VM: Improve unoptimized code size by avoid emitting field guards.

runtime/vm/flow_graph_builder.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/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/class_finalizer.h"
@@ skipping 24 matching lines @@
             "Eliminate type checks when allowed by static type analysis.");
 DEFINE_FLAG(bool, print_ast, false, "Print abstract syntax tree.");
 DEFINE_FLAG(bool, print_scopes, false, "Print scopes of local variables.");
 DEFINE_FLAG(bool, trace_type_check_elimination, false,
             "Trace type check elimination at compile time.");
 
 DECLARE_FLAG(bool, enable_asserts);
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(int, optimization_counter_threshold);
 DECLARE_FLAG(bool, warn_on_javascript_compatibility);
+DECLARE_FLAG(bool, use_field_guards);
 
 // Quick access to the locally defined zone() method.
 #define Z (zone())
 
 // TODO(srdjan): Allow compiler to add constants as they are encountered in
 // the compilation.
 const double kCommonDoubleConstants[] =
     {-1.0, -0.5, -0.1, 0.0, 0.1, 0.5, 1.0, 2.0, 4.0, 5.0,
      10.0, 20.0, 30.0, 64.0, 255.0, NAN,
      // From dart:math
@@ skipping 3440 matching lines @@
   if (Isolate::Current()->TypeChecksEnabled()) {
     const AbstractType& type =
         AbstractType::ZoneHandle(Z, node->field().type());
     const String& dst_name = String::ZoneHandle(Z, node->field().name());
     store_value = BuildAssignableValue(node->value()->token_pos(),
                                        store_value,
                                        type,
                                        dst_name);
   }
 
-  store_value = Bind(BuildStoreExprTemp(store_value));
-  GuardFieldClassInstr* guard_field_class =
-      new(Z) GuardFieldClassInstr(store_value,
-                               node->field(),
-                               isolate()->GetNextDeoptId());
-  AddInstruction(guard_field_class);
-
-  store_value = Bind(BuildLoadExprTemp());
-  GuardFieldLengthInstr* guard_field_length =
-      new(Z) GuardFieldLengthInstr(store_value,
+  if (FLAG_use_field_guards) {
+    if (node->field().guarded_cid() != kDynamicCid) {
+      store_value = Bind(BuildStoreExprTemp(store_value));
+      GuardFieldClassInstr* guard_field_class =
+          new(Z) GuardFieldClassInstr(store_value,
                                    node->field(),
                                    isolate()->GetNextDeoptId());
-  AddInstruction(guard_field_length);
-
-  store_value = Bind(BuildLoadExprTemp());
+      AddInstruction(guard_field_class);
+      store_value = Bind(BuildLoadExprTemp());
+      if (node->field().guarded_list_length() != Field::kNoFixedLength) {
+        GuardFieldLengthInstr* guard_field_length =
+            new(Z) GuardFieldLengthInstr(store_value,
+                                         node->field(),
+                                         isolate()->GetNextDeoptId());
+        AddInstruction(guard_field_length);
+        store_value = Bind(BuildLoadExprTemp());
+      } else {
+        // Advance deopt-id counter to remain in sync.
+        isolate()->GetNextDeoptId();
+      }
+    } else {
+      // Advance deopt-id counter to remain in sync.
+      isolate()->GetNextDeoptId();
+      isolate()->GetNextDeoptId();
+    }
+  }
   StoreInstanceFieldInstr* store =
       new(Z) StoreInstanceFieldInstr(node->field(),
                                      for_instance.value(),
                                      store_value,
                                      kEmitStoreBarrier,
                                      node->token_pos());
   // Maybe initializing unboxed store.
   store->set_is_potential_unboxed_initialization(true);
   ReturnDefinition(store);
 }
@@ skipping 846 matching lines @@
   Report::MessageF(Report::kBailout,
                    Script::Handle(function.script()),
                    function.token_pos(),
                    "FlowGraphBuilder Bailout: %s %s",
                    String::Handle(function.name()).ToCString(),
                    reason);
   UNREACHABLE();
 }
 
 }  // namespace dart