Remove usages of Heap::NewSpaceStart and its external reference

src/x64/macro-assembler-x64.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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 5597 matching lines @@
   movp(rcx, FieldOperand(rbx, Map::kPrototypeOffset));
   CompareRoot(rcx, Heap::kNullValueRootIndex);
   j(not_equal, &next);
 }
 
 
 void MacroAssembler::TestJSArrayForAllocationMemento(
     Register receiver_reg,
     Register scratch_reg,
     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;
 
-  leap(scratch_reg, Operand(receiver_reg,
-      JSArray::kSize + AllocationMemento::kSize - kHeapObjectTag));
-  Move(kScratchRegister, new_space_start);
-  cmpp(scratch_reg, kScratchRegister);
-  j(less, no_memento_found);
+  // Bail out if the object sits on the page boundary as no memento can follow
+  // and we cannot touch the memory following it.
+  leap(scratch_reg, Operand(receiver_reg, kMementoEndOffset));
+  xorp(scratch_reg, receiver_reg);
+  cmpp(scratch_reg, Immediate(Page::kPageSize));
+  j(greater, no_memento_found);
+  // Bail out if the object is not in new space.
+  leap(scratch_reg, Operand(receiver_reg, kMementoEndOffset));
+  JumpIfNotInNewSpace(scratch_reg, scratch_reg, 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.
+  leap(scratch_reg, Operand(receiver_reg, kMementoEndOffset));
+  xorp(scratch_reg, ExternalOperand(new_space_allocation_top));
+  testp(scratch_reg, Immediate(~Page::kPageAlignmentMask));
+  // If top is not on the same page as the current object, we can just continue
+  // with the map check.
+  j(not_zero, &map_check);
+  // Otherwise, we have to check whether we are still below top, to ensure that
+  // we are not checking against a stale memento.
+  leap(scratch_reg, Operand(receiver_reg, kMementoEndOffset));
   cmpp(scratch_reg, ExternalOperand(new_space_allocation_top));
   j(greater, no_memento_found);
-  CompareRoot(MemOperand(scratch_reg, -AllocationMemento::kSize),
+  bind(&map_check);
+  CompareRoot(MemOperand(receiver_reg, kMementoMapOffset),
               Heap::kAllocationMementoMapRootIndex);
 }
 
 
 void MacroAssembler::JumpIfDictionaryInPrototypeChain(
     Register object,
     Register scratch0,
     Register scratch1,
     Label* found) {
   DCHECK(!(scratch0.is(kScratchRegister) && scratch1.is(kScratchRegister)));
@@ skipping 40 matching lines @@
   movl(rax, dividend);
   shrl(rax, Immediate(31));
   addl(rdx, rax);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64