This basically processes UBO loads as uniform loads by writing
the load address to the unifa register and reading sequential
values with ldunifa.
This process is faster than going through the TMU, but we can only
use it when the address we are reading from is uniform across all
channels, since we are basically reading from the UBO address
as if it was a uniform stream.
This leads to better performance in the UE4 Shooter demo.
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8980>
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