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
  12 #include "llvm/Support/ErrorHandling.h"
  13 #include "llvm/MC/MCAssembler.h"
  14 #include "llvm/MC/MCCodeEmitter.h"
  15 #include "llvm/MC/MCDwarf.h"
  16 #include "llvm/MC/MCExpr.h"
  17 #include "llvm/MC/MCSymbol.h"
  18 #include "llvm/Target/TargetAsmBackend.h"
  19 using namespace llvm;
  20
  21 MCObjectStreamer::MCObjectStreamer(MCContext &Context, TargetAsmBackend &TAB,
  22                                    raw_ostream &_OS, MCCodeEmitter *_Emitter,
  23                                    bool _PadSectionToAlignment)
  24   : MCStreamer(Context), Assembler(new MCAssembler(Context, TAB,
  25                                                    *_Emitter,
  26                                                    _PadSectionToAlignment,
  27                                                    _OS)),
  28     CurSectionData(0)
  29 {
  30 }
  31
  32 MCObjectStreamer::~MCObjectStreamer() {
  33   delete &Assembler->getBackend();
  34   delete &Assembler->getEmitter();
  35   delete Assembler;
  36 }
  37
  38 MCFragment *MCObjectStreamer::getCurrentFragment() const {
  39   assert(getCurrentSectionData() && "No current section!");
  40
  41   if (!getCurrentSectionData()->empty())
  42     return &getCurrentSectionData()->getFragmentList().back();
  43
  44   return 0;
  45 }
  46
  47 MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() const {
  48   MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
  49   if (!F)
  50     F = new MCDataFragment(getCurrentSectionData());
  51   return F;
  52 }
  53
  54 const MCExpr *MCObjectStreamer::AddValueSymbols(const MCExpr *Value) {
  55   switch (Value->getKind()) {
  56   case MCExpr::Target: llvm_unreachable("Can't handle target exprs yet!");
  57   case MCExpr::Constant:
  58     break;
  59
  60   case MCExpr::Binary: {
  61     const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
  62     AddValueSymbols(BE->getLHS());
  63     AddValueSymbols(BE->getRHS());
  64     break;
  65   }
  66
  67   case MCExpr::SymbolRef:
  68     Assembler->getOrCreateSymbolData(cast<MCSymbolRefExpr>(Value)->getSymbol());
  69     break;
  70
  71   case MCExpr::Unary:
  72     AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
  73     break;
  74   }
  75
  76   return Value;
  77 }
  78
  79 void MCObjectStreamer::EmitValue(const MCExpr *Value, unsigned Size,
  80                                  unsigned AddrSpace, bool UseSet) {
  81   assert(AddrSpace == 0 && "Address space must be 0!");
  82   MCDataFragment *DF = getOrCreateDataFragment();
  83
  84   // Avoid fixups when possible.
  85   int64_t AbsValue;
  86   if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
  87     // FIXME: Endianness assumption.
  88     for (unsigned i = 0; i != Size; ++i)
  89       DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
  90   } else {
  91     DF->addFixup(MCFixup::Create(DF->getContents().size(),
  92                                  AddValueSymbols(Value),
  93                                  MCFixup::getKindForSize(Size, false)));
  94     DF->getContents().resize(DF->getContents().size() + Size, 0);
  95   }
  96 }
  97
  98 void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
  99   assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
 100   assert(CurSection && "Cannot emit before setting section!");
 101
 102   Symbol->setSection(*CurSection);
 103
 104   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 105
 106   // FIXME: This is wasteful, we don't necessarily need to create a data
 107   // fragment. Instead, we should mark the symbol as pointing into the data
 108   // fragment if it exists, otherwise we should just queue the label and set its
 109   // fragment pointer when we emit the next fragment.
 110   MCDataFragment *F = getOrCreateDataFragment();
 111   assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
 112   SD.setFragment(F);
 113   SD.setOffset(F->getContents().size());
 114 }
 115
 116 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value,
 117                                         unsigned AddrSpace) {
 118   new MCLEBFragment(*Value, false, getCurrentSectionData());
 119 }
 120
 121 void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value,
 122                                         unsigned AddrSpace) {
 123   new MCLEBFragment(*Value, true, getCurrentSectionData());
 124 }
 125
 126 void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
 127                                          const MCSymbol *Symbol) {
 128   report_fatal_error("This file format doesn't support weak aliases.");
 129 }
 130
 131 void MCObjectStreamer::SwitchSection(const MCSection *Section) {
 132   assert(Section && "Cannot switch to a null section!");
 133
 134   // If already in this section, then this is a noop.
 135   if (Section == CurSection) return;
 136
 137   PrevSection = CurSection;
 138   CurSection = Section;
 139   CurSectionData = &getAssembler().getOrCreateSectionData(*Section);
 140 }
 141
 142 void MCObjectStreamer::EmitInstruction(const MCInst &Inst) {
 143   // Scan for values.
 144   for (unsigned i = Inst.getNumOperands(); i--; )
 145     if (Inst.getOperand(i).isExpr())
 146       AddValueSymbols(Inst.getOperand(i).getExpr());
 147
 148   getCurrentSectionData()->setHasInstructions(true);
 149
 150   // Now that a machine instruction has been assembled into this section, make
 151   // a line entry for any .loc directive that has been seen.
 152   MCLineEntry::Make(this, getCurrentSection());
 153
 154   // If this instruction doesn't need relaxation, just emit it as data.
 155   if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
 156     EmitInstToData(Inst);
 157     return;
 158   }
 159
 160   // Otherwise, if we are relaxing everything, relax the instruction as much as
 161   // possible and emit it as data.
 162   if (getAssembler().getRelaxAll()) {
 163     MCInst Relaxed;
 164     getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
 165     while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
 166       getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
 167     EmitInstToData(Relaxed);
 168     return;
 169   }
 170
 171   // Otherwise emit to a separate fragment.
 172   EmitInstToFragment(Inst);
 173 }
 174
 175 void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst) {
 176   MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
 177
 178   raw_svector_ostream VecOS(IF->getCode());
 179   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, IF->getFixups());
 180 }
 181
 182 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
 183                                                 const MCSymbol *LastLabel,
 184                                                 const MCSymbol *Label) {
 185   if (!LastLabel) {
 186     int PointerSize = getAssembler().getBackend().getPointerSize();
 187     EmitDwarfSetLineAddr(LineDelta, Label, PointerSize);
 188     return;
 189   }
 190   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
 191   const MCExpr *LabelRef =
 192     MCSymbolRefExpr::Create(Label, Variant, getContext());
 193   const MCExpr *LastLabelRef =
 194     MCSymbolRefExpr::Create(LastLabel, Variant, getContext());
 195   const MCExpr *AddrDelta =
 196     MCBinaryExpr::Create(MCBinaryExpr::Sub, LabelRef, LastLabelRef,
 197                          getContext());
 198   int64_t Res;
 199   if (AddrDelta->EvaluateAsAbsolute(Res, &getAssembler())) {
 200     MCDwarfLineAddr::Emit(this, LineDelta, Res);
 201     return;
 202   }
 203   new MCDwarfLineAddrFragment(LineDelta, *AddrDelta, getCurrentSectionData());
 204 }
 205
 206 void MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
 207                                         unsigned char Value) {
 208   new MCOrgFragment(*Offset, Value, getCurrentSectionData());
 209 }
 210
 211 void MCObjectStreamer::Finish() {
 212   getAssembler().Finish();
 213 }