mesa: fix blending when using luminance/intensity emulation

neither of these have a real alpha channel, so reuse the xrgb blend
clamping here to ensure the "right" alpha value is used

cc: mesa-stable

fixes:
spec@arb_texture_float@fbo-blending-formats

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17687>

src/broadcom/ci/broadcom-rpi4-fails.txt

@@ -144,9 +144,7 @@ spec@arb_shader_texture_lod@execution@arb_shader_texture_lod-texgrad,Fail
 spec@arb_shader_texture_lod@execution@arb_shader_texture_lod-texgradcube,Fail
 spec@arb_texture_float@fbo-blending-formats,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_ALPHA32F_ARB,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_INTENSITY16F_ARB,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_INTENSITY32F_ARB,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_LUMINANCE16F_ARB,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_LUMINANCE32F_ARB,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_LUMINANCE_ALPHA32F_ARB,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_RGB16F,Fail

src/gallium/drivers/crocus/ci/crocus-g41-fails.txt

@@ -129,8 +129,6 @@ spec@arb_texture_cube_map@copyteximage cube,Fail
 # 16-bit so that texture filtering worked, since GL 2.1 let you do that.
 # Crocus instead decided to follow r300 and other GL2 hardware in using the
 # requested size for storage even if the HW can't filter textures with it.
-spec@arb_texture_float@fbo-blending-formats,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_LUMINANCE32F_ARB,Fail
 spec@arb_texture_rg@fbo-blending-formats-float,Fail
 spec@arb_texture_rg@fbo-blending-formats-float@GL_RG32F,Fail
 spec@arb_texture_float@texwrap formats bordercolor,Fail

src/gallium/drivers/virgl/ci/virpipe-gl-fails.txt

@@ -579,8 +579,6 @@ spec@arb_texture_cube_map_array@fbo-generatemipmap-cubemap array s3tc_dxt1,Fail
 spec@arb_texture_float@fbo-blending-formats,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_ALPHA16F_ARB,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_ALPHA32F_ARB,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_INTENSITY16F_ARB,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_INTENSITY32F_ARB,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_RGB32F,Fail
 spec@arb_texture_float@fbo-clear-formats,Fail
 spec@arb_texture_float@fbo-clear-formats@GL_ALPHA16F_ARB,Fail
@@ -778,10 +776,6 @@ spec@ext_texture_shared_exponent@texwrap formats bordercolor,Fail
 spec@ext_texture_shared_exponent@texwrap formats bordercolor-swizzled,Fail
 spec@ext_texture_shared_exponent@texwrap formats bordercolor-swizzled@GL_RGB9_E5- swizzled- border color only,Fail
 spec@ext_texture_shared_exponent@texwrap formats bordercolor@GL_RGB9_E5- border color only,Fail
-spec@ext_texture_snorm@fbo-blending-formats,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_INTENSITY16_SNORM,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_INTENSITY8_SNORM,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_INTENSITY_SNORM,Fail
 spec@ext_texture_snorm@texwrap formats bordercolor,Fail
 spec@ext_texture_snorm@texwrap formats bordercolor-swizzled,Fail
 spec@ext_texture_snorm@texwrap formats bordercolor-swizzled@GL_ALPHA16_SNORM- swizzled- border color only,Fail

src/gallium/drivers/zink/ci/zink-lvp-fails.txt

@@ -137,10 +137,6 @@ spec@arb_sample_shading@samplemask 4 all@noms partition,Fail
 spec@arb_sample_shading@samplemask 4 all@sample mask_in_one,Fail
 spec@arb_shader_texture_lod@execution@arb_shader_texture_lod-texgrad,Fail
 spec@arb_texture_float@fbo-blending-formats,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_INTENSITY16F_ARB,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_INTENSITY32F_ARB,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_LUMINANCE16F_ARB,Fail
-spec@arb_texture_float@fbo-blending-formats@GL_LUMINANCE32F_ARB,Fail
 spec@arb_texture_float@fbo-blending-formats@GL_RGB32F,Fail
 
 spec@egl 1.4@eglterminate then unbind context,Fail
@@ -165,11 +161,6 @@ spec@ext_framebuffer_multisample@interpolation 4 centroid-edges,Fail
 spec@ext_framebuffer_multisample@interpolation 4 non-centroid-deriv-disabled,Fail
 spec@ext_framebuffer_multisample@interpolation 4 non-centroid-disabled,Fail
 spec@ext_framebuffer_object@fbo-blending-formats,Fail
-spec@ext_framebuffer_object@fbo-blending-formats@GL_INTENSITY,Fail
-spec@ext_framebuffer_object@fbo-blending-formats@GL_INTENSITY12,Fail
-spec@ext_framebuffer_object@fbo-blending-formats@GL_INTENSITY16,Fail
-spec@ext_framebuffer_object@fbo-blending-formats@GL_INTENSITY4,Fail
-spec@ext_framebuffer_object@fbo-blending-formats@GL_INTENSITY8,Fail
 spec@ext_framebuffer_object@fbo-blending-formats@GL_LUMINANCE12,Fail
 spec@ext_framebuffer_object@fbo-blending-formats@GL_LUMINANCE16,Fail
 spec@ext_framebuffer_object@fbo-blending-formats@GL_RGB10,Fail
@@ -201,13 +192,6 @@ spec@ext_image_dma_buf_import@ext_image_dma_buf_import-sample_yvu420,Fail
 spec@ext_image_dma_buf_import@ext_image_dma_buf_import-transcode-nv12-as-r8-gr88,Fail
 spec@ext_image_dma_buf_import@ext_image_dma_buf_import-unsupported_format,Fail
 spec@ext_packed_float@query-rgba-signed-components,Fail
-spec@ext_texture_snorm@fbo-blending-formats,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_INTENSITY16_SNORM,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_INTENSITY8_SNORM,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_INTENSITY_SNORM,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_LUMINANCE16_SNORM,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_LUMINANCE8_SNORM,Fail
-spec@ext_texture_snorm@fbo-blending-formats@GL_LUMINANCE_SNORM,Fail
 spec@ext_texture_swizzle@depth_texture_mode_and_swizzle,Fail
 spec@intel_performance_query@intel_performance_query-issue_2235,Fail
 spec@khr_texture_compression_astc@array-gl,Fail

src/mesa/main/fbobject.c

@@ -1290,7 +1290,7 @@ _mesa_test_framebuffer_completeness(struct gl_context *ctx,
    fb->_HasSNormOrFloatColorBuffer = GL_FALSE;
    fb->_HasAttachments = true;
    fb->_IntegerBuffers = 0;
-   fb->_RGBBuffers = 0;
+   fb->_BlendForceAlphaToOne = 0;
    fb->_FP32Buffers = 0;
 
    /* Start at -2 to more easily loop over all attachment points.
@@ -1451,8 +1451,10 @@ _mesa_test_framebuffer_completeness(struct gl_context *ctx,
          if (_mesa_is_format_integer_color(attFormat))
             fb->_IntegerBuffers |= (1 << i);
 
-         if (baseFormat == GL_RGB)
+         if ((baseFormat == GL_RGB && ctx->st->needs_rgb_dst_alpha_override) ||
-            fb->_RGBBuffers |= (1 << i);
+             (baseFormat == GL_LUMINANCE && !util_format_is_luminance(attFormat)) ||
+             (baseFormat == GL_INTENSITY && !util_format_is_intensity(attFormat)))
+            fb->_BlendForceAlphaToOne |= (1 << i);
 
          if (type == GL_FLOAT && _mesa_get_format_max_bits(attFormat) > 16)
             fb->_FP32Buffers |= (1 << i);

src/mesa/main/mtypes.h

@@ -2722,7 +2722,7 @@ struct gl_framebuffer
    bool _HasAttachments;
 
    GLbitfield _IntegerBuffers;  /**< Which color buffers are integer valued */
-   GLbitfield _RGBBuffers;  /**< Which color buffers have baseformat == RGB */
+   GLbitfield _BlendForceAlphaToOne;  /**< Which color buffers need blend factor adjustment */
    GLbitfield _FP32Buffers; /**< Which color buffers are FP32 */
 
    /* ARB_color_buffer_float */

src/mesa/state_tracker/st_atom_blend.c

@@ -148,14 +148,14 @@ blend_per_rt(const struct st_context *st, unsigned num_cb)
       return GL_TRUE;
    }
 
-   if (st->needs_rgb_dst_alpha_override && ctx->DrawBuffer->_RGBBuffers) {
+   if (ctx->DrawBuffer->_BlendForceAlphaToOne) {
       /* Overriding requires independent blend functions (not just enables),
        * require drivers exposing PIPE_CAP_RGB_OVERRIDE_DST_ALPHA_BLEND to
        * also expose PIPE_CAP_INDEP_BLEND_FUNC.
        */
       assert(st->has_indep_blend_func);
 
-      /* If some of the buffers are RGB, we may need to override blend
+      /* If some of the buffers are RGB or emulated L/I, we may need to override blend
        * factors that reference destination-alpha to constants.  We may
        * need different blend factor overrides per buffer (say one uses
        * a DST_ALPHA factor and another uses INV_DST_ALPHA), so we flip
@@ -269,8 +269,7 @@ st_update_blend( struct st_context *st )
          const struct gl_renderbuffer *rb =
             ctx->DrawBuffer->_ColorDrawBuffers[i];
 
-         if (st->needs_rgb_dst_alpha_override && rb &&
+         if (rb && (ctx->DrawBuffer->_BlendForceAlphaToOne & (1 << i))) {
-             (ctx->DrawBuffer->_RGBBuffers & (1 << i))) {
             struct pipe_rt_blend_state *rt = &blend->rt[i];
             rt->rgb_src_factor = fix_xrgb_alpha(rt->rgb_src_factor);
             rt->rgb_dst_factor = fix_xrgb_alpha(rt->rgb_dst_factor);