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[ELF] ObjFile<ELFT>::initializeSymbols: Batch allocate local symbols 

and detangle local/global symbol initialization.

My x86-64 lld executable is 8k smaller due to the removal of SpecificAlloc<Undefined>.
This commit is contained in:
Fangrui Song 2021-12-15 12:54:38 -08:00
parent ebed0ca715
commit 509153f1e7
2 changed files with 31 additions and 38 deletions
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66
lld/ELF/InputFiles.cpp
View File

@ -1047,33 +1047,18 @@ InputSectionBase *ObjFile<ELFT>::createInputSection(uint32_t idx,
template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
ArrayRef<Elf_Sym> eSyms = this->getELFSyms<ELFT>();
this->symbols.resize(eSyms.size());
SymbolUnion *locals =
getSpecificAllocSingleton<SymbolUnion>().Allocate(firstGlobal);
// Fill in InputFile::symbols. Some entries have been initialized
// because of LazyObjFile.
for (size_t i = 0, end = eSyms.size(); i != end; ++i) {
if (this->symbols[i])
continue;
for (size_t i = 0; i != firstGlobal; ++i) {
const Elf_Sym &eSym = eSyms[i];
uint32_t secIdx = getSectionIndex(eSym);
if (secIdx >= this->sections.size())
fatal(toString(this) + ": invalid section index: " + Twine(secIdx));
if (eSym.getBinding() != STB_LOCAL) {
if (i < firstGlobal)
error(toString(this) + ": non-local symbol (" + Twine(i) +
") found at index < .symtab's sh_info (" + Twine(firstGlobal) +
")");
this->symbols[i] =
symtab->insert(CHECK(eSyms[i].getName(this->stringTable), this));
continue;
}
// Handle local symbols. Local symbols are not added to the symbol
// table because they are not visible from other object files. We
// allocate symbol instances and add their pointers to symbols.
if (i >= firstGlobal)
errorOrWarn(toString(this) + ": STB_LOCAL symbol (" + Twine(i) +
") found at index >= .symtab's sh_info (" +
Twine(firstGlobal) + ")");
if (eSym.getBinding() != STB_LOCAL)
error(toString(this) + ": non-local symbol (" + Twine(i) +
") found at index < .symtab's sh_info (" + Twine(firstGlobal) +
")");
InputSectionBase *sec = this->sections[secIdx];
uint8_t type = eSym.getType();
@ -1083,27 +1068,36 @@ template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
fatal(toString(this) + ": invalid symbol name offset");
StringRefZ name = this->stringTable.data() + eSym.st_name;
if (eSym.st_shndx == SHN_UNDEF)
this->symbols[i] =
make<Undefined>(this, name, STB_LOCAL, eSym.st_other, type);
else if (sec == &InputSection::discarded)
this->symbols[i] =
make<Undefined>(this, name, STB_LOCAL, eSym.st_other, type,
/*discardedSecIdx=*/secIdx);
this->symbols[i] = reinterpret_cast<Symbol *>(locals + i);
if (eSym.st_shndx == SHN_UNDEF || sec == &InputSection::discarded)
new (this->symbols[i])
Undefined(this, name, STB_LOCAL, eSym.st_other, type,
/*discardedSecIdx=*/secIdx);
else
this->symbols[i] = make<Defined>(this, name, STB_LOCAL, eSym.st_other,
type, eSym.st_value, eSym.st_size, sec);
new (this->symbols[i]) Defined(this, name, STB_LOCAL, eSym.st_other, type,
eSym.st_value, eSym.st_size, sec);
}
// Symbol resolution of non-local symbols.
// Some entries have been filled by LazyObjFile.
for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i)
if (!this->symbols[i])
this->symbols[i] =
symtab->insert(CHECK(eSyms[i].getName(this->stringTable), this));
// Perform symbol resolution on non-local symbols.
SmallVector<unsigned, 32> undefineds;
for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i) {
const Elf_Sym &eSym = eSyms[i];
uint8_t binding = eSym.getBinding();
if (binding == STB_LOCAL)
continue; // Errored above.
if (binding == STB_LOCAL) {
errorOrWarn(toString(this) + ": STB_LOCAL symbol (" + Twine(i) +
") found at index >= .symtab's sh_info (" +
Twine(firstGlobal) + ")");
continue;
}
uint32_t secIdx = getSectionIndex(eSym);
if (secIdx >= this->sections.size())
fatal(toString(this) + ": invalid section index: " + Twine(secIdx));
InputSectionBase *sec = this->sections[secIdx];
uint8_t stOther = eSym.st_other;
uint8_t type = eSym.getType();
@ -1111,13 +1105,11 @@ template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
uint64_t size = eSym.st_size;
StringRefZ name = this->stringTable.data() + eSym.st_name;
// Handle global undefined symbols.
if (eSym.st_shndx == SHN_UNDEF) {
undefineds.push_back(i);
continue;
}
// Handle global common symbols.
if (eSym.st_shndx == SHN_COMMON) {
if (value == 0 || value >= UINT32_MAX)
fatal(toString(this) + ": common symbol '" + StringRef(name.data) +

3
lld/test/ELF/invalid/symtab-sh-info-dup.test
View File

@ -9,10 +9,11 @@
# RUN: not ld.lld %t.o %t.o -o /dev/null 2>&1 | FileCheck %s
# CHECK: error: {{.*}}.o: STB_LOCAL symbol (2) found at index >= .symtab's sh_info (1)
# CHECK-NEXT: error: {{.*}}.o: STB_LOCAL symbol (2) found at index >= .symtab's sh_info (1)
# CHECK-NEXT: error: duplicate symbol: _start
# CHECK-NEXT: >>> defined at {{.*}}.o:(.text+0x0)
# CHECK-NEXT: >>> defined at {{.*}}.o:(.text+0x0)
# CHECK-EMPTY:
# CHECK-NEXT: error: {{.*}}.o: STB_LOCAL symbol (2) found at index >= .symtab's sh_info (1)
# RUN: ld.lld --noinhibit-exec %t.o -o /dev/null 2>&1 | FileCheck %s --check-prefix=WARN
# WARN: warning: {{.*}}.o: STB_LOCAL symbol (2) found at index >= .symtab's sh_info (1)