Let the strcat optimizer return the pointer to the start of the buffer,
instead of the place where it started to perform the string copy.

- PR3661
- Patch by Benjamin Kramer!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68443 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index b878e4b..c84c233 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -514,11 +514,11 @@
     // Now that we have the destination's length, we must index into the
     // destination's pointer to get the actual memcpy destination (end of
     // the string .. we're concatenating).
-    Dst = B.CreateGEP(Dst, DstLen, "endptr");
+    Value *CpyDst = B.CreateGEP(Dst, DstLen, "endptr");
     
     // We have enough information to now generate the memcpy call to do the
     // concatenation for us.  Make a memcpy to copy the nul byte with align = 1.
-    EmitMemCpy(Dst, Src, ConstantInt::get(TD->getIntPtrType(), Len+1), 1, B);
+    EmitMemCpy(CpyDst, Src, ConstantInt::get(TD->getIntPtrType(), Len+1), 1, B);
     return Dst;
   }
 };