tree a700373e065755a3069e466e7fad62eb3f1eb6f8
parent 92dc20779e7bbf52ef3ea63a7794126e0066aa30
author Albin Bernhardsson <albin.bernhardsson@arm.com> 1699381527 +0000
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> 1699381527 +0000

Improve Vulkan synchronization

Track resources per shader stage by using the visibility flags in the
bind group layout. This means we can insert more precise barriers,
allowing vertex and/or compute to execute in parallel with fragment
shading. Eg. if we have two render passes where the second render
pass samples an image rendered in the first in the fragment shader,
this would previously result in a FRAGMENT->VERTEX|FRAGMENT|COMPUTE
barrier as a texture can be sampled in any shader stage and only the
usage is considered when inserting the barrier. By considering the
shader stages, we can instead insert a FRAGMENT->FRAGMENT barrier.

Fix an issue where empty image memory barriers cause a
TOP_OF_PIPE->TOP_OF_PIPE barrier. On its own, this is a NOP, but when
merged with other barriers, the TOP_OF_PIPE in the destination stages
could cause unnecessarily conservative barriers.

Previously, all barriers in a sync scope were merged into one
pipeline barrier. Eg. if we have a render pass with one resource
being used in a vertex shader and was last written in compute (eg.
compute skinning), and a resource used in a fragment shader and last
written to by a render pass (eg. ambient occlusion), merging these
COMPUTE->VERTEX and FRAGMENT->FRAGMENT barriers would lead to a
COMPUTE|FRAGMENT->VERTEX|FRAGMENT barrier, inadvertently introducing
an unnecessary FRAGMENT->VERTEX dependency and disallowing parallel
execution. Change this so that all barriers which contain a vertex
stage in the destination stages are merged into one pipeline barrier,
and all remaining barriers into another.

In a Sponza test scene this reduces frame times by 17% on a Mali-G78
device.

Bug: dawn:851
Change-Id: I50e2f00f845670d7f161a0afa6579eba6057afa3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/151340
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Albin Bernhardsson <albin.bernhardsson@arm.com>