Fix optimizations on static fields in precompiled code.

runtime/vm/constant_propagator.cc

 // Copyright (c) 2013, 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/constant_propagator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/flow_graph_range_analysis.h"
 #include "vm/il_printer.h"
 #include "vm/intermediate_language.h"
 #include "vm/parser.h"
 #include "vm/symbols.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, remove_redundant_phis, true, "Remove redundant phis.");
 DEFINE_FLAG(bool, trace_constant_propagation, false,
     "Print constant propagation and useless code elimination.");
 
+DECLARE_FLAG(bool, fields_may_be_reset);
+
 // Quick access to the current zone and isolate.
 #define I (isolate())
 #define Z (graph_->zone())
 
 
 ConstantPropagator::ConstantPropagator(
     FlowGraph* graph,
     const GrowableArray<BlockEntryInstr*>& ignored)
     : FlowGraphVisitor(ignored),
       graph_(graph),
@@ skipping 665 matching lines @@
   SetValue(instr, instr->value()->definition()->constant_value());
 }
 
 
 void ConstantPropagator::VisitInitStaticField(InitStaticFieldInstr* instr) {
   // Nothing to do.
 }
 
 
 void ConstantPropagator::VisitLoadStaticField(LoadStaticFieldInstr* instr) {
-  const Field& field = instr->StaticField();
-  ASSERT(field.is_static());
-  Instance& obj = Instance::Handle(Z, field.StaticValue());
-  if (field.is_final() && (obj.raw() != Object::sentinel().raw()) &&
-      (obj.raw() != Object::transition_sentinel().raw())) {
-    if (obj.IsSmi() || obj.IsOld()) {
-      SetValue(instr, obj);
-      return;
+  if (!FLAG_fields_may_be_reset) {
+    const Field& field = instr->StaticField();
+    ASSERT(field.is_static());
+    Instance& obj = Instance::Handle(Z, field.StaticValue());
+    if (field.is_final() && (obj.raw() != Object::sentinel().raw()) &&
+        (obj.raw() != Object::transition_sentinel().raw())) {
+      if (obj.IsSmi() || obj.IsOld()) {
+        SetValue(instr, obj);
+        return;
+      }
     }
   }
   SetValue(instr, non_constant_);
 }
 
 
 void ConstantPropagator::VisitStoreStaticField(StoreStaticFieldInstr* instr) {
   SetValue(instr, instr->value()->definition()->constant_value());
 }
 
@@ skipping 954 matching lines @@
   graph_->MergeBlocks();
   GrowableArray<BitVector*> dominance_frontier;
   graph_->ComputeDominators(&dominance_frontier);
 
   if (FLAG_trace_constant_propagation) {
     FlowGraphPrinter::PrintGraph("After CP", graph_);
   }
 }
 
 }  // namespace dart