From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jianbo Liu <Jianbo.Liu@arm.com>
Subject: Re: [PATCH] examples/l3fwd: fix NEON instructions
Date: Mon, 30 Oct 2017 14:27:09 +0800
Message-ID: <20171030062623.GA26958@arm.com>
References: <20171029074807.30785-1-gprathyusha@caviumnetworks.com>
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Cc: tomasz.kantecki@intel.com, jianbo.liu@linaro.org,
 guduriprathyusha@gmail.com, dev@dpdk.org
To: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
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The 10/29/2017 13:18, Guduri Prathyusha wrote:
> To group consecutive packets with same destination port in bursts of 4
> neon intrinsic data types dp1 and dp2 are calculated such that if
> dst_port[]=3D{a,b,c,d,e,f,g,h,i...} dp1 should contain: <a,b,c,d> and
> dp2 should contain: <b,c,d,e> in the first iteration. dp1 should
> be <e,f,g,h> and dp2 should be <f,g,h,i> in the next iteration. dp2 in
> the last iteration should be <w,x,y,y>.
>
> Whereas the existing code incorrectly calculates dp1 as <d,e,f,g> from
> second iteration and thus incorrect calculation of dp2 as <d,e,f,f>
> in the last iteration.
>
> This patch fixes the incorrect ARM NEON instructions on dp1 and dp2.
>
> Fixes: 569b290cdb36 ("examples/l3fwd: add NEON implementation")
>
> Signed-off-by: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
> ---
>  examples/l3fwd/l3fwd_neon.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/examples/l3fwd/l3fwd_neon.h b/examples/l3fwd/l3fwd_neon.h
> index 42d50d3c2..1eace4e03 100644
> --- a/examples/l3fwd/l3fwd_neon.h
> +++ b/examples/l3fwd/l3fwd_neon.h
> @@ -192,13 +192,13 @@ send_packets_multi(struct lcore_conf *qconf, struct=
 rte_mbuf **pkts_burst,
>                        * dp1:
>                        * <d[j], d[j+1], d[j+2], d[j+3], ... >
>                        */
> -                     dp1 =3D vextq_u16(dp1, dp1, FWDSTEP - 1);
> +                     dp1 =3D vextq_u16(dp2, vdupq_n_u16(0), FWDSTEP - 1)=
;
>               }
>
>               /*
>                * dp2: <d[j-3], d[j-2], d[j-1], d[j-1], ... >
>                */
> -             dp2 =3D vextq_u16(dp1, dp1, 1);
> +             dp2 =3D vextq_u16(dp1, vdupq_n_u16(0), 1);

Sorry, I don't think you need to change this line. Please ignore my
comment about it in the last email.

>               dp2 =3D vsetq_lane_u16(vgetq_lane_u16(dp2, 2), dp2, 3);
>               lp  =3D port_groupx4(&pnum[j - FWDSTEP], lp, dp1, dp2);
>
> --
> 2.14.1
>

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