Bug 706885 - Add a pointer to the JSRuntime on the gc::Chunk; r=billm

--HG--
extra : rebase_source : f6ac0b0db7791b365d0e63f6fea2e5f451964453

js/public/HeapAPI.h

@@ -41,7 +41,7 @@ const size_t CellSize = size_t(1) << CellShift;
 const size_t CellMask = CellSize - 1;
 
 /* These are magic constants derived from actual offsets in gc/Heap.h. */
-const size_t ChunkMarkBitmapOffset = 1032376;
+const size_t ChunkMarkBitmapOffset = 1032368;
 const size_t ChunkMarkBitmapBits = 129024;
 
 /*

js/src/gc/Heap.h

@@ -85,6 +85,7 @@ struct Cell
     MOZ_ALWAYS_INLINE bool markIfUnmarked(uint32_t color = BLACK) const;
     MOZ_ALWAYS_INLINE void unmark(uint32_t color) const;
 
+    inline JSRuntime *runtime() const;
     inline JSCompartment *compartment() const;
     inline Zone *zone() const;
 
@@ -593,7 +594,7 @@ struct ChunkInfo
      * Calculating sizes and offsets is simpler if sizeof(ChunkInfo) is
      * architecture-independent.
      */
-    char            padding[12];
+    char            padding[16];
 #endif
 
     /*
@@ -611,6 +612,9 @@ struct ChunkInfo
 
     /* Number of GC cycles this chunk has survived. */
     uint32_t        age;
+
+    /* This is findable from any address in the Chunk by aligning to 1MiB. */
+    JSRuntime       *runtime;
 };
 
 /*
@@ -947,6 +951,12 @@ Cell::chunk() const
     return reinterpret_cast<Chunk *>(addr);
 }
 
+inline JSRuntime *
+Cell::runtime() const
+{
+    return chunk()->info.runtime;
+}
+
 AllocKind
 Cell::getAllocKind() const
 {