How do you index into a &[&T] and deref a element?

[codecnotsupported]

#[spirv(vertex)]
pub fn vertex(
    #[spirv(instance_index)] instance: u32,
    #[spirv(uniform, descriptor_set = 0, binding = 0)] array_of_refs: &[&u32],
) {
    let val = *array_of_refs[instance as usize]; // Error
}

error: error:0:0 - [VUID-StandaloneSpirv-OpTypeRuntimeArray-04680] For Vulkan, an OpTypeStruct variable containing an OpTypeRuntimeArray must be decorated with BufferBlock if it has storage class Uniform.
         %array_of_refs = OpVariable %_ptr_Uniform__struct_42 Uniform

I'll be frank, I don't quite get the Spir-V validation error.

[codecnotsupported]

Well I just realized that this is due:
#68
However with:

#[spirv(vertex)]
pub fn fragment(
    #[spirv(instance_index)] instance: u32,
    #[spirv(storage_buffer, descriptor_set = 0, binding = 0)] array_of_refs: &[&u32],
) {
    let index_ref = *array_of_refs[instance as usize];
}

I still get:

error: error:0:0 - OpLoad Pointer <id> '657[%657]' is not a logical pointer.
         %658 = OpLoad %uint %657

[codecnotsupported]

It's not supported yet?
#237

[Firestar99]

I don't understand what &[&T] should do, in terms of function entry point signature. Like what are you trying to express, in plain English?

Here's some valid entry point args:

• &T / TypedBuffer<T>: a buffer descriptor pointing to (a single T)
• &[T] / TypedBuffer<[T]>: a buffer descriptor pointing to (many Ts)
• &RuntimeArray<TypedBuffer<T>> an array of (buffer descriptors pointing to (a single T)), using descriptor_indexing
• &RuntimeArray<TypedBuffer<[T]>> an array of (buffer descriptors pointing to (many Ts)), using descriptor_indexing

(RuntimeArray should really be named DescriptorArray IMO)

Or do you actually want "a buffer device address (BDA) pointer pointing to many (BDA pointers pointing to (T))", cause we don't have support for BDA yet.

[codecnotsupported]

Yep I wanted BDA but as you said it's not supported yet. #237

[Firestar99]

I will honestly say that BDA is just not a priority from our side right now. There's bigger issues to fix first, such as Rust enums (tagged unions), qptr (proper pointer emulation so slicing and taking reference works properly), the entry point redesign... And some of that stuff would have a significant impact on how BDA would be implemented, so I'm hesitant to start making something right now. But if you want to finish off that branch, we'd take the contribution!

[codecnotsupported]

Sounds like you already got your plate full.
I'm willing to give it a shot, though I've no experience with making a compiler backend so no promises.

What's the recommended place of discourse for asking questions on how Rust-GPU works?
Is it Github discussions, SPIR-V Wizards Club on Discord, or elsewhere?

[Firestar99]

There's an unofficial rust-gpu discord but github issues / discussions or the wizards club works as well