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[PECOFF] Do not scan the symbol table twice but instead cache aux symbols. 

We scanned the symbol table twice; first to gather all regular symbols, and
second to process aux symbols. That's a bit inefficient and complicated. We
can instead cache aux symbols in the first pass, to eliminate the need of the
second pass.

llvm-svn: 189525
This commit is contained in:
Rui Ueyama 2013-08-28 22:27:05 +00:00
parent 38874731f6
commit 184a4b83d8
1 changed files with 19 additions and 14 deletions
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33
lld/lib/ReaderWriter/PECOFF/ReaderCOFF.cpp
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@ -187,8 +187,18 @@ private:
return ec;
_symbolName[sym] = name;
// Skip aux symbols.
i += sym->NumberOfAuxSymbols;
// Symbol may be followed by auxiliary symbol table records. The aux
// record can be in any format, but the size is always the same as the
// regular symbol. The aux record supplies additional information for the
// standard symbol. We do not interpret the aux record here, but just
// store it to _auxSymbol.
if (sym->NumberOfAuxSymbols > 0) {
const coff_symbol *aux = nullptr;
if (error_code ec = _obj->getAuxSymbol(i + 1, aux))
return ec;
_auxSymbol[sym] = aux;
i += sym->NumberOfAuxSymbols;
}
}
return error_code::success();
}
@ -304,18 +314,12 @@ private:
// Cache the COMDAT attributes, which indicate whether the symbols in the
// section can be merged or not.
error_code cacheSectionAttributes() {
const llvm::object::coff_file_header *header = nullptr;
if (error_code ec = _obj->getHeader(header))
return ec;
// The COMDAT section attribute is not an attribute of coff_section, but is
// stored in the auxiliary symbol for the first symbol referring a COMDAT
// section. It feels to me that it's unnecessarily complicated, but this is
// how COFF works.
for (uint32_t i = 0, e = header->NumberOfSymbols; i != e; ++i) {
const coff_symbol *sym;
if (error_code ec = _obj->getSymbol(i, sym))
return ec;
for (auto i : _auxSymbol) {
const coff_symbol *sym = i.first;
if (sym->SectionNumber == llvm::COFF::IMAGE_SYM_ABSOLUTE ||
sym->SectionNumber == llvm::COFF::IMAGE_SYM_UNDEFINED)
continue;
@ -331,10 +335,8 @@ private:
if (sym->NumberOfAuxSymbols == 0)
return llvm::object::object_error::parse_failed;
const coff_aux_section_definition *aux = nullptr;
if (error_code ec = _obj->getAuxSymbol(i + 1, aux))
return ec;
const coff_aux_section_definition *aux = reinterpret_cast<
const coff_aux_section_definition *>(i.second);
_merge[sec] = getMerge(aux);
}
@ -619,6 +621,9 @@ private:
// A map from symbol to its resultant atom.
std::map<const coff_symbol *, Atom *> _symbolAtom;
// A map from symbol to its aux symbol.
std::map<const coff_symbol *, const coff_symbol *> _auxSymbol;
// A map from section to its atoms.
std::map<const coff_section *, vector<COFFDefinedFileAtom *>> _sectionAtoms;