Remove dead code. Improve llvm_unreachable text. Simplify some control flow.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150918 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Sparc/SparcISelDAGToDAG.cpp

@@ -176,7 +176,6 @@ SDNode *SparcDAGToDAGISel::Select(SDNode *N) {
                                          MulLHS, MulRHS);
     // The high part is in the Y register.
     return CurDAG->SelectNodeTo(N, SP::RDY, MVT::i32, SDValue(Mul, 1));
-    return NULL;
   }
   }