[Mesa-dev] [PATCH] radeonsi: fix texture gather on stencil textures

[Edward O'Callaghan]

Acked-by: Edward O'Callaghan <funfunctor at folklore1984.net>

On 01/18/2017 07:32 PM, Nicolai Hähnle wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
> 
> 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.
> ---
>  src/gallium/drivers/radeonsi/si_state.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
> index 865a75d..c1a6652 100644
> --- a/src/gallium/drivers/radeonsi/si_state.c
> +++ b/src/gallium/drivers/radeonsi/si_state.c
> @@ -1363,11 +1363,17 @@ 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:
> @@ -2794,14 +2800,22 @@ 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);
>  		}
> 

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