DwarfDebug: Store the filename/dirname pair as a zero-separated string in a stringmap, instead of using a highly inefficient std::map of a pair of std::strings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152541 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 11 deletions

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index fa62169b0b..388cef4d8b 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -523,20 +523,19 @@ unsigned DwarfDebug::GetOrCreateSourceID(StringRef FileName,
     DirName = "";
 
   unsigned SrcId = SourceIdMap.size()+1;
-  std::pair<std::string, std::string> SourceName =
-      std::make_pair(FileName, DirName);
-  std::pair<std::pair<std::string, std::string>, unsigned> Entry =
-      make_pair(SourceName, SrcId);
 
-  std::map<std::pair<std::string, std::string>, unsigned>::iterator I;
-  bool NewlyInserted;
-  llvm::tie(I, NewlyInserted) = SourceIdMap.insert(Entry);
-  if (!NewlyInserted)
-    return I->second;
+  // We look up the file/dir pair by concatenating them with a zero byte.
+  SmallString<128> NamePair;
+  NamePair += DirName;
+  NamePair += '\0'; // Zero bytes are not allowed in paths.
+  NamePair += FileName;
+
+  StringMapEntry<unsigned> &Ent = SourceIdMap.GetOrCreateValue(NamePair, SrcId);
+  if (Ent.getValue() != SrcId)
+    return Ent.getValue();
 
   // Print out a .file directive to specify files for .loc directives.
-  Asm->OutStreamer.EmitDwarfFileDirective(SrcId, Entry.first.second,
-                                          Entry.first.first);
+  Asm->OutStreamer.EmitDwarfFileDirective(SrcId, DirName, FileName);
 
   return SrcId;
 }