cacc3f03e6
When per-sample shading is forced and all input variables have a flat interpolation, DXIL validation detects a mismatch between the SampleFrequency property and the fact that no variables are per-sample and SV_SampleIndex is never read. When that happens, add a dummy SV_SampleIndex. Reviewed-by: Jesse Natalie <jenatali@microsoft.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15916>