369 //     GenCollectedHeap(ParNew,DefNew,Tenured) and
 370 //     ParallelScavengeHeap(ParallelGC, ParallelOldGC)
 371 //     need the card-mark if and only if the region is
 372 //     in the old gen, and do not care if the card-mark
 373 //     succeeds or precedes the initializing stores themselves,
 374 //     so long as the card-mark is completed before the next
 375 //     scavenge. For all these cases, we can do a card mark
 376 //     at the point at which we do a slow path allocation
 377 //     in the old gen, i.e. in this call.
 378 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
 379 //     in addition that the card-mark for an old gen allocated
 380 //     object strictly follow any associated initializing stores.
 381 //     In these cases, the memRegion remembered below is
 382 //     used to card-mark the entire region either just before the next
 383 //     slow-path allocation by this thread or just before the next scavenge or
 384 //     CMS-associated safepoint, whichever of these events happens first.
 385 //     (The implicit assumption is that the object has been fully
 386 //     initialized by this point, a fact that we assert when doing the
 387 //     card-mark.)
 388 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
 389 //     G1 concurrent marking is in progress an SATB (pre-write-)barrier is
 390 //     is used to remember the pre-value of any store. Initializing
 391 //     stores will not need this barrier, so we need not worry about
 392 //     compensating for the missing pre-barrier here. Turning now
 393 //     to the post-barrier, we note that G1 needs a RS update barrier
 394 //     which simply enqueues a (sequence of) dirty cards which may
 395 //     optionally be refined by the concurrent update threads. Note
 396 //     that this barrier need only be applied to a non-young write,
 397 //     but, like in CMS, because of the presence of concurrent refinement
 398 //     (much like CMS' precleaning), must strictly follow the oop-store.
 399 //     Thus, using the same protocol for maintaining the intended
 400 //     invariants turns out, serendepitously, to be the same for both
 401 //     G1 and CMS.
 402 //
 403 // For any future collector, this code should be reexamined with
 404 // that specific collector in mind, and the documentation above suitably
 405 // extended and updated.
 406 oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {
 407   // If a previous card-mark was deferred, flush it now.
 408   flush_deferred_store_barrier(thread);
 409   if (can_elide_initializing_store_barrier(new_obj) ||

 369 //     GenCollectedHeap(ParNew,DefNew,Tenured) and
 370 //     ParallelScavengeHeap(ParallelGC, ParallelOldGC)
 371 //     need the card-mark if and only if the region is
 372 //     in the old gen, and do not care if the card-mark
 373 //     succeeds or precedes the initializing stores themselves,
 374 //     so long as the card-mark is completed before the next
 375 //     scavenge. For all these cases, we can do a card mark
 376 //     at the point at which we do a slow path allocation
 377 //     in the old gen, i.e. in this call.
 378 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
 379 //     in addition that the card-mark for an old gen allocated
 380 //     object strictly follow any associated initializing stores.
 381 //     In these cases, the memRegion remembered below is
 382 //     used to card-mark the entire region either just before the next
 383 //     slow-path allocation by this thread or just before the next scavenge or
 384 //     CMS-associated safepoint, whichever of these events happens first.
 385 //     (The implicit assumption is that the object has been fully
 386 //     initialized by this point, a fact that we assert when doing the
 387 //     card-mark.)
 388 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
 389 //     G1 concurrent marking is in progress an SATB (pre-write-)barrier
 390 //     is used to remember the pre-value of any store. Initializing
 391 //     stores will not need this barrier, so we need not worry about
 392 //     compensating for the missing pre-barrier here. Turning now
 393 //     to the post-barrier, we note that G1 needs a RS update barrier
 394 //     which simply enqueues a (sequence of) dirty cards which may
 395 //     optionally be refined by the concurrent update threads. Note
 396 //     that this barrier need only be applied to a non-young write,
 397 //     but, like in CMS, because of the presence of concurrent refinement
 398 //     (much like CMS' precleaning), must strictly follow the oop-store.
 399 //     Thus, using the same protocol for maintaining the intended
 400 //     invariants turns out, serendepitously, to be the same for both
 401 //     G1 and CMS.
 402 //
 403 // For any future collector, this code should be reexamined with
 404 // that specific collector in mind, and the documentation above suitably
 405 // extended and updated.
 406 oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {
 407   // If a previous card-mark was deferred, flush it now.
 408   flush_deferred_store_barrier(thread);
 409   if (can_elide_initializing_store_barrier(new_obj) ||