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

[Alejandro Piñeiro]

Reviewed-by: Alejandro Piñeiro <apinheiro at igalia.com>

On 17/08/16 16:15, Kenneth Graunke wrote:
> 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();
>  
> 

-- 
Alejandro Piñeiro <apinheiro at igalia.com>