From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Cc: "naohirot@fujitsu.com" <naohirot@fujitsu.com>,
'GNU C Library' <libc-alpha@sourceware.org>
Subject: Re: [PATCH v4 1/5] AArch64: Improve A64FX memset for small sizes
Date: Tue, 10 Aug 2021 10:36:53 +0100 [thread overview]
Message-ID: <20210810093652.GC20410@arm.com> (raw)
In-Reply-To: <VE1PR08MB5599551B9E7A13B3B131B0D783F69@VE1PR08MB5599.eurprd08.prod.outlook.com>
The 08/09/2021 13:07, Wilco Dijkstra via Libc-alpha wrote:
> v4: Don't remove ZF_DIST yet
>
> Improve performance of small memsets by reducing instruction counts and improving
> alignment. Bench-memset shows 35-45% performance gain for small sizes.
thanks, this is OK to commit.
(if further tweaks needed that can be in follow up commits)
>
> ---
>
> diff --git a/sysdeps/aarch64/multiarch/memset_a64fx.S b/sysdeps/aarch64/multiarch/memset_a64fx.S
> index ce54e5418b08c8bc0ecc7affff68a59272ba6397..cf3d402ef681a9d98964d1751537945692a1ae68 100644
> --- a/sysdeps/aarch64/multiarch/memset_a64fx.S
> +++ b/sysdeps/aarch64/multiarch/memset_a64fx.S
> @@ -51,78 +51,54 @@
> .endm
>
> .macro st1b_unroll first=0, last=7
> - st1b z0.b, p0, [dst, #\first, mul vl]
> + st1b z0.b, p0, [dst, \first, mul vl]
> .if \last-\first
> st1b_unroll "(\first+1)", \last
> .endif
> .endm
>
> - .macro shortcut_for_small_size exit
> - // if rest <= vector_length * 2
> - whilelo p0.b, xzr, count
> - whilelo p1.b, vector_length, count
> - b.last 1f
> - st1b z0.b, p0, [dstin, #0, mul vl]
> - st1b z0.b, p1, [dstin, #1, mul vl]
> - ret
> -1: // if rest > vector_length * 8
> - cmp count, vector_length, lsl 3 // vector_length * 8
> - b.hi \exit
> - // if rest <= vector_length * 4
> - lsl tmp1, vector_length, 1 // vector_length * 2
> - whilelo p2.b, tmp1, count
> - incb tmp1
> - whilelo p3.b, tmp1, count
> - b.last 1f
> - st1b z0.b, p0, [dstin, #0, mul vl]
> - st1b z0.b, p1, [dstin, #1, mul vl]
> - st1b z0.b, p2, [dstin, #2, mul vl]
> - st1b z0.b, p3, [dstin, #3, mul vl]
> - ret
> -1: // if rest <= vector_length * 8
> - lsl tmp1, vector_length, 2 // vector_length * 4
> - whilelo p4.b, tmp1, count
> - incb tmp1
> - whilelo p5.b, tmp1, count
> - b.last 1f
> - st1b z0.b, p0, [dstin, #0, mul vl]
> - st1b z0.b, p1, [dstin, #1, mul vl]
> - st1b z0.b, p2, [dstin, #2, mul vl]
> - st1b z0.b, p3, [dstin, #3, mul vl]
> - st1b z0.b, p4, [dstin, #4, mul vl]
> - st1b z0.b, p5, [dstin, #5, mul vl]
> - ret
> -1: lsl tmp1, vector_length, 2 // vector_length * 4
> - incb tmp1 // vector_length * 5
> - incb tmp1 // vector_length * 6
> - whilelo p6.b, tmp1, count
> - incb tmp1
> - whilelo p7.b, tmp1, count
> - st1b z0.b, p0, [dstin, #0, mul vl]
> - st1b z0.b, p1, [dstin, #1, mul vl]
> - st1b z0.b, p2, [dstin, #2, mul vl]
> - st1b z0.b, p3, [dstin, #3, mul vl]
> - st1b z0.b, p4, [dstin, #4, mul vl]
> - st1b z0.b, p5, [dstin, #5, mul vl]
> - st1b z0.b, p6, [dstin, #6, mul vl]
> - st1b z0.b, p7, [dstin, #7, mul vl]
> - ret
> - .endm
>
> -ENTRY (MEMSET)
> +#undef BTI_C
> +#define BTI_C
>
> +ENTRY (MEMSET)
> PTR_ARG (0)
> SIZE_ARG (2)
>
> - cbnz count, 1f
> - ret
> -1: dup z0.b, valw
> cntb vector_length
> - // shortcut for less than vector_length * 8
> - // gives a free ptrue to p0.b for n >= vector_length
> - shortcut_for_small_size L(vl_agnostic)
> - // end of shortcut
> + dup z0.b, valw
> + whilelo p0.b, vector_length, count
> + b.last 1f
> + whilelo p1.b, xzr, count
> + st1b z0.b, p1, [dstin, 0, mul vl]
> + st1b z0.b, p0, [dstin, 1, mul vl]
> + ret
> +
> + // count >= vector_length * 2
> +1: cmp count, vector_length, lsl 2
> + add dstend, dstin, count
> + b.hi 1f
> + st1b z0.b, p0, [dstin, 0, mul vl]
> + st1b z0.b, p0, [dstin, 1, mul vl]
> + st1b z0.b, p0, [dstend, -2, mul vl]
> + st1b z0.b, p0, [dstend, -1, mul vl]
> + ret
> +
> + // count > vector_length * 4
> +1: lsl tmp1, vector_length, 3
> + cmp count, tmp1
> + b.hi L(vl_agnostic)
> + st1b z0.b, p0, [dstin, 0, mul vl]
> + st1b z0.b, p0, [dstin, 1, mul vl]
> + st1b z0.b, p0, [dstin, 2, mul vl]
> + st1b z0.b, p0, [dstin, 3, mul vl]
> + st1b z0.b, p0, [dstend, -4, mul vl]
> + st1b z0.b, p0, [dstend, -3, mul vl]
> + st1b z0.b, p0, [dstend, -2, mul vl]
> + st1b z0.b, p0, [dstend, -1, mul vl]
> + ret
>
> + .p2align 4
> L(vl_agnostic): // VL Agnostic
> mov rest, count
> mov dst, dstin
--
prev parent reply other threads:[~2021-08-10 9:37 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-09 13:07 Wilco Dijkstra
2021-08-10 9:36 ` Szabolcs Nagy [this message]
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