panfrost: Identify glProvokingVertex flag

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

src/gallium/drivers/panfrost/pan_context.c

@@ -1476,9 +1476,8 @@ panfrost_draw_vbo(
 
         draw_flags |= 0x3000;
 
-        if (mode == PIPE_PRIM_LINE_STRIP) {
-                draw_flags |= 0x800;
-        }
+        if (ctx->rasterizer && ctx->rasterizer->base.flatshade_first)
+                draw_flags |= MALI_DRAW_FLATSHADE_FIRST;
 
         panfrost_statistics_record(ctx, info);
 

src/panfrost/include/panfrost-job.h

@@ -884,6 +884,12 @@ struct mali_uniform_buffer_meta {
 #define MALI_DRAW_INDEXED_SHIFT  (4)
 
 #define MALI_DRAW_VARYING_SIZE   (0x100)
+
+/* Set to use first vertex as the provoking vertex for flatshading. Clear to
+ * use the last vertex. This is the default in DX and VK, but not in GL. */
+
+#define MALI_DRAW_FLATSHADE_FIRST (0x800)
+
 #define MALI_DRAW_PRIMITIVE_RESTART_FIXED_INDEX (0x10000)
 
 struct mali_vertex_tiler_prefix {