Infer range for BIT_XOR.

runtime/vm/flow_graph_compiler_x64.cc

Index: runtime/vm/flow_graph_compiler_x64.cc
diff --git a/runtime/vm/flow_graph_compiler_x64.cc b/runtime/vm/flow_graph_compiler_x64.cc
index 1c4b7d7380f4011d06d150375ba0f057969f6425..a7b1e2d5357e33241b9cc4d6f87a6bdbed687b83 100644
--- a/runtime/vm/flow_graph_compiler_x64.cc
+++ b/runtime/vm/flow_graph_compiler_x64.cc
@@ -1595,6 +1595,9 @@ void ParallelMoveResolver::EmitMove(int index) {
     if (destination.IsRegister()) {
       if (constant.IsSmi() && (Smi::Cast(constant).Value() == 0)) {
         __ xorq(destination.reg(), destination.reg());
+      } else if (constant.IsSmi() &&
+          (source.constant_instruction()->representation() == kUnboxedInt32)) {
+        __ movl(destination.reg(), Immediate(Smi::Cast(constant).Value()));
       } else {
         __ LoadObject(destination.reg(), constant, PP);
       }
@@ -1616,7 +1619,13 @@ void ParallelMoveResolver::EmitMove(int index) {
       __ movsd(destination.ToStackSlotAddress(), XMM0);
     } else {
       ASSERT(destination.IsStackSlot());
-      StoreObject(destination.ToStackSlotAddress(), constant);
+      if (constant.IsSmi() &&
+          (source.constant_instruction()->representation() == kUnboxedInt32)) {
+        __ movl(destination.ToStackSlotAddress(),
+                Immediate(Smi::Cast(constant).Value()));
+      } else {
+        StoreObject(destination.ToStackSlotAddress(), constant);
+      }
     }
   }