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MachO: support N_INDR aliases in assembly files.

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This makes LLVM create N_INDR aliases (to be resolved by the linker) when
appropriate.

rdar://problem/15125513

llvm-svn: 209894
This commit is contained in:
Tim Northover
2014-05-30 13:22:59 +00:00
parent 6bfdaf5a20
commit eaef074d45
7 changed files with 168 additions and 13 deletions
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50
llvm/lib/MC/MachObjectWriter.cpp
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@@ -303,20 +303,50 @@ void MachObjectWriter::WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
assert(OS.tell() - Start == sizeof(MachO::dysymtab_command));
}
MachObjectWriter::MachSymbolData *
MachObjectWriter::findSymbolData(const MCSymbol &Sym) {
for (auto &Entry : LocalSymbolData)
if (&Entry.SymbolData->getSymbol() == &Sym)
return &Entry;
for (auto &Entry : ExternalSymbolData)
if (&Entry.SymbolData->getSymbol() == &Sym)
return &Entry;
for (auto &Entry : UndefinedSymbolData)
if (&Entry.SymbolData->getSymbol() == &Sym)
return &Entry;
return nullptr;
}
void MachObjectWriter::WriteNlist(MachSymbolData &MSD,
const MCAsmLayout &Layout) {
MCSymbolData &Data = *MSD.SymbolData;
const MCSymbol &Symbol = Data.getSymbol();
const MCSymbol *Symbol = &Data.getSymbol();
const MCSymbol *AliasedSymbol = &Symbol->AliasedSymbol();
uint8_t SectionIndex = MSD.SectionIndex;
uint8_t Type = 0;
uint16_t Flags = Data.getFlags();
uint64_t Address = 0;
bool IsAlias = Symbol != AliasedSymbol;
MachSymbolData *AliaseeInfo;
if (IsAlias) {
AliaseeInfo = findSymbolData(*AliasedSymbol);
if (AliaseeInfo)
SectionIndex = AliaseeInfo->SectionIndex;
Symbol = AliasedSymbol;
}
// Set the N_TYPE bits. See <mach-o/nlist.h>.
//
// FIXME: Are the prebound or indirect fields possible here?
if (Symbol.isUndefined())
if (IsAlias && Symbol->isUndefined())
Type = MachO::N_INDR;
else if (Symbol->isUndefined())
Type = MachO::N_UNDF;
else if (Symbol.isAbsolute())
else if (Symbol->isAbsolute())
Type = MachO::N_ABS;
else
Type = MachO::N_SECT;
@@ -327,13 +357,15 @@ void MachObjectWriter::WriteNlist(MachSymbolData &MSD,
Type |= MachO::N_PEXT;
// Set external bit.
if (Data.isExternal() || Symbol.isUndefined())
if (Data.isExternal() || (!IsAlias && Symbol->isUndefined()))
Type |= MachO::N_EXT;
// Compute the symbol address.
if (Symbol.isDefined()) {
if (IsAlias && Symbol->isUndefined())
Address = AliaseeInfo->StringIndex;
else if (Symbol->isDefined())
Address = getSymbolAddress(&Data, Layout);
} else if (Data.isCommon()) {
else if (Data.isCommon()) {
// Common symbols are encoded with the size in the address
// field, and their alignment in the flags.
Address = Data.getCommonSize();
@@ -344,21 +376,21 @@ void MachObjectWriter::WriteNlist(MachSymbolData &MSD,
assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
if (Log2Size > 15)
report_fatal_error("invalid 'common' alignment '" +
Twine(Align) + "' for '" + Symbol.getName() + "'",
Twine(Align) + "' for '" + Symbol->getName() + "'",
false);
// FIXME: Keep this mask with the SymbolFlags enumeration.
Flags = (Flags & 0xF0FF) | (Log2Size << 8);
}
}
if (Layout.getAssembler().isThumbFunc(&Symbol))
if (Layout.getAssembler().isThumbFunc(Symbol))
Flags |= SF_ThumbFunc;
// struct nlist (12 bytes)
Write32(MSD.StringIndex);
Write8(Type);
Write8(MSD.SectionIndex);
Write8(SectionIndex);
// The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
// value.