VM: Fix allocation size stats for contexts on ia32 and x64.

runtime/vm/stub_code_ia32.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"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 859 matching lines @@
 #endif  // DEBUG
       __ j(ABOVE_EQUAL, &slow_case, kJumpLength);
     }
 
     // Successfully allocated the object, now update top to point to
     // next object start and initialize the object.
     // EAX: new object.
     // EBX: next object start.
     // EDX: number of context variables.
     __ movl(Address(ECX, Heap::TopOffset(space)), EBX);
-    __ addl(EAX, Immediate(kHeapObjectTag));
     // EBX: Size of allocation in bytes.
     __ subl(EBX, EAX);
+    __ addl(EAX, Immediate(kHeapObjectTag));
     // Generate isolate-independent code to allow sharing between isolates.
     __ UpdateAllocationStatsWithSize(cid, EBX, EDI, space,
                                      /* inline_isolate = */ false);
 
     // Calculate the size tag.
     // EAX: new object.
     // EDX: number of context variables.
     {
       Label size_tag_overflow, done;
       __ leal(EBX, Address(EDX, TIMES_4, fixed_size));
@@ skipping 1234 matching lines @@
 //  EBX: entry point.
 void StubCode::GenerateMegamorphicLookupStub(Assembler* assembler) {
   EmitMegamorphicLookup(assembler, EDI, EBX, EBX);
   __ ret();
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32