Revert r138278 now that r138289 has fixed the root issue.

llvm-svn: 138299
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb.td b/llvm/lib/Target/ARM/ARMInstrThumb.td
index cfc4a55..f58cb34 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb.td
@@ -1047,7 +1047,7 @@
 } // neverHasSideEffects
 
 // Multiply register
-//let isCommutable = 1 in
+let isCommutable = 1 in
 def tMUL :                      // A8.6.105 T1
   Thumb1sI<(outs tGPR:$Rd), (ins tGPR:$Rn, tGPR:$Rm), AddrModeNone, 2,
            IIC_iMUL32, "mul", "\t$Rd, $Rn, $Rm", "$Rm = $Rd",