Previous code was assuming that load_sample_id loaded the hardware
sample ID register, which is 32 when sample shading is disabled. The
expectation was that we would read (0.5,0.5) from sample_positions[32].
Because the top 3 bits of the sample ID register are masked out in
bi_load_sample_id_to, we were instead reading the position of the first
sample.
This doesn't affect OpenGL, because opengl never uses
nir_load_sample_pos when sample shading is disabled.
Signed-off-by: Benjamin Lee <benjamin.lee@collabora.com>
Fixes: 60146cc57c ("panvk: implement sampleRateShading")
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Mary Guillemard <mary.guillemard@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32601>
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