radeonsi: fix texture gather on stencil textures

At least on VI, texture gather doesn't work with a 24_8 data format, so
use 8_8_8_8 and a modified swizzle instead.

A bit of background: When creating a GL_STENCIL_INDEX8 texture, we select
the X24S8 pipe format because we don't support stencil-only render targets
properly. With mip-mapping this can lead to a setup where the tiling is
incompatible with stencil texturing, and a flushed stencil texture is
used. For the flushed stencil, a literal X24S8 is used because there were
issues with an 8bpp DB->CB copy.

Longer term, it would be good if we could get away from these workarounds,
i.e. properly support an S8 format for stencil-only rendering and flushed
stencil. Since stencil texturing is somewhat rare, it's not a high
priority.

Fixes GL45-CTS.texture_cube_map_array.sampling.

Cc: 17.0 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Acked-by: Edward O'Callaghan <funfunctor@folklore1984.net>

diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
index 0ec34f961acc60bf4764c007e000351b3f42092a..876cbf6a34b9ff78bcfe227e3a71644f57bcd9e1 100644 (file)
--- a/src/gallium/drivers/radeonsi/si_state.c
+++ b/src/gallium/drivers/radeonsi/si_state.c
@@ -1365,11 +1365,17 @@ static uint32_t si_translate_texformat(struct pipe_screen *screen,
                case PIPE_FORMAT_Z16_UNORM:
                        return V_008F14_IMG_DATA_FORMAT_16;
                case PIPE_FORMAT_X24S8_UINT:
+               case PIPE_FORMAT_S8X24_UINT:
+                       /*
+                        * Implemented as an 8_8_8_8 data format to fix texture
+                        * gathers in stencil sampling. This affects at least
+                        * GL45-CTS.texture_cube_map_array.sampling on VI.
+                        */
+                       return V_008F14_IMG_DATA_FORMAT_8_8_8_8;
                case PIPE_FORMAT_Z24X8_UNORM:
                case PIPE_FORMAT_Z24_UNORM_S8_UINT:
                        return V_008F14_IMG_DATA_FORMAT_8_24;
                case PIPE_FORMAT_X8Z24_UNORM:
-               case PIPE_FORMAT_S8X24_UINT:
                case PIPE_FORMAT_S8_UINT_Z24_UNORM:
                        return V_008F14_IMG_DATA_FORMAT_24_8;
                case PIPE_FORMAT_S8_UINT:
@@ -2796,14 +2802,22 @@ si_make_texture_descriptor(struct si_screen *screen,
        if (desc->colorspace == UTIL_FORMAT_COLORSPACE_ZS) {
                const unsigned char swizzle_xxxx[4] = {0, 0, 0, 0};
                const unsigned char swizzle_yyyy[4] = {1, 1, 1, 1};
+               const unsigned char swizzle_wwww[4] = {3, 3, 3, 3};
 
                switch (pipe_format) {
                case PIPE_FORMAT_S8_UINT_Z24_UNORM:
-               case PIPE_FORMAT_X24S8_UINT:
                case PIPE_FORMAT_X32_S8X24_UINT:
                case PIPE_FORMAT_X8Z24_UNORM:
                        util_format_compose_swizzles(swizzle_yyyy, state_swizzle, swizzle);
                        break;
+               case PIPE_FORMAT_X24S8_UINT:
+                       /*
+                        * X24S8 is implemented as an 8_8_8_8 data format, to
+                        * fix texture gathers. This affects at least
+                        * GL45-CTS.texture_cube_map_array.sampling on VI.
+                        */
+                       util_format_compose_swizzles(swizzle_wwww, state_swizzle, swizzle);
+                       break;
                default:
                        util_format_compose_swizzles(swizzle_xxxx, state_swizzle, swizzle);
                }