Resolve some disagreements between SIMARM and XARM on offsets used in compiled code.

runtime/vm/heap.h

Index: runtime/vm/heap.h
diff --git a/runtime/vm/heap.h b/runtime/vm/heap.h
index 8feb555470ab0364177434828d2c6fdbf1ce5740..04d2d2d9fe74bd43ef101ba70590b50dd3478c87 100644
--- a/runtime/vm/heap.h
+++ b/runtime/vm/heap.h
@@ -310,12 +310,12 @@ class Heap {
   // of this heap.
   void GetMergedAddressRange(uword* start, uword* end) const;
 
-  Isolate* isolate_;
-
   // The different spaces used for allocation.
   Scavenger new_space_;
   PageSpace old_space_;
 
+  Isolate* isolate_;

[Florian Schneider, 2015/09/30 09:38:13]

This seems still fragile, since there are members of Scavenger that may be
packed differently. I think we would need to add ALIGNx to all those as well to
be sure that isolate_ is at the same offset.

Maybe add a COMPILE_ASSERT for 32 and 64 bit to be sure it does not break.

[rmacnak, 2015/10/01 22:00:49]

This is to get Heap::Top/EndOffset(kNew) consistent. We shouldn't be using
isolate_ or anything below.

+
   WeakTable* new_weak_tables_[kNumWeakSelectors];
   WeakTable* old_weak_tables_[kNumWeakSelectors];