Atomic operations and control barriers.

[jaankaup]

Are there any plans/scheludes to implement atomic types and control barriers on wgsl?

It seems the use of atomicAdd and barrier are working in GLSL => SPIR-V when I disable the shader validations (tested only with Vulkan/linux/win10). The wgpu-rs logs some warnings:

WARN [wgpu_core::device] Failed to parse shader SPIR-V code: UnsupportedInstruction(Function, ControlBarrier)
WARN [wgpu_core::device] Failed to parse shader SPIR-V code: UnsupportedInstruction(Function, AtomicIAdd)
WARN [wgpu_core::device] Proceeding unsafely without validation

What aren't these instructions supported? Some undefined behavior, compatibility issues?

I converted my marching cubes GLSL shader to wgsl, but it looks like there are no implementation for atomic<T> types yet.

https://github.com/jaankaup/wgpu_rs_project/blob/main/shaders_wgsl/mc_test.wgsl

The atomic types and atomicAdd seems to be the bottleneck in this case. If I comment out atomic related stuff, it compiles.

I'm really excited to get these compute shaders to work on web some day : ) .

[kvark]

WGSL's specification for these have been merged very recently, see:

• Add atomics to WGSL gpuweb/gpuweb#1448
• Add workgroupBarrier to WGSL gpuweb/gpuweb#1449

We are in process of adding support for these into Naga's IR, and consequently - the validation will recognize these constructs.
gfx-rs/naga#817