Use DenseMap instead std::map for GVSummaryMapTy.

Summary: This speeds-up thin-link by ~47% for large programs.

Reviewers: tejohnson

Reviewed By: tejohnson

Subscribers: sanjoy, llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D35148

llvm-svn: 307578

llvm/include/llvm/IR/ModuleSummaryIndex.h

@@ -522,7 +522,7 @@ using ModulePathStringTableTy = StringMap<std::pair<uint64_t, ModuleHash>>;
 
 /// Map of global value GUID to its summary, used to identify values defined in
 /// a particular module, and provide efficient access to their summary.
-using GVSummaryMapTy = std::map<GlobalValue::GUID, GlobalValueSummary *>;
+using GVSummaryMapTy = DenseMap<GlobalValue::GUID, GlobalValueSummary *>;
 
 /// Class to hold module path string table and global value map,
 /// and encapsulate methods for operating on them.

llvm/lib/LTO/LTO.cpp

@@ -1030,7 +1030,7 @@ Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
 
   // Collect for each module the list of function it defines (GUID ->
   // Summary).
-  StringMap<std::map<GlobalValue::GUID, GlobalValueSummary *>>
+  StringMap<GVSummaryMapTy>
       ModuleToDefinedGVSummaries(ThinLTO.ModuleMap.size());
   ThinLTO.CombinedIndex.collectDefinedGVSummariesPerModule(
       ModuleToDefinedGVSummaries);