intel/fs: Add the group to the flag subreg number on SNB and older

We want consistent behavior in the meaning of the flag_subreg field
between SNB and IVB+.

v2 (Jason Ekstrand):
 - Add some extra commentary

Reviewed-by: Jason Ekstrand <[email protected]>
Reviewed-by: Matt Turner <[email protected]>

1 files changed, 7 insertions, 1 deletions

diff --git a/src/intel/compiler/brw_fs_generator.cpp b/src/intel/compiler/brw_fs_generator.cpp
index b06cd0f576c..a01d32000b2 100644
--- a/src/intel/compiler/brw_fs_generator.cpp
+++ b/src/intel/compiler/brw_fs_generator.cpp
@@ -1815,7 +1815,13 @@ fs_generator::generate_code(const cfg_t *cfg, int dispatch_width)
       brw_set_default_access_mode(p, BRW_ALIGN_1);
       brw_set_default_predicate_control(p, inst->predicate);
       brw_set_default_predicate_inverse(p, inst->predicate_inverse);
-      brw_set_default_flag_reg(p, inst->flag_subreg / 2, inst->flag_subreg % 2);
+      /* On gen7 and above, hardware automatically adds the group onto the
+       * flag subregister number.  On Sandy Bridge and older, we have to do it
+       * ourselves.
+       */
+      const unsigned flag_subreg = inst->flag_subreg +
+         (devinfo->gen >= 7 ? 0 : inst->group / 16);
+      brw_set_default_flag_reg(p, flag_subreg / 2, flag_subreg % 2);
       brw_set_default_saturate(p, inst->saturate);
       brw_set_default_mask_control(p, inst->force_writemask_all);
       brw_set_default_acc_write_control(p, inst->writes_accumulator);