gallium/util: Introduce a helper for finding whole-resource blits.

This can be useful for tilers to discard previous rendering to a buffer
instead of reloading before drawing all the pixels.

Reviewed-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11455>

1 files changed, 47 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/util/u_inlines.h b/src/gallium/auxiliary/util/u_inlines.h
index 958b117ddc3..cd6e9351352 100644
--- a/src/gallium/auxiliary/util/u_inlines.h
+++ b/src/gallium/auxiliary/util/u_inlines.h
@@ -34,6 +34,7 @@
 #include "pipe/p_state.h"
 #include "pipe/p_screen.h"
 #include "util/compiler.h"
+#include "util/format/u_format.h"
 #include "util/u_debug.h"
 #include "util/u_debug_describe.h"
 #include "util/u_debug_refcnt.h"
@@ -781,6 +782,52 @@ util_texrange_covers_whole_level(const struct pipe_resource *tex,
           depth == util_num_layers(tex, level);
 }
 
+/**
+ * Returns true if the blit will fully initialize all pixels in the resource.
+ */
+static inline bool
+util_blit_covers_whole_resource(const struct pipe_blit_info *info)
+{
+   /* No conditional rendering or scissoring.  (We assume that the caller would
+    * have dropped any redundant scissoring)
+    */
+   if (info->scissor_enable || info->window_rectangle_include || info->render_condition_enable || info->alpha_blend)
+      return false;
+
+   const struct pipe_resource *dst = info->dst.resource;
+   /* A single blit can't initialize a miptree. */
+   if (dst->last_level != 0)
+      return false;
+
+   assert(info->dst.level == 0);
+
+   /* Make sure the dst box covers the whole resource. */
+   if (!(util_texrange_covers_whole_level(dst, 0,
+         0, 0, 0,
+         info->dst.box.width, info->dst.box.height, info->dst.box.depth))) {
+      return false;
+   }
+
+   /* Make sure the mask actually updates all the channels present in the dst format. */
+   if (info->mask & PIPE_MASK_RGBA) {
+      if ((info->mask & PIPE_MASK_RGBA) != PIPE_MASK_RGBA)
+         return false;
+   }
+
+   if (info->mask & PIPE_MASK_ZS) {
+      const struct util_format_description *format_desc = util_format_description(info->dst.format);
+      uint32_t dst_has = 0;
+      if (util_format_has_depth(format_desc))
+         dst_has |= PIPE_MASK_Z;
+      if (util_format_has_stencil(format_desc))
+         dst_has |= PIPE_MASK_S;
+      if (dst_has & ~(info->mask & PIPE_MASK_ZS))
+         return false;
+   }
+
+   return true;
+}
+
 static inline bool
 util_logicop_reads_dest(enum pipe_logicop op)
 {