Use type propagation to eliminate store barriers.

runtime/vm/intermediate_language.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/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 274 matching lines @@
   // However, the 'more specific than' relation is transitive and is used
   // here. In other words, if the compile type of the value is more specific
   // than the destination type, the run time type of the value, which is
   // guaranteed to be a subtype of the compile type, is also guaranteed to be
   // a subtype of the destination type and the type check can therefore be
   // eliminated.
   return compile_type.IsMoreSpecificThan(dst_type, NULL);
 }
 
 
+bool Value::NeedsStoreBuffer() const {
+  const intptr_t cid = ResultCid();
+  if ((cid == kSmiCid) || (cid == kBoolCid) || (cid == kNullCid)) {
+    return false;
+  }
+  return !BindsToConstant();
+}
+
+
 RawAbstractType* PhiInstr::CompileType() const {
   ASSERT(!HasPropagatedType());
   // Since type propagation has not yet occured, we are reaching this phi via a
   // back edge phi input. Return null as compile type so that this input is
   // ignored in the first iteration of type propagation.
   return AbstractType::null();
 }
 
 
 RawAbstractType* PhiInstr::LeastSpecificInputType() const {
@@ skipping 1120 matching lines @@
                                Location::SameAsFirstInput(),
                                LocationSummary::kNoCall);
 }
 
 
 void StoreVMFieldComp::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register value_reg = locs()->in(0).reg();
   Register dest_reg = locs()->in(1).reg();
   ASSERT(value_reg == locs()->out().reg());
 
-  __ StoreIntoObject(dest_reg, FieldAddress(dest_reg, offset_in_bytes()),
-                     value_reg);
+  if (value()->NeedsStoreBuffer()) {
+    __ StoreIntoObject(dest_reg, FieldAddress(dest_reg, offset_in_bytes()),
+                       value_reg);
+  } else {
+    __ StoreIntoObjectNoBarrier(
+        dest_reg, FieldAddress(dest_reg, offset_in_bytes()), value_reg);
+  }
 }
 
 
 LocationSummary* AllocateObjectComp::MakeLocationSummary() const {
   return MakeCallSummary();
 }
 
 
 void AllocateObjectComp::EmitNativeCode(FlowGraphCompiler* compiler) {
   const Class& cls = Class::ZoneHandle(constructor().Owner());
@@ skipping 78 matching lines @@
                      ? UseDefinition(values()[i]->AsUse()->definition())
                      : val);
   }
   return copy;
 }
 
 
 #undef __
 
 }  // namespace dart