Quote from the OpenGL Shading Language spec, version 4.40, section 8.9.2
"Texel Lookup Functions":
> The offset value must be a constant expression.
So, until we start consuming SPIR-V shaders, it seems we don't need to
deal with non-constant offsets.
This means we can avoid lowering this away in some cases.
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8327>
b77f43f253