Remove usages of Heap::NewSpaceStart and its external reference

src/arm64/macro-assembler-arm64.cc

 // Copyright 2013 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.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 1538 matching lines @@
   Ldr(current_object, FieldMemOperand(map, Map::kPrototypeOffset));
   Cmp(current_object, null_value);
   B(ne, &next);
 }
 
 
 void MacroAssembler::TestJSArrayForAllocationMemento(Register receiver,
                                                      Register scratch1,
                                                      Register scratch2,
                                                      Label* no_memento_found) {
-  ExternalReference new_space_start =
-      ExternalReference::new_space_start(isolate());
+  Label map_check;
   ExternalReference new_space_allocation_top =
       ExternalReference::new_space_allocation_top_address(isolate());
+  const int kMementoMapOffset = JSArray::kSize - kHeapObjectTag;
+  const int kMementoEndOffset = kMementoMapOffset + AllocationMemento::kSize;
 
-  Add(scratch1, receiver,
-      JSArray::kSize + AllocationMemento::kSize - kHeapObjectTag);
-  Cmp(scratch1, new_space_start);
-  B(lt, no_memento_found);
-
-  Mov(scratch2, new_space_allocation_top);
-  Ldr(scratch2, MemOperand(scratch2));
-  Cmp(scratch1, scratch2);
+  // Bail out if the object sits on the page boundary as no memento can follow
+  // and we cannot touch the memory following it.
+  Add(scratch1, receiver, kMementoEndOffset);
+  Eor(scratch2, scratch1, receiver);
+  Cmp(scratch2, Operand(Page::kPageSize));
   B(gt, no_memento_found);
-
-  Ldr(scratch1, MemOperand(scratch1, -AllocationMemento::kSize));
-  Cmp(scratch1,
-      Operand(isolate()->factory()->allocation_memento_map()));
+  // Bail out if the object is not in new space. Reuse scratch1 from above.
+  JumpIfNotInNewSpace(scratch1, no_memento_found);
+  // If the object is in new space, we need to check whether it is on the same
+  // page as the current top.
+  Add(scratch2, receiver, kMementoEndOffset);
+  Eor(scratch2, scratch2, new_space_allocation_top);
+  Tst(scratch2, ~Page::kPageAlignmentMask);
+  B(ne, no_memento_found);
+  // Otherwise, we have to check whether we are still below top, to ensure that
+  // we are not checking against a stale memento.
+  Cmp(scratch1, new_space_allocation_top);
+  B(gt, no_memento_found);
+  bind(&map_check);
+  Ldr(scratch1, MemOperand(receiver, kMementoMapOffset));
+  Cmp(scratch1, Operand(isolate()->factory()->allocation_memento_map()));
 }
 
 
 void MacroAssembler::InNewSpace(Register object,
                                 Condition cond,
                                 Label* branch) {
   DCHECK(cond == eq || cond == ne);
   UseScratchRegisterScope temps(this);
   const int mask =
       (1 << MemoryChunk::IN_FROM_SPACE) | (1 << MemoryChunk::IN_TO_SPACE);
@@ skipping 3492 matching lines @@
 }
 
 
 #undef __
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64