Allocate fewer empty arrays.

runtime/vm/object.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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 6450 matching lines @@
 void Function::SaveICDataMap(
     const ZoneGrowableArray<const ICData*>& deopt_id_to_ic_data) const {
   // Compute number of ICData objectsto save.
   intptr_t count = 0;
   for (intptr_t i = 0; i < deopt_id_to_ic_data.length(); i++) {
     if (deopt_id_to_ic_data[i] != NULL) {
       count++;
     }
   }
 
-  const Array& a = Array::Handle(Array::New(count, Heap::kOld));
+  const Array& a = Array::Handle(Array::NewOrEmpty(count, Heap::kOld));
   count = 0;
   for (intptr_t i = 0; i < deopt_id_to_ic_data.length(); i++) {
     if (deopt_id_to_ic_data[i] != NULL) {
       a.SetAt(count++, *deopt_id_to_ic_data[i]);
     }
   }

[siva, 2014/07/09 20:08:02]

Similarly here we could go with
if (count == 0) {
  set_ic_data_array(Object::empty_array());
} else {
  const Array& a = Array::Handle(Array::New(...));
  ...
  ...
}

   set_ic_data_array(a);
 }
 
 
 void Function::RestoreICDataMap(
     ZoneGrowableArray<const ICData*>* deopt_id_to_ic_data) const {
   Isolate* isolate = Isolate::Current();
   const Array& saved_icd = Array::Handle(isolate, ic_data_array());
   if (saved_icd.Length() == 0) {
     deopt_id_to_ic_data->Clear();
@@ skipping 4098 matching lines @@
   LocalVarDescriptors& result = LocalVarDescriptors::Handle();
   {
     uword size = LocalVarDescriptors::InstanceSize(num_variables);
     RawObject* raw = Object::Allocate(LocalVarDescriptors::kClassId,
                                       size,
                                       Heap::kOld);
     NoGCScope no_gc;
     result ^= raw;
     result.raw_ptr()->length_ = num_variables;
   }
-  const Array& names = Array::Handle(Array::New(num_variables, Heap::kOld));
+  const Array& names =
+      Array::Handle(Array::NewOrEmpty(num_variables, Heap::kOld));
   result.raw_ptr()->names_ = names.raw();

[siva, 2014/07/09 20:08:02]

ditto here too, avoids the handle creation.

   return result.raw();
 }
 
 
 intptr_t LocalVarDescriptors::Length() const {
   return raw_ptr()->length_;
 }
 
 
 intptr_t ExceptionHandlers::Length() const {
@@ skipping 79 matching lines @@
   ExceptionHandlers& result = ExceptionHandlers::Handle();
   {
     uword size = ExceptionHandlers::InstanceSize(num_handlers);
     RawObject* raw = Object::Allocate(ExceptionHandlers::kClassId,
                                       size,
                                       Heap::kOld);
     NoGCScope no_gc;
     result ^= raw;
     result.raw_ptr()->length_ = num_handlers;
   }
-  const Array& handled_types_data = Array::Handle(Array::New(num_handlers));
+  const Array& handled_types_data =
+      Array::Handle(Array::NewOrEmpty(num_handlers));

[siva, 2014/07/09 20:08:02]

Ditto.

   result.set_handled_types_data(handled_types_data);
   return result.raw();
 }
 
 
 const char* ExceptionHandlers::ToCString() const {
   if (Length() == 0) {
     return "No exception handlers\n";
   }
   Array& handled_types = Array::Handle();
@@ skipping 8346 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart