Re: [PATCH v15 0/4] MR564: vkd3d-shader/ir: Transform clip/cull signature elements into an array.

[Zebediah Figura (＠zfigura)]

Zebediah Figura (@zfigura) commented about libs/vkd3d-shader/ir.c:
> - memmove(&reg->idx[1], &reg->idx[0], reg->idx_count * sizeof(reg->idx[0]));
> - memset(&reg->idx[0], 0, sizeof(reg->idx[0]));
> - ++reg->idx_count;
> -
> - if (vsir_write_mask_component_count(write_mask) == 1)
> - {
> -
>    reg->idx[0].offset = array_offset + vsir_swizzle_get_component(src_param->swizzle,
> -
>            vsir_write_mask_get_component_idx(write_mask));
> -
>    src_param->swizzle = 0;
> -
>    return;
> - }
> -
> - for (i = 0, handled_mask = 0; i < VKD3D_VEC4_SIZE; ++i)
> - {
> -
>    if (!(write_mask & (1u << i)))
> -
>        continue;

That said, though, the write mask logic here assumes that all instructions consuming clip/cull behave like mov with respect to write mask. Is that actually valid? E.g. for a somewhat pathological example, the coords argument of SAMPLE doesn't.

If the point is to avoid writing any out of bounds accesses (i.e. component_idx >= signature->s[element_idx].register_count), should we instead just replace such out of bounds accesses with zero or something?