If dual blending is enabled, only 1 output is supported. Multiple
outputs confuse the write combining pass in this case, leading to
incorrect output and/or an assert failure in emit_fragment_store.
The fix is straightforward, just skip the speculative emitting of
multiple outputs in the case where dual source blending is enabled.
This also adds an extra sanity check in `pan_nir_lower_zs_store` to
check for only one blend store being present.
Fixes: c65a9be421 ("panfrost: Preprocess shaders at CSO create time")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9487
Co-Authored-By: Eric R. Smith <eric.smith@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26474>
(cherry picked from commit 49c1b404e5)
7a27b2afba