tblgen: Use semantically correct RTTI functions.

Also, some minor cleanup.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165647 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/FastISelEmitter.cpp b/utils/TableGen/FastISelEmitter.cpp
index c6d71ff..03e918f 100644
--- a/utils/TableGen/FastISelEmitter.cpp
+++ b/utils/TableGen/FastISelEmitter.cpp
@@ -406,13 +406,12 @@
   if (!Op->isLeaf())
     return PhysReg;
 
-  DefInit *OpDI = dyn_cast<DefInit>(Op->getLeafValue());
-  Record *OpLeafRec = OpDI->getDef();
+  Record *OpLeafRec = cast<DefInit>(Op->getLeafValue())->getDef();
   if (!OpLeafRec->isSubClassOf("Register"))
     return PhysReg;
 
-  PhysReg += static_cast<StringInit*>(OpLeafRec->getValue( \
-             "Namespace")->getValue())->getValue();
+  PhysReg += cast<StringInit>(OpLeafRec->getValue("Namespace")->getValue())
+               ->getValue();
   PhysReg += "::";
   PhysReg += Target.getRegBank().getReg(OpLeafRec)->getName();
   return PhysReg;