Save more memory by compacting LocalVarDescriptors

runtime/vm/raw_object.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_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/atomic.h"
 #include "vm/globals.h"
@@ skipping 1079 matching lines @@
     int32_t index() const {
       return IndexBits::decode(index_kind) - kIndexBias;
     }
     void set_index(int32_t index) {
       index_kind = IndexBits::update(index + kIndexBias, index_kind);
     }
   };
 
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(LocalVarDescriptors);
-  RawArray* names_;  // Array of [length_] variable names.
-  int32_t length_;  // Number of descriptors.
+  int32_t num_entries_;  // Number of descriptors.
 
-  // Variable info with [length_] entries.
-  VarInfo* data() { OPEN_ARRAY_START(VarInfo, int32_t); }
+  RawObject** from() {
+    return reinterpret_cast<RawObject**>(&ptr()->names()[0]);
+  }
+  RawString** names() {
+    // Array of [num_entries_] variable names.
+    OPEN_ARRAY_START(RawString*, RawString*);
+  }

[siva, 2014/09/12 22:08:39]

For better readability I think it would make sense to have a method
RawString* nameAt(intptr_t index) const {
  return names()[index];
}

[hausner, 2014/09/12 23:48:04]

Added a function to return the address of name[i].

+  RawObject** to(intptr_t num_entries) {
+    return reinterpret_cast<RawObject**>(&ptr()->names()[num_entries - 1]);

[siva, 2014/09/12 22:08:39]

return reinterpret_cast<RawObject**>(&nameAt(num_enties - 1));

[hausner, 2014/09/12 23:48:04]

You can't take the address of a return value.

+  }
+
+  // Variable info with [num_entries_] entries.
+  VarInfo* data() {
+    return reinterpret_cast<VarInfo*>(&(names()[num_entries_]));
+  }
 
   friend class Object;
 };
 
 
 class RawExceptionHandlers : public RawObject {
  public:
   // The index into the ExceptionHandlers table corresponds to
   // the try_index of the handler.
   struct HandlerInfo {
@@ skipping 921 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_