[Mesa-dev] [PATCH v3 21/24] i965: Use correct VertStride on align16 instructions.

[Francisco Jerez]

Samuel Iglesias Gonsálvez <siglesias at igalia.com> writes:

> From: Matt Turner <mattst88 at gmail.com>
>
> In commit c35fa7a, we changed the "width" of DF source registers to 2,
> which is conceptually fine. Unfortunately a VertStride of 2 is not
> allowed by align16 instructions on IVB/BYT, and the regular VertStride
> of 4 works fine in any case.
>
> See generated_tests/spec/arb_gpu_shader_fp64/execution/built-in-functions/vs-round-double.shader_test
> for example:
>
> cmp.ge.f0(8)    g18<1>DF        g1<0>.xyxyDF    -g8<2>DF        { align16 1Q };
>         ERROR: In Align16 mode, only VertStride of 0 or 4 is allowed
> cmp.ge.f0(8)    g19<1>DF        g1<0>.xyxyDF    -g9<2>DF        { align16 2N };
>         ERROR: In Align16 mode, only VertStride of 0 or 4 is allowed
>
> v2:
> - Add spec quote (Curro).
> - Change the condition to only BRW_VERTICAL_STRIDE_2 (Curro)
>
> Reviewed-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
> ---
>  src/mesa/drivers/dri/i965/brw_eu_emit.c | 44 +++++++++++++++++++++++++--------
>  1 file changed, 34 insertions(+), 10 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_eu_emit.c b/src/mesa/drivers/dri/i965/brw_eu_emit.c
> index 03aaa760163..d221405db4d 100644
> --- a/src/mesa/drivers/dri/i965/brw_eu_emit.c
> +++ b/src/mesa/drivers/dri/i965/brw_eu_emit.c
> @@ -512,13 +512,25 @@ brw_set_src0(struct brw_codegen *p, brw_inst *inst, struct brw_reg reg)
>           brw_inst_set_src0_da16_swiz_w(devinfo, inst,
>              BRW_GET_SWZ(reg.swizzle, BRW_CHANNEL_W));
>  
> -	 /* This is an oddity of the fact we're using the same
> -	  * descriptions for registers in align_16 as align_1:
> -	  */
> -	 if (reg.vstride == BRW_VERTICAL_STRIDE_8)
> +         if (reg.vstride == BRW_VERTICAL_STRIDE_8) {
> +            /* This is an oddity of the fact we're using the same
> +             * descriptions for registers in align_16 as align_1:
> +             */
> +            brw_inst_set_src0_vstride(devinfo, inst, BRW_VERTICAL_STRIDE_4);
> +         } else if (devinfo->gen == 7 && !devinfo->is_haswell &&
> +                    reg.type == BRW_REGISTER_TYPE_DF &&
> +                    reg.vstride == BRW_VERTICAL_STRIDE_2) {
> +            /* From HSW PRM:

This workaround is IVB-specific so the HSW PRM quotation doesn't seem
particularly relevant.  With that fixed here and below patch is:

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

> +             *
> +             * "For Align16 access mode, only encodings of 0000, 0010
> +             *  and 0011 are allowed. Other codes are reserved."
> +             *
> +             * Presumably the DevSNB behavior applies to IVB as well.
> +             */
>              brw_inst_set_src0_vstride(devinfo, inst, BRW_VERTICAL_STRIDE_4);
> -	 else
> +         } else {
>              brw_inst_set_src0_vstride(devinfo, inst, reg.vstride);
> +         }
>        }
>     }
>  }
> @@ -594,13 +606,25 @@ brw_set_src1(struct brw_codegen *p, brw_inst *inst, struct brw_reg reg)
>           brw_inst_set_src1_da16_swiz_w(devinfo, inst,
>              BRW_GET_SWZ(reg.swizzle, BRW_CHANNEL_W));
>  
> -	 /* This is an oddity of the fact we're using the same
> -	  * descriptions for registers in align_16 as align_1:
> -	  */
> -	 if (reg.vstride == BRW_VERTICAL_STRIDE_8)
> +         if (reg.vstride == BRW_VERTICAL_STRIDE_8) {
> +            /* This is an oddity of the fact we're using the same
> +             * descriptions for registers in align_16 as align_1:
> +             */
> +            brw_inst_set_src1_vstride(devinfo, inst, BRW_VERTICAL_STRIDE_4);
> +         } else if (devinfo->gen == 7 && !devinfo->is_haswell &&
> +                    reg.type == BRW_REGISTER_TYPE_DF &&
> +                    reg.vstride == BRW_VERTICAL_STRIDE_2) {
> +            /* From HSW PRM:
> +             *
> +             * "For Align16 access mode, only encodings of 0000, 0010
> +             *  and 0011 are allowed. Other codes are reserved."
> +             *
> +             * Presumably the DevSNB behavior applies to IVB as well.
> +             */
>              brw_inst_set_src1_vstride(devinfo, inst, BRW_VERTICAL_STRIDE_4);
> -	 else
> +         } else {
>              brw_inst_set_src1_vstride(devinfo, inst, reg.vstride);
> +         }
>        }
>     }
>  }
> -- 
> 2.11.0
>
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