1 //===- lib/MC/MCObjectStreamer.cpp - Object File MCStreamer Interface -----===// 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 #include "llvm/MC/MCObjectStreamer.h" 11 #include "llvm/ADT/STLExtras.h" 12 #include "llvm/MC/MCAsmBackend.h" 13 #include "llvm/MC/MCAsmInfo.h" 14 #include "llvm/MC/MCAssembler.h" 15 #include "llvm/MC/MCCodeEmitter.h" 16 #include "llvm/MC/MCContext.h" 17 #include "llvm/MC/MCDwarf.h" 18 #include "llvm/MC/MCExpr.h" 19 #include "llvm/MC/MCObjectWriter.h" 20 #include "llvm/MC/MCSection.h" 21 #include "llvm/MC/MCSymbol.h" 22 #include "llvm/Support/ErrorHandling.h" 23 #include "llvm/Support/TargetRegistry.h" 24 using namespace llvm; 25 26 MCObjectStreamer::MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB, 27 raw_pwrite_stream &OS, 28 MCCodeEmitter *Emitter_) 29 : MCStreamer(Context), 30 Assembler(new MCAssembler(Context, TAB, *Emitter_, 31 *TAB.createObjectWriter(OS), OS)), 32 CurSectionData(nullptr), EmitEHFrame(true), EmitDebugFrame(false) {} 33 34 MCObjectStreamer::~MCObjectStreamer() { 35 delete &Assembler->getBackend(); 36 delete &Assembler->getEmitter(); 37 delete &Assembler->getWriter(); 38 delete Assembler; 39 } 40 41 void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) { 42 if (PendingLabels.size()) { 43 if (!F) { 44 F = new MCDataFragment(); 45 CurSectionData->getFragmentList().insert(CurInsertionPoint, F); 46 F->setParent(CurSectionData); 47 } 48 for (MCSymbolData *SD : PendingLabels) { 49 SD->setFragment(F); 50 SD->setOffset(FOffset); 51 } 52 PendingLabels.clear(); 53 } 54 } 55 56 void MCObjectStreamer::reset() { 57 if (Assembler) 58 Assembler->reset(); 59 CurSectionData = nullptr; 60 CurInsertionPoint = MCSectionData::iterator(); 61 EmitEHFrame = true; 62 EmitDebugFrame = false; 63 PendingLabels.clear(); 64 MCStreamer::reset(); 65 } 66 67 void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) { 68 if (!getNumFrameInfos()) 69 return; 70 71 if (EmitEHFrame) 72 MCDwarfFrameEmitter::Emit(*this, MAB, true); 73 74 if (EmitDebugFrame) 75 MCDwarfFrameEmitter::Emit(*this, MAB, false); 76 } 77 78 MCFragment *MCObjectStreamer::getCurrentFragment() const { 79 assert(getCurrentSectionData() && "No current section!"); 80 81 if (CurInsertionPoint != getCurrentSectionData()->getFragmentList().begin()) 82 return std::prev(CurInsertionPoint); 83 84 return nullptr; 85 } 86 87 MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() { 88 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment()); 89 // When bundling is enabled, we don't want to add data to a fragment that 90 // already has instructions (see MCELFStreamer::EmitInstToData for details) 91 if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() && 92 F->hasInstructions())) { 93 F = new MCDataFragment(); 94 insert(F); 95 } 96 return F; 97 } 98 99 void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) { 100 Assembler->getOrCreateSymbolData(Sym); 101 } 102 103 void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) { 104 MCStreamer::EmitCFISections(EH, Debug); 105 EmitEHFrame = EH; 106 EmitDebugFrame = Debug; 107 } 108 109 void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size, 110 const SMLoc &Loc) { 111 MCStreamer::EmitValueImpl(Value, Size, Loc); 112 MCDataFragment *DF = getOrCreateDataFragment(); 113 114 MCLineEntry::Make(this, getCurrentSection().first); 115 116 // Avoid fixups when possible. 117 int64_t AbsValue; 118 if (Value->EvaluateAsAbsolute(AbsValue, getAssembler())) { 119 EmitIntValue(AbsValue, Size); 120 return; 121 } 122 DF->getFixups().push_back( 123 MCFixup::Create(DF->getContents().size(), Value, 124 MCFixup::getKindForSize(Size, false), Loc)); 125 DF->getContents().resize(DF->getContents().size() + Size, 0); 126 } 127 128 void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) { 129 // We need to create a local symbol to avoid relocations. 130 Frame.Begin = getContext().CreateTempSymbol(); 131 EmitLabel(Frame.Begin); 132 } 133 134 void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) { 135 Frame.End = getContext().CreateTempSymbol(); 136 EmitLabel(Frame.End); 137 } 138 139 void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) { 140 MCStreamer::EmitLabel(Symbol); 141 142 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol); 143 assert(!SD.getFragment() && "Unexpected fragment on symbol data!"); 144 145 // If there is a current fragment, mark the symbol as pointing into it. 146 // Otherwise queue the label and set its fragment pointer when we emit the 147 // next fragment. 148 auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment()); 149 if (F && !(getAssembler().isBundlingEnabled() && 150 getAssembler().getRelaxAll())) { 151 SD.setFragment(F); 152 SD.setOffset(F->getContents().size()); 153 } else { 154 PendingLabels.push_back(&SD); 155 } 156 } 157 158 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) { 159 int64_t IntValue; 160 if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) { 161 EmitULEB128IntValue(IntValue); 162 return; 163 } 164 insert(new MCLEBFragment(*Value, false)); 165 } 166 167 void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) { 168 int64_t IntValue; 169 if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) { 170 EmitSLEB128IntValue(IntValue); 171 return; 172 } 173 insert(new MCLEBFragment(*Value, true)); 174 } 175 176 void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias, 177 const MCSymbol *Symbol) { 178 report_fatal_error("This file format doesn't support weak aliases."); 179 } 180 181 void MCObjectStreamer::ChangeSection(const MCSection *Section, 182 const MCExpr *Subsection) { 183 changeSectionImpl(Section, Subsection); 184 } 185 186 bool MCObjectStreamer::changeSectionImpl(const MCSection *Section, 187 const MCExpr *Subsection) { 188 assert(Section && "Cannot switch to a null section!"); 189 flushPendingLabels(nullptr); 190 191 bool Created; 192 CurSectionData = &getAssembler().getOrCreateSectionData(*Section, &Created); 193 194 int64_t IntSubsection = 0; 195 if (Subsection && 196 !Subsection->EvaluateAsAbsolute(IntSubsection, getAssembler())) 197 report_fatal_error("Cannot evaluate subsection number"); 198 if (IntSubsection < 0 || IntSubsection > 8192) 199 report_fatal_error("Subsection number out of range"); 200 CurInsertionPoint = 201 CurSectionData->getSubsectionInsertionPoint(unsigned(IntSubsection)); 202 return Created; 203 } 204 205 void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) { 206 getAssembler().getOrCreateSymbolData(*Symbol); 207 MCStreamer::EmitAssignment(Symbol, Value); 208 } 209 210 void MCObjectStreamer::EmitInstruction(const MCInst &Inst, 211 const MCSubtargetInfo &STI) { 212 MCStreamer::EmitInstruction(Inst, STI); 213 214 MCSectionData *SD = getCurrentSectionData(); 215 SD->setHasInstructions(true); 216 217 // Now that a machine instruction has been assembled into this section, make 218 // a line entry for any .loc directive that has been seen. 219 MCLineEntry::Make(this, getCurrentSection().first); 220 221 // If this instruction doesn't need relaxation, just emit it as data. 222 MCAssembler &Assembler = getAssembler(); 223 if (!Assembler.getBackend().mayNeedRelaxation(Inst)) { 224 EmitInstToData(Inst, STI); 225 return; 226 } 227 228 // Otherwise, relax and emit it as data if either: 229 // - The RelaxAll flag was passed 230 // - Bundling is enabled and this instruction is inside a bundle-locked 231 // group. We want to emit all such instructions into the same data 232 // fragment. 233 if (Assembler.getRelaxAll() || 234 (Assembler.isBundlingEnabled() && SD->isBundleLocked())) { 235 MCInst Relaxed; 236 getAssembler().getBackend().relaxInstruction(Inst, Relaxed); 237 while (getAssembler().getBackend().mayNeedRelaxation(Relaxed)) 238 getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed); 239 EmitInstToData(Relaxed, STI); 240 return; 241 } 242 243 // Otherwise emit to a separate fragment. 244 EmitInstToFragment(Inst, STI); 245 } 246 247 void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst, 248 const MCSubtargetInfo &STI) { 249 if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled()) 250 llvm_unreachable("All instructions should have already been relaxed"); 251 252 // Always create a new, separate fragment here, because its size can change 253 // during relaxation. 254 MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI); 255 insert(IF); 256 257 SmallString<128> Code; 258 raw_svector_ostream VecOS(Code); 259 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, IF->getFixups(), 260 STI); 261 VecOS.flush(); 262 IF->getContents().append(Code.begin(), Code.end()); 263 } 264 265 #ifndef NDEBUG 266 static const char *const BundlingNotImplementedMsg = 267 "Aligned bundling is not implemented for this object format"; 268 #endif 269 270 void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) { 271 llvm_unreachable(BundlingNotImplementedMsg); 272 } 273 274 void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) { 275 llvm_unreachable(BundlingNotImplementedMsg); 276 } 277 278 void MCObjectStreamer::EmitBundleUnlock() { 279 llvm_unreachable(BundlingNotImplementedMsg); 280 } 281 282 void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line, 283 unsigned Column, unsigned Flags, 284 unsigned Isa, 285 unsigned Discriminator, 286 StringRef FileName) { 287 // In case we see two .loc directives in a row, make sure the 288 // first one gets a line entry. 289 MCLineEntry::Make(this, getCurrentSection().first); 290 291 this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags, 292 Isa, Discriminator, FileName); 293 } 294 295 static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A, 296 const MCSymbol *B) { 297 MCContext &Context = OS.getContext(); 298 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None; 299 const MCExpr *ARef = MCSymbolRefExpr::Create(A, Variant, Context); 300 const MCExpr *BRef = MCSymbolRefExpr::Create(B, Variant, Context); 301 const MCExpr *AddrDelta = 302 MCBinaryExpr::Create(MCBinaryExpr::Sub, ARef, BRef, Context); 303 return AddrDelta; 304 } 305 306 static void emitDwarfSetLineAddr(MCObjectStreamer &OS, int64_t LineDelta, 307 const MCSymbol *Label, int PointerSize) { 308 // emit the sequence to set the address 309 OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1); 310 OS.EmitULEB128IntValue(PointerSize + 1); 311 OS.EmitIntValue(dwarf::DW_LNE_set_address, 1); 312 OS.EmitSymbolValue(Label, PointerSize); 313 314 // emit the sequence for the LineDelta (from 1) and a zero address delta. 315 MCDwarfLineAddr::Emit(&OS, LineDelta, 0); 316 } 317 318 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta, 319 const MCSymbol *LastLabel, 320 const MCSymbol *Label, 321 unsigned PointerSize) { 322 if (!LastLabel) { 323 emitDwarfSetLineAddr(*this, LineDelta, Label, PointerSize); 324 return; 325 } 326 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel); 327 int64_t Res; 328 if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) { 329 MCDwarfLineAddr::Emit(this, LineDelta, Res); 330 return; 331 } 332 insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta)); 333 } 334 335 void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel, 336 const MCSymbol *Label) { 337 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel); 338 int64_t Res; 339 if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) { 340 MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res); 341 return; 342 } 343 insert(new MCDwarfCallFrameFragment(*AddrDelta)); 344 } 345 346 void MCObjectStreamer::EmitBytes(StringRef Data) { 347 MCLineEntry::Make(this, getCurrentSection().first); 348 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end()); 349 } 350 351 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment, 352 int64_t Value, 353 unsigned ValueSize, 354 unsigned MaxBytesToEmit) { 355 if (MaxBytesToEmit == 0) 356 MaxBytesToEmit = ByteAlignment; 357 insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit)); 358 359 // Update the maximum alignment on the current section if necessary. 360 if (ByteAlignment > getCurrentSectionData()->getAlignment()) 361 getCurrentSectionData()->setAlignment(ByteAlignment); 362 } 363 364 void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment, 365 unsigned MaxBytesToEmit) { 366 EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit); 367 cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true); 368 } 369 370 bool MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset, 371 unsigned char Value) { 372 int64_t Res; 373 if (Offset->EvaluateAsAbsolute(Res, getAssembler())) { 374 insert(new MCOrgFragment(*Offset, Value)); 375 return false; 376 } 377 378 MCSymbol *CurrentPos = getContext().CreateTempSymbol(); 379 EmitLabel(CurrentPos); 380 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None; 381 const MCExpr *Ref = 382 MCSymbolRefExpr::Create(CurrentPos, Variant, getContext()); 383 const MCExpr *Delta = 384 MCBinaryExpr::Create(MCBinaryExpr::Sub, Offset, Ref, getContext()); 385 386 if (!Delta->EvaluateAsAbsolute(Res, getAssembler())) 387 return true; 388 EmitFill(Res, Value); 389 return false; 390 } 391 392 // Associate GPRel32 fixup with data and resize data area 393 void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) { 394 MCDataFragment *DF = getOrCreateDataFragment(); 395 396 DF->getFixups().push_back(MCFixup::Create(DF->getContents().size(), 397 Value, FK_GPRel_4)); 398 DF->getContents().resize(DF->getContents().size() + 4, 0); 399 } 400 401 // Associate GPRel32 fixup with data and resize data area 402 void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) { 403 MCDataFragment *DF = getOrCreateDataFragment(); 404 405 DF->getFixups().push_back(MCFixup::Create(DF->getContents().size(), 406 Value, FK_GPRel_4)); 407 DF->getContents().resize(DF->getContents().size() + 8, 0); 408 } 409 410 void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) { 411 // FIXME: A MCFillFragment would be more memory efficient but MCExpr has 412 // problems evaluating expressions across multiple fragments. 413 getOrCreateDataFragment()->getContents().append(NumBytes, FillValue); 414 } 415 416 void MCObjectStreamer::EmitZeros(uint64_t NumBytes) { 417 const MCSection *Sec = getCurrentSection().first; 418 assert(Sec && "need a section"); 419 unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1; 420 insert(new MCFillFragment(0, ItemSize, NumBytes)); 421 } 422 423 void MCObjectStreamer::FinishImpl() { 424 // If we are generating dwarf for assembly source files dump out the sections. 425 if (getContext().getGenDwarfForAssembly()) 426 MCGenDwarfInfo::Emit(this); 427 428 // Dump out the dwarf file & directory tables and line tables. 429 MCDwarfLineTable::Emit(this); 430 431 flushPendingLabels(nullptr); 432 getAssembler().Finish(); 433 } 434