d3d12, dxil: Rework clip/cull distance handling
Clip/cull distance in DXIL is similar to GLSL in that it's up to 8 scalar floats between clip and cull, but looks a little different in that they're required to be chunked as 2 float4s, largely because that's how D3D has always expressed its I/O signatures. This series:
- Adds support for "compact" arrays of scalars to
nir_to_dxil, under the assumption that each compact array doesn't straddle a 4-component boundary.
- Adds a lowering pass to break apart arrays that would otherwise not be handled by
- Adds lowering/optimization passes to
spirv_to_dxilso that the above lowering pass can realistically work (requires a direct set of derefs from array var -> store).
- Opts the
d3d12driver into using compact arrays instead of the float4 representation, largely just for testing.
The goal here is to be able to handle clip/cull from SPIR-V, which currently always outputs the compact array scalars. Rather than try to back-convert them to the float4 approach, we can just handle the compact array directly.