Compute Shaders + ExecutionMode's #195

charles-r-earp · 2020-10-30T21:39:13Z

Adds a wgpu compute shader example, "wgpu-example-compute-runner" and "wgpu-example-compute-shader". At minimum to compile and execute a compute shader, ie GLCompute, the execution mode LocalSize must be set. So this PR additionally adds a mechanism to do that:

#[spirv(gl_compute(local_size_x=64, local_size_y=16, local_size_z=4))]
pub fn main_cs() {}

Emulating GLSL, dimensions not specified default to 1 (gl_compute only).

The execution modes specified within a execution model, are collected into a Vec along with their arguments, and then this is sent as a SpirvAttribute::Entry, which is now special Entry struct. In entry.rs, the stub functions submit these execution modes.

I also added the fn compute_shader_entry_stub as a duplicate of shader_entry_stub, which in the future may handle function parameters differently.

I added the complete list of execution modes. There may be some additional logic for default values that I'm not familiar with, notably you can now specify OriginLowerLeft to vertex shaders, (OriginUpperLeft is the default). There isn't any error handling about which modes are valid per execution model, or specifying multiple conflicting modes. In general they are collected and submitted left to right.

All the tests passed.

…shader.

…ed changes do not break rendering example.

…cutionModel. Replaced SpirvAttribute::Entry ExecutionModel with an Entry struct, which includes a Vec of ExecutionMode, ExecutionModeExtra to be submitted in entry.rs. Compute example runs. Passes all tests.

repi · 2020-10-30T22:01:40Z

wow thanks for the contribution!

linking to #180

khyperia

Oh my goodness, I was gearing up to implement this, and then you just come along and, do it??? Thank you so so so very much, this is incredible! I'm very happy taking this as-is right now (with the -> bool rustc nightly version fixed) and addressing the other feedback in a follow-up (either me or you, either is fine by me).

khyperia · 2020-10-30T21:55:17Z

rustc_codegen_spirv/src/builder/mod.rs

        todo!()
    }

-    fn add_unreachable_region(&mut self, _instance: Instance<'tcx>, _region: CodeRegion) -> bool {
+    fn add_unreachable_region(&mut self, _instance: Instance<'tcx>, _region: CodeRegion) {


ah, these should actually return bool - make sure you're up to date with the nightly specified in rust-toolchain! (these were changed to return bool recently)

khyperia · 2020-10-30T22:00:40Z

rustc_codegen_spirv/src/codegen_cx/entry.rs

+            });
+    }
+
+    fn compute_shader_entry_stub(


There's a decent amount of duplication between this and shader_entry_stub (and the existing duplication with kernel too), it might be nice to refactor things into something a little better structured - but probably in a later PR (I can do so), this is fine as-is as a temp solution.

khyperia · 2020-10-30T22:08:57Z

rustc_codegen_spirv/src/symbols.rs

+                                        Fragment => {
+                                            //FIXME: Is this the correct default?
+                                            let origin_mode = origin_mode.unwrap_or(OriginUpperLeft);
+                                            e.execution_modes.push((origin_mode, ExecutionModeExtra::new([])));


This is a little convoluted code so I might be missing something, but it might be nice to only specify this if the user didn't do so themselves. (Considering we didn't even allow users to specify it before this PR, this is fine as-is for now, mostly just making a note that we should follow up on this later!)

This isn't a breaking change. The origin_mode variable is None, and replaced with OriginUpperLeft or OriginLowerLeft if specified. Before it was hardcoded in entry.rs for fragment shaders.

khyperia · 2020-10-30T22:09:51Z

rustc_codegen_spirv/src/symbols.rs

                }
+                result


This whole thing is super nested, it'd be really nice if we could split it into some smaller functions.

khyperia · 2020-10-30T22:10:45Z

examples/wgpu-example-compute-runner/src/main.rs

+
+fn main() {
+    let spirv = include_bytes_align_as!(u32, env!("wgpu_example_compute_shader.spv"));
+    println!("{}\n", disassemble_spirv(bytemuck::cast_slice(spirv)));


prooobably shouldn't include this, as all the other examples don't? but shrug, doesn't really matter either way.

examples/wgpu-example-compute-runner/Cargo.toml

…unner to be more similar to other wgpu example. Split of entry logic in symbol.rs to separate function. Fixed issue in builder/mod.rs.

khyperia · 2020-10-31T11:14:23Z

I'm not sure why CI isn't running on this - perhaps the merge conflicts need to get resolved first?

…moved really_unsafe_ignore_bitcasts to its own Symbol match. In entry.rs, entry stubs now return the fn_id, so that entry_stub() can add the execution modes in one place. Passed all tests.

charles-r-earp · 2020-11-07T04:16:26Z

Yes, merge conflicts are fixed.

khyperia

thanks so much!

khyperia · 2020-11-10T08:03:47Z

crates/rustc_codegen_spirv/src/symbols.rs

-        let custom = std::iter::once((
-            "really_unsafe_ignore_bitcasts",
-            SpirvAttribute::ReallyUnsafeIgnoreBitcasts,
-        ));


why split this out into its own thing?

I figured it was commonly used. And this logic matches descriptor_set, binding. But it probably should be reverted to how it was, in attributes.

khyperia · 2020-11-10T08:06:42Z

crates/rustc_codegen_spirv/src/symbols.rs

+                        .attributes
+                        .get(&name.name)
+                        .map(|a| match a {
+                            SpirvAttribute::Entry(entry) => SpirvAttribute::Entry(


I would prefer this gets handled in the same way descriptor_set and binding is handled, but whatever, that can be cleaned up later.

So you're saying add additional if else statements for each entry / execution_model? Wouldn't putting everything in the attributes HashMap scale better?

charles-r-earp added 3 commits October 27, 2020 11:51

Created examples/ wgpu-example-compute-runner + wgpu-example-compute-…

4b50875

…shader.

Working compute example, can compile and run, set local_size. Validat…

064824d

…ed changes do not break rendering example.

Added complete list of ExecutionMode's to be specified underneath Exe…

8aad72a

…cutionModel. Replaced SpirvAttribute::Entry ExecutionModel with an Entry struct, which includes a Vec of ExecutionMode, ExecutionModeExtra to be submitted in entry.rs. Compute example runs. Passes all tests.

repi requested a review from khyperia October 30, 2020 22:00

khyperia reviewed Oct 30, 2020

View reviewed changes

Changed Cargo license info for compute examples. Simplified compute r…

a1fea33

…unner to be more similar to other wgpu example. Split of entry logic in symbol.rs to separate function. Fixed issue in builder/mod.rs.

charles-r-earp mentioned this pull request Oct 31, 2020

Compute shader support & basic example #180

Closed

Kamayuq approved these changes Oct 31, 2020

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XAMPPRocky added the s: waiting on author PRs that blocked on the author implementing feedback. label Nov 2, 2020

charles-r-earp added 4 commits November 6, 2020 17:44

Pulled in reorganization changes to crates + examples. In symbols.rs …

990bee5

…moved really_unsafe_ignore_bitcasts to its own Symbol match. In entry.rs, entry stubs now return the fn_id, so that entry_stub() can add the execution modes in one place. Passed all tests.

Merge branch 'compute-shaders2' into compute-shaders

439cf78

cargo fmt

93b2859

Removed duplicate examples. Fixed cargo fmt bug in compute runner.

4de9fc7

XAMPPRocky added s: waiting on review PRs that blocked on a team member's review. and removed s: waiting on author PRs that blocked on the author implementing feedback. labels Nov 9, 2020

khyperia approved these changes Nov 10, 2020

View reviewed changes

mergify bot merged commit 32c2ea5 into EmbarkStudios:main Nov 10, 2020

charles-r-earp deleted the compute-shaders branch November 27, 2020 02:23

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Compute Shaders + ExecutionMode's #195

Compute Shaders + ExecutionMode's #195

charles-r-earp commented Oct 30, 2020

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Compute Shaders + ExecutionMode's #195

Compute Shaders + ExecutionMode's #195

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