Revert "Remove SminessPropagator and FlowGraphTypePropagator and all associated infrastructure and …

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
diff --git a/runtime/vm/flow_graph_builder.cc b/runtime/vm/flow_graph_builder.cc
index ce2e218b5d125153590e02a7581e165dcb211f26..236c4d9dd7ea7069257f6131573bb0871530638f 100644
--- a/runtime/vm/flow_graph_builder.cc
+++ b/runtime/vm/flow_graph_builder.cc
@@ -762,7 +762,12 @@ bool EffectGraphVisitor::CanSkipTypeCheck(intptr_t token_pos,
     return false;
   }
 
-  const bool eliminated = value->Type()->IsAssignableTo(dst_type);
+  // Propagated types are not set yet.
+  // More checks will possibly be eliminated during type propagation.
+  bool is_null, is_instance;
+  const bool eliminated =
+      (value->CanComputeIsNull(&is_null) && is_null) ||
+      (value->CanComputeIsInstanceOf(dst_type, &is_instance) && is_instance);
   if (FLAG_trace_type_check_elimination) {
     FlowGraphPrinter::PrintTypeCheck(owner()->parsed_function(),
                                      token_pos,