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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
This commit is contained in:
Pete Cooper 2015-05-20 19:12:14 +00:00
parent 56a781495a
commit b78008171b
1 changed files with 3 additions and 1 deletions
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4
llvm/lib/MC/MCDwarf.cpp
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@ -360,8 +360,10 @@ unsigned MCDwarfLineTableHeader::getFile(StringRef &Directory,
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;
}