radv: fix enabling sample shading with SampleID/SamplePosition

When a fragment shader includes an input variable decorated with
SampleId or SamplePosition, sample shading should be enabled
because minSampleShadingFactor is expected to be 1.0.

Cc: 19.2, 19.3 <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

diff --git a/src/amd/vulkan/radv_pipeline.c b/src/amd/vulkan/radv_pipeline.c
index dc2cbc4884be3aebfc03a960ce09f6d8ecfbe50b..95b1684fdf827da35a185464718299471592db05 100644 (file)
--- a/src/amd/vulkan/radv_pipeline.c
+++ b/src/amd/vulkan/radv_pipeline.c
@@ -1099,15 +1099,32 @@ radv_pipeline_init_multisample_state(struct radv_pipeline *pipeline,
        int ps_iter_samples = 1;
        uint32_t mask = 0xffff;
 
-       if (vkms)
+       if (vkms) {
                ms->num_samples = vkms->rasterizationSamples;
-       else
-               ms->num_samples = 1;
 
-       if (vkms)
-               ps_iter_samples = radv_pipeline_get_ps_iter_samples(vkms);
-       if (vkms && !vkms->sampleShadingEnable && pipeline->shaders[MESA_SHADER_FRAGMENT]->info.ps.force_persample) {
-               ps_iter_samples = ms->num_samples;
+               /* From the Vulkan 1.1.129 spec, 26.7. Sample Shading:
+                *
+                * "Sample shading is enabled for a graphics pipeline:
+                *
+                * - If the interface of the fragment shader entry point of the
+                *   graphics pipeline includes an input variable decorated
+                *   with SampleId or SamplePosition. In this case
+                *   minSampleShadingFactor takes the value 1.0.
+                * - Else if the sampleShadingEnable member of the
+                *   VkPipelineMultisampleStateCreateInfo structure specified
+                *   when creating the graphics pipeline is set to VK_TRUE. In
+                *   this case minSampleShadingFactor takes the value of
+                *   VkPipelineMultisampleStateCreateInfo::minSampleShading.
+                *
+                * Otherwise, sample shading is considered disabled."
+                */
+               if (pipeline->shaders[MESA_SHADER_FRAGMENT]->info.ps.force_persample) {
+                       ps_iter_samples = ms->num_samples;
+               } else {
+                       ps_iter_samples = radv_pipeline_get_ps_iter_samples(vkms);
+               }
+       } else {
+               ms->num_samples = 1;
        }
 
        const struct VkPipelineRasterizationStateRasterizationOrderAMD *raster_order =