IRgen: Fix debug info regression in r106970; when we eliminate the return value

store make sure to move the debug metadata from the store (which is actual
'return' statement location) to the return instruction (which otherwise would
have the function end location as its debug info).
 - Tested by gdb test suite.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107322 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGCall.cpp

@@ -976,6 +976,7 @@ void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI) {
     return;
   }
 
+  llvm::MDNode *RetDbgInfo = 0;
   llvm::Value *RV = 0;
   QualType RetTy = FI.getReturnType();
   const ABIArgInfo &RetAI = FI.getReturnInfo();
@@ -1009,6 +1010,7 @@ void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI) {
       RV = Builder.CreateLoad(ReturnValue);
     } else {
       // Get the stored value and nuke the now-dead store.
+      RetDbgInfo = SI->getDbgMetadata();
       RV = SI->getValueOperand();
       SI->eraseFromParent();
       
@@ -1031,10 +1033,9 @@ void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI) {
     assert(0 && "Invalid ABI kind for return argument");
   }
 
-  if (RV)
-    Builder.CreateRet(RV);
-  else
-    Builder.CreateRetVoid();
+  llvm::Instruction *Ret = RV ? Builder.CreateRet(RV) : Builder.CreateRetVoid();
+  if (RetDbgInfo)
+    Ret->setDbgMetadata(RetDbgInfo);
 }
 
 RValue CodeGenFunction::EmitDelegateCallArg(const VarDecl *Param) {