runtime: use buffered write barrier for bulkBarrierPreWrite

This modifies bulkBarrierPreWrite to use the buffered write barrier
instead of the eager write barrier. This reduces the number of system
stack switches and sanity checks by a factor of the buffer size
(currently 256). This affects both typedmemmove and typedmemclr.

Since this is purely a runtime change, it applies to all arches
(unlike the pointer write barrier).

name                 old time/op  new time/op  delta
BulkWriteBarrier-12  7.33ns ± 6%  4.46ns ± 9%  -39.10%  (p=0.000 n=20+19)

Updates #22460.

Change-Id: I6a686a63bbf08be02b9b97250e37163c5a90cdd8
Reviewed-on: https://go-review.googlesource.com/73832
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

0 files changed, 0 insertions, 0 deletions