anv: Always use point size from the shader

There is no API for setting the point size and the shader is always
required to set it. Section 24.4:

   "If the value written to PointSize is less than or equal to zero, or
    if no value was written to PointSize, results are undefined."

As such, we can just always program PointWidthSource to Vertex. This
simplifies anv_pipeline a bit and avoids trouble when we enable the
pipeline cache and don't have writes_point_size in the prog_data.

src/intel/vulkan/anv_pipeline.c

@@ -469,8 +469,6 @@ anv_pipeline_compile_vs(struct anv_pipeline *pipeline,
          ralloc_steal(mem_ctx, nir);
 
       prog_data.inputs_read = nir->info.inputs_read;
-      if (nir->info.outputs_written & (1ull << VARYING_SLOT_PSIZ))
-         pipeline->writes_point_size = true;
 
       brw_compute_vue_map(&pipeline->device->info,
                           &prog_data.base.vue_map,
@@ -556,9 +554,6 @@ anv_pipeline_compile_gs(struct anv_pipeline *pipeline,
       if (module->nir == NULL)
          ralloc_steal(mem_ctx, nir);
 
-      if (nir->info.outputs_written & (1ull << VARYING_SLOT_PSIZ))
-         pipeline->writes_point_size = true;
-
       brw_compute_vue_map(&pipeline->device->info,
                           &prog_data.base.vue_map,
                           nir->info.outputs_written,
@@ -1122,7 +1117,6 @@ anv_pipeline_init(struct anv_pipeline *pipeline,
       anv_finishme("VK_STRUCTURE_TYPE_PIPELINE_TESSELLATION_STATE_CREATE_INFO");
 
    pipeline->use_repclear = extra && extra->use_repclear;
-   pipeline->writes_point_size = false;
 
    /* When we free the pipeline, we detect stages based on the NULL status
     * of various prog_data pointers.  Make them NULL by default.

src/intel/vulkan/anv_private.h

@@ -1409,7 +1409,6 @@ struct anv_pipeline {
 
    bool                                         use_repclear;
 
-   bool                                         writes_point_size;
    const struct brw_stage_prog_data *           prog_data[MESA_SHADER_STAGES];
    uint32_t                                     scratch_start[MESA_SHADER_STAGES];
    uint32_t                                     total_scratch;

src/intel/vulkan/gen7_pipeline.c

@@ -65,7 +65,7 @@ gen7_emit_rs_state(struct anv_pipeline *pipeline,
 
       /* uint32_t                                     AALineDistanceMode; */
       /* uint32_t                                     VertexSubPixelPrecisionSelect; */
-      .UsePointWidthState                       = !pipeline->writes_point_size,
+      .UsePointWidthState                       = false,
       .PointWidth                               = 1.0,
       .GlobalDepthOffsetEnableSolid             = info->depthBiasEnable,
       .GlobalDepthOffsetEnableWireframe         = info->depthBiasEnable,

src/intel/vulkan/gen8_pipeline.c

@@ -60,7 +60,7 @@ emit_rs_state(struct anv_pipeline *pipeline,
       .TriangleStripListProvokingVertexSelect = 0,
       .LineStripListProvokingVertexSelect = 0,
       .TriangleFanProvokingVertexSelect = 1,
-      .PointWidthSource = pipeline->writes_point_size ? Vertex : State,
+      .PointWidthSource = Vertex,
       .PointWidth = 1.0,
    };