[Mesa-dev] [PATCH 3/4] i965: Fix execution size of scalar TCS barrier setup code.

[Kenneth Graunke]

Previously, the scalar TCS backend was generating:

mov(8)   g17<1>UD     0x00000000UD    { align1 WE_all 1Q compacted };
and(8)   g17.2<1>UD   g0.2<0,1,0>UD   0x0001e000UD  { align1 WE_all 1Q };
shl(8)   g17.2<1>UD   g17.2<8,8,1>UD  0x0000000bUD  { align1 WE_all 1Q };
or(8)    g17.2<1>UD   g17.2<8,8,1>UD  0x00008200UD  { align1 WE_all 1Q };
send(8)  null<1>UW    g17<8,8,1>UD
         gateway (barrier msg) mlen 1 rlen 0 { align1 WE_all 1Q };

This is rubbish - g17.2<8,8,1>UD spans two registers, and is an illegal
region.  Not to mention it clobbers 8 channels of data when we only
wanted to touch m0.2.

Instead, we want:

mov(8)   g17<1>UD     0x00000000UD    { align1 WE_all 1Q compacted };
and(1)   g17.2<1>UD   g0.2<0,1,0>UD   0x0001e000UD  { align1 WE_all };
shl(1)   g17.2<1>UD   g17.2<0,1,0>UD  0x0000000bUD  { align1 WE_all };
or(1)    g17.2<1>UD   g17.2<0,1,0>UD  0x00008200UD  { align1 WE_all };
send(8)  null<1>UW    g17<8,8,1>UD
         gateway (barrier msg) mlen 1 rlen 0 { align1 WE_all 1Q };

Using component() accomplishes this.

Fixes GL44-CTS.tessellation_shader.tessellation_shader_tc_barriers.
barrier_guarded_read_write_calls on Skylake.  Probably fixes other
barrier issues on Gen8+.

Cc: mesa-stable at lists.freedesktop.org
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index df033e1..bb254d6 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -2420,7 +2420,7 @@ fs_visitor::nir_emit_tcs_intrinsic(const fs_builder &bld,
          break;
 
       fs_reg m0 = bld.vgrf(BRW_REGISTER_TYPE_UD, 1);
-      fs_reg m0_2 = byte_offset(m0, 2 * sizeof(uint32_t));
+      fs_reg m0_2 = component(m0, 2);
 
       const fs_builder fwa_bld = bld.exec_all();
 
-- 
2.9.3