Use a SmallString buffer instead of a std::string for debug info path lookup. NFC.
This code appends the filename to the directory then looks that up in a StringMap. We should be using the existing Twine::toStringRef method instead of Twine::str() as most times we'll succeed in the lookup.
Its possible that we should also consider allowing StringMap to lookup a key using a Twine in addition to a StringRef but that would complicate the code with little known benefit above and beyond this change.
This saves 170k temporary allocations when running llc on the verify_use_list_order bitcode with debug info for x86.
llvm-svn: 237823
diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index 05c2a02..74eee83 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -360,8 +360,10 @@
FileNumber = SourceIdMap.size() + 1;
assert((MCDwarfFiles.empty() || FileNumber == MCDwarfFiles.size()) &&
"Don't mix autonumbered and explicit numbered line table usage");
+ SmallString<256> Buffer;
auto IterBool = SourceIdMap.insert(
- std::make_pair((Directory + Twine('\0') + FileName).str(), FileNumber));
+ std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
+ FileNumber));
if (!IterBool.second)
return IterBool.first->second;
}
