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/MCAsmInfo.h"
  11 #include "llvm/MC/MCObjectStreamer.h"
  12
  13 #include "llvm/Support/ErrorHandling.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/MCSymbol.h"
  20 #include "llvm/Target/TargetAsmBackend.h"
  21 #include "llvm/Target/TargetAsmInfo.h"
  22 using namespace llvm;
  23
  24 MCObjectStreamer::MCObjectStreamer(MCContext &Context, TargetAsmBackend &TAB,
  25                                    raw_ostream &OS, MCCodeEmitter *Emitter_)
  26   : MCStreamer(Context),
  27     Assembler(new MCAssembler(Context, TAB,
  28                               *Emitter_, *TAB.createObjectWriter(OS),
  29                               OS)),
  30     CurSectionData(0)
  31 {
  32 }
  33
  34 MCObjectStreamer::MCObjectStreamer(MCContext &Context, TargetAsmBackend &TAB,
  35                                    raw_ostream &OS, MCCodeEmitter *Emitter_,
  36                                    MCAssembler *_Assembler)
  37   : MCStreamer(Context), Assembler(_Assembler), CurSectionData(0)
  38 {
  39 }
  40
  41 MCObjectStreamer::~MCObjectStreamer() {
  42   delete &Assembler->getBackend();
  43   delete &Assembler->getEmitter();
  44   delete &Assembler->getWriter();
  45   delete Assembler;
  46 }
  47
  48 MCFragment *MCObjectStreamer::getCurrentFragment() const {
  49   assert(getCurrentSectionData() && "No current section!");
  50
  51   if (!getCurrentSectionData()->empty())
  52     return &getCurrentSectionData()->getFragmentList().back();
  53
  54   return 0;
  55 }
  56
  57 MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() const {
  58   MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
  59   if (!F)
  60     F = new MCDataFragment(getCurrentSectionData());
  61   return F;
  62 }
  63
  64 const MCExpr *MCObjectStreamer::AddValueSymbols(const MCExpr *Value) {
  65   switch (Value->getKind()) {
  66   case MCExpr::Target:
  67     cast<MCTargetExpr>(Value)->AddValueSymbols(Assembler);
  68     break;
  69
  70   case MCExpr::Constant:
  71     break;
  72
  73   case MCExpr::Binary: {
  74     const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
  75     AddValueSymbols(BE->getLHS());
  76     AddValueSymbols(BE->getRHS());
  77     break;
  78   }
  79
  80   case MCExpr::SymbolRef:
  81     Assembler->getOrCreateSymbolData(cast<MCSymbolRefExpr>(Value)->getSymbol());
  82     break;
  83
  84   case MCExpr::Unary:
  85     AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
  86     break;
  87   }
  88
  89   return Value;
  90 }
  91
  92 void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
  93                                      bool isPCRel, unsigned AddrSpace) {
  94   assert(AddrSpace == 0 && "Address space must be 0!");
  95   MCDataFragment *DF = getOrCreateDataFragment();
  96
  97   // Avoid fixups when possible.
  98   int64_t AbsValue;
  99   if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue, getAssembler())) {
 100     EmitIntValue(AbsValue, Size, AddrSpace);
 101     return;
 102   }
 103   DF->addFixup(MCFixup::Create(DF->getContents().size(),
 104                                Value,
 105                                MCFixup::getKindForSize(Size, isPCRel)));
 106   DF->getContents().resize(DF->getContents().size() + Size, 0);
 107 }
 108
 109 void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
 110   assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
 111   assert(getCurrentSection() && "Cannot emit before setting section!");
 112
 113   Symbol->setSection(*getCurrentSection());
 114
 115   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 116
 117   // FIXME: This is wasteful, we don't necessarily need to create a data
 118   // fragment. Instead, we should mark the symbol as pointing into the data
 119   // fragment if it exists, otherwise we should just queue the label and set its
 120   // fragment pointer when we emit the next fragment.
 121   MCDataFragment *F = getOrCreateDataFragment();
 122   assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
 123   SD.setFragment(F);
 124   SD.setOffset(F->getContents().size());
 125 }
 126
 127 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value,
 128                                         unsigned AddrSpace) {
 129   int64_t IntValue;
 130   if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
 131     EmitULEB128IntValue(IntValue, AddrSpace);
 132     return;
 133   }
 134   new MCLEBFragment(*Value, false, getCurrentSectionData());
 135 }
 136
 137 void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value,
 138                                         unsigned AddrSpace) {
 139   int64_t IntValue;
 140   if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
 141     EmitSLEB128IntValue(IntValue, AddrSpace);
 142     return;
 143   }
 144   new MCLEBFragment(*Value, true, getCurrentSectionData());
 145 }
 146
 147 void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
 148                                          const MCSymbol *Symbol) {
 149   report_fatal_error("This file format doesn't support weak aliases.");
 150 }
 151
 152 void MCObjectStreamer::ChangeSection(const MCSection *Section) {
 153   assert(Section && "Cannot switch to a null section!");
 154
 155   CurSectionData = &getAssembler().getOrCreateSectionData(*Section);
 156 }
 157
 158 void MCObjectStreamer::EmitInstruction(const MCInst &Inst) {
 159   // Scan for values.
 160   for (unsigned i = Inst.getNumOperands(); i--; )
 161     if (Inst.getOperand(i).isExpr())
 162       AddValueSymbols(Inst.getOperand(i).getExpr());
 163
 164   getCurrentSectionData()->setHasInstructions(true);
 165
 166   // Now that a machine instruction has been assembled into this section, make
 167   // a line entry for any .loc directive that has been seen.
 168   MCLineEntry::Make(this, getCurrentSection());
 169
 170   // If this instruction doesn't need relaxation, just emit it as data.
 171   if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
 172     EmitInstToData(Inst);
 173     return;
 174   }
 175
 176   // Otherwise, if we are relaxing everything, relax the instruction as much as
 177   // possible and emit it as data.
 178   if (getAssembler().getRelaxAll()) {
 179     MCInst Relaxed;
 180     getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
 181     while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
 182       getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
 183     EmitInstToData(Relaxed);
 184     return;
 185   }
 186
 187   // Otherwise emit to a separate fragment.
 188   EmitInstToFragment(Inst);
 189 }
 190
 191 void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst) {
 192   MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
 193
 194   raw_svector_ostream VecOS(IF->getCode());
 195   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, IF->getFixups());
 196 }
 197
 198 static const MCExpr *BuildSymbolDiff(MCContext &Context,
 199                                      const MCSymbol *A, const MCSymbol *B) {
 200   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
 201   const MCExpr *ARef =
 202     MCSymbolRefExpr::Create(A, Variant, Context);
 203   const MCExpr *BRef =
 204     MCSymbolRefExpr::Create(B, Variant, Context);
 205   const MCExpr *AddrDelta =
 206     MCBinaryExpr::Create(MCBinaryExpr::Sub, ARef, BRef, Context);
 207   return AddrDelta;
 208 }
 209
 210 static const MCExpr *ForceExpAbs(MCObjectStreamer *Streamer,
 211                                   MCContext &Context, const MCExpr* Expr) {
 212  if (Context.getAsmInfo().hasAggressiveSymbolFolding())
 213    return Expr;
 214
 215  MCSymbol *ABS = Context.CreateTempSymbol();
 216  Streamer->EmitAssignment(ABS, Expr);
 217  return MCSymbolRefExpr::Create(ABS, Context);
 218 }
 219
 220 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
 221                                                 const MCSymbol *LastLabel,
 222                                                 const MCSymbol *Label) {
 223   if (!LastLabel) {
 224     int PointerSize = getContext().getTargetAsmInfo().getPointerSize();
 225     EmitDwarfSetLineAddr(LineDelta, Label, PointerSize);
 226     return;
 227   }
 228   const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
 229   int64_t Res;
 230   if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
 231     MCDwarfLineAddr::Emit(this, LineDelta, Res);
 232     return;
 233   }
 234   AddrDelta = ForceExpAbs(this, getContext(), AddrDelta);
 235   new MCDwarfLineAddrFragment(LineDelta, *AddrDelta, getCurrentSectionData());
 236 }
 237
 238 void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
 239                                                  const MCSymbol *Label) {
 240   const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
 241   int64_t Res;
 242   if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
 243     MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
 244     return;
 245   }
 246   AddrDelta = ForceExpAbs(this, getContext(), AddrDelta);
 247   new MCDwarfCallFrameFragment(*AddrDelta, getCurrentSectionData());
 248 }
 249
 250 void MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
 251                                         unsigned char Value) {
 252   int64_t Res;
 253   if (Offset->EvaluateAsAbsolute(Res, getAssembler())) {
 254     new MCOrgFragment(*Offset, Value, getCurrentSectionData());
 255     return;
 256   }
 257
 258   MCSymbol *CurrentPos = getContext().CreateTempSymbol();
 259   EmitLabel(CurrentPos);
 260   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
 261   const MCExpr *Ref =
 262     MCSymbolRefExpr::Create(CurrentPos, Variant, getContext());
 263   const MCExpr *Delta =
 264     MCBinaryExpr::Create(MCBinaryExpr::Sub, Offset, Ref, getContext());
 265
 266   if (!Delta->EvaluateAsAbsolute(Res, getAssembler()))
 267     report_fatal_error("expected assembly-time absolute expression");
 268   EmitFill(Res, Value, 0);
 269 }
 270
 271 void MCObjectStreamer::Finish() {
 272   // Dump out the dwarf file & directory tables and line tables.
 273   if (getContext().hasDwarfFiles())
 274     MCDwarfFileTable::Emit(this);
 275
 276   getAssembler().Finish();
 277 }