Allow array_index to be unsigned

[daxpedda]

Following the spec, functions with the parameter array_index, e.g. in combination with texture_2d_array, should be able to take a u32 as well:
https://www.w3.org/TR/WGSL/#textureload
https://www.w3.org/TR/WGSL/#texturesample
https://www.w3.org/TR/WGSL/#texturestore

(I have no clue how to link to a more permanent version of the spec)

[daxpedda]

Alright, this is far outside my comfort zone. Any help would be appreciated.

I assume that either some code was relying on this value being a i32 and has to be adjusted to take that into account or SPIR-V just doesn't allow a i32 in this case.

[teoxoy]

SPIR-V requires a vector containing the coordinates and the array index. The type of the vector has to match with the type of the scalars that compose it and it's here that we assume the array_index is signed:

naga/src/back/spv/image.rs

Lines 317 to 352 in 7c00548

	let array_index_i32_id = self.cached[array_index];
	let reconciled_array_index_id = if component_kind == crate::ScalarKind::Sint {
	array_index_i32_id
	} else if component_kind == crate::ScalarKind::Uint {
	let u32_id = self.get_type_id(LookupType::Local(LocalType::Value {
	vector_size: None,
	kind: crate::ScalarKind::Uint,
	width: 4,
	pointer_space: None,
	}));
	let reconciled_id = self.gen_id();
	block.body.push(Instruction::unary(
	spirv::Op::Bitcast,
	u32_id,
	reconciled_id,
	array_index_i32_id,
	));
	reconciled_id
	} else {
	let component_type_id = self.get_type_id(LookupType::Local(LocalType::Value {
	vector_size: None,
	kind: component_kind,
	width: 4,
	pointer_space: None,
	}));
	let reconciled_id = self.gen_id();
	block.body.push(Instruction::unary(
	spirv::Op::ConvertUToF,
	component_type_id,
	reconciled_id,
	array_index_i32_id,
	));
	reconciled_id
	};

[daxpedda]

@teoxoy thank you for the help. I hope I didn't go overkill on the checks here.
Happy to take advice on any code/style preferences you use in this repo.

[teoxoy]

@teoxoy thank you for the help. I hope I didn't go overkill on the checks here. Happy to take advice on any code/style preferences you use in this repo.

No problem :)
Could you also add a few more tests for this?

[daxpedda]

Could you also add a few more tests for this?

Could you point me in any specific direction, or do you have something in mind?

[teoxoy]

Thanks for addressing all the comments - looks great!

Could you also add a few more tests for this?

Could you point me in any specific direction, or do you have something in mind?

It seems the only test updated was textureLoad. I think we should at least test textureStore and textureSample as well. The other texture sampling functions use the same code paths so we might not need to test those.

[daxpedda]

Added a bunch more tests, hope that's not overkill.