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))), 32 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.empty()) 43 return; 44 if (!F) { 45 F = new MCDataFragment(); 46 MCSection *CurSection = getCurrentSectionOnly(); 47 CurSection->getFragmentList().insert(CurInsertionPoint, F); 48 F->setParent(CurSection); 49 } 50 for (MCSymbol *Sym : PendingLabels) { 51 Sym->setFragment(F); 52 Sym->setOffset(FOffset); 53 } 54 PendingLabels.clear(); 55 } 56 57 void MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi, 58 const MCSymbol *Lo, 59 unsigned Size) { 60 // If not assigned to the same (valid) fragment, fallback. 61 if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment() || 62 Hi->isVariable() || Lo->isVariable()) { 63 MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size); 64 return; 65 } 66 67 assert(Hi->getOffset() >= Lo->getOffset() && 68 "Expected Hi to be greater than Lo"); 69 EmitIntValue(Hi->getOffset() - Lo->getOffset(), Size); 70 } 71 72 void MCObjectStreamer::reset() { 73 if (Assembler) 74 Assembler->reset(); 75 CurInsertionPoint = MCSection::iterator(); 76 EmitEHFrame = true; 77 EmitDebugFrame = false; 78 PendingLabels.clear(); 79 MCStreamer::reset(); 80 } 81 82 void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) { 83 if (!getNumFrameInfos()) 84 return; 85 86 if (EmitEHFrame) 87 MCDwarfFrameEmitter::Emit(*this, MAB, true); 88 89 if (EmitDebugFrame) 90 MCDwarfFrameEmitter::Emit(*this, MAB, false); 91 } 92 93 MCFragment *MCObjectStreamer::getCurrentFragment() const { 94 assert(getCurrentSectionOnly() && "No current section!"); 95 96 if (CurInsertionPoint != getCurrentSectionOnly()->getFragmentList().begin()) 97 return &*std::prev(CurInsertionPoint); 98 99 return nullptr; 100 } 101 102 MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() { 103 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment()); 104 // When bundling is enabled, we don't want to add data to a fragment that 105 // already has instructions (see MCELFStreamer::EmitInstToData for details) 106 if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() && 107 F->hasInstructions())) { 108 F = new MCDataFragment(); 109 insert(F); 110 } 111 return F; 112 } 113 114 void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) { 115 Assembler->registerSymbol(Sym); 116 } 117 118 void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) { 119 MCStreamer::EmitCFISections(EH, Debug); 120 EmitEHFrame = EH; 121 EmitDebugFrame = Debug; 122 } 123 124 void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size, 125 SMLoc Loc) { 126 MCStreamer::EmitValueImpl(Value, Size, Loc); 127 MCDataFragment *DF = getOrCreateDataFragment(); 128 flushPendingLabels(DF, DF->getContents().size()); 129 130 MCLineEntry::Make(this, getCurrentSection().first); 131 132 // Avoid fixups when possible. 133 int64_t AbsValue; 134 if (Value->evaluateAsAbsolute(AbsValue, getAssembler())) { 135 EmitIntValue(AbsValue, Size); 136 return; 137 } 138 DF->getFixups().push_back( 139 MCFixup::create(DF->getContents().size(), Value, 140 MCFixup::getKindForSize(Size, false), Loc)); 141 DF->getContents().resize(DF->getContents().size() + Size, 0); 142 } 143 144 void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) { 145 // We need to create a local symbol to avoid relocations. 146 Frame.Begin = getContext().createTempSymbol(); 147 EmitLabel(Frame.Begin); 148 } 149 150 void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) { 151 Frame.End = getContext().createTempSymbol(); 152 EmitLabel(Frame.End); 153 } 154 155 void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) { 156 MCStreamer::EmitLabel(Symbol); 157 158 getAssembler().registerSymbol(*Symbol); 159 160 // If there is a current fragment, mark the symbol as pointing into it. 161 // Otherwise queue the label and set its fragment pointer when we emit the 162 // next fragment. 163 auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment()); 164 if (F && !(getAssembler().isBundlingEnabled() && 165 getAssembler().getRelaxAll())) { 166 Symbol->setFragment(F); 167 Symbol->setOffset(F->getContents().size()); 168 } else { 169 PendingLabels.push_back(Symbol); 170 } 171 } 172 173 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) { 174 int64_t IntValue; 175 if (Value->evaluateAsAbsolute(IntValue, getAssembler())) { 176 EmitULEB128IntValue(IntValue); 177 return; 178 } 179 insert(new MCLEBFragment(*Value, false)); 180 } 181 182 void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) { 183 int64_t IntValue; 184 if (Value->evaluateAsAbsolute(IntValue, getAssembler())) { 185 EmitSLEB128IntValue(IntValue); 186 return; 187 } 188 insert(new MCLEBFragment(*Value, true)); 189 } 190 191 void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias, 192 const MCSymbol *Symbol) { 193 report_fatal_error("This file format doesn't support weak aliases."); 194 } 195 196 void MCObjectStreamer::ChangeSection(MCSection *Section, 197 const MCExpr *Subsection) { 198 changeSectionImpl(Section, Subsection); 199 } 200 201 bool MCObjectStreamer::changeSectionImpl(MCSection *Section, 202 const MCExpr *Subsection) { 203 assert(Section && "Cannot switch to a null section!"); 204 flushPendingLabels(nullptr); 205 206 bool Created = getAssembler().registerSection(*Section); 207 208 int64_t IntSubsection = 0; 209 if (Subsection && 210 !Subsection->evaluateAsAbsolute(IntSubsection, getAssembler())) 211 report_fatal_error("Cannot evaluate subsection number"); 212 if (IntSubsection < 0 || IntSubsection > 8192) 213 report_fatal_error("Subsection number out of range"); 214 CurInsertionPoint = 215 Section->getSubsectionInsertionPoint(unsigned(IntSubsection)); 216 return Created; 217 } 218 219 void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) { 220 getAssembler().registerSymbol(*Symbol); 221 MCStreamer::EmitAssignment(Symbol, Value); 222 } 223 224 bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const { 225 return Sec.hasInstructions(); 226 } 227 228 void MCObjectStreamer::EmitInstruction(const MCInst &Inst, 229 const MCSubtargetInfo &STI) { 230 MCStreamer::EmitInstruction(Inst, STI); 231 232 MCSection *Sec = getCurrentSectionOnly(); 233 Sec->setHasInstructions(true); 234 235 // Now that a machine instruction has been assembled into this section, make 236 // a line entry for any .loc directive that has been seen. 237 MCLineEntry::Make(this, getCurrentSection().first); 238 239 // If this instruction doesn't need relaxation, just emit it as data. 240 MCAssembler &Assembler = getAssembler(); 241 if (!Assembler.getBackend().mayNeedRelaxation(Inst)) { 242 EmitInstToData(Inst, STI); 243 return; 244 } 245 246 // Otherwise, relax and emit it as data if either: 247 // - The RelaxAll flag was passed 248 // - Bundling is enabled and this instruction is inside a bundle-locked 249 // group. We want to emit all such instructions into the same data 250 // fragment. 251 if (Assembler.getRelaxAll() || 252 (Assembler.isBundlingEnabled() && Sec->isBundleLocked())) { 253 MCInst Relaxed; 254 getAssembler().getBackend().relaxInstruction(Inst, Relaxed); 255 while (getAssembler().getBackend().mayNeedRelaxation(Relaxed)) 256 getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed); 257 EmitInstToData(Relaxed, STI); 258 return; 259 } 260 261 // Otherwise emit to a separate fragment. 262 EmitInstToFragment(Inst, STI); 263 } 264 265 void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst, 266 const MCSubtargetInfo &STI) { 267 if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled()) 268 llvm_unreachable("All instructions should have already been relaxed"); 269 270 // Always create a new, separate fragment here, because its size can change 271 // during relaxation. 272 MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI); 273 insert(IF); 274 275 SmallString<128> Code; 276 raw_svector_ostream VecOS(Code); 277 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(), 278 STI); 279 IF->getContents().append(Code.begin(), Code.end()); 280 } 281 282 #ifndef NDEBUG 283 static const char *const BundlingNotImplementedMsg = 284 "Aligned bundling is not implemented for this object format"; 285 #endif 286 287 void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) { 288 llvm_unreachable(BundlingNotImplementedMsg); 289 } 290 291 void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) { 292 llvm_unreachable(BundlingNotImplementedMsg); 293 } 294 295 void MCObjectStreamer::EmitBundleUnlock() { 296 llvm_unreachable(BundlingNotImplementedMsg); 297 } 298 299 void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line, 300 unsigned Column, unsigned Flags, 301 unsigned Isa, 302 unsigned Discriminator, 303 StringRef FileName) { 304 // In case we see two .loc directives in a row, make sure the 305 // first one gets a line entry. 306 MCLineEntry::Make(this, getCurrentSection().first); 307 308 this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags, 309 Isa, Discriminator, FileName); 310 } 311 312 static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A, 313 const MCSymbol *B) { 314 MCContext &Context = OS.getContext(); 315 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None; 316 const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context); 317 const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context); 318 const MCExpr *AddrDelta = 319 MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context); 320 return AddrDelta; 321 } 322 323 static void emitDwarfSetLineAddr(MCObjectStreamer &OS, 324 MCDwarfLineTableParams Params, 325 int64_t LineDelta, const MCSymbol *Label, 326 int PointerSize) { 327 // emit the sequence to set the address 328 OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1); 329 OS.EmitULEB128IntValue(PointerSize + 1); 330 OS.EmitIntValue(dwarf::DW_LNE_set_address, 1); 331 OS.EmitSymbolValue(Label, PointerSize); 332 333 // emit the sequence for the LineDelta (from 1) and a zero address delta. 334 MCDwarfLineAddr::Emit(&OS, Params, LineDelta, 0); 335 } 336 337 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta, 338 const MCSymbol *LastLabel, 339 const MCSymbol *Label, 340 unsigned PointerSize) { 341 if (!LastLabel) { 342 emitDwarfSetLineAddr(*this, Assembler->getDWARFLinetableParams(), LineDelta, 343 Label, PointerSize); 344 return; 345 } 346 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel); 347 int64_t Res; 348 if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) { 349 MCDwarfLineAddr::Emit(this, Assembler->getDWARFLinetableParams(), LineDelta, 350 Res); 351 return; 352 } 353 insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta)); 354 } 355 356 void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel, 357 const MCSymbol *Label) { 358 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel); 359 int64_t Res; 360 if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) { 361 MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res); 362 return; 363 } 364 insert(new MCDwarfCallFrameFragment(*AddrDelta)); 365 } 366 367 void MCObjectStreamer::EmitBytes(StringRef Data) { 368 MCLineEntry::Make(this, getCurrentSection().first); 369 MCDataFragment *DF = getOrCreateDataFragment(); 370 flushPendingLabels(DF, DF->getContents().size()); 371 DF->getContents().append(Data.begin(), Data.end()); 372 } 373 374 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment, 375 int64_t Value, 376 unsigned ValueSize, 377 unsigned MaxBytesToEmit) { 378 if (MaxBytesToEmit == 0) 379 MaxBytesToEmit = ByteAlignment; 380 insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit)); 381 382 // Update the maximum alignment on the current section if necessary. 383 MCSection *CurSec = getCurrentSection().first; 384 if (ByteAlignment > CurSec->getAlignment()) 385 CurSec->setAlignment(ByteAlignment); 386 } 387 388 void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment, 389 unsigned MaxBytesToEmit) { 390 EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit); 391 cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true); 392 } 393 394 void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset, 395 unsigned char Value) { 396 insert(new MCOrgFragment(*Offset, Value)); 397 } 398 399 // Associate GPRel32 fixup with data and resize data area 400 void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) { 401 MCDataFragment *DF = getOrCreateDataFragment(); 402 flushPendingLabels(DF, DF->getContents().size()); 403 404 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(), 405 Value, FK_GPRel_4)); 406 DF->getContents().resize(DF->getContents().size() + 4, 0); 407 } 408 409 // Associate GPRel32 fixup with data and resize data area 410 void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) { 411 MCDataFragment *DF = getOrCreateDataFragment(); 412 flushPendingLabels(DF, DF->getContents().size()); 413 414 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(), 415 Value, FK_GPRel_4)); 416 DF->getContents().resize(DF->getContents().size() + 8, 0); 417 } 418 419 bool MCObjectStreamer::EmitRelocDirective(const MCExpr &Offset, StringRef Name, 420 const MCExpr *Expr, SMLoc Loc) { 421 int64_t OffsetValue; 422 if (!Offset.evaluateAsAbsolute(OffsetValue)) 423 llvm_unreachable("Offset is not absolute"); 424 425 MCDataFragment *DF = getOrCreateDataFragment(); 426 flushPendingLabels(DF, DF->getContents().size()); 427 428 MCFixupKind Kind; 429 if (!Assembler->getBackend().getFixupKind(Name, Kind)) 430 return true; 431 432 if (Expr == nullptr) 433 Expr = 434 MCSymbolRefExpr::create(getContext().createTempSymbol(), getContext()); 435 DF->getFixups().push_back(MCFixup::create(OffsetValue, Expr, Kind, Loc)); 436 return false; 437 } 438 439 void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) { 440 const MCSection *Sec = getCurrentSection().first; 441 assert(Sec && "need a section"); 442 unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1; 443 insert(new MCFillFragment(FillValue, ItemSize, NumBytes)); 444 } 445 446 void MCObjectStreamer::FinishImpl() { 447 // If we are generating dwarf for assembly source files dump out the sections. 448 if (getContext().getGenDwarfForAssembly()) 449 MCGenDwarfInfo::Emit(this); 450 451 // Dump out the dwarf file & directory tables and line tables. 452 MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams()); 453 454 flushPendingLabels(nullptr); 455 getAssembler().Finish(); 456 } 457