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371 lines
12 KiB
C++
371 lines
12 KiB
C++
//===- lib/MC/MCMachOStreamer.cpp - Mach-O Object Output ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCCodeEmitter.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/MC/MCSection.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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namespace {
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class MCMachOStreamer : public MCStreamer {
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/// SymbolFlags - We store the value for the 'desc' symbol field in the lowest
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/// 16 bits of the implementation defined flags.
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enum SymbolFlags { // See <mach-o/nlist.h>.
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SF_DescFlagsMask = 0xFFFF,
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// Reference type flags.
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SF_ReferenceTypeMask = 0x0007,
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SF_ReferenceTypeUndefinedNonLazy = 0x0000,
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SF_ReferenceTypeUndefinedLazy = 0x0001,
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SF_ReferenceTypeDefined = 0x0002,
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SF_ReferenceTypePrivateDefined = 0x0003,
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SF_ReferenceTypePrivateUndefinedNonLazy = 0x0004,
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SF_ReferenceTypePrivateUndefinedLazy = 0x0005,
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// Other 'desc' flags.
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SF_NoDeadStrip = 0x0020,
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SF_WeakReference = 0x0040,
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SF_WeakDefinition = 0x0080
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};
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private:
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MCAssembler Assembler;
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MCCodeEmitter *Emitter;
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MCSectionData *CurSectionData;
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DenseMap<const MCSection*, MCSectionData*> SectionMap;
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DenseMap<const MCSymbol*, MCSymbolData*> SymbolMap;
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private:
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MCFragment *getCurrentFragment() const {
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assert(CurSectionData && "No current section!");
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if (!CurSectionData->empty())
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return &CurSectionData->getFragmentList().back();
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return 0;
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}
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MCSectionData &getSectionData(const MCSection &Section) {
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MCSectionData *&Entry = SectionMap[&Section];
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if (!Entry)
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Entry = new MCSectionData(Section, &Assembler);
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return *Entry;
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}
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MCSymbolData &getSymbolData(const MCSymbol &Symbol) {
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MCSymbolData *&Entry = SymbolMap[&Symbol];
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if (!Entry)
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Entry = new MCSymbolData(Symbol, 0, 0, &Assembler);
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return *Entry;
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}
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public:
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MCMachOStreamer(MCContext &Context, raw_ostream &_OS, MCCodeEmitter *_Emitter)
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: MCStreamer(Context), Assembler(Context, _OS), Emitter(_Emitter),
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CurSectionData(0) {}
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~MCMachOStreamer() {}
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const MCExpr *AddValueSymbols(const MCExpr *Value) {
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switch (Value->getKind()) {
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case MCExpr::Constant:
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break;
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case MCExpr::Binary: {
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const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
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AddValueSymbols(BE->getLHS());
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AddValueSymbols(BE->getRHS());
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break;
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}
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case MCExpr::SymbolRef:
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getSymbolData(cast<MCSymbolRefExpr>(Value)->getSymbol());
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break;
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case MCExpr::Unary:
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AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
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break;
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}
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return Value;
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}
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/// @name MCStreamer Interface
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/// @{
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virtual void SwitchSection(const MCSection *Section);
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virtual void EmitLabel(MCSymbol *Symbol);
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virtual void EmitAssemblerFlag(AssemblerFlag Flag);
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virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
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virtual void EmitSymbolAttribute(MCSymbol *Symbol, SymbolAttr Attribute);
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virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
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virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
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unsigned ByteAlignment);
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virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
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unsigned Size = 0, unsigned ByteAlignment = 0);
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virtual void EmitBytes(const StringRef &Data);
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virtual void EmitValue(const MCExpr *Value, unsigned Size);
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virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
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unsigned ValueSize = 1,
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unsigned MaxBytesToEmit = 0);
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virtual void EmitValueToOffset(const MCExpr *Offset,
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unsigned char Value = 0);
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virtual void EmitInstruction(const MCInst &Inst);
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virtual void Finish();
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/// @}
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};
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} // end anonymous namespace.
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void MCMachOStreamer::SwitchSection(const MCSection *Section) {
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assert(Section && "Cannot switch to a null section!");
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// If already in this section, then this is a noop.
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if (Section == CurSection) return;
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CurSection = Section;
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CurSectionData = &getSectionData(*Section);
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}
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void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
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assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
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// FIXME: We should also use offsets into Fill fragments.
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MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
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if (!F)
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F = new MCDataFragment(CurSectionData);
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MCSymbolData &SD = getSymbolData(*Symbol);
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assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
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SD.setFragment(F);
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SD.setOffset(F->getContents().size());
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// This causes the reference type and weak reference flags to be cleared.
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SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
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Symbol->setSection(*CurSection);
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}
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void MCMachOStreamer::EmitAssemblerFlag(AssemblerFlag Flag) {
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switch (Flag) {
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case SubsectionsViaSymbols:
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Assembler.setSubsectionsViaSymbols(true);
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return;
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}
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assert(0 && "invalid assembler flag!");
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}
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void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
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// Only absolute symbols can be redefined.
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assert((Symbol->isUndefined() || Symbol->isAbsolute()) &&
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"Cannot define a symbol twice!");
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// FIXME: Lift context changes into super class.
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// FIXME: Set associated section.
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Symbol->setValue(Value);
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}
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void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
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SymbolAttr Attribute) {
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// Indirect symbols are handled differently, to match how 'as' handles
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// them. This makes writing matching .o files easier.
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if (Attribute == MCStreamer::IndirectSymbol) {
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// Note that we intentionally cannot use the symbol data here; this is
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// important for matching the string table that 'as' generates.
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IndirectSymbolData ISD;
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ISD.Symbol = Symbol;
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ISD.SectionData = CurSectionData;
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Assembler.getIndirectSymbols().push_back(ISD);
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return;
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}
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// Adding a symbol attribute always introduces the symbol, note that an
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// important side effect of calling getSymbolData here is to register the
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// symbol with the assembler.
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MCSymbolData &SD = getSymbolData(*Symbol);
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// The implementation of symbol attributes is designed to match 'as', but it
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// leaves much to desired. It doesn't really make sense to arbitrarily add and
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// remove flags, but 'as' allows this (in particular, see .desc).
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//
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// In the future it might be worth trying to make these operations more well
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// defined.
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switch (Attribute) {
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case MCStreamer::IndirectSymbol:
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case MCStreamer::Hidden:
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case MCStreamer::Internal:
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case MCStreamer::Protected:
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case MCStreamer::Weak:
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assert(0 && "Invalid symbol attribute for Mach-O!");
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break;
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case MCStreamer::Global:
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SD.setExternal(true);
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break;
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case MCStreamer::LazyReference:
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// FIXME: This requires -dynamic.
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SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
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if (Symbol->isUndefined())
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SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
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break;
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// Since .reference sets the no dead strip bit, it is equivalent to
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// .no_dead_strip in practice.
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case MCStreamer::Reference:
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case MCStreamer::NoDeadStrip:
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SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
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break;
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case MCStreamer::PrivateExtern:
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SD.setExternal(true);
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SD.setPrivateExtern(true);
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break;
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case MCStreamer::WeakReference:
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// FIXME: This requires -dynamic.
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if (Symbol->isUndefined())
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SD.setFlags(SD.getFlags() | SF_WeakReference);
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break;
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case MCStreamer::WeakDefinition:
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// FIXME: 'as' enforces that this is defined and global. The manual claims
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// it has to be in a coalesced section, but this isn't enforced.
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SD.setFlags(SD.getFlags() | SF_WeakDefinition);
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break;
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}
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}
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void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
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// Encode the 'desc' value into the lowest implementation defined bits.
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assert(DescValue == (DescValue & SF_DescFlagsMask) &&
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"Invalid .desc value!");
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getSymbolData(*Symbol).setFlags(DescValue & SF_DescFlagsMask);
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}
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void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
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unsigned ByteAlignment) {
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// FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
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assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
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MCSymbolData &SD = getSymbolData(*Symbol);
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SD.setExternal(true);
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SD.setCommon(Size, ByteAlignment);
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}
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void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
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unsigned Size, unsigned ByteAlignment) {
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MCSectionData &SectData = getSectionData(*Section);
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// The symbol may not be present, which only creates the section.
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if (!Symbol)
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return;
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// FIXME: Assert that this section has the zerofill type.
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assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
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MCSymbolData &SD = getSymbolData(*Symbol);
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MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
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SD.setFragment(F);
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Symbol->setSection(*Section);
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// Update the maximum alignment on the zero fill section if necessary.
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if (ByteAlignment > SectData.getAlignment())
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SectData.setAlignment(ByteAlignment);
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}
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void MCMachOStreamer::EmitBytes(const StringRef &Data) {
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MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
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if (!DF)
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DF = new MCDataFragment(CurSectionData);
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DF->getContents().append(Data.begin(), Data.end());
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}
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void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size) {
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new MCFillFragment(*AddValueSymbols(Value), Size, 1, CurSectionData);
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}
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void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
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int64_t Value, unsigned ValueSize,
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unsigned MaxBytesToEmit) {
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if (MaxBytesToEmit == 0)
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MaxBytesToEmit = ByteAlignment;
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new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
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CurSectionData);
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// Update the maximum alignment on the current section if necessary.
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if (ByteAlignment > CurSectionData->getAlignment())
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CurSectionData->setAlignment(ByteAlignment);
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}
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void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
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unsigned char Value) {
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new MCOrgFragment(*Offset, Value, CurSectionData);
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}
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void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
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// Scan for values.
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for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
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if (Inst.getOperand(i).isExpr())
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AddValueSymbols(Inst.getOperand(i).getExpr());
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if (!Emitter)
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llvm_unreachable("no code emitter available!");
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// FIXME: Relocations!
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SmallString<256> Code;
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raw_svector_ostream VecOS(Code);
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Emitter->EncodeInstruction(Inst, VecOS);
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EmitBytes(VecOS.str());
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}
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void MCMachOStreamer::Finish() {
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Assembler.Finish();
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}
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MCStreamer *llvm::createMachOStreamer(MCContext &Context, raw_ostream &OS,
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MCCodeEmitter *CE) {
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return new MCMachOStreamer(Context, OS, CE);
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}
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