Remove usages of Heap::NewSpaceStart and its external reference

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index abd517480f2c97bc87868a743a5549c44eb274f4..755b3ea653a2a139b77ad72fdbc41487fe8e7b80 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -3764,29 +3764,41 @@ void MacroAssembler::CheckEnumCache(Label* call_runtime) {
   b(ne, &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());
-  add(scratch_reg, receiver_reg,
-      Operand(JSArray::kSize + AllocationMemento::kSize - kHeapObjectTag));
-  cmp(scratch_reg, Operand(new_space_start));
-  b(lt, no_memento_found);
-  mov(ip, Operand(new_space_allocation_top));
-  ldr(ip, MemOperand(ip));
-  cmp(scratch_reg, ip);
+  const int kMementoMapOffset = JSArray::kSize - kHeapObjectTag;
+  const int kMementoEndOffset = kMementoMapOffset + AllocationMemento::kSize;
+
+  // Bail out if the object sits on the page boundary as no memento can follow
+  // and we cannot touch the memory following it.
+  add(scratch_reg, receiver_reg, Operand(kMementoEndOffset));
+  eor(scratch_reg, scratch_reg, Operand(receiver_reg));
+  cmp(scratch_reg, Operand(Page::kPageSize));
+  b(gt, no_memento_found);
+  // Bail out if the object is not in new space.
+  add(scratch_reg, receiver_reg, Operand(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.
+  add(scratch_reg, receiver_reg, Operand(kMementoEndOffset));
+  eor(scratch_reg, scratch_reg, Operand(new_space_allocation_top));
+  tst(scratch_reg, Operand(~Page::kPageAlignmentMask));
+  b(ne, &map_check);
+  // Otherwise, we have to check whether we are still below top, to ensure that
+  // we are not checking against a stale memento.
+  add(scratch_reg, receiver_reg, Operand(kMementoEndOffset));
+  cmp(scratch_reg, Operand(new_space_allocation_top));
   b(gt, no_memento_found);
-  ldr(scratch_reg, MemOperand(scratch_reg, -AllocationMemento::kSize));
-  cmp(scratch_reg,
-      Operand(isolate()->factory()->allocation_memento_map()));
+  bind(&map_check);
+  ldr(scratch_reg, MemOperand(receiver_reg, kMementoMapOffset));
+  cmp(scratch_reg, Operand(isolate()->factory()->allocation_memento_map()));
 }
 
-
 Register GetRegisterThatIsNotOneOf(Register reg1,
                                    Register reg2,
                                    Register reg3,