[Mesa-dev] [PATCH v2 43/53] intel/eu: force stride of 2 on NULL register for Byte instructions

[Iago Toral Quiroga]

The hardware only allows a stride of 1 on a Byte destination for raw
byte MOV instructions. This is required even when the destination
is the NULL register.

Rather than making sure that we emit a proper NULL:B destination
every time we need one, just fix it at emission time.

Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
---
 src/intel/compiler/brw_eu_emit.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/intel/compiler/brw_eu_emit.c b/src/intel/compiler/brw_eu_emit.c
index 9232adcadc7..81474ae24f2 100644
--- a/src/intel/compiler/brw_eu_emit.c
+++ b/src/intel/compiler/brw_eu_emit.c
@@ -94,6 +94,17 @@ brw_set_dest(struct brw_codegen *p, brw_inst *inst, struct brw_reg dest)
    else if (dest.file != BRW_ARCHITECTURE_REGISTER_FILE)
       assert(dest.nr < 128);
 
+   /* The hardware has a restriction where if the destination is Byte,
+    * the instruction needs to have a stride of 2 (except for packed byte
+    * MOV). This seems to be required even if the destination is the NULL
+    * register.
+    */
+   if (dest.file == BRW_ARCHITECTURE_REGISTER_FILE &&
+       dest.nr == BRW_ARF_NULL &&
+       type_sz(dest.type) == 1) {
+      dest.hstride = BRW_HORIZONTAL_STRIDE_2;
+   }
+
    gen7_convert_mrf_to_grf(p, &dest);
 
    brw_inst_set_dst_file_type(devinfo, inst, dest.file, dest.type);
-- 
2.17.1