llvm-project/llvm/lib/MC/MCMachOStreamer.cpp

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//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCMachOSymbolFlags.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
namespace {
class MCMachOStreamer : public MCObjectStreamer {
private:
virtual void EmitInstToData(const MCInst &Inst);
void EmitDataRegion(DataRegionData::KindTy Kind);
void EmitDataRegionEnd();
public:
MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
raw_ostream &OS, MCCodeEmitter *Emitter)
: MCObjectStreamer(Context, MAB, OS, Emitter) {}
/// @name MCStreamer Interface
/// @{
virtual void InitSections();
virtual void InitToTextSection();
virtual void EmitLabel(MCSymbol *Symbol);
This patch is needed to make c++ exceptions work for mips16. Mips16 is really a processor decoding mode (ala thumb 1) and in the same program, mips16 and mips32 functions can exist and can call each other. If a jal type instruction encounters an address with the lower bit set, then the processor switches to mips16 mode (if it is not already in it). If the lower bit is not set, then it switches to mips32 mode. The linker knows which functions are mips16 and which are mips32. When relocation is performed on code labels, this lower order bit is set if the code label is a mips16 code label. In general this works just fine, however when creating exception handling tables and dwarf, there are cases where you don't want this lower order bit added in. This has been traditionally distinguished in gas assembly source by using a different syntax for the label. lab1: ; this will cause the lower order bit to be added lab2=. ; this will not cause the lower order bit to be added In some cases, it does not matter because in dwarf and debug tables the difference of two labels is used and in that case the lower order bits subtract each other out. To fix this, I have added to mcstreamer the notion of a debuglabel. The default is for label and debug label to be the same. So calling EmitLabel and EmitDebugLabel produce the same result. For various reasons, there is only one set of labels that needs to be modified for the mips exceptions to work. These are the "$eh_func_beginXXX" labels. Mips overrides the debug label suffix from ":" to "=." . This initial patch fixes exceptions. More changes most likely will be needed to DwarfCFException to make all of this work for actual debugging. These changes will be to emit debug labels in some places where a simple label is emitted now. Some historical discussion on this from gcc can be found at: http://gcc.gnu.org/ml/gcc-patches/2008-08/msg00623.html http://gcc.gnu.org/ml/gcc-patches/2008-11/msg01273.html llvm-svn: 170279
2012-12-16 12:00:45 +08:00
virtual void EmitDebugLabel(MCSymbol *Symbol);
virtual void EmitEHSymAttributes(const MCSymbol *Symbol,
MCSymbol *EHSymbol);
virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
virtual void EmitLinkerOptions(ArrayRef<std::string> Options);
virtual void EmitDataRegion(MCDataRegionType Kind);
virtual void EmitThumbFunc(MCSymbol *Func);
virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment);
virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
llvm_unreachable("macho doesn't support this directive");
}
virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
llvm_unreachable("macho doesn't support this directive");
}
virtual void EmitCOFFSymbolType(int Type) {
llvm_unreachable("macho doesn't support this directive");
}
virtual void EndCOFFSymbolDef() {
llvm_unreachable("macho doesn't support this directive");
}
virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
llvm_unreachable("macho doesn't support this directive");
}
virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment);
virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
uint64_t Size = 0, unsigned ByteAlignment = 0);
virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment = 0);
virtual void EmitFileDirective(StringRef Filename) {
// FIXME: Just ignore the .file; it isn't important enough to fail the
// entire assembly.
//report_fatal_error("unsupported directive: '.file'");
}
virtual void FinishImpl();
/// @}
};
} // end anonymous namespace.
void MCMachOStreamer::InitSections() {
InitToTextSection();
}
void MCMachOStreamer::InitToTextSection() {
SwitchSection(getContext().getMachOSection(
"__TEXT", "__text",
MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS, 0,
SectionKind::getText()));
}
void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
MCSymbol *EHSymbol) {
MCSymbolData &SD =
getAssembler().getOrCreateSymbolData(*Symbol);
if (SD.isExternal())
EmitSymbolAttribute(EHSymbol, MCSA_Global);
if (SD.getFlags() & SF_WeakDefinition)
EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
if (SD.isPrivateExtern())
EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
}
void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
// isSymbolLinkerVisible uses the section.
Symbol->setSection(*getCurrentSection());
// We have to create a new fragment if this is an atom defining symbol,
// fragments cannot span atoms.
if (getAssembler().isSymbolLinkerVisible(*Symbol))
new MCDataFragment(getCurrentSectionData());
MCObjectStreamer::EmitLabel(Symbol);
MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
// This causes the reference type flag to be cleared. Darwin 'as' was "trying"
// to clear the weak reference and weak definition bits too, but the
// implementation was buggy. For now we just try to match 'as', for
// diffability.
//
// FIXME: Cleanup this code, these bits should be emitted based on semantic
// properties, not on the order of definition, etc.
SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
}
This patch is needed to make c++ exceptions work for mips16. Mips16 is really a processor decoding mode (ala thumb 1) and in the same program, mips16 and mips32 functions can exist and can call each other. If a jal type instruction encounters an address with the lower bit set, then the processor switches to mips16 mode (if it is not already in it). If the lower bit is not set, then it switches to mips32 mode. The linker knows which functions are mips16 and which are mips32. When relocation is performed on code labels, this lower order bit is set if the code label is a mips16 code label. In general this works just fine, however when creating exception handling tables and dwarf, there are cases where you don't want this lower order bit added in. This has been traditionally distinguished in gas assembly source by using a different syntax for the label. lab1: ; this will cause the lower order bit to be added lab2=. ; this will not cause the lower order bit to be added In some cases, it does not matter because in dwarf and debug tables the difference of two labels is used and in that case the lower order bits subtract each other out. To fix this, I have added to mcstreamer the notion of a debuglabel. The default is for label and debug label to be the same. So calling EmitLabel and EmitDebugLabel produce the same result. For various reasons, there is only one set of labels that needs to be modified for the mips exceptions to work. These are the "$eh_func_beginXXX" labels. Mips overrides the debug label suffix from ":" to "=." . This initial patch fixes exceptions. More changes most likely will be needed to DwarfCFException to make all of this work for actual debugging. These changes will be to emit debug labels in some places where a simple label is emitted now. Some historical discussion on this from gcc can be found at: http://gcc.gnu.org/ml/gcc-patches/2008-08/msg00623.html http://gcc.gnu.org/ml/gcc-patches/2008-11/msg01273.html llvm-svn: 170279
2012-12-16 12:00:45 +08:00
void MCMachOStreamer::EmitDebugLabel(MCSymbol *Symbol) {
EmitLabel(Symbol);
}
void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
if (!getAssembler().getBackend().hasDataInCodeSupport())
return;
// Create a temporary label to mark the start of the data region.
MCSymbol *Start = getContext().CreateTempSymbol();
EmitLabel(Start);
// Record the region for the object writer to use.
DataRegionData Data = { Kind, Start, NULL };
std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
Regions.push_back(Data);
}
void MCMachOStreamer::EmitDataRegionEnd() {
if (!getAssembler().getBackend().hasDataInCodeSupport())
return;
std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
assert(Regions.size() && "Mismatched .end_data_region!");
DataRegionData &Data = Regions.back();
assert(Data.End == NULL && "Mismatched .end_data_region!");
// Create a temporary label to mark the end of the data region.
Data.End = getContext().CreateTempSymbol();
EmitLabel(Data.End);
}
void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
// Let the target do whatever target specific stuff it needs to do.
getAssembler().getBackend().handleAssemblerFlag(Flag);
// Do any generic stuff we need to do.
switch (Flag) {
case MCAF_SyntaxUnified: return; // no-op here.
case MCAF_Code16: return; // Change parsing mode; no-op here.
case MCAF_Code32: return; // Change parsing mode; no-op here.
case MCAF_Code64: return; // Change parsing mode; no-op here.
case MCAF_SubsectionsViaSymbols:
getAssembler().setSubsectionsViaSymbols(true);
return;
}
}
void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
getAssembler().getLinkerOptions().push_back(Options);
}
void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
switch (Kind) {
case MCDR_DataRegion:
EmitDataRegion(DataRegionData::Data);
return;
case MCDR_DataRegionJT8:
EmitDataRegion(DataRegionData::JumpTable8);
return;
case MCDR_DataRegionJT16:
EmitDataRegion(DataRegionData::JumpTable16);
return;
case MCDR_DataRegionJT32:
EmitDataRegion(DataRegionData::JumpTable32);
return;
case MCDR_DataRegionEnd:
EmitDataRegionEnd();
return;
}
}
void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
// Remember that the function is a thumb function. Fixup and relocation
// values will need adjusted.
getAssembler().setIsThumbFunc(Symbol);
// Mark the thumb bit on the symbol.
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
SD.setFlags(SD.getFlags() | SF_ThumbFunc);
}
void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
MCSymbolAttr Attribute) {
// Indirect symbols are handled differently, to match how 'as' handles
// them. This makes writing matching .o files easier.
if (Attribute == MCSA_IndirectSymbol) {
// Note that we intentionally cannot use the symbol data here; this is
// important for matching the string table that 'as' generates.
IndirectSymbolData ISD;
ISD.Symbol = Symbol;
ISD.SectionData = getCurrentSectionData();
getAssembler().getIndirectSymbols().push_back(ISD);
return;
}
// Adding a symbol attribute always introduces the symbol, note that an
// important side effect of calling getOrCreateSymbolData here is to register
// the symbol with the assembler.
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
// The implementation of symbol attributes is designed to match 'as', but it
// leaves much to desired. It doesn't really make sense to arbitrarily add and
// remove flags, but 'as' allows this (in particular, see .desc).
//
// In the future it might be worth trying to make these operations more well
// defined.
switch (Attribute) {
case MCSA_Invalid:
case MCSA_ELF_TypeFunction:
case MCSA_ELF_TypeIndFunction:
case MCSA_ELF_TypeObject:
case MCSA_ELF_TypeTLS:
case MCSA_ELF_TypeCommon:
case MCSA_ELF_TypeNoType:
case MCSA_ELF_TypeGnuUniqueObject:
case MCSA_Hidden:
case MCSA_IndirectSymbol:
case MCSA_Internal:
case MCSA_Protected:
case MCSA_Weak:
case MCSA_Local:
llvm_unreachable("Invalid symbol attribute for Mach-O!");
case MCSA_Global:
SD.setExternal(true);
// This effectively clears the undefined lazy bit, in Darwin 'as', although
// it isn't very consistent because it implements this as part of symbol
// lookup.
//
// FIXME: Cleanup this code, these bits should be emitted based on semantic
// properties, not on the order of definition, etc.
SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
break;
case MCSA_LazyReference:
// FIXME: This requires -dynamic.
SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
if (Symbol->isUndefined())
SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
break;
// Since .reference sets the no dead strip bit, it is equivalent to
// .no_dead_strip in practice.
case MCSA_Reference:
case MCSA_NoDeadStrip:
SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
break;
case MCSA_SymbolResolver:
SD.setFlags(SD.getFlags() | SF_SymbolResolver);
break;
case MCSA_PrivateExtern:
SD.setExternal(true);
SD.setPrivateExtern(true);
break;
case MCSA_WeakReference:
// FIXME: This requires -dynamic.
if (Symbol->isUndefined())
SD.setFlags(SD.getFlags() | SF_WeakReference);
break;
case MCSA_WeakDefinition:
// FIXME: 'as' enforces that this is defined and global. The manual claims
// it has to be in a coalesced section, but this isn't enforced.
SD.setFlags(SD.getFlags() | SF_WeakDefinition);
break;
case MCSA_WeakDefAutoPrivate:
SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
break;
}
}
void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
// Encode the 'desc' value into the lowest implementation defined bits.
assert(DescValue == (DescValue & SF_DescFlagsMask) &&
"Invalid .desc value!");
getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
DescValue & SF_DescFlagsMask);
}
void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment) {
// FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
SD.setExternal(true);
SD.setCommon(Size, ByteAlignment);
}
void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment) {
// '.lcomm' is equivalent to '.zerofill'.
return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
MCSectionMachO::S_ZEROFILL,
0, SectionKind::getBSS()),
Symbol, Size, ByteAlignment);
}
void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment) {
MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
// The symbol may not be present, which only creates the section.
if (!Symbol)
return;
// FIXME: Assert that this section has the zerofill type.
assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
// Emit an align fragment if necessary.
if (ByteAlignment != 1)
new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
SD.setFragment(F);
Symbol->setSection(*Section);
// Update the maximum alignment on the zero fill section if necessary.
if (ByteAlignment > SectData.getAlignment())
SectData.setAlignment(ByteAlignment);
}
2010-05-22 07:03:53 +08:00
// This should always be called with the thread local bss section. Like the
// .zerofill directive this doesn't actually switch sections on us.
void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment) {
EmitZerofill(Section, Symbol, Size, ByteAlignment);
return;
}
void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
MCDataFragment *DF = getOrCreateDataFragment();
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
VecOS.flush();
// Add the fixups and data.
for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
DF->getFixups().push_back(Fixups[i]);
}
DF->getContents().append(Code.begin(), Code.end());
}
void MCMachOStreamer::FinishImpl() {
EmitFrames(true);
// We have to set the fragment atom associations so we can relax properly for
// Mach-O.
// First, scan the symbol table to build a lookup table from fragments to
// defining symbols.
DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
ie = getAssembler().symbol_end(); it != ie; ++it) {
if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
it->getFragment()) {
// An atom defining symbol should never be internal to a fragment.
assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
DefiningSymbolMap[it->getFragment()] = it;
}
}
// Set the fragment atom associations by tracking the last seen atom defining
// symbol.
for (MCAssembler::iterator it = getAssembler().begin(),
ie = getAssembler().end(); it != ie; ++it) {
MCSymbolData *CurrentAtom = 0;
for (MCSectionData::iterator it2 = it->begin(),
ie2 = it->end(); it2 != ie2; ++it2) {
if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
CurrentAtom = SD;
it2->setAtom(CurrentAtom);
}
}
this->MCObjectStreamer::FinishImpl();
}
MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
raw_ostream &OS, MCCodeEmitter *CE,
bool RelaxAll) {
MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
if (RelaxAll)
S->getAssembler().setRelaxAll(true);
return S;
}