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WinCOFF: Emit common symbols as specified in the COFF spec

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Summary:
Local common symbols were properly inserted into the .bss section.
However, putting external common symbols in the .bss section would give
them a strong definition.

Instead, encode them as undefined, external symbols who's symbol value
is equivalent to their size.

Reviewers: Bigcheese, rafael, rnk

CC: llvm-commits

Differential Revision: http://reviews.llvm.org/D3324

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205811 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2014-04-08 22:33:40 +00:00
parent 1507319299
commit e4d89ec8de
6 changed files with 45 additions and 36 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/MC/WinCOFFStreamer.cpp
+28 -28
View File
@@ -45,9 +45,6 @@ public:
MCCodeEmitter &CE,
raw_ostream &OS);
void AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment, bool External);
// MCStreamer interface
void InitSections() override;
@@ -101,26 +98,6 @@ WinCOFFStreamer::WinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
MCCodeEmitter &CE, raw_ostream &OS)
: MCObjectStreamer(Context, MAB, OS, &CE), CurSymbol(NULL) {}
void WinCOFFStreamer::AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment, bool External) {
assert(!Symbol->isInSection() && "Symbol must not already have a section!");
const MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
MCSectionData &SectionData = getAssembler().getOrCreateSectionData(*Section);
if (SectionData.getAlignment() < ByteAlignment)
SectionData.setAlignment(ByteAlignment);
MCSymbolData &SymbolData = getAssembler().getOrCreateSymbolData(*Symbol);
SymbolData.setExternal(External);
AssignSection(Symbol, Section);
if (ByteAlignment != 1)
new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectionData);
SymbolData.setFragment(new MCFillFragment(0, 0, Size, &SectionData));
}
// MCStreamer interface
void WinCOFFStreamer::InitSections() {
@@ -244,15 +221,38 @@ void WinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
assert((Symbol->isInSection()
? Symbol->getSection().getVariant() == MCSection::SV_COFF
: true) && "Got non-COFF section in the COFF backend!");
AddCommonSymbol(Symbol, Size, ByteAlignment, true);
if (ByteAlignment > 32)
report_fatal_error(
"The linker won't align common symbols beyond 32 bytes.");
AssignSection(Symbol, NULL);
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
SD.setExternal(true);
SD.setCommon(Size, ByteAlignment);
}
void WinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment) {
assert((Symbol->isInSection()
? Symbol->getSection().getVariant() == MCSection::SV_COFF
: true) && "Got non-COFF section in the COFF backend!");
AddCommonSymbol(Symbol, Size, ByteAlignment, false);
assert(!Symbol->isInSection() && "Symbol must not already have a section!");
const MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
MCSectionData &SectionData = getAssembler().getOrCreateSectionData(*Section);
if (SectionData.getAlignment() < ByteAlignment)
SectionData.setAlignment(ByteAlignment);
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
SD.setExternal(false);
AssignSection(Symbol, Section);
if (ByteAlignment != 1)
new MCAlignFragment(ByteAlignment, /*_Value=*/0, /*_ValueSize=*/0,
ByteAlignment, &SectionData);
SD.setFragment(
new MCFillFragment(/*_Value=*/0, /*_ValueSize=*/0, Size, &SectionData));
}
void WinCOFFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,