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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 73e8ecbf7f
commit 6eb5aa7fce
7 changed files with 168 additions and 13 deletions
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2
include/llvm/MC/MCMachObjectWriter.h
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@ -111,6 +111,8 @@ class MachObjectWriter : public MCObjectWriter {
/// @}
MachSymbolData *findSymbolData(const MCSymbol &Sym);
public:
MachObjectWriter(MCMachObjectTargetWriter *MOTW, raw_ostream &_OS,
bool _IsLittleEndian)

1
include/llvm/Object/SymbolicFile.h
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@ -86,6 +86,7 @@ public:
SF_Weak = 1U << 2, // Weak symbol
SF_Absolute = 1U << 3, // Absolute symbol
SF_Common = 1U << 4, // Symbol has common linkage
SF_Indirect = 1U << 5,
SF_FormatSpecific = 1U << 5 // Specific to the object file format
// (e.g. section symbols)
};

50
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.

3
lib/Object/MachOObjectFile.cpp
View File

@ -584,6 +584,9 @@ uint32_t MachOObjectFile::getSymbolFlags(DataRefImpl DRI) const {
if ((MachOType & MachO::N_TYPE) == MachO::N_UNDF)
Result |= SymbolRef::SF_Undefined;
if ((MachOType & MachO::N_TYPE) == MachO::N_INDR)
Result |= SymbolRef::SF_Indirect;
if (MachOType & MachO::N_STAB)
Result |= SymbolRef::SF_FormatSpecific;

115
test/MC/MachO/aliased-symbols.s Normal file
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@ -0,0 +1,115 @@
// RUN: llvm-mc -triple thumbv7m-apple-darwin-eabi %s -filetype=obj -o %t
// RUN: llvm-readobj -symbols %t | FileCheck %s
.data
var1 = var2
.long var1
.long var2
.long var2 + 4
defined_early:
.long 0
alias_to_early = defined_early
alias_to_late = defined_late
defined_late:
.long 0
.global extern_test
extern_test = var2
alias_to_local = Ltmp0
Ltmp0:
// CHECK: Symbols [
// defined_early was defined. Actually has value 0xc.
// CHECK: Symbol {
// CHECK-NEXT: Name: defined_early
// CHECK-NEXT: Type: Section (0xE)
// CHECK-NEXT: Section: __data (0x2)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x[[DEFINED_EARLY:[0-9A-F]+]]
// CHECK-NEXT: }
// alias_to_early was an alias to defined_early. But we can resolve it.
// CHECK: Symbol {
// CHECK-NEXT: Name: alias_to_early
// CHECK-NEXT: Type: Section (0xE)
// CHECK-NEXT: Section: __data (0x2)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x[[DEFINED_EARLY]]
// CHECK-NEXT: }
// defined_late was defined. Just after defined_early.
// CHECK: Symbol {
// CHECK-NEXT: Name: defined_late
// CHECK-NEXT: Type: Section (0xE)
// CHECK-NEXT: Section: __data (0x2)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x[[DEFINED_LATE:[0-9A-F]+]]
// CHECK-NEXT: }
// alias_to_late was an alias to defined_late. But we can resolve it.
// CHECK: Symbol {
// CHECK-NEXT: Name: alias_to_late
// CHECK-NEXT: Type: Section (0xE)
// CHECK-NEXT: Section: __data (0x2)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x[[DEFINED_LATE]]
// CHECK-NEXT: }
// alias_to_local is an alias, but what it points to has no
// MachO representation. We must resolve it.
// CHECK: Symbol {
// CHECK-NEXT: Name: alias_to_local (37)
// CHECK-NEXT: Type: Section (0xE)
// CHECK-NEXT: Section: (0x0)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x14
// CHECK-NEXT: }
// extern_test was a pure alias to the unknown "var2".
// N_INDR and Extern.
// CHECK: Name: extern_test
// CHECK-NEXT: Extern
// CHECK-NEXT: Type: Indirect (0xA)
// CHECK-NEXT: Section: (0x0)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x[[VAR2_STRINGINDEX:[0-9a-f]+]]
// CHECK-NEXT: }
// var1 was another alias to an unknown variable. Not extern this time.
// CHECK: Symbol {
// CHECK-NEXT: Name: var1 (1)
// CHECK-NEXT: Type: Indirect (0xA)
// CHECK-NEXT: Section: (0x0)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x[[VAR2_STRINGINDEX]]
// CHECK-NEXT: }
// var2 was a normal undefined (extern) symbol.
// CHECK: Symbol {
// CHECK-NEXT: Name: var2
// CHECK-NEXT: Extern
// CHECK-NEXT: Type: Undef (0x0)
// CHECK-NEXT: Section: (0x0)
// CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
// CHECK-NEXT: Flags [ (0x0)
// CHECK-NEXT: ]
// CHECK-NEXT: Value: 0x0
// CHECK-NEXT: }

8
test/MC/MachO/variable-exprs.s
View File

@ -202,10 +202,10 @@ Lt0_x = Lt0_a - Lt0_b
// CHECK-I386: ),
// CHECK-I386: # Symbol 8
// CHECK-I386: (('n_strx', 1)
// CHECK-I386: ('n_type', 0x1)
// CHECK-I386: ('n_type', 0xb)
// CHECK-I386: ('n_sect', 0)
// CHECK-I386: ('n_desc', 0)
// CHECK-I386: ('n_value', 0)
// CHECK-I386: ('n_value', 4)
// CHECK-I386: ('_string', 'd2')
// CHECK-I386: ),
// CHECK-I386: # Symbol 9
@ -403,10 +403,10 @@ Lt0_x = Lt0_a - Lt0_b
// CHECK-X86_64: ),
// CHECK-X86_64: # Symbol 8
// CHECK-X86_64: (('n_strx', 1)
// CHECK-X86_64: ('n_type', 0x1)
// CHECK-X86_64: ('n_type', 0xb)
// CHECK-X86_64: ('n_sect', 0)
// CHECK-X86_64: ('n_desc', 0)
// CHECK-X86_64: ('n_value', 0)
// CHECK-X86_64: ('n_value', 4)
// CHECK-X86_64: ('_string', 'd2')
// CHECK-X86_64: ),
// CHECK-X86_64: # Symbol 9

2
tools/llvm-nm/llvm-nm.cpp
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@ -395,6 +395,8 @@ static char getSymbolNMTypeChar(MachOObjectFile &Obj, basic_symbol_iterator I) {
switch (NType & MachO::N_TYPE) {
case MachO::N_ABS:
return 's';
case MachO::N_INDR:
return 'i';
case MachO::N_SECT: {
section_iterator Sec = Obj.section_end();
Obj.getSymbolSection(Symb, Sec);