Reapply r112091 and r111922, support for metadata linking, with a

fix: add a flag to MapValue and friends which indicates whether
any module-level mappings are being made. In the common case of
inlining, no module-level mappings are needed, so MapValue doesn't
need to examine non-function-local metadata, which can be very
expensive in the case of a large module with really deep metadata
(e.g. a large C++ program compiled with -g).

This flag is a little awkward; perhaps eventually it can be moved
into the ClonedCodeInfo class.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112190 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Utils/Cloning.h

@@ -121,8 +121,12 @@ Loop *CloneLoop(Loop *L, LPPassManager *LPM, LoopInfo *LI,
 /// the function from their old to new values.  The final argument captures
 /// information about the cloned code if non-null.
 ///
+/// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
+/// mappings.
+///
 Function *CloneFunction(const Function *F,
                         ValueMap<const Value*, Value*> &VMap,
+                        bool ModuleLevelChanges,
                         ClonedCodeInfo *CodeInfo = 0);
 
 /// CloneFunction - Version of the function that doesn't need the VMap.
@@ -133,13 +137,17 @@ inline Function *CloneFunction(const Function *F, ClonedCodeInfo *CodeInfo = 0){
 }
 
 /// Clone OldFunc into NewFunc, transforming the old arguments into references
-/// to ArgMap values.  Note that if NewFunc already has basic blocks, the ones
+/// to VMap values.  Note that if NewFunc already has basic blocks, the ones
 /// cloned into it will be added to the end of the function.  This function
 /// fills in a list of return instructions, and can optionally append the
 /// specified suffix to all values cloned.
 ///
+/// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
+/// mappings.
+///
 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
                        ValueMap<const Value*, Value*> &VMap,
+                       bool ModuleLevelChanges,
                        SmallVectorImpl<ReturnInst*> &Returns,
                        const char *NameSuffix = "", 
                        ClonedCodeInfo *CodeInfo = 0);
@@ -151,8 +159,13 @@ void CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
 /// constant arguments cause a significant amount of code in the callee to be
 /// dead.  Since this doesn't produce an exactly copy of the input, it can't be
 /// used for things like CloneFunction or CloneModule.
+///
+/// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
+/// mappings.
+///
 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
                                ValueMap<const Value*, Value*> &VMap,
+                               bool ModuleLevelChanges,
                                SmallVectorImpl<ReturnInst*> &Returns,
                                const char *NameSuffix = "", 
                                ClonedCodeInfo *CodeInfo = 0,

include/llvm/Transforms/Utils/ValueMapper.h

@@ -22,8 +22,10 @@ namespace llvm {
   class Instruction;
   typedef ValueMap<const Value *, Value *> ValueToValueMapTy;
 
-  Value *MapValue(const Value *V, ValueToValueMapTy &VM);
-  void RemapInstruction(Instruction *I, ValueToValueMapTy &VM);
+  Value *MapValue(const Value *V, ValueToValueMapTy &VM,
+                  bool ModuleLevelChanges);
+  void RemapInstruction(Instruction *I, ValueToValueMapTy &VM,
+                        bool ModuleLevelChanges);
 } // End llvm namespace
 
 #endif