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WGSL 2021 10 05 Minutes

Jeff Gilbert edited this page Oct 6, 2021 · 1 revision

WGSL 2021-10-05 Minutes

🪑 Chair: Jeff Gilbert

⌨️ Scribe: David Neto, Jeff Gilbert

🗺 Location:

🌐 Timezone: America/Los_Angeles

⌚ Time: Tuesday 5pm-6pm (APAC)


Meeting Issues: Marked Issues

Open Issues: WGSL Issues

Note: These are the minutes taken in real-time. The official minutes can be found on the WebGPU wiki.

If you didn't receive a invitation and plan on participating, please send dneto a Google Apps enabled address and he'll add you.

📋 Attendance

WIP, the list of all the people invited to the meeting. In bold, the people that have been seen in the meeting:

  • Apple
    • Myles C. Maxfield
    • Robin Morisset
  • Google
    • Alan Baker
    • Antonio Maiorano
    • Ben Clayton
    • Brandon Jones
    • Corentin Wallez
    • David Neto
    • Ekaterina Ignasheva
    • Kai Ninomiya
    • James Darpinian
    • James Price
    • Rahul Garg
    • Ryan Harrison
    • Sarah Mashayekhi
  • Intel
    • Narifumi Iwamoto
    • Yunchao He
  • Microsoft
    • Damyan Pepper
    • Greg Roth
    • Michael Dougherty
    • Rafael Cintron
    • Tex Riddell
  • Mozilla
    • Dzmitry Malyshau
    • Jeff Gilbert
    • Jim Blandy
  • Kings Distributed Systems
    • Daniel Desjardins
    • Hamada Gasmallah
    • Wes Garland
  • Dominic Cerisano
  • Eduardo H.P. Souza
  • Joshua Groves
  • Kris & Paul Leathers
  • Lukasz Pasek
  • Matijs Toonen
  • Mehmet Oguz Derin
  • Michael Shannon
  • Pelle Johnsen
  • Timo de Kort
  • Tyler Larson

📢 Announcements

Unscheduled News

  • MM: Apple is ok removing depth types for samplers.
  • DM: Under the assumption that users specify it in the binding layout?
  • DM: If the pipeline layout knows it’s depth, we can generate the right MSL when compiling at pipeline compilation time
  • MM: We would be ok if shaders that used depth textures didn’t need to be distinguished from non-depth textures within the shader.
  • MM to take AI to write about this in its issue
  • MM: BTW: Metal argument encoders (objective C argument that is used to populate an argument buffer) don’t differentiate between depth and normal textures, fwiw. Just like passing a depth texture to a non-depth type de facto works, it should work just the same there.

Office Hour

On Todos

  • (JG: I will make a spreadsheet for thumbs-up/down/maybe for each todo)

⏳ Timeboxes

  • DN: Trying to use “memory” instead of “storage” in most places. Some other minor fixes.
  • DM: I feel that “storage” etc in WGSL has been confusing from the start, and I like that we should fix it.
  • DN: Would like to have that larger talk in another issue** (DM to follow up)**
  • MM: PR seems good though.
  • JG will merge
  • Since last time:
    • rebased against main
    • as requested, unify phony-assignment more closely with regular assignment
    • regular assignment is now called "updating assignment"
    • Also, for a phony assignment, the type of the right-hand-side is not restricted. So you can do nice things like _ = buffer_with_runtime_sized_array because that RHS is a reference, and the Load Rule does not kick in.
    • Still removes the ignore builtin. (So speak up if you want to keep it)
  • MM: I wonder how the wording is going to work with e.g. let a,_ = foo(), like would it be required to be constructable?
  • DN: Well we don’t have multiple assignment yet.
  • DM: Why not just require &tex, instead of having this extra complication in the specification we write.
  • DN: I can put that back.
  • MM: Either sounds fine.
  • DN to fix and merge after DM approval
  • MOD: Applied some straightforward feedback. Can bikeshed over some details offline. Makes it easier to read on mobile (wraps the formatting). Uses Bikeshed dfn to create each node.
  • DN: Have you changed the flow to keep the grammar rules as before, but then generate to inser bikeshed definitions.?
  • MOD: That’s what I did originally, and then inserted the result. But didn’t want to introduce an extra script in everyone else’s flow.
  • DM: Outcome is what we definitely want. The boilerplate of writing bikeshed definitions will be painful to maintain. Will hit the editor most.
  • DM: Do other groups have script-processed bikeshed?
  • MM: CSS has a grammar, but bikeshed has special support for CSS because BS was originally made for CSS.
  • MM: Good direction, but has a positive result we definitely want
  • DN: Take 2 actions 1. Will reconsider how bad it really is to maintain the grammar in the proposed form (is it that big a burden), and 2. Reach out to Tab Atkins (Bikeshed maintainer) to see if there are grammar-friendly facilities in Bikeshed that we could use better, or perhaps add some.
  • MOD: Making them optional can be simpler for authors, when writing original source. Otherwise, can always add p0 exponent at the end.
  • DN: Want to keep it the same as C99, which is where feature came from.
  • JG: Is it necessary to disambiguate?
  • DN:: No. Already have 0x and a mandatory ‘.’ that already disinguishes.
  • JB: I’d like to write hex floats, and would like it to be optional. It’s more convenient
  • MOD to write PR
  • DN: I looked at the registry and could not find GLSL, C, or many other languages. CLosest I could find was application/javascript. That’s a close enough analog to suggest application/wgsl. But I’m no expert.
  • JG: Let’s do application/wgsl until someone says we’re wrong.
  • JG: This seems like a harsh reality that we have to accept
  • MM: If you don’t like it, don’t use vectors
  • Accept PR

⚖️ Discussions

  • Let’s do it!
  • MM: For these limit values, where are they from?
  • DN: SPIR-V
  • MM: Can we lower after V1
  • DN: Not really. Implementation could emit an “uncategorized error”, but that’s a bad experience. We should test before V1 and change if we need to.
  • MM: Haven’t heard anyone complain about MSL not supporting this. Would rather forbid in the language than try to emulate somehow.
  • DN: One approach would be to translate vec4 as float[4], which would work in MTL. There could be a perf cliff, but that’s up to the user to run into and solve if needed.
  • MM: Seems scary. E.g. builtins would need to handle both? Go in and out?
  • DN: Yeah, but that’s probably ok? I think we’re investigating it. I’m pretty aggressive about this one, and we’re not at-consensus within Google yet.
  • MM: So you may have already paid the implementation cost, and you are evaluating the perf cost. How do you feel about my assertion about usefulness?
  • DN: I feel like removing this adds an orthogonality to the language, which I would like to avoid.
  • DM: Maybe could have reference to the element of vector, but not a pointer to the element of the vector?
  • JB: So we’d have a carve-out to forbid converting certain refs into pointers?
  • JB: Maybe we should ask MSL people, if they were to support this, how would they do it?
  • MM: Can’t speak for them, but I expect them to say “drivers don’t have that functionality”.
  • Check back next meeting, but no promises

📆 Next Meeting Agenda

  • Next meeting: 2021-10-12 (non-APAC 11am time)
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