WGSL Validation tests for textureSampleCompare

[greggman]

I notice the offset option was missing in one case in the textureSample tests so that's included here. I can put it in another PR if it's important.

---

Requirements for reviewer sign-off:

• Tests are properly located in the test tree.
• Test descriptions allow a reader to "read only the test plans and evaluate coverage completeness", and accurately reflect the test code.
• Tests provide complete coverage (including validation control cases). Missing coverage MUST be covered by TODOs.
• Helpers and types promote readability and maintainability.

When landing this PR, be sure to make any necessary issue status updates.

[ben-clayton]

Looks good. Just some nits.

[ben-clayton]

It took me a while to figure out why this was not causing failures for u32. value includes -9, -8, and I was expecting this to result in -9u, -8u which would result in: error: no matching overload for operator - (u32).

However, ScalarType.create() calls u32(value), which is implemented as:

cts/src/webgpu/util/conversion.ts

Lines 1631 to 1635 in f1aa942

	/** Create a u32 from a numeric value, a JS `number`. */
	export function u32(value: number) {
	workingDataU32[0] = value;
	return new U32Value(workingDataU32[0]);
	}

So, we end up with the two's complement. This is unexpected in this context.

We're not trying to test for unsigned integers handling negative numbers, so I'd suggest changing the value range to just include positive numbers.

Same thing applies for the other tests.

[greggman]

I see what you're saying about -8u getting converted via Uint32Array but I need negative numbers to test offset which is required to generate an error for values < -8 and it will end up doing the same thing, passing -8 to offsetArgType.create() with those values when offsetArgType is u32.

I switched to filtering out negative values with unsigned types

[ben-clayton]

The same test could be achieved with var l : ${offsetArgType};, which would reduce the complexity of the shader.

[greggman]

It needed to be var l : ${offsetArgType.create(0).wgsl()};, AFAICT. Just checking I'm not missing something.