[ARM] Improve longMAC codegen test

Added thumb targets and dataflow checks to the longMAC test.

Differential Revision: https://reviews.llvm.org/D22684

llvm-svn: 276629
diff --git a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 96cb691..0ee5944 100644
--- a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -2612,6 +2612,10 @@
 }
 
 bool ARMDAGToDAGISel::trySMLAWSMULW(SDNode *N) {
+  if (!Subtarget->hasV6Ops() ||
+      (Subtarget->isThumb() && !Subtarget->hasThumb2()))
+    return false;
+
   SDLoc dl(N);
   SDValue Src0 = N->getOperand(0);
   SDValue Src1 = N->getOperand(1);