OldPtr is llvm::Instruction. Remove unneeded cast<>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186880 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/SROA.cpp

@@ -2540,7 +2540,7 @@ private:
     // as local as possible to the PHI. To do that, we re-use the location of
     // the old pointer, which necessarily must be in the right position to
     // dominate the PHI.
-    IRBuilderTy PtrBuilder(cast<Instruction>(OldPtr));
+    IRBuilderTy PtrBuilder(OldPtr);
     PtrBuilder.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) +
                              ".");