Run constant propagation one more time after canonicalization so that following code can always ret…

runtime/vm/compiler.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/compiler.h"
 
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
 #include "vm/code_generator.h"
@@ skipping 206 matching lines @@
 
       IfConverter::Simplify(flow_graph);
       DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
       if (FLAG_constant_propagation) {
         ConstantPropagator::Optimize(flow_graph);
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
         // A canonicalization pass to remove e.g. smi checks on smi constants.
         optimizer.Canonicalize();
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
+        // Canonicalization introduced more opportunities for constant
+        // propagation.
+        ConstantPropagator::Optimize(flow_graph);
+        DEBUG_ASSERT(flow_graph->VerifyUseLists());
       }
 
       // Propagate types and eliminate even more type tests.
       if (FLAG_propagate_types) {
         // Recompute types after constant propagation to infer more precise
         // types for uses that were previously reached by now eliminated phis.
         FlowGraphTypePropagator propagator(flow_graph);
         propagator.Propagate();
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
       }
@@ skipping 453 matching lines @@
       Object::Handle(isolate->object_store()->sticky_error());
     isolate->object_store()->clear_sticky_error();
     isolate->set_long_jump_base(base);
     return result.raw();
   }
   UNREACHABLE();
   return Object::null();
 }
 
 }  // namespace dart