4d802df3aa loosened the type restrictions
on these opcodes to enable support for 64-bit ballot operations. In
doing so, it enabled 8-bit and 16-bit sizes as well.
It's impossible to get these sizes through GLSL or SPIR-V. None of the
lowering in nir_opt_algebraic can handle non-32-bit sizes. Almost no
drivers can handle non-32-bit sizes.
It doesn't seem possible to enforce anything other than "one bit size"
or "all bit sizes" in nir_opcodes.py. The only way it seems possible to
enforce this is in nir_validate. This is not ideal, but it be what it
be.
v2: Remove restriction on find_lsb. It is acutally possible to get this
via GLSL by doing findLSB() on a lowp value. findMSB declares its
parameter as highp, so that path is still impossible.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19042>
db6d1edc1b