panfrost: Refactor sample shading state

Moves the decision to evaluate per-sample to link time instead of
draw-time, with an explicit property. No functional change.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8774>

src/gallium/drivers/panfrost/pan_assemble.c

@@ -350,6 +350,9 @@ panfrost_shader_compile(struct panfrost_context *ctx,
 
                 state->outputs_read = outputs_read >> FRAG_RESULT_DATA0;
 
+                /* EXT_shader_framebuffer_fetch requires per-sample */
+                state->sample_shading = outputs_read;
+
                 /* List of reasons we need to execute frag shaders when things
                  * are masked off */
 

src/gallium/drivers/panfrost/pan_cmdstream.c

@@ -527,9 +527,9 @@ panfrost_prepare_fs_state(struct panfrost_context *ctx,
         state->multisample_misc.multisample_enable = msaa;
         state->multisample_misc.sample_mask = (msaa ? ctx->sample_mask : ~0) & 0xFFFF;
 
-        /* EXT_shader_framebuffer_fetch requires per-sample */
-        bool per_sample = ctx->min_samples > 1 || fs->outputs_read;
-        state->multisample_misc.evaluate_per_sample = msaa && per_sample;
+        state->multisample_misc.evaluate_per_sample =
+                msaa && (ctx->min_samples > 1 || fs->sample_shading);
+
         state->multisample_misc.depth_function = zsa->base.depth_enabled ?
                 panfrost_translate_compare_func(zsa->base.depth_func) :
                 MALI_FUNC_ALWAYS;

src/gallium/drivers/panfrost/pan_context.h

@@ -216,6 +216,7 @@ struct panfrost_shader_state {
 
         /* Non-descript information */
         unsigned work_reg_count;
+        bool sample_shading;
         bool can_discard;
         bool writes_point_size;
         bool writes_depth;