diff mbox series

[v4,1/5] AArch64: Improve A64FX memset for small sizes

Message ID VE1PR08MB5599551B9E7A13B3B131B0D783F69@VE1PR08MB5599.eurprd08.prod.outlook.com
State Committed
Commit 07b427296b8d59f439144029d9a948f6c1ce0a31
Delegated to: Szabolcs Nagy
Headers
Series [v4,1/5] AArch64: Improve A64FX memset for small sizes |

Commit Message

Wilco Dijkstra Aug. 9, 2021, 1:07 p.m. UTC 
  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.

---

Comments

Szabolcs Nagy Aug. 10, 2021, 9:36 a.m. UTC | #1 
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

--
diff mbox series

Patch

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