[Mesa-dev] [PATCH] i965: Align all depth miplevels to 8 in the X direction.

[Eric Anholt]

On an INTEL_DEBUG=perf piglit run on IVB, reduces the instances of "HW
workaround: blit" (the printouts from the misaligned-depth workaround
blits) from 725 to 684

It doesn't totally eliminate the workaround blit, because we still have
problems with Y offsets that we can't fix (since texturing can only align
miplevels up to 2 or 4, not 8).

No regressions on piglit/es3conform on IVB.
---
 src/mesa/drivers/dri/intel/intel_tex_layout.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/intel/intel_tex_layout.c b/src/mesa/drivers/dri/intel/intel_tex_layout.c
index 35030df..95242f8 100644
--- a/src/mesa/drivers/dri/intel/intel_tex_layout.c
+++ b/src/mesa/drivers/dri/intel/intel_tex_layout.c
@@ -77,7 +77,15 @@ intel_horizontal_texture_alignment_unit(struct intel_context *intel,
    if (format == MESA_FORMAT_S8)
       return 8;
 
-   if (intel->gen >= 7 && format == MESA_FORMAT_Z16)
+   /* The depth alignment requirements in the table above are for rendering to
+    * depth miplevels using the LOD control fields.  We don't use LOD control
+    * fields, and instead use page offsets plus intra-tile x/y offsets, which
+    * require that the low 3 bits are zero.  To reduce the number of x/y
+    * offset workaround blits we do, align the X to 8, which depth texturing
+    * can handle (sadly, it can't handle 8 in the Y direction).
+    */
+   if (intel->gen >= 4 &&
+       _mesa_get_format_base_format(format) == GL_DEPTH_COMPONENT)
       return 8;
 
    return 4;
-- 
1.7.10.4