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[ELF][LTO] Cache symbol table of lazy BitcodeFile 

Similar to D62188: a BitcodeFile's symbol table may be iterated twice, once in
--start-lib (lazy) state, and once in the non-lazy state. This patch
makes `parseLazy` save `symbols[i]` so that the non-lazy state does not need to
re-insert to the global symbol table. Avoiding a redundant `saver.save` may save
memory.

`Maximum resident set size (kbytes)` for a large --thinlto-index-only link:

* without the patch: 10164000
* with the patch: 10095716 (0.6% decrease)

Note: we can remove `saver.save` if `BitcodeCompiler::add` does not transfer the ownership
of `f.obj` in `checkError(ltoObj->add(std::move(f.obj), resols));`.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D116390
This commit is contained in:
Fangrui Song 2021-12-30 12:03:29 -08:00
parent 15787ccd45
commit dabac5feec
1 changed files with 34 additions and 23 deletions
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57
lld/ELF/InputFiles.cpp
View File

@ -1680,34 +1680,42 @@ static uint8_t mapVisibility(GlobalValue::VisibilityTypes gvVisibility) {
} }
template <class ELFT> template <class ELFT>
static Symbol *createBitcodeSymbol(const std::vector<bool> &keptComdats, static void
const lto::InputFile::Symbol &objSym, createBitcodeSymbol(Symbol *&sym, const std::vector<bool> &keptComdats,
BitcodeFile &f) { const lto::InputFile::Symbol &objSym, BitcodeFile &f) {
StringRef name = saver.save(objSym.getName());
uint8_t binding = objSym.isWeak() ? STB_WEAK : STB_GLOBAL; uint8_t binding = objSym.isWeak() ? STB_WEAK : STB_GLOBAL;
uint8_t type = objSym.isTLS() ? STT_TLS : STT_NOTYPE; uint8_t type = objSym.isTLS() ? STT_TLS : STT_NOTYPE;
uint8_t visibility = mapVisibility(objSym.getVisibility()); uint8_t visibility = mapVisibility(objSym.getVisibility());
bool canOmitFromDynSym = objSym.canBeOmittedFromSymbolTable(); bool canOmitFromDynSym = objSym.canBeOmittedFromSymbolTable();
StringRef name;
if (sym) {
name = sym->getName();
} else {
name = saver.save(objSym.getName());
sym = symtab->insert(name);
}
int c = objSym.getComdatIndex(); int c = objSym.getComdatIndex();
if (objSym.isUndefined() || (c != -1 && !keptComdats[c])) { if (objSym.isUndefined() || (c != -1 && !keptComdats[c])) {
Undefined newSym(&f, name, binding, visibility, type); Undefined newSym(&f, name, binding, visibility, type);
if (canOmitFromDynSym) if (canOmitFromDynSym)
newSym.exportDynamic = false; newSym.exportDynamic = false;
Symbol *ret = symtab->addSymbol(newSym); sym->resolve(newSym);
ret->referenced = true; sym->referenced = true;
return ret; return;
} }
if (objSym.isCommon()) if (objSym.isCommon()) {
return symtab->addSymbol( sym->resolve(CommonSymbol{&f, name, binding, visibility, STT_OBJECT,
CommonSymbol{&f, name, binding, visibility, STT_OBJECT, objSym.getCommonAlignment(),
objSym.getCommonAlignment(), objSym.getCommonSize()}); objSym.getCommonSize()});
} else {
Defined newSym(&f, name, binding, visibility, type, 0, 0, nullptr); Defined newSym(&f, name, binding, visibility, type, 0, 0, nullptr);
if (canOmitFromDynSym) if (canOmitFromDynSym)
newSym.exportDynamic = false; newSym.exportDynamic = false;
return symtab->addSymbol(newSym); sym->resolve(newSym);
}
} }
template <class ELFT> void BitcodeFile::parse() { template <class ELFT> void BitcodeFile::parse() {
@ -1719,10 +1727,11 @@ template <class ELFT> void BitcodeFile::parse() {
.second); .second);
} }
symbols.assign(obj->symbols().size(), nullptr); symbols.resize(obj->symbols().size());
for (auto it : llvm::enumerate(obj->symbols())) for (auto it : llvm::enumerate(obj->symbols())) {
symbols[it.index()] = Symbol *&sym = symbols[it.index()];
createBitcodeSymbol<ELFT>(keptComdats, it.value(), *this); createBitcodeSymbol<ELFT>(sym, keptComdats, it.value(), *this);
}
for (auto l : obj->getDependentLibraries()) for (auto l : obj->getDependentLibraries())
addDependentLibrary(l, this); addDependentLibrary(l, this);
@ -1730,9 +1739,11 @@ template <class ELFT> void BitcodeFile::parse() {
void BitcodeFile::parseLazy() { void BitcodeFile::parseLazy() {
SymbolTable &symtab = *elf::symtab; SymbolTable &symtab = *elf::symtab;
for (const lto::InputFile::Symbol &sym : obj->symbols()) symbols.resize(obj->symbols().size());
if (!sym.isUndefined()) for (auto it : llvm::enumerate(obj->symbols()))
symtab.addSymbol(LazyObject{*this, saver.save(sym.getName())}); if (!it.value().isUndefined())
symbols[it.index()] =
symtab.addSymbol(LazyObject{*this, saver.save(it.value().getName())});
} }
void BinaryFile::parse() { void BinaryFile::parse() {