when transforming a MULHS into a wider MUL, there is no need to SRA the
result, the top bits are truncated off anyway, just use SRL.

llvm-svn: 121846
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 740b29b..6f0c167 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1940,7 +1940,7 @@
       N0 = DAG.getNode(ISD::SIGN_EXTEND, DL, NewVT, N0);
       N1 = DAG.getNode(ISD::SIGN_EXTEND, DL, NewVT, N1);
       N1 = DAG.getNode(ISD::MUL, DL, NewVT, N0, N1);
-      N1 = DAG.getNode(ISD::SRA, DL, NewVT, N1,
+      N1 = DAG.getNode(ISD::SRL, DL, NewVT, N1,
                        DAG.getConstant(SimpleSize, getShiftAmountTy()));
       return DAG.getNode(ISD::TRUNCATE, DL, VT, N1);
     }