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" 24using namespace llvm; 25 26MCObjectStreamer::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 34MCObjectStreamer::~MCObjectStreamer() { 35 delete &Assembler->getBackend(); 36 delete &Assembler->getEmitter(); 37 delete &Assembler->getWriter(); 38 delete Assembler; 39} 40 41void 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 57void 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 EmitIntValue(Hi->getOffset() - Lo->getOffset(), Size); 68} 69 70void MCObjectStreamer::reset() { 71 if (Assembler) 72 Assembler->reset(); 73 CurInsertionPoint = MCSection::iterator(); 74 EmitEHFrame = true; 75 EmitDebugFrame = false; 76 PendingLabels.clear(); 77 MCStreamer::reset(); 78} 79 80void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) { 81 if (!getNumFrameInfos()) 82 return; 83 84 if (EmitEHFrame) 85 MCDwarfFrameEmitter::Emit(*this, MAB, true); 86 87 if (EmitDebugFrame) 88 MCDwarfFrameEmitter::Emit(*this, MAB, false); 89} 90 91MCFragment *MCObjectStreamer::getCurrentFragment() const { 92 assert(getCurrentSectionOnly() && "No current section!"); 93 94 if (CurInsertionPoint != getCurrentSectionOnly()->getFragmentList().begin()) 95 return &*std::prev(CurInsertionPoint); 96 97 return nullptr; 98} 99 100MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() { 101 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment()); 102 // When bundling is enabled, we don't want to add data to a fragment that 103 // already has instructions (see MCELFStreamer::EmitInstToData for details) 104 if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() && 105 F->hasInstructions())) { 106 F = new MCDataFragment(); 107 insert(F); 108 } 109 return F; 110} 111 112void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) { 113 Assembler->registerSymbol(Sym); 114} 115 116void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) { 117 MCStreamer::EmitCFISections(EH, Debug); 118 EmitEHFrame = EH; 119 EmitDebugFrame = Debug; 120} 121 122void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size, 123 SMLoc Loc) { 124 MCStreamer::EmitValueImpl(Value, Size, Loc); 125 MCDataFragment *DF = getOrCreateDataFragment(); 126 flushPendingLabels(DF, DF->getContents().size()); 127 128 MCLineEntry::Make(this, getCurrentSection().first); 129 130 // Avoid fixups when possible. 131 int64_t AbsValue; 132 if (Value->evaluateAsAbsolute(AbsValue, getAssembler())) { 133 EmitIntValue(AbsValue, Size); 134 return; 135 } 136 DF->getFixups().push_back( 137 MCFixup::create(DF->getContents().size(), Value, 138 MCFixup::getKindForSize(Size, false), Loc)); 139 DF->getContents().resize(DF->getContents().size() + Size, 0); 140} 141 142void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) { 143 // We need to create a local symbol to avoid relocations. 144 Frame.Begin = getContext().createTempSymbol(); 145 EmitLabel(Frame.Begin); 146} 147 148void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) { 149 Frame.End = getContext().createTempSymbol(); 150 EmitLabel(Frame.End); 151} 152 153void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) { 154 MCStreamer::EmitLabel(Symbol); 155 156 getAssembler().registerSymbol(*Symbol); 157 158 // If there is a current fragment, mark the symbol as pointing into it. 159 // Otherwise queue the label and set its fragment pointer when we emit the 160 // next fragment. 161 auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment()); 162 if (F && !(getAssembler().isBundlingEnabled() && 163 getAssembler().getRelaxAll())) { 164 Symbol->setFragment(F); 165 Symbol->setOffset(F->getContents().size()); 166 } else { 167 PendingLabels.push_back(Symbol); 168 } 169} 170 171void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) { 172 int64_t IntValue; 173 if (Value->evaluateAsAbsolute(IntValue, getAssembler())) { 174 EmitULEB128IntValue(IntValue); 175 return; 176 } 177 insert(new MCLEBFragment(*Value, false)); 178} 179 180void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) { 181 int64_t IntValue; 182 if (Value->evaluateAsAbsolute(IntValue, getAssembler())) { 183 EmitSLEB128IntValue(IntValue); 184 return; 185 } 186 insert(new MCLEBFragment(*Value, true)); 187} 188 189void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias, 190 const MCSymbol *Symbol) { 191 report_fatal_error("This file format doesn't support weak aliases."); 192} 193 194void MCObjectStreamer::ChangeSection(MCSection *Section, 195 const MCExpr *Subsection) { 196 changeSectionImpl(Section, Subsection); 197} 198 199bool MCObjectStreamer::changeSectionImpl(MCSection *Section, 200 const MCExpr *Subsection) { 201 assert(Section && "Cannot switch to a null section!"); 202 flushPendingLabels(nullptr); 203 204 bool Created = getAssembler().registerSection(*Section); 205 206 int64_t IntSubsection = 0; 207 if (Subsection && 208 !Subsection->evaluateAsAbsolute(IntSubsection, getAssembler())) 209 report_fatal_error("Cannot evaluate subsection number"); 210 if (IntSubsection < 0 || IntSubsection > 8192) 211 report_fatal_error("Subsection number out of range"); 212 CurInsertionPoint = 213 Section->getSubsectionInsertionPoint(unsigned(IntSubsection)); 214 return Created; 215} 216 217void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) { 218 getAssembler().registerSymbol(*Symbol); 219 MCStreamer::EmitAssignment(Symbol, Value); 220} 221 222bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const { 223 return Sec.hasInstructions(); 224} 225 226void MCObjectStreamer::EmitInstruction(const MCInst &Inst, 227 const MCSubtargetInfo &STI) { 228 MCStreamer::EmitInstruction(Inst, STI); 229 230 MCSection *Sec = getCurrentSectionOnly(); 231 Sec->setHasInstructions(true); 232 233 // Now that a machine instruction has been assembled into this section, make 234 // a line entry for any .loc directive that has been seen. 235 MCLineEntry::Make(this, getCurrentSection().first); 236 237 // If this instruction doesn't need relaxation, just emit it as data. 238 MCAssembler &Assembler = getAssembler(); 239 if (!Assembler.getBackend().mayNeedRelaxation(Inst)) { 240 EmitInstToData(Inst, STI); 241 return; 242 } 243 244 // Otherwise, relax and emit it as data if either: 245 // - The RelaxAll flag was passed 246 // - Bundling is enabled and this instruction is inside a bundle-locked 247 // group. We want to emit all such instructions into the same data 248 // fragment. 249 if (Assembler.getRelaxAll() || 250 (Assembler.isBundlingEnabled() && Sec->isBundleLocked())) { 251 MCInst Relaxed; 252 getAssembler().getBackend().relaxInstruction(Inst, Relaxed); 253 while (getAssembler().getBackend().mayNeedRelaxation(Relaxed)) 254 getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed); 255 EmitInstToData(Relaxed, STI); 256 return; 257 } 258 259 // Otherwise emit to a separate fragment. 260 EmitInstToFragment(Inst, STI); 261} 262 263void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst, 264 const MCSubtargetInfo &STI) { 265 if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled()) 266 llvm_unreachable("All instructions should have already been relaxed"); 267 268 // Always create a new, separate fragment here, because its size can change 269 // during relaxation. 270 MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI); 271 insert(IF); 272 273 SmallString<128> Code; 274 raw_svector_ostream VecOS(Code); 275 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(), 276 STI); 277 IF->getContents().append(Code.begin(), Code.end()); 278} 279 280#ifndef NDEBUG 281static const char *const BundlingNotImplementedMsg = 282 "Aligned bundling is not implemented for this object format"; 283#endif 284 285void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) { 286 llvm_unreachable(BundlingNotImplementedMsg); 287} 288 289void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) { 290 llvm_unreachable(BundlingNotImplementedMsg); 291} 292 293void MCObjectStreamer::EmitBundleUnlock() { 294 llvm_unreachable(BundlingNotImplementedMsg); 295} 296 297void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line, 298 unsigned Column, unsigned Flags, 299 unsigned Isa, 300 unsigned Discriminator, 301 StringRef FileName) { 302 // In case we see two .loc directives in a row, make sure the 303 // first one gets a line entry. 304 MCLineEntry::Make(this, getCurrentSection().first); 305 306 this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags, 307 Isa, Discriminator, FileName); 308} 309 310static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A, 311 const MCSymbol *B) { 312 MCContext &Context = OS.getContext(); 313 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None; 314 const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context); 315 const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context); 316 const MCExpr *AddrDelta = 317 MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context); 318 return AddrDelta; 319} 320 321static void emitDwarfSetLineAddr(MCObjectStreamer &OS, 322 MCDwarfLineTableParams Params, 323 int64_t LineDelta, const MCSymbol *Label, 324 int PointerSize) { 325 // emit the sequence to set the address 326 OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1); 327 OS.EmitULEB128IntValue(PointerSize + 1); 328 OS.EmitIntValue(dwarf::DW_LNE_set_address, 1); 329 OS.EmitSymbolValue(Label, PointerSize); 330 331 // emit the sequence for the LineDelta (from 1) and a zero address delta. 332 MCDwarfLineAddr::Emit(&OS, Params, LineDelta, 0); 333} 334 335void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta, 336 const MCSymbol *LastLabel, 337 const MCSymbol *Label, 338 unsigned PointerSize) { 339 if (!LastLabel) { 340 emitDwarfSetLineAddr(*this, Assembler->getDWARFLinetableParams(), LineDelta, 341 Label, PointerSize); 342 return; 343 } 344 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel); 345 int64_t Res; 346 if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) { 347 MCDwarfLineAddr::Emit(this, Assembler->getDWARFLinetableParams(), LineDelta, 348 Res); 349 return; 350 } 351 insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta)); 352} 353 354void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel, 355 const MCSymbol *Label) { 356 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel); 357 int64_t Res; 358 if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) { 359 MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res); 360 return; 361 } 362 insert(new MCDwarfCallFrameFragment(*AddrDelta)); 363} 364 365void MCObjectStreamer::EmitBytes(StringRef Data) { 366 MCLineEntry::Make(this, getCurrentSection().first); 367 MCDataFragment *DF = getOrCreateDataFragment(); 368 flushPendingLabels(DF, DF->getContents().size()); 369 DF->getContents().append(Data.begin(), Data.end()); 370} 371 372void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment, 373 int64_t Value, 374 unsigned ValueSize, 375 unsigned MaxBytesToEmit) { 376 if (MaxBytesToEmit == 0) 377 MaxBytesToEmit = ByteAlignment; 378 insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit)); 379 380 // Update the maximum alignment on the current section if necessary. 381 MCSection *CurSec = getCurrentSection().first; 382 if (ByteAlignment > CurSec->getAlignment()) 383 CurSec->setAlignment(ByteAlignment); 384} 385 386void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment, 387 unsigned MaxBytesToEmit) { 388 EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit); 389 cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true); 390} 391 392void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset, 393 unsigned char Value) { 394 insert(new MCOrgFragment(*Offset, Value)); 395} 396 397// Associate GPRel32 fixup with data and resize data area 398void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) { 399 MCDataFragment *DF = getOrCreateDataFragment(); 400 flushPendingLabels(DF, DF->getContents().size()); 401 402 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(), 403 Value, FK_GPRel_4)); 404 DF->getContents().resize(DF->getContents().size() + 4, 0); 405} 406 407// Associate GPRel32 fixup with data and resize data area 408void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) { 409 MCDataFragment *DF = getOrCreateDataFragment(); 410 flushPendingLabels(DF, DF->getContents().size()); 411 412 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(), 413 Value, FK_GPRel_4)); 414 DF->getContents().resize(DF->getContents().size() + 8, 0); 415} 416 417bool MCObjectStreamer::EmitRelocDirective(const MCExpr &Offset, StringRef Name, 418 const MCExpr *Expr, SMLoc Loc) { 419 int64_t OffsetValue; 420 if (!Offset.evaluateAsAbsolute(OffsetValue)) 421 llvm_unreachable("Offset is not absolute"); 422 423 MCDataFragment *DF = getOrCreateDataFragment(); 424 flushPendingLabels(DF, DF->getContents().size()); 425 426 MCFixupKind Kind; 427 if (!Assembler->getBackend().getFixupKind(Name, Kind)) 428 return true; 429 430 if (Expr == nullptr) 431 Expr = 432 MCSymbolRefExpr::create(getContext().createTempSymbol(), getContext()); 433 DF->getFixups().push_back(MCFixup::create(OffsetValue, Expr, Kind, Loc)); 434 return false; 435} 436 437void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) { 438 const MCSection *Sec = getCurrentSection().first; 439 assert(Sec && "need a section"); 440 unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1; 441 insert(new MCFillFragment(FillValue, ItemSize, NumBytes)); 442} 443 444void MCObjectStreamer::FinishImpl() { 445 // If we are generating dwarf for assembly source files dump out the sections. 446 if (getContext().getGenDwarfForAssembly()) 447 MCGenDwarfInfo::Emit(this); 448 449 // Dump out the dwarf file & directory tables and line tables. 450 MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams()); 451 452 flushPendingLabels(nullptr); 453 getAssembler().Finish(); 454} 455