src/llvm/lib/MC/MCObjectStreamer.cpp

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