Don't constant fold operation if result is incompatible with it.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index 0a2269df88151841d57bdfdd2939733b2482cc72..168bd371bcaf48a8ecdefc96bfcd9da02fbe0bff 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -657,6 +657,9 @@ static bool CompileParsedFunctionHelper(CompilationPipeline* pipeline,
         DeadCodeElimination::EliminateDeadPhis(flow_graph);
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
+        FlowGraphTypePropagator::Propagate(flow_graph);
+        DEBUG_ASSERT(flow_graph->VerifyUseLists());
+
         // Ensure that all phis inserted by optimization passes have consistent
         // representations.
         optimizer.SelectRepresentations();