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Add support for emitting a .data section and .bss section.

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Add support for emitting external and .bss symbols.

llvm-svn: 22358
This commit is contained in:
Chris Lattner 2005-07-08 05:47:00 +00:00
parent 00f7df2ba0
commit de44e16474
1 changed files with 66 additions and 21 deletions
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87
lib/CodeGen/ELFWriter.cpp
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@ -96,9 +96,22 @@ bool ELFWriter::doInitialization(Module &M) {
void ELFWriter::EmitGlobal(GlobalVariable *GV, ELFSection &DataSection,
ELFSection &BSSSection) {
// If this is an external global, emit it...
assert(GV->hasInitializer() && "FIXME: unimp");
// If this is an external global, emit it now. TODO: Note that it would be
// better to ignore the symbol here and only add it to the symbol table if
// referenced.
if (!GV->hasInitializer()) {
ELFSym ExternalSym(GV);
ExternalSym.SetBind(ELFSym::STB_GLOBAL);
ExternalSym.SetType(ELFSym::STT_NOTYPE);
ExternalSym.SectionIdx = ELFSection::SHN_UNDEF;
SymbolTable.push_back(ExternalSym);
return;
}
const Type *GVType = (const Type*)GV->getType();
unsigned Align = TM.getTargetData().getTypeAlignment(GVType);
unsigned Size = TM.getTargetData().getTypeSize(GVType);
// If this global has a zero initializer, it is part of the .bss or common
// section.
if (GV->getInitializer()->isNullValue()) {
@ -108,9 +121,8 @@ void ELFWriter::EmitGlobal(GlobalVariable *GV, ELFSection &DataSection,
if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage()) {
ELFSym CommonSym(GV);
// Value for common symbols is the alignment required.
const Type *GVType = (const Type*)GV->getType();
CommonSym.Value = TM.getTargetData().getTypeAlignment(GVType);
CommonSym.Size = TM.getTargetData().getTypeSize(GVType);
CommonSym.Value = Align;
CommonSym.Size = Size;
CommonSym.SetBind(ELFSym::STB_GLOBAL);
CommonSym.SetType(ELFSym::STT_OBJECT);
// TODO SOMEDAY: add ELF visibility.
@ -119,7 +131,40 @@ void ELFWriter::EmitGlobal(GlobalVariable *GV, ELFSection &DataSection,
return;
}
// FIXME: Implement the .bss section.
// Otherwise, this symbol is part of the .bss section. Emit it now.
// Handle alignment. Ensure section is aligned at least as much as required
// by this symbol.
BSSSection.Align = std::max(BSSSection.Align, Align);
// Within the section, emit enough virtual padding to get us to an alignment
// boundary.
if (Align)
BSSSection.Size = (BSSSection.Size + Align - 1) & ~(Align-1);
ELFSym BSSSym(GV);
BSSSym.Value = BSSSection.Size;
BSSSym.Size = Size;
BSSSym.SetType(ELFSym::STT_OBJECT);
switch (GV->getLinkage()) {
default: // weak/linkonce handled above
assert(0 && "Unexpected linkage type!");
case GlobalValue::AppendingLinkage: // FIXME: This should be improved!
case GlobalValue::ExternalLinkage:
BSSSym.SetBind(ELFSym::STB_GLOBAL);
break;
case GlobalValue::InternalLinkage:
BSSSym.SetBind(ELFSym::STB_LOCAL);
break;
}
// Set the idx of the .bss section
BSSSym.SectionIdx = &BSSSection-&SectionList[0];
SymbolTable.push_back(BSSSym);
// Reserve space in the .bss section for this symbol.
BSSSection.Size += Size;
return;
}
@ -143,26 +188,26 @@ bool ELFWriter::doFinalization(Module &M) {
// Okay, the ELF header and .text sections have been completed, build the
// .data, .bss, and "common" sections next.
ELFSection DataSection(".data", OutputBuffer.size());
ELFSection BSSSection (".bss");
SectionList.push_back(ELFSection(".data", OutputBuffer.size()));
SectionList.push_back(ELFSection(".bss"));
ELFSection &DataSection = *(SectionList.end()-2);
ELFSection &BSSSection = SectionList.back();
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I)
EmitGlobal(I, DataSection, BSSSection);
// If the .data section is nonempty, add it to our list.
if (DataSection.Size) {
DataSection.Align = 4; // FIXME: Compute!
// FIXME: Set the right flags and stuff.
SectionList.push_back(DataSection);
}
// Finish up the data section.
DataSection.Type = ELFSection::SHT_PROGBITS;
DataSection.Flags = ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC;
// If the .bss section is nonempty, add it to our list.
if (BSSSection.Size) {
BSSSection.Offset = OutputBuffer.size();
BSSSection.Align = 4; // FIXME: Compute!
// FIXME: Set the right flags and stuff.
SectionList.push_back(BSSSection);
}
// The BSS Section logically starts at the end of the Data Section (adjusted
// to the required alignment of the BSSSection).
BSSSection.Offset = DataSection.Offset+DataSection.Size;
BSSSection.Type = ELFSection::SHT_NOBITS;
BSSSection.Flags = ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC;
if (BSSSection.Align)
BSSSection.Offset = (BSSSection.Offset+BSSSection.Align-1) &
~(BSSSection.Align-1);
// Emit the symbol table now, if non-empty.
EmitSymbolTable();