Remove remaining uses of null's absolute address from non-IA32.

runtime/vm/assembler_arm64.cc

Index: runtime/vm/assembler_arm64.cc
diff --git a/runtime/vm/assembler_arm64.cc b/runtime/vm/assembler_arm64.cc
index 16220b4a0d3ca7f7156384bc936067deda162268..a360a2d8d854f762fc04637cddbf8865b9c36ce1 100644
--- a/runtime/vm/assembler_arm64.cc
+++ b/runtime/vm/assembler_arm64.cc
@@ -20,6 +20,7 @@
 
 namespace dart {
 
+DECLARE_FLAG(bool, allow_absolute_addresses);
 DEFINE_FLAG(bool, use_far_branches, false, "Always use far branches");
 DEFINE_FLAG(bool, print_stop_message, false, "Print stop message.");
 DECLARE_FLAG(bool, inline_alloc);
@@ -430,6 +431,7 @@ void Assembler::LoadObjectHelper(Register dst,
     LoadWordFromPoolOffset(dst, offset);
   } else {
     ASSERT(object.IsSmi() || object.InVMHeap());
+    ASSERT(object.IsSmi() || FLAG_allow_absolute_addresses);
     LoadDecodableImmediate(dst, reinterpret_cast<int64_t>(object.raw()));
   }
 }
@@ -465,6 +467,7 @@ void Assembler::CompareObject(Register reg, const Object& object) {
     LoadObject(TMP, object);
     CompareRegisters(reg, TMP);
   } else {
+    ASSERT(object.IsSmi() || FLAG_allow_absolute_addresses);
     CompareImmediate(reg, reinterpret_cast<int64_t>(object.raw()));
   }
 }
@@ -1253,6 +1256,7 @@ void Assembler::UpdateAllocationStats(intptr_t cid,
   intptr_t counter_offset =
       ClassTable::CounterOffsetFor(cid, space == Heap::kNew);
   if (inline_isolate) {
+    ASSERT(FLAG_allow_absolute_addresses);
     ClassTable* class_table = Isolate::Current()->class_table();
     ClassHeapStats** table_ptr = class_table->TableAddressFor(cid);
     if (cid < kNumPredefinedCids) {
@@ -1322,6 +1326,7 @@ void Assembler::MaybeTraceAllocation(intptr_t cid,
   ASSERT(cid > 0);
   intptr_t state_offset = ClassTable::StateOffsetFor(cid);
   if (inline_isolate) {
+    ASSERT(FLAG_allow_absolute_addresses);
     ClassTable* class_table = Isolate::Current()->class_table();
     ClassHeapStats** table_ptr = class_table->TableAddressFor(cid);
     if (cid < kNumPredefinedCids) {