[Mesa-dev] [PATCH 09/12] i965/fs/skl+: Fix calculating gl_SampleID for 16x MSAA

[Neil Roberts]

In order to accomodate 16x MSAA, the starting sample pair index is now
3 bits rather than 2 on SKL+.
---
 src/mesa/drivers/dri/i965/brw_fs.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 82f49b4..bd9bcdd 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1300,9 +1300,16 @@ fs_visitor::emit_sampleid_setup()
        * are sample 1 of subspan 0; the third group is sample 0 of
        * subspan 1, and finally sample 1 of subspan 1.
        */
+
+      /* SKL+ has an extra bit for the Starting Sample Pair Index to
+       * accomodate 16x MSAA.
+       */
+      unsigned sspi_bits = devinfo->gen >= 9 ? 3 : 2;
+      unsigned sspi_mask = ((1 << sspi_bits) - 1) << 6;
+
       abld.exec_all()
           .AND(t1, fs_reg(retype(brw_vec1_grf(0, 0), BRW_REGISTER_TYPE_UD)),
-               fs_reg(0xc0));
+               fs_reg(sspi_mask));
       abld.exec_all().SHR(t1, t1, fs_reg(5));
 
       /* This works for both SIMD8 and SIMD16 */
-- 
1.9.3