Guarantee that OOB writes to storage textures will be ignored

[teoxoy]

See #3893 (comment)

[alan-baker]

We shipped the clamping behaviour on backends that need clamping. So we can't strengthen the spec in this way.

[teoxoy]

I see that tint is indeed clamping. But as far as I found that shouldn't be necessary.

Would this have to land in a v2 of the WGSL spec instead?

[jimblandy]

on backends that need clamping

@alan-baker Which backends need clamping? Teo is saying that none exist; if that's not the case, then that changes everything.

[alan-baker]

I thought remembered reading it UB on one platform, but I can't find that text anywhere. When I look through the various specs it does seem to that writes are discarded.

[jimblandy]

@alan-baker So, did Dawn actually ship clamping OOB texture writes on any backends, then?

[ben-clayton]

@alan-baker So, did Dawn actually ship clamping OOB texture writes on any backends, then?

Yes. We shipped M113 with clamping on all backends. Texture write clamping was recently disabled for D3D.

Based on #3893 (comment), perhaps we can do the same for other backends. We do have a GLSL backend - I haven't done my homework to determine whether OOB writes there are also automatically discarded.

[teoxoy]

The OpenGL 4.2+ and OpenGL ES 3.1+ specs say "Invalid image stores will have no effect.".