[Mesa-dev] [Mesa-stable] [PATCH 3/4 v2] i965: Fix execution size of scalar TCS barrier setup code.

[Francisco Jerez]

Kenneth Graunke <kenneth at whitecape.org> writes:

> 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+.
>
> v2: Use a group(1, 0) builder so inst->exec_size is set correctly
>     (thanks to Francisco Jerez for catching that it was incorrect).
>
> Cc: mesa-stable at lists.freedesktop.org
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> Reviewed-by: Alejandro Piñeiro <apinheiro at igalia.com> [v1]
> ---
>  src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> Oh yuck.  I hadn't realized that inst->exec_size would still be bogus.
> We definitely want that to match up.  Thanks Curro!  This look better?
>
Yeah, thanks, this looks good, patch is:

Reviewed-by: Francisco Jerez <currojerez at riseup.net>

> diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> index df033e1..a36765c 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> @@ -2420,22 +2420,22 @@ 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();
> +      const fs_builder chanbld = bld.exec_all().group(1, 0);
>  
>        /* Zero the message header */
> -      fwa_bld.MOV(m0, brw_imm_ud(0u));
> +      bld.exec_all().MOV(m0, brw_imm_ud(0u));
>  
>        /* Copy "Barrier ID" from r0.2, bits 16:13 */
> -      fwa_bld.AND(m0_2, retype(brw_vec1_grf(0, 2), BRW_REGISTER_TYPE_UD),
> +      chanbld.AND(m0_2, retype(brw_vec1_grf(0, 2), BRW_REGISTER_TYPE_UD),
>                    brw_imm_ud(INTEL_MASK(16, 13)));
>  
>        /* Shift it up to bits 27:24. */
> -      fwa_bld.SHL(m0_2, m0_2, brw_imm_ud(11));
> +      chanbld.SHL(m0_2, m0_2, brw_imm_ud(11));
>  
>        /* Set the Barrier Count and the enable bit */
> -      fwa_bld.OR(m0_2, m0_2,
> +      chanbld.OR(m0_2, m0_2,
>                   brw_imm_ud(tcs_prog_data->instances << 8 | (1 << 15)));
>  
>        bld.emit(SHADER_OPCODE_BARRIER, bld.null_reg_ud(), m0);
> -- 
> 2.9.3
>
> _______________________________________________
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> mesa-stable at lists.freedesktop.org
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