Eliminate 99% of allocated ExceptionHandler objects

runtime/vm/code_descriptors.h

 // 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.
 
 #ifndef VM_CODE_DESCRIPTORS_H_
 #define VM_CODE_DESCRIPTORS_H_
 
 #include "vm/ast.h"
 #include "vm/code_generator.h"
 #include "vm/globals.h"
@@ skipping 56 matching lines @@
 
  private:
   GrowableArray<struct PcDesc> list_;
   bool has_try_index_;
   DISALLOW_COPY_AND_ASSIGN(DescriptorList);
 };
 
 
 class StackmapTableBuilder : public ZoneAllocated {
  public:
-  explicit StackmapTableBuilder()

[hausner, 2014/09/15 23:33:16]

Unrelated to this CL. gcl upload complained about the explicit on a zero
parameter constructor. Interestingly, this line has been in the code sind
revision 11000 or so.

[srdjan, 2014/09/15 23:47:14]

gcl and its rules/tools get also occasionally updated, I guess.

+  StackmapTableBuilder()
       : stack_map_(Stackmap::ZoneHandle()),
         list_(GrowableObjectArray::ZoneHandle(
             GrowableObjectArray::New(Heap::kOld))) { }
   ~StackmapTableBuilder() { }
 
   void AddEntry(intptr_t pc_offset,
                 BitmapBuilder* bitmap,
                 intptr_t register_bit_count);
 
   bool Verify();
@@ skipping 67 matching lines @@
       if (array.At(i) == Type::DynamicType()) {
         return true;
       }
     }
     return false;
   }
 
 
   RawExceptionHandlers* FinalizeExceptionHandlers(uword entry_point) {
     intptr_t num_handlers = Length();
+    if (num_handlers == 0) {
+      return Object::empty_exception_handlers().raw();
+    }
     const ExceptionHandlers& handlers =
         ExceptionHandlers::Handle(ExceptionHandlers::New(num_handlers));
     for (intptr_t i = 0; i < num_handlers; i++) {
       // Assert that every element in the array has been initialized.
       ASSERT(list_[i].handler_types != NULL);
       bool has_catch_all = ContainsDynamic(*list_[i].handler_types);
       handlers.SetHandlerInfo(i,
                               list_[i].outer_try_index,
                               (entry_point + list_[i].pc_offset),
                               list_[i].needs_stacktrace,
                               has_catch_all);
       handlers.SetHandledTypes(i, *list_[i].handler_types);
     }
     return handlers.raw();
   }
 
  private:
   GrowableArray<struct HandlerDesc> list_;
   DISALLOW_COPY_AND_ASSIGN(ExceptionHandlerList);
 };
 
 }  // namespace dart
 
 #endif  // VM_CODE_DESCRIPTORS_H_