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Avoid calculating the string hash twice in GsymCreator::insertString. 

Do the single hash calculation before acquiring the lock, to reduce
lock contention. If Copy is true, and the string was not yet contained
in the StringStorage, use the new address from StringStorage, but
reuse the hash we already calculated.

Differential Revision: https://reviews.llvm.org/D102484
This commit is contained in:
Simon Giesecke 2021-05-14 10:59:51 +00:00
parent e102fd50f9
commit f29c4c6097
1 changed files with 6 additions and 3 deletions
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9
llvm/lib/DebugInfo/GSYM/GsymCreator.cpp
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@ -293,6 +293,9 @@ llvm::Error GsymCreator::finalize(llvm::raw_ostream &OS) {
uint32_t GsymCreator::insertString(StringRef S, bool Copy) {
if (S.empty())
return 0;
// The hash can be calculated outside the lock.
CachedHashStringRef CHStr(S);
std::lock_guard<std::recursive_mutex> Guard(Mutex);
if (Copy) {
// We need to provide backing storage for the string if requested
@ -301,11 +304,11 @@ uint32_t GsymCreator::insertString(StringRef S, bool Copy) {
// copied, but any string created by code will need to be copied.
// This allows GsymCreator to be really fast when parsing DWARF and
// other object files as most strings don't need to be copied.
CachedHashStringRef CHStr(S);
if (!StrTab.contains(CHStr))
S = StringStorage.insert(S).first->getKey();
CHStr = CachedHashStringRef{StringStorage.insert(S).first->getKey(),
CHStr.hash()};
}
return StrTab.add(S);
return StrTab.add(CHStr);
}
void GsymCreator::addFunctionInfo(FunctionInfo &&FI) {