492 lines
18 KiB
C++
492 lines
18 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/MCObjectStreamer.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/MCMachOSymbolFlags.h"
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#include "llvm/MC/MCSectionMachO.h"
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#include "llvm/MC/MCDwarf.h"
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#include "llvm/Support/Dwarf.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetAsmBackend.h"
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using namespace llvm;
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namespace {
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class MCMachOStreamer : public MCObjectStreamer {
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private:
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void EmitInstToFragment(const MCInst &Inst);
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void EmitInstToData(const MCInst &Inst);
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public:
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MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
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raw_ostream &OS, MCCodeEmitter *Emitter)
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: MCObjectStreamer(Context, TAB, OS, Emitter, true) {}
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/// @name MCStreamer Interface
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/// @{
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virtual void InitSections();
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virtual void EmitLabel(MCSymbol *Symbol);
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virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
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virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
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virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
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virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
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virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
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unsigned ByteAlignment);
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virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
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assert(0 && "macho doesn't support this directive");
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}
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virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
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assert(0 && "macho doesn't support this directive");
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}
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virtual void EmitCOFFSymbolType(int Type) {
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assert(0 && "macho doesn't support this directive");
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}
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virtual void EndCOFFSymbolDef() {
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assert(0 && "macho doesn't support this directive");
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}
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virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
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assert(0 && "macho doesn't support this directive");
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}
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virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
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assert(0 && "macho doesn't support this directive");
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}
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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 EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
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uint64_t Size, unsigned ByteAlignment = 0);
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virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
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virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
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virtual void EmitGPRel32Value(const MCExpr *Value) {
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assert(0 && "macho doesn't support this directive");
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}
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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 EmitCodeAlignment(unsigned ByteAlignment,
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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 EmitFileDirective(StringRef Filename) {
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// FIXME: Just ignore the .file; it isn't important enough to fail the
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// entire assembly.
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//report_fatal_error("unsupported directive: '.file'");
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}
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virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
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// FIXME: Just ignore the .file; it isn't important enough to fail the
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// entire assembly.
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//report_fatal_error("unsupported directive: '.file'");
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}
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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::InitSections() {
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SwitchSection(getContext().getMachOSection("__TEXT", "__text",
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MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
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0, SectionKind::getText()));
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}
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void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
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// TODO: This is almost exactly the same as WinCOFFStreamer. Consider merging
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// into MCObjectStreamer.
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assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
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assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
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assert(CurSection && "Cannot emit before setting section!");
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Symbol->setSection(*CurSection);
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MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
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// We have to create a new fragment if this is an atom defining symbol,
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// fragments cannot span atoms.
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if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()))
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new MCDataFragment(getCurrentSectionData());
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// FIXME: This is wasteful, we don't necessarily need to create a data
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// fragment. Instead, we should mark the symbol as pointing into the data
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// fragment if it exists, otherwise we should just queue the label and set its
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// fragment pointer when we emit the next fragment.
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MCDataFragment *F = getOrCreateDataFragment();
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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 flag to be cleared. Darwin 'as' was "trying"
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// to clear the weak reference and weak definition bits too, but the
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// implementation was buggy. For now we just try to match 'as', for
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// diffability.
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//
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// FIXME: Cleanup this code, these bits should be emitted based on semantic
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// properties, not on the order of definition, etc.
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SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
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}
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void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
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switch (Flag) {
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case MCAF_SubsectionsViaSymbols:
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getAssembler().setSubsectionsViaSymbols(true);
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return;
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default:
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llvm_unreachable("invalid assembler flag!");
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}
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}
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void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
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// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
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// MCObjectStreamer.
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// FIXME: Lift context changes into super class.
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getAssembler().getOrCreateSymbolData(*Symbol);
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Symbol->setVariableValue(AddValueSymbols(Value));
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}
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void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
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MCSymbolAttr 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 == MCSA_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 = getCurrentSectionData();
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getAssembler().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 getOrCreateSymbolData here is to register
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// the symbol with the assembler.
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MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*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 MCSA_Invalid:
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case MCSA_ELF_TypeFunction:
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case MCSA_ELF_TypeIndFunction:
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case MCSA_ELF_TypeObject:
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case MCSA_ELF_TypeTLS:
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case MCSA_ELF_TypeCommon:
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case MCSA_ELF_TypeNoType:
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case MCSA_IndirectSymbol:
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case MCSA_Hidden:
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case MCSA_Internal:
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case MCSA_Protected:
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case MCSA_Weak:
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case MCSA_Local:
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assert(0 && "Invalid symbol attribute for Mach-O!");
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break;
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case MCSA_Global:
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SD.setExternal(true);
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// This effectively clears the undefined lazy bit, in Darwin 'as', although
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// it isn't very consistent because it implements this as part of symbol
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// lookup.
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//
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// FIXME: Cleanup this code, these bits should be emitted based on semantic
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// properties, not on the order of definition, etc.
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SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
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break;
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case MCSA_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 MCSA_Reference:
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case MCSA_NoDeadStrip:
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SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
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break;
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case MCSA_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 MCSA_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 MCSA_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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case MCSA_WeakDefAutoPrivate:
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SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
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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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getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
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DescValue & SF_DescFlagsMask);
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}
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void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t 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 = getAssembler().getOrCreateSymbolData(*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 = getAssembler().getOrCreateSectionData(*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 = getAssembler().getOrCreateSymbolData(*Symbol);
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// Emit an align fragment if necessary.
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if (ByteAlignment != 1)
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new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
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MCFragment *F = new MCFillFragment(0, 0, Size, &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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// This should always be called with the thread local bss section. Like the
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// .zerofill directive this doesn't actually switch sections on us.
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void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
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uint64_t Size, unsigned ByteAlignment) {
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EmitZerofill(Section, Symbol, Size, ByteAlignment);
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return;
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}
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void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
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// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
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// MCObjectStreamer.
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getOrCreateDataFragment()->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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unsigned AddrSpace) {
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// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
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// MCObjectStreamer.
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MCDataFragment *DF = getOrCreateDataFragment();
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// Avoid fixups when possible.
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int64_t AbsValue;
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if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
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// FIXME: Endianness assumption.
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for (unsigned i = 0; i != Size; ++i)
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DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
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} else {
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DF->addFixup(MCFixup::Create(DF->getContents().size(),
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AddValueSymbols(Value),
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MCFixup::getKindForSize(Size)));
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DF->getContents().resize(DF->getContents().size() + Size, 0);
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}
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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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// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
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// MCObjectStreamer.
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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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getCurrentSectionData());
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// Update the maximum alignment on the current section if necessary.
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if (ByteAlignment > getCurrentSectionData()->getAlignment())
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getCurrentSectionData()->setAlignment(ByteAlignment);
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}
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void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
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unsigned MaxBytesToEmit) {
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// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
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// MCObjectStreamer.
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if (MaxBytesToEmit == 0)
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MaxBytesToEmit = ByteAlignment;
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MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
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getCurrentSectionData());
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F->setEmitNops(true);
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// Update the maximum alignment on the current section if necessary.
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if (ByteAlignment > getCurrentSectionData()->getAlignment())
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getCurrentSectionData()->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, getCurrentSectionData());
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}
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void MCMachOStreamer::EmitInstToFragment(const MCInst &Inst) {
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MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
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// Add the fixups and data.
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//
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// FIXME: Revisit this design decision when relaxation is done, we may be
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// able to get away with not storing any extra data in the MCInst.
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SmallVector<MCFixup, 4> Fixups;
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SmallString<256> Code;
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raw_svector_ostream VecOS(Code);
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getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
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VecOS.flush();
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IF->getCode() = Code;
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IF->getFixups() = Fixups;
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}
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void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
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MCDataFragment *DF = getOrCreateDataFragment();
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SmallVector<MCFixup, 4> Fixups;
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SmallString<256> Code;
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raw_svector_ostream VecOS(Code);
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getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
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VecOS.flush();
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// Add the fixups and data.
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for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
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Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
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DF->addFixup(Fixups[i]);
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}
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DF->getContents().append(Code.begin(), Code.end());
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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 = 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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getCurrentSectionData()->setHasInstructions(true);
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// Now that a machine instruction has been assembled into this section, make
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// a line entry for any .loc directive that has been seen.
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MCLineEntry::Make(this, getCurrentSection());
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// If this instruction doesn't need relaxation, just emit it as data.
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if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
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EmitInstToData(Inst);
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return;
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}
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// Otherwise, if we are relaxing everything, relax the instruction as much as
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// possible and emit it as data.
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if (getAssembler().getRelaxAll()) {
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MCInst Relaxed;
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getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
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while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
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getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
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EmitInstToData(Relaxed);
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return;
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}
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// Otherwise emit to a separate fragment.
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EmitInstToFragment(Inst);
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}
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void MCMachOStreamer::Finish() {
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// Dump out the dwarf file & directory tables and line tables.
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if (getContext().hasDwarfFiles()) {
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const MCSection *DwarfLineSection = getContext().getMachOSection("__DWARF",
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"__debug_line",
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MCSectionMachO::S_ATTR_DEBUG,
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0, SectionKind::getDataRelLocal());
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MCDwarfFileTable::Emit(this, DwarfLineSection);
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}
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// We have to set the fragment atom associations so we can relax properly for
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// Mach-O.
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// First, scan the symbol table to build a lookup table from fragments to
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// defining symbols.
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DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
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for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
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ie = getAssembler().symbol_end(); it != ie; ++it) {
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if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
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it->getFragment()) {
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// An atom defining symbol should never be internal to a fragment.
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assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
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DefiningSymbolMap[it->getFragment()] = it;
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}
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}
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// Set the fragment atom associations by tracking the last seen atom defining
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// symbol.
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for (MCAssembler::iterator it = getAssembler().begin(),
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ie = getAssembler().end(); it != ie; ++it) {
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MCSymbolData *CurrentAtom = 0;
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for (MCSectionData::iterator it2 = it->begin(),
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ie2 = it->end(); it2 != ie2; ++it2) {
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if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
|
|
CurrentAtom = SD;
|
|
it2->setAtom(CurrentAtom);
|
|
}
|
|
}
|
|
|
|
this->MCObjectStreamer::Finish();
|
|
}
|
|
|
|
MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
|
|
raw_ostream &OS, MCCodeEmitter *CE,
|
|
bool RelaxAll) {
|
|
MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
|
|
if (RelaxAll)
|
|
S->getAssembler().setRelaxAll(true);
|
|
return S;
|
|
}
|