8329261: G1: interpreter post-barrier x86 code asserts index size of wrong buffer

Backport-of: 1131bb77ec94dd131a10df4ba0f3fab32c65c0f2

Author: Satyen Subramaniam

src/hotspot/cpu/x86/gc/g1/g1BarrierSetAssembler_x86.cpp

@@ -265,8 +265,6 @@ void G1BarrierSetAssembler::g1_write_barrier_post(MacroAssembler* masm,
                                                   Register thread,
                                                   Register tmp,
                                                   Register tmp2) {
-  // Generated code assumes that buffer index is pointer sized.
-  STATIC_ASSERT(in_bytes(SATBMarkQueue::byte_width_of_index()) == sizeof(intptr_t));
 #ifdef _LP64
   assert(thread == r15_thread, "must be");
 #endif // _LP64
@@ -317,6 +315,9 @@ void G1BarrierSetAssembler::g1_write_barrier_post(MacroAssembler* masm,
 
   __ movb(Address(card_addr, 0), (int)G1CardTable::dirty_card_val());
 
+  // The code below assumes that buffer index is pointer sized.
+  STATIC_ASSERT(in_bytes(G1DirtyCardQueue::byte_width_of_index()) == sizeof(intptr_t));
+
   __ movptr(tmp2, queue_index);
   __ testptr(tmp2, tmp2);
   __ jcc(Assembler::zero, runtime);