Move the "findUsedStructTypes" functionality outside of the Module class.

The "findUsedStructTypes" method is very expensive to run. It needs to be
optimized so that LTO can run faster. Splitting this method out of the Module
class will help this occur. For instance, it can keep a list of seen objects so
that it doesn't process them over and over again.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161228 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Linker/LinkModules.cpp

@@ -16,6 +16,7 @@
 #include "llvm/DerivedTypes.h"
 #include "llvm/Instructions.h"
 #include "llvm/Module.h"
+#include "llvm/TypeFinder.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SetVector.h"
@@ -595,13 +596,13 @@ void ModuleLinker::computeTypeMapping() {
   // At this point, the destination module may have a type "%foo = { i32 }" for
   // example.  When the source module got loaded into the same LLVMContext, if
   // it had the same type, it would have been renamed to "%foo.42 = { i32 }".
-  std::vector<StructType*> SrcStructTypes;
-  SrcM->findUsedStructTypes(SrcStructTypes, true);
+  TypeFinder SrcStructTypes;
+  SrcStructTypes.run(*SrcM, true);
   SmallPtrSet<StructType*, 32> SrcStructTypesSet(SrcStructTypes.begin(),
                                                  SrcStructTypes.end());
 
-  std::vector<StructType*> DstStructTypes;
-  DstM->findUsedStructTypes(DstStructTypes, true);
+  TypeFinder DstStructTypes;
+  DstStructTypes.run(*DstM, true);
   SmallPtrSet<StructType*, 32> DstStructTypesSet(DstStructTypes.begin(),
                                                  DstStructTypes.end());