[Function] Clean up {prefix,prologue} data routines (NFC)

Factor out some common code used to get+set function prefix/prologue
data. This may come in handy if we ever decide to store personality
functions in the same way we store prefix/prologue data.

Differential Revision: http://reviews.llvm.org/D13120

Reviewed-by: bogner
llvm-svn: 249460
diff --git a/llvm/lib/IR/LLVMContextImpl.h b/llvm/lib/IR/LLVMContextImpl.h
index 1d41069..2df7d04 100644
--- a/llvm/lib/IR/LLVMContextImpl.h
+++ b/llvm/lib/IR/LLVMContextImpl.h
@@ -972,16 +972,16 @@
   /// instructions in different blocks at the same location.
   DenseMap<std::pair<const char *, unsigned>, unsigned> DiscriminatorTable;
 
+  typedef DenseMap<const Function *, ReturnInst *> FunctionDataMapTy;
+
   /// \brief Mapping from a function to its prefix data, which is stored as the
   /// operand of an unparented ReturnInst so that the prefix data has a Use.
-  typedef DenseMap<const Function *, ReturnInst *> PrefixDataMapTy;
-  PrefixDataMapTy PrefixDataMap;
+  FunctionDataMapTy PrefixDataMap;
 
   /// \brief Mapping from a function to its prologue data, which is stored as
   /// the operand of an unparented ReturnInst so that the prologue data has a
   /// Use.
-  typedef DenseMap<const Function *, ReturnInst *> PrologueDataMapTy;
-  PrologueDataMapTy PrologueDataMap;
+  FunctionDataMapTy PrologueDataMap;
 
   int getOrAddScopeRecordIdxEntry(MDNode *N, int ExistingIdx);
   int getOrAddScopeInlinedAtIdxEntry(MDNode *Scope, MDNode *IA,int ExistingIdx);