blorp: Properly handle Z24X8 blits.

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.

Fixes: 804856fa57 (intel/blorp: Handle more exotic destination formats)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

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;
 

src/intel/blorp/blorp_blit.c

@@ -2250,6 +2250,17 @@ 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,