Revamp the ValueMapper interfaces in a couple ways:

1. Take a flags argument instead of a bool.  This makes
   it more clear to the reader what it is used for.
2. Add a flag that says that "remapping a value not in the
   map is ok".
3. Reimplement MapValue to share a bunch of code and be a lot
   more efficient.  For lookup failures, don't drop null values
   into the map.
4. Using the new flag a bunch of code can vaporize in LinkModules
   and LoopUnswitch, kill it.

No functionality change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123058 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Utils/ValueMapper.h

@@ -22,10 +22,29 @@ namespace llvm {
   class Instruction;
   typedef ValueMap<const Value *, TrackingVH<Value> > ValueToValueMapTy;
 
+  /// RemapFlags - These are flags that the value mapping APIs allow.
+  enum RemapFlags {
+    RF_None = 0,
+    
+    /// RF_NoModuleLevelChanges - If this flag is set, the remapper knows that
+    /// only local values within a function (such as an instruction or argument)
+    /// are mapped, not global values like functions and global metadata.
+    RF_NoModuleLevelChanges = 1,
+    
+    /// RF_IgnoreMissingEntries - If this flag is set, the remapper ignores
+    /// entries that are not in the value map.  If it is unset, it aborts if an
+    /// operand is asked to be remapped which doesn't exist in the mapping.
+    RF_IgnoreMissingEntries = 2
+  };
+  
+  static inline RemapFlags operator|(RemapFlags LHS, RemapFlags RHS) {
+    return RemapFlags(unsigned(LHS)|unsigned(RHS));
+  }
+  
   Value *MapValue(const Value *V, ValueToValueMapTy &VM,
-                  bool ModuleLevelChanges);
+                  RemapFlags Flags = RF_None);
   void RemapInstruction(Instruction *I, ValueToValueMapTy &VM,
-                        bool ModuleLevelChanges);
+                        RemapFlags Flags = RF_None);
 } // End llvm namespace
 
 #endif