Allocate fewer empty arrays.

runtime/vm/flow_graph_compiler.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/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
@@ skipping 713 matching lines @@
 
 
 void FlowGraphCompiler::FinalizeDeoptInfo(const Code& code) {
   // For functions with optional arguments, all incoming arguments are copied
   // to spill slots. The deoptimization environment does not track them.
   const Function& function = parsed_function().function();
   const intptr_t incoming_arg_count =
       function.HasOptionalParameters() ? 0 : function.num_fixed_parameters();
   DeoptInfoBuilder builder(isolate(), incoming_arg_count);
 
-  const Array& array =
-      Array::Handle(Array::New(DeoptTable::SizeFor(deopt_infos_.length()),
-                               Heap::kOld));
-  Smi& offset = Smi::Handle();
-  DeoptInfo& info = DeoptInfo::Handle();
-  Smi& reason = Smi::Handle();
-  for (intptr_t i = 0; i < deopt_infos_.length(); i++) {
-    offset = Smi::New(deopt_infos_[i]->pc_offset());
-    info = deopt_infos_[i]->CreateDeoptInfo(this, &builder, array);
-    reason = Smi::New(deopt_infos_[i]->reason());
-    DeoptTable::SetEntry(array, i, offset, info, reason);
+  intptr_t deopt_info_table_size = DeoptTable::SizeFor(deopt_infos_.length());
+  if (deopt_info_table_size == 0) {
+    code.set_deopt_info_array(Object::empty_array());
+    code.set_object_table(Object::empty_array());
+  } else {
+    const Array& array =
+        Array::Handle(Array::New(deopt_info_table_size, Heap::kOld));
+    Smi& offset = Smi::Handle();
+    DeoptInfo& info = DeoptInfo::Handle();
+    Smi& reason = Smi::Handle();
+    for (intptr_t i = 0; i < deopt_infos_.length(); i++) {
+      offset = Smi::New(deopt_infos_[i]->pc_offset());
+      info = deopt_infos_[i]->CreateDeoptInfo(this, &builder, array);
+      reason = Smi::New(deopt_infos_[i]->reason());
+      DeoptTable::SetEntry(array, i, offset, info, reason);
+    }
+    code.set_deopt_info_array(array);
+    const Array& object_array =
+        Array::Handle(Array::MakeArray(builder.object_table()));
+    ASSERT(code.object_table() == Array::null());
+    code.set_object_table(object_array);
   }
-  code.set_deopt_info_array(array);
-  const Array& object_array =
-      Array::Handle(Array::MakeArray(builder.object_table()));
-  ASSERT(code.object_table() == Array::null());
-  code.set_object_table(object_array);
 }
 
 
 void FlowGraphCompiler::FinalizeStackmaps(const Code& code) {
   if (stackmap_table_builder_ == NULL) {
     // The unoptimizing compiler has no stack maps.
     code.set_stackmaps(Object::null_array());
   } else {
     // Finalize the stack map array and add it to the code object.
     ASSERT(is_optimizing());
@@ skipping 629 matching lines @@
   }
   const ICData& ic_data = ICData::ZoneHandle(isolate(), ICData::New(
       parsed_function().function(), String::Handle(isolate(), target.name()),
       arguments_descriptor, deopt_id, num_args_tested));
   ic_data.AddTarget(target);
   (*deopt_id_to_ic_data_)[deopt_id] = &ic_data;
   return &ic_data;
 }
 
 }  // namespace dart