Suballocation works incorrectly

[xiaopengli89]

Description
Related to #3544

Repro steps
Uploading transparent pixel data

Expected vs observed behavior
Transparent pixels should be rendered correctly

Extra materials

Platform
os: Win10
gpu: Intel iris xe
wgpu: 0.15 with dx12 backend

[Elabajaba]

I can't reproduce this on windows+AMD. Do you have a small example to demonstrate this? (also Intel's Xe GPU drivers are a mess, have you updated them recently?)

[xiaopengli89]

This problem does not necessarily happen, it needs to repeatedly create textures and upload data, the intel driver version has been updated to the latest. I guess it is a driver bug, so I added a feature to manually turn off suballocation optimization.

[xiaopengli89]

Initializing DX12 Textures After Allocation and Aliasing, I think we should initialize the memory before writing data to it.

[xiaopengli89]

It informs the driver that the current content of the resource might be garbage; we know about it, and we don't care, we don't need it, not going to read it, just going to fill the entire resource with a new content.

[teoxoy]

@xiaopengli89 does this happen only when uploading data to RGBA textures?

Would it be possible for you to put together an example we could try to reproduce?

[xiaopengli89]

Since I can't solve this problem, can wgpu add a feature to disable suballoction?

[teoxoy]

Do you have any updates from intel?

I don't think requiring users to manually work around it is something we want to rely on. If this is driver issue we should instead try to implement a workaround in wgpu.

cc @cwfitzgerald

[xiaopengli89]

Do you have any updates from intel?

No, even after installing the latest xe driver, the problem still exists.

[cwfitzgerald]

Yes, we should deal with this internally by using the old route on Xe