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 6493 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));
-  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]);
+  if (count == 0) {
+    set_ic_data_array(Object::empty_array());
+  } else {
+    const Array& a = Array::Handle(Array::New(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]);
+      }
     }
+    set_ic_data_array(a);
   }
-  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();
     return;;
@@ skipping 4159 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 = (num_variables == 0) ? Object::empty_array() :
+      Array::Handle(Array::New(num_variables, Heap::kOld));
   result.raw_ptr()->names_ = names.raw();
   return result.raw();
 }
 
 
 intptr_t LocalVarDescriptors::Length() const {
   return raw_ptr()->length_;
 }
 
 
@@ skipping 80 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 = (num_handlers == 0) ?
+      Object::empty_array() :
+      Array::Handle(Array::New(num_handlers));
   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 8344 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart