[Mesa-dev] [PATCH 7/7] i965/blorp: Allow format conversions.

[Kenneth Graunke]

BLORP performs blits by drawing a rectangle with a shader that samples
from the source texture, and writes color data to the destination.

The sampler always returns 32-bit RGBA float data, regardless of the
source format's component ordering or data type.  Likewise, the render
target write message takes 32-bit RGBA float data, and converts it
appropriately.  So the bulk of the work is already taken care of for us.

This greatly accelerates a lot of blits and CopyTexSubImage calls, and
makes Legends of Aethereus playable on Ivybridge.  At the default
settings, LOA continually blits between SRGBA8888 (the window format)
and RGBA16_FLOAT.  Since neither BLORP nor our BLT paths supported this,
it fell back to meta, spending 33% of the CPU in floorf() converting
between floats and half-floats.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_blorp_blit.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
index 2427085..c44f7c4 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
@@ -353,10 +353,23 @@ brw_blorp_copytexsubimage(struct brw_context *brw,
    if (brw->gen < 6)
       return false;
 
-   if (!color_formats_match(src_mt->format, dst_mt->format)) {
+   if (_mesa_get_format_base_format(src_mt->format) !=
+       _mesa_get_format_base_format(dst_mt->format)) {
       return false;
    }
 
+   /* We can't handle format conversions between Z24 and other formats since
+    * we have to lie about the surface format.  See the comments in
+    * brw_blorp_surface_info::set().
+    */
+   if ((src_mt->format == MESA_FORMAT_X8_Z24) ^
+       (dst_mt->format == MESA_FORMAT_X8_Z24)) {
+      return false;
+   }
+
+   if (!brw->format_supported_as_render_target[dst_mt->format])
+      return false;
+
    /* Source clipping shouldn't be necessary, since copytexsubimage (in
     * src/mesa/main/teximage.c) calls _mesa_clip_copytexsubimage() which
     * takes care of it.
-- 
1.8.3.2