zink: add helper for applying/discarding clears based on a rect

this lets us test whether we're going to overwrite a scissored clear
region in order to correctly no-op it

Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9206>

src/gallium/drivers/zink/zink_clear.c

@@ -525,3 +525,46 @@ zink_clear_apply_conditionals(struct zink_context *ctx)
       }
    }
 }
+
+static void
+fb_clears_apply_or_discard_internal(struct zink_context *ctx, struct pipe_resource *pres, struct u_rect region, bool discard_only, int i)
+{
+   struct zink_framebuffer_clear *fb_clear = &ctx->fb_clears[i];
+   if (fb_clear->enabled) {
+      if (zink_blit_region_fills(region, pres->width0, pres->height0)) {
+         /* we know we can skip these */
+         zink_fb_clears_discard(ctx, pres);
+         return;
+      }
+      for (int j = 0; j < zink_fb_clear_count(fb_clear); j++) {
+         struct zink_framebuffer_clear_data *clear = zink_fb_clear_element(fb_clear, j);
+         struct u_rect scissor = {clear->scissor.minx, clear->scissor.maxx,
+                                  clear->scissor.miny, clear->scissor.maxy};
+         if (!clear->has_scissor || zink_blit_region_covers(region, scissor)) {
+            /* this is a clear that isn't fully covered by our pending write */
+            if (!discard_only)
+               fb_clears_apply_internal(ctx, pres, i);
+            return;
+         }
+      }
+      /* if we haven't already returned, then we know we can discard */
+      zink_fb_clears_discard(ctx, pres);
+   }
+}
+
+void
+zink_fb_clears_apply_or_discard(struct zink_context *ctx, struct pipe_resource *pres, struct u_rect region, bool discard_only)
+{
+   if (zink_resource(pres)->aspect == VK_IMAGE_ASPECT_COLOR_BIT) {
+      for (int i = 0; i < ctx->fb_state.nr_cbufs; i++) {
+         if (ctx->fb_state.cbufs[i] && ctx->fb_state.cbufs[i]->texture == pres) {
+            fb_clears_apply_or_discard_internal(ctx, pres, region, discard_only, i);
+            return;
+         }
+      }
+   }  else {
+      if (ctx->fb_clears[PIPE_MAX_COLOR_BUFS].enabled && ctx->fb_state.zsbuf && ctx->fb_state.zsbuf->texture == pres) {
+         fb_clears_apply_or_discard_internal(ctx, pres, region, discard_only, PIPE_MAX_COLOR_BUFS);
+      }
+   }
+}

src/gallium/drivers/zink/zink_context.h

@@ -340,6 +340,9 @@ zink_fb_clears_apply(struct zink_context *ctx, struct pipe_resource *pres);
 void
 zink_fb_clears_discard(struct zink_context *ctx, struct pipe_resource *pres);
 
+void
+zink_fb_clears_apply_or_discard(struct zink_context *ctx, struct pipe_resource *pres, struct u_rect region, bool discard_only);
+
 void
 zink_draw_vbo(struct pipe_context *pctx,
               const struct pipe_draw_info *dinfo,