors or COFF debug section 109 // is not available, skip any debug info related stuff. 110 if (!MMI->getModule()->getNamedMetadata("llvm.dbg.cu") || 111 !AP->getObjFileLowering().getCOFFDebugSymbolsSection()) 112 return; 113 114 // Tell MMI that we have debug info. 115 MMI->setDebugInfoAvailability(true); 116 Asm = AP; 117} 118 119void WinCodeViewLineTables::endModule() { 120 if (FnDebugInfo.empty()) 121 return; 122 123 assert(Asm != nullptr); 124 Asm->OutStreamer.SwitchSection( 125 Asm->getObjFileLowering().getCOFFDebugSymbolsSection()); 126 Asm->EmitInt32(COFF::DEBUG_SECTION_MAGIC); 127 128 // The COFF .debug$S section consists of several subsections, each starting 129 // with a 4-byte control code (e.g. 0xF1, 0xF2, etc) and then a 4-byte length 130 // of the payload followed by the payload itself. The subsections are 4-byte 131 // aligned. 132 133 // Emit per-function debug information. This code is extracted into a 134 // separate function for readability. 135 for (size_t I = 0, E = VisitedFunctions.size(); I != E; ++I) 136 emitDebugInfoForFunction(VisitedFunctions[I]); 137 138 // This subsection holds a file index to offset in string table table. 139 Asm->OutStreamer.AddComment("File index to string table offset subsection"); 140 Asm->EmitInt32(COFF::DEBUG_INDEX_SUBSECTION); 141 size_t NumFilenames = FileNameRegistry.Infos.size(); 142 Asm->EmitInt32(8 * NumFilenames); 143 for (size_t I = 0, E = FileNameRegistry.Filenames.size(); I != E; ++I) { 144 StringRef Filename = FileNameRegistry.Filenames[I]; 145 // For each unique filename, just write its offset in the string table. 146 Asm->EmitInt32(FileNameRegistry.Infos[Filename].StartOffset); 147 // The function name offset is not followed by any additional data. 148 Asm->EmitInt32(0); 149 } 150 151 // This subsection holds the string table. 152 Asm->OutStreamer.AddComment("String table"); 153 Asm->EmitInt32(COFF::DEBUG_STRING_TABLE_SUBSECTION); 154 Asm->EmitInt32(FileNameRegistry.LastOffset); 155 // The payload starts with a null character. 156 Asm->EmitInt8(0); 157 158 for (size_t I = 0, E = FileNameRegistry.Filenames.size(); I != E; ++I) { 159 // Just emit unique filenames one by one, separated by a null character. 160 Asm->OutStreamer.EmitBytes(FileNameRegistry.Filenames[I]); 161 Asm->EmitInt8(0); 162 } 163 164 // No more subsections. Fill with zeros to align the end of the section by 4. 165 Asm->OutStreamer.EmitFill((-FileNameRegistry.LastOffset) % 4, 0); 166 167 clear(); 168} 169 170static void EmitLabelDiff(MCStreamer &Streamer, 171 const MCSymbol *From, const MCSymbol *To, 172 unsigned int Size = 4) { 173 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None; 174 MCContext &Context = Streamer.getContext(); 175 const MCExpr *FromRef = MCSymbolRefExpr::Create(From, Variant, Context), 176 *ToRef = MCSymbolRefExpr::Create(To, Variant, Context); 177 const MCExpr *AddrDelta = 178 MCBinaryExpr::Create(MCBinaryExpr::Sub, ToRef, FromRef, Context); 179 Streamer.EmitValue(AddrDelta, Size); 180} 181 182void WinCodeViewLineTables::emitDebugInfoForFunction(const Function *GV) { 183 // For each function there is a separate subsection 184 // which holds the PC to file:line table. 185 const MCSymbol *Fn = Asm->getSymbol(GV); 186 assert(Fn); 187 188 const FunctionInfo &FI = FnDebugInfo[GV]; 189 if (FI.Instrs.empty()) 190 return; 191 assert(FI.End && "Don't know where the function ends?"); 192 193 StringRef FuncName = getDISubprogram(GV).getDisplayName(), 194 GVName = GV->getName(); 195 // FIXME Clang currently sets DisplayName to "bar" for a C++ 196 // "namespace_foo::bar" function, see PR21528. Luckily, dbghelp.dll is trying 197 // to demangle display names anyways, so let's just put a mangled name into 198 // the symbols subsection until Clang gives us what we need. 199 if (GVName.startswith("\01?")) 200 FuncName = GVName.substr(1); 201 // Emit a symbol subsection, required by VS2012+ to find function boundaries. 202 MCSymbol *SymbolsBegin = Asm->MMI->getContext().CreateTempSymbol(), 203 *SymbolsEnd = Asm->MMI->getContext().CreateTempSymbol(); 204 Asm->OutStreamer.AddComment("Symbol subsection for " + Twine(FuncName)); 205 Asm->EmitInt32(COFF::DEBUG_SYMBOL_SUBSECTION); 206 EmitLabelDiff(Asm->OutStreamer, SymbolsBegin, SymbolsEnd); 207 Asm->OutStreamer.EmitLabel(SymbolsBegin); 208 { 209 MCSymbol *ProcSegmentBegin = Asm->MMI->getContext().CreateTempSymbol(), 210 *ProcSegmentEnd = Asm->MMI->getContext().CreateTempSymbol(); 211 EmitLabelDiff(Asm->OutStreamer, ProcSegmentBegin, ProcSegmentEnd, 2); 212 Asm->OutStreamer.EmitLabel(ProcSegmentBegin); 213 214 Asm->EmitInt16(COFF::DEBUG_SYMBOL_TYPE_PROC_START); 215 // Some bytes of this segment don't seem to be required for basic debugging, 216 // so just fill them with zeroes. 217 Asm->OutStreamer.EmitFill(12, 0); 218 // This is the important bit that tells the debugger where the function 219 // code is located and what's its size: 220 EmitLabelDiff(Asm->OutStreamer, Fn, FI.End); 221 Asm->OutStreamer.EmitFill(12, 0); 222 Asm->OutStreamer.EmitCOFFSecRel32(Fn); 223 Asm->OutStreamer.EmitCOFFSectionIndex(Fn); 224 Asm->EmitInt8(0); 225 // Emit the function display name as a null-terminated string. 226 Asm->OutStreamer.EmitBytes(FuncName); 227 Asm->EmitInt8(0); 228 Asm->OutStreamer.EmitLabel(ProcSegmentEnd); 229 230 // We're done with this function. 231 Asm->EmitInt16(0x0002); 232 Asm->EmitInt16(COFF::DEBUG_SYMBOL_TYPE_PROC_END); 233 } 234 Asm->OutStreamer.EmitLabel(SymbolsEnd); 235 // Every subsection must be aligned to a 4-byte boundary. 236 Asm->OutStreamer.EmitFill((-FuncName.size()) % 4, 0); 237 238 // PCs/Instructions are grouped into segments sharing the same filename. 239 // Pre-calculate the lengths (in instructions) of these segments and store 240 // them in a map for convenience. Each index in the map is the sequential 241 // number of the respective instruction that starts a new segment. 242 DenseMap<size_t, size_t> FilenameSegmentLengths; 243 size_t LastSegmentEnd = 0; 244 StringRef PrevFilename = InstrInfo[FI.Instrs[0]].Filename; 245 for (size_t J = 1, F = FI.Instrs.size(); J != F; ++J) { 246 if (PrevFilename == InstrInfo[FI.Instrs[J]].Filename) 247 continue; 248 FilenameSegmentLengths[LastSegmentEnd] = J - LastSegmentEnd; 249 LastSegmentEnd = J; 250 PrevFilename = InstrInfo[FI.Instrs[J]].Filename; 251 } 252 FilenameSegmentLengths[LastSegmentEnd] = FI.Instrs.size() - LastSegmentEnd; 253 254 // Emit a line table subsection, requred to do PC-to-file:line lookup. 255 Asm->OutStreamer.AddComment("Line table subsection for " + Twine(FuncName)); 256 Asm->EmitInt32(COFF::DEBUG_LINE_TABLE_SUBSECTION); 257 MCSymbol *LineTableBegin = Asm->MMI->getContext().CreateTempSymbol(), 258 *LineTableEnd = Asm->MMI->getContext().CreateTempSymbol(); 259 EmitLabelDiff(Asm->OutStreamer, LineTableBegin, LineTableEnd); 260 Asm->OutStreamer.EmitLabel(LineTableBegin); 261 262 // Identify the function this subsection is for. 263 Asm->OutStreamer.EmitCOFFSecRel32(Fn); 264 Asm->OutStreamer.EmitCOFFSectionIndex(Fn); 265 // Insert padding after a 16-bit section index. 266 Asm->EmitInt16(0); 267 268 // Length of the function's code, in bytes. 269 EmitLabelDiff(Asm->OutStreamer, Fn, FI.End); 270 271 // PC-to-linenumber lookup table: 272 MCSymbol *FileSegmentEnd = nullptr; 273 for (size_t J = 0, F = FI.Instrs.size(); J != F; ++J) { 274 MCSymbol *Instr = FI.Instrs[J]; 275 assert(InstrInfo.count(Instr)); 276 277 if (FilenameSegmentLengths.count(J)) { 278 // We came to a beginning of a new filename segment. 279 if (FileSegmentEnd) 280 Asm->OutStreamer.EmitLabel(FileSegmentEnd); 281 StringRef CurFilename = InstrInfo[FI.Instrs[J]].Filename; 282 assert(FileNameRegistry.Infos.count(CurFilename)); 283 size_t IndexInStringTable = 284 FileNameRegistry.Infos[CurFilename].FilenameID; 285 // Each segment starts with the offset of the filename 286 // in the string table. 287 Asm->OutStreamer.AddComment( 288 "Segment for file '" + Twine(CurFilename) + "' begins"); 289 MCSymbol *FileSegmentBegin = Asm->MMI->getContext().CreateTempSymbol(); 290 Asm->OutStreamer.EmitLabel(FileSegmentBegin); 291 Asm->EmitInt32(8 * IndexInStringTable); 292 293 // Number of PC records in the lookup table. 294 size_t SegmentLength = FilenameSegmentLengths[J]; 295 Asm->EmitInt32(SegmentLength); 296 297 // Full size of the segment for this filename, including the prev two 298 // records. 299 FileSegmentEnd = Asm->MMI->getContext().CreateTempSymbol(); 300 EmitLabelDiff(Asm->OutStreamer, FileSegmentBegin, FileSegmentEnd); 301 } 302 303 // The first PC with the given linenumber and the linenumber itself. 304 EmitLabelDiff(Asm->OutStreamer, Fn, Instr); 305 Asm->EmitInt32(InstrInfo[Instr].LineNumber); 306 } 307 308 if (FileSegmentEnd) 309 Asm->OutStreamer.EmitLabel(FileSegmentEnd); 310 Asm->OutStreamer.EmitLabel(LineTableEnd); 311} 312 313void WinCodeViewLineTables::beginFunction(const MachineFunction *MF) { 314 assert(!CurFn && "Can't process two functions at once!"); 315 316 if (!Asm || !Asm->MMI->hasDebugInfo()) 317 return; 318 319 const Function *GV = MF->getFunction(); 320 assert(FnDebugInfo.count(GV) == false); 321 VisitedFunctions.push_back(GV); 322 CurFn = &FnDebugInfo[GV]; 323 324 // Find the end of the function prolog. 325 // FIXME: is there a simpler a way to do this? Can we just search 326 // for the first instruction of the function, not the last of the prolog? 327 DebugLoc PrologEndLoc; 328 bool EmptyPrologue = true; 329 for (const auto &MBB : *MF) { 330 if (!PrologEndLoc.isUnknown()) 331 break; 332 for (const auto &MI : MBB) { 333 if (MI.isDebugValue()) 334 continue; 335 336 // First known non-DBG_VALUE and non-frame setup location marks 337 // the beginning of the function body. 338 // FIXME: do we need the first subcondition? 339 if (!MI.getFlag(MachineInstr::FrameSetup) && 340 (!MI.getDebugLoc().isUnknown())) { 341 PrologEndLoc = MI.getDebugLoc(); 342 break; 343 } 344 EmptyPrologue = false; 345 } 346 } 347 // Record beginning of function if we have a non-empty prologue. 348 if (!PrologEndLoc.isUnknown() && !EmptyPrologue) { 349 DebugLoc FnStartDL = 350 PrologEndLoc.getFnDebugLoc(MF->getFunction()->getContext()); 351 maybeRecordLocation(FnStartDL, MF); 352 } 353} 354 355void WinCodeViewLineTables::endFunction(const MachineFunction *MF) { 356 if (!Asm || !CurFn) // We haven't created any debug info for this function. 357 return; 358 359 const Function *GV = MF->getFunction(); 360 assert(FnDebugInfo.count(GV)); 361 assert(CurFn == &FnDebugInfo[GV]); 362 363 if (CurFn->Instrs.empty()) { 364 FnDebugInfo.erase(GV); 365 VisitedFunctions.pop_back(); 366 } else { 367 // Define end label for subprogram. 368 MCSymbol *FunctionEndSym = Asm->OutStreamer.getContext().CreateTempSymbol(); 369 Asm->OutStreamer.EmitLabel(FunctionEndSym); 370 CurFn->End = FunctionEndSym; 371 } 372 CurFn = nullptr; 373} 374 375void WinCodeViewLineTables::beginInstruction(const MachineInstr *MI) { 376 // Ignore DBG_VALUE locations and function prologue. 377 if (!Asm || MI->isDebugValue() || MI->getFlag(MachineInstr::FrameSetup)) 378 return; 379 DebugLoc DL = MI->getDebugLoc(); 380 if (DL == PrevInstLoc || DL.isUnknown()) 381 return; 382 maybeRecordLocation(DL, Asm->MF); 383} 384} 385