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- This fixes a string table mismatch with 'as' when two new symbols are defined in a single instruction. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103979 91177308-0d34-0410-b5e6-96231b3b80d8
488 lines
17 KiB
C++
488 lines
17 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/MCMachOSymbolFlags.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 MCStreamer {
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private:
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MCAssembler Assembler;
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MCSectionData *CurSectionData;
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/// Track the current atom for each section.
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DenseMap<const MCSectionData*, MCSymbolData*> CurrentAtomMap;
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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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/// Get a data fragment to write into, creating a new one if the current
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/// fragment is not a data fragment.
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MCDataFragment *getOrCreateDataFragment() const {
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MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
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if (!F)
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F = createDataFragment();
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return F;
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}
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/// Create a new data fragment in the current section.
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MCDataFragment *createDataFragment() const {
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MCDataFragment *DF = new MCDataFragment(CurSectionData);
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DF->setAtom(CurrentAtomMap.lookup(CurSectionData));
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return DF;
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}
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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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: MCStreamer(Context), Assembler(Context, TAB, *_Emitter, _OS),
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CurSectionData(0) {}
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~MCMachOStreamer() {}
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MCAssembler &getAssembler() { return Assembler; }
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const MCExpr *AddValueSymbols(const MCExpr *Value) {
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switch (Value->getKind()) {
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case MCExpr::Target: assert(0 && "Can't handle target exprs yet!");
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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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Assembler.getOrCreateSymbolData(
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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(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(MCSymbol *Symbol, uint64_t Size,
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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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errs() << "FIXME: MCMachoStreamer:EmitFileDirective not implemented\n";
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}
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virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
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errs() << "FIXME: MCMachoStreamer:EmitDwarfFileDirective not implemented\n";
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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::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 = &Assembler.getOrCreateSectionData(*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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assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
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assert(CurSection && "Cannot emit before setting section!");
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MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
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// Update the current atom map, if necessary.
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bool MustCreateFragment = false;
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if (Assembler.isSymbolLinkerVisible(&SD)) {
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CurrentAtomMap[CurSectionData] = &SD;
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// We have to create a new fragment, fragments cannot span atoms.
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MustCreateFragment = true;
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}
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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 =
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MustCreateFragment ? createDataFragment() : 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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Symbol->setSection(*CurSection);
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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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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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// FIXME: Lift context changes into super class.
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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 = 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 getOrCreateSymbolData here is to register
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// the symbol with the assembler.
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MCSymbolData &SD = Assembler.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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}
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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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Assembler.getOrCreateSymbolData(*Symbol).setFlags(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 = Assembler.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 = Assembler.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 = Assembler.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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if (Assembler.isSymbolLinkerVisible(&SD))
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F->setAtom(&SD);
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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::EmitTBSSSymbol(MCSymbol *Symbol, uint64_t Size,
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unsigned ByteAlignment) {
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assert(false && "Implement me!");
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}
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void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
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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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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(MCAsmFixup(DF->getContents().size(), *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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if (MaxBytesToEmit == 0)
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MaxBytesToEmit = ByteAlignment;
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MCFragment *F = new MCAlignFragment(ByteAlignment, Value, ValueSize,
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MaxBytesToEmit, CurSectionData);
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F->setAtom(CurrentAtomMap.lookup(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::EmitCodeAlignment(unsigned ByteAlignment,
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unsigned MaxBytesToEmit) {
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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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CurSectionData);
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F->setEmitNops(true);
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F->setAtom(CurrentAtomMap.lookup(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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MCFragment *F = new MCOrgFragment(*Offset, Value, CurSectionData);
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F->setAtom(CurrentAtomMap.lookup(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 = 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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CurSectionData->setHasInstructions(true);
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// FIXME-PERF: Common case is that we don't need to relax, encode directly
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// onto the data fragments buffers.
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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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Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
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VecOS.flush();
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// FIXME: Eliminate this copy.
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SmallVector<MCAsmFixup, 4> AsmFixups;
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for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
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MCFixup &F = Fixups[i];
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AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
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F.getKind()));
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}
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// See if we might need to relax this instruction, if so it needs its own
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// fragment.
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//
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// FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
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// when we can immediately tell that we will get something which might need
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// relaxation (and compute its size).
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//
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// FIXME-PERF: We should also be smart about immediately relaxing instructions
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// which we can already show will never possibly fit (we can also do a very
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// good job of this before we do the first relaxation pass, because we have
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// total knowledge about undefined symbols at that point). Even now, though,
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// we can do a decent job, especially on Darwin where scattering means that we
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// are going to often know that we can never fully resolve a fixup.
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if (Assembler.getBackend().MayNeedRelaxation(Inst, AsmFixups)) {
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MCInstFragment *IF = new MCInstFragment(Inst, CurSectionData);
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IF->setAtom(CurrentAtomMap.lookup(CurSectionData));
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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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IF->getCode() = Code;
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IF->getFixups() = AsmFixups;
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return;
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}
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// Add the fixups and data.
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MCDataFragment *DF = getOrCreateDataFragment();
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for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
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AsmFixups[i].Offset += DF->getContents().size();
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DF->addFixup(AsmFixups[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::Finish() {
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Assembler.Finish();
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}
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MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
|
|
raw_ostream &OS, MCCodeEmitter *CE,
|
|
bool RelaxAll) {
|
|
MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
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|
if (RelaxAll)
|
|
S->getAssembler().setRelaxAll(true);
|
|
return S;
|
|
}
|