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[IRSymtab] Replace linear time lookup with DenseSet (#66376)

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There is an inefficiency in the IRSymtab Builder where it does a lookup
of PreservedSymbols when calling addSymbol. This lookup is linear in
time, so it tends to be quite slow. Replacing it with DenseSet gives a
0.1% speedup:

https://llvm-compile-time-tracker.com/compare.php?from=02d27eac0f3f470a93635fc98ae990bf2a9809ed&to=62b09786fff4d53aa0c75b64aea48de241e4a856&stat=instructions:u

This change is quite similar to https://reviews.llvm.org/D157951.
This commit is contained in:
Dhruv Chawla 2023-09-15 17:49:31 +05:30 committed by GitHub
parent 24a082878f
commit ff9ae3f49d
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1 changed files with 8 additions and 1 deletions
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9
llvm/lib/Object/IRSymtab.cpp
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@ -215,6 +215,11 @@ Expected<int> Builder::getComdatIndex(const Comdat *C, const Module *M) {
return P.first->second;
}
static DenseSet<StringRef> buildPreservedSymbolsSet() {
return DenseSet<StringRef>(std::begin(PreservedSymbols),
std::end(PreservedSymbols));
}
Error Builder::addSymbol(const ModuleSymbolTable &Msymtab,
const SmallPtrSet<GlobalValue *, 4> &Used,
ModuleSymbolTable::Symbol Msym) {
@ -270,7 +275,9 @@ Error Builder::addSymbol(const ModuleSymbolTable &Msymtab,
setStr(Sym.IRName, GV->getName());
bool IsPreservedSymbol = llvm::is_contained(PreservedSymbols, GV->getName());
static const DenseSet<StringRef> PreservedSymbolsSet =
buildPreservedSymbolsSet();
bool IsPreservedSymbol = PreservedSymbolsSet.contains(GV->getName());
if (Used.count(GV) || IsPreservedSymbol)
Sym.Flags |= 1 << storage::Symbol::FB_used;