PPC: [Heap] Fix comparing against new space top pointer

src/ppc/macro-assembler-ppc.cc

Index: src/ppc/macro-assembler-ppc.cc
diff --git a/src/ppc/macro-assembler-ppc.cc b/src/ppc/macro-assembler-ppc.cc
index ef90ff4b815789b8d15a34bfd3227ad7ccbdb5eb..e6e05da152ecf15036a7886089643529b47efa1f 100644
--- a/src/ppc/macro-assembler-ppc.cc
+++ b/src/ppc/macro-assembler-ppc.cc
@@ -4698,7 +4698,7 @@ void MacroAssembler::TestJSArrayForAllocationMemento(Register receiver_reg,
                                                      Label* no_memento_found) {
   Label map_check;
   Label top_check;
-  ExternalReference new_space_allocation_top =
+  ExternalReference new_space_allocation_top_adr =
       ExternalReference::new_space_allocation_top_address(isolate());
   const int kMementoMapOffset = JSArray::kSize - kHeapObjectTag;
   const int kMementoEndOffset = kMementoMapOffset + AllocationMemento::kSize;
@@ -4715,7 +4715,9 @@ void MacroAssembler::TestJSArrayForAllocationMemento(Register receiver_reg,
 
   // If the object is in new space, we need to check whether it is on the same
   // page as the current top.
-  Xor(r0, scratch_reg, Operand(new_space_allocation_top));
+  mov(ip, Operand(new_space_allocation_top_adr));
+  LoadP(ip, MemOperand(ip));
+  Xor(r0, scratch_reg, Operand(ip));
   and_(r0, r0, mask, SetRC);
   beq(&top_check, cr0);
   // The object is on a different page than allocation top. Bail out if the
@@ -4729,7 +4731,9 @@ void MacroAssembler::TestJSArrayForAllocationMemento(Register receiver_reg,
   // If top is on the same page as the current object, we need to check whether
   // we are below top.
   bind(&top_check);
-  Cmpi(scratch_reg, Operand(new_space_allocation_top), r0);
+  mov(ip, Operand(new_space_allocation_top_adr));

[john.yan, 2016/06/16 05:13:49]

I am not sure why we need to do the load again.

+  LoadP(ip, MemOperand(ip));
+  cmp(scratch_reg, ip);
   bgt(no_memento_found);
   // Memento map check.
   bind(&map_check);