tree b0f6109841b6e48d14f4f37e0fae72f856f4bab1
parent 464d52cded161948f58a9f24fc1df3c4a0a3e2d7
author Austin Eng <enga@chromium.org> 1629495158 +0000
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> 1629495158 +0000

Initialize padding on buffer allocations

Buffer allocations in Dawn may be padded. This padding
could be visible, depending on how the backend
implements robust vertex buffer access. This commit
updates buffer creation to clear all padding bytes
immediately after creation.
It is not counted as a lazy clear.
And, add a test which reads off the end of a padded
vertex buffer to check that the padding bytes are also
initialized.

Also: Update Metal buffers to always allocate enough
space for Tint's vertex pulling, and pass the full
allocated size to Tint. While writing the test in this
commit, a bug was found where Tint assumes there is at
least 4 bytes in the vertex pulling buffer. The WebGPU
API currently allows zero-sized bindings, so Dawn needs
to always allocate enough space for one element.

Also: Update Vulkan vertex/index buffers to allocate
at least one more byte than requested because
vkCmdSetVertexBuffers and vkCmdSetIndexBuffer disallow
the offset to be equal to the buffer size. We need
at least one more byte to make zero-sized bindings
as the end of the buffer valid.

Lastly: Update helper so that a T2B copy of a single
row that touches all bytes in a buffer updates the
buffer state to be fully initialized. This is a small
optimization that is necessary to write the test.

Tested-In: https://chromium-review.googlesource.com/c/chromium/src/+/3107782
No-Try: true
Bug: dawn:837
Change-Id: I829f4764509c4ec784c5aeaaf40b6dcbd4be6866
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/62161
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
(cherry picked from commit ddd0a0a856a2bd7013e82291974f1107f02fc1a9)
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/62382