Re: [Mesa-dev] [PATCH 2/2] blorp: Properly handle Z24X8 blits.

[Jason Ekstrand]

On August 10, 2018 04:18:51 Kenneth Graunke <kenn...@whitecape.org> wrote:
One of the reasons we didn't notice that R24_UNORM_X8_TYPELESS
destinations were broken was that an earlier layer was swapping it
out for B8G8R8A8_UNORM.  That made Z24X8 -> Z24X8 blits work.

However, R32_FLOAT -> R24_UNORM_X8_TYPELESS was still totally broken.
The old code only considered one format at a time, without thinking
that format conversion may need to occur.

This patch moves the translation out to a place where it can consider
both formats.  If both are Z24X8, we continue using B8G8R8A8_UNORM to
avoid having to do shader math workarounds.  If we have a Z24X8
destination, but a non-matching source, we use our shader hacks to
actually render to it properly.

Is the hack even all that useful? It's one more blorp shader compile.  I 
could see scaled depth blits being a thing people care about.  In fact, I 
know they will fairly soon if you catch my drift. :-)  Mind just dropping 
it completely?

--Jason


---
src/intel/blorp/blorp.c      | 12 ------------
src/intel/blorp/blorp_blit.c | 11 +++++++++++
2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/intel/blorp/blorp.c b/src/intel/blorp/blorp.c
index c36ec703b18..ffe26076e16 100644
--- a/src/intel/blorp/blorp.c
+++ b/src/intel/blorp/blorp.c
@@ -75,18 +75,6 @@ brw_blorp_surface_info_init(struct blorp_context *blorp,
   if (format == ISL_FORMAT_UNSUPPORTED)
      format = surf->surf->format;

-   if (format == ISL_FORMAT_R24_UNORM_X8_TYPELESS) {
-      /* Unfortunately, ISL_FORMAT_R24_UNORM_X8_TYPELESS it isn't supported as
-       * a render target, which would prevent us from blitting to 24-bit
-       * depth.  The miptree consists of 32 bits per pixel, arranged as 24-bit
-       * depth values interleaved with 8 "don't care" bits.  Since depth
-       * values don't require any blending, it doesn't matter how we interpret
-       * the bit pattern as long as we copy the right amount of data, so just
-       * map it as 8-bit BGRA.
-       */
-      format = ISL_FORMAT_B8G8R8A8_UNORM;
-   }
-
   info->surf = *surf->surf;
   info->addr = surf->addr;

diff --git a/src/intel/blorp/blorp_blit.c b/src/intel/blorp/blorp_blit.c
index 7b49f9afa35..3b84e634bd9 100644
--- a/src/intel/blorp/blorp_blit.c
+++ b/src/intel/blorp/blorp_blit.c
@@ -2241,6 +2241,17 @@ blorp_blit(struct blorp_batch *batch,
      }
   }

+   /* ISL_FORMAT_R24_UNORM_X8_TYPELESS it isn't supported as a render target,
+    * which requires shader math to render to it.  Blitting Z24X8 to Z24X8
+    * is fairly common though, so we'd like to avoid it.  Since we don't need
+    * to blend depth values, we can simply pick a renderable format with the
+    * right number of bits-per-pixel, like 8-bit BGRA.
+    */
+   if (dst_surf->surf->format == ISL_FORMAT_R24_UNORM_X8_TYPELESS &&
+       src_surf->surf->format == ISL_FORMAT_R24_UNORM_X8_TYPELESS) {
+      src_format = dst_format = ISL_FORMAT_B8G8R8A8_UNORM;
+   }
+
   brw_blorp_surface_info_init(batch->blorp, &params.src, src_surf, src_level,
                               src_layer, src_format, false);
   brw_blorp_surface_info_init(batch->blorp, &params.dst, dst_surf, dst_level,
--
2.18.0

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