Introduce a base pointer field in FixedTypedArrayBase and teach GC about it

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 2761 matching lines @@
     Memory::Object_at(dst_slot) = value;
     RecordMigratedSlot(value, dst_slot);
     src_slot += kPointerSize;
     dst_slot += kPointerSize;
   }
 }
 
 
 void MarkCompactCollector::MigrateObjectMixed(HeapObject* dst, HeapObject* src,
                                               int size) {
-  if (FLAG_unbox_double_fields) {
+  if (src->IsFixedTypedArrayBase()) {
+    heap()->MoveBlock(dst->address(), src->address(), size);
+    Address base_pointer_slot =
+        dst->address() + FixedTypedArrayBase::kBasePointerOffset;
+    RecordMigratedSlot(Memory::Object_at(base_pointer_slot), base_pointer_slot);
+  } else if (FLAG_unbox_double_fields) {
     Address dst_addr = dst->address();
     Address src_addr = src->address();
     Address src_slot = src_addr;
     Address dst_slot = dst_addr;
 
     LayoutDescriptorHelper helper(src->map());
     DCHECK(!helper.all_fields_tagged());
     for (int remaining = size / kPointerSize; remaining > 0; remaining--) {
       Object* value = Memory::Object_at(src_slot);
 
@@ skipping 398 matching lines @@
         InstanceType type = object->map()->instance_type();
         // Slots in maps and code can't be invalid because they are never
         // shrunk.
         if (type == MAP_TYPE || type == CODE_TYPE) return true;
 
         // Consider slots in objects that contain ONLY raw data as invalid.
         return false;
       }
 
       case HeapObjectContents::kMixedValues: {
-        if (FLAG_unbox_double_fields) {
+        if (object->IsFixedTypedArrayBase()) {
+          return static_cast<int>(slot - object->address()) ==
+                 FixedTypedArrayBase::kBasePointerOffset;
+        } else if (FLAG_unbox_double_fields) {
           // Filter out slots that happen to point to unboxed double fields.
           LayoutDescriptorHelper helper(object->map());
           DCHECK(!helper.all_fields_tagged());
           return helper.IsTagged(static_cast<int>(slot - object->address()));
         }
         break;
       }
     }
     UNREACHABLE();
   }
@@ skipping 1516 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }  // namespace internal
 }  // namespace v8