Allow smi comparisons to have constant operands.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
diff --git a/runtime/vm/flow_graph_allocator.cc b/runtime/vm/flow_graph_allocator.cc
index 7766f98ee045e6ede3b2121a798de105b9c06b15..d7ebf5b2be61720054c471cc9f9b86926ba03f9e 100644
--- a/runtime/vm/flow_graph_allocator.cc
+++ b/runtime/vm/flow_graph_allocator.cc
@@ -655,6 +655,14 @@ Instruction* FlowGraphAllocator::ConnectOutgoingPhiMoves(
 
     Value* val = phi->InputAt(pred_idx);
     MoveOperands* move = parallel_move->MoveOperandsAt(move_idx);
+
+    ConstantInstr* constant = val->definition()->AsConstant();
+    if (constant != NULL) {
+      move->set_src(Location::Constant(constant->value()));
+      move_idx++;
+      continue;
+    }
+
     // Expected shape of live ranges:
     //
     //                 g  g'