[2/2] aarch64,falkor: Use vector registers for copy

Message ID 20180629104331.13263-2-siddhesh@sourceware.org
State New
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Series
  • [1/2] aarch64,falkor: Use vector registers for memmove
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Commit Message

Siddhesh Poyarekar June 29, 2018, 10:43 a.m.
Vector registers perform better than scalar register pairs for copying
data so prefer them instead.  This results in a time reduction of over
50% (i.e. 2x speed improvemnet) for some smaller sizes for memcpy-walk.
Larger sizes show improvements of around 1% to 2%.  memcpy-random shows
a very small improvement, in the range of 1-2%.

	* sysdeps/aarch64/multiarch/memcpy_falkor.S (__memcpy_falkor):
	Use vector registers.

---
 sysdeps/aarch64/multiarch/memcpy_falkor.S | 135 ++++++++++------------
 1 file changed, 64 insertions(+), 71 deletions(-)

Comments

Adhemerval Zanella June 29, 2018, 2:05 p.m. | #1
On 29/06/2018 07:43, Siddhesh Poyarekar wrote:
> Vector registers perform better than scalar register pairs for copying
> data so prefer them instead.  This results in a time reduction of over
> 50% (i.e. 2x speed improvemnet) for some smaller sizes for memcpy-walk.
> Larger sizes show improvements of around 1% to 2%.  memcpy-random shows
> a very small improvement, in the range of 1-2%.
> 
> 	* sysdeps/aarch64/multiarch/memcpy_falkor.S (__memcpy_falkor):
> 	Use vector registers.


LGTM, although I can't really voucher for the performance improvement (I d
id not see any different on a A72).


> 
> ---
>  sysdeps/aarch64/multiarch/memcpy_falkor.S | 135 ++++++++++------------
>  1 file changed, 64 insertions(+), 71 deletions(-)
> 
> diff --git a/sysdeps/aarch64/multiarch/memcpy_falkor.S b/sysdeps/aarch64/multiarch/memcpy_falkor.S
> index eef1fb02e4..f1e905d34d 100644
> --- a/sysdeps/aarch64/multiarch/memcpy_falkor.S
> +++ b/sysdeps/aarch64/multiarch/memcpy_falkor.S
> @@ -30,25 +30,19 @@
>  #define dst	x3
>  #define srcend	x4
>  #define dstend	x5
> -#define A_l	x6
> -#define A_lw	w6
> -#define A_h	x7
> -#define A_hw	w7
>  #define tmp1	x14
> +#define A_x	x6
> +#define B_x	x7
> +#define A_w	w6
> +#define B_w	w7
>  
> -#define B_l	x8
> -#define B_lw	w8
> -#define B_h	x9
> -#define C_l	x10
> -#define C_h	x11
> -#define D_l	x12
> -#define D_h	x13
> -#define E_l	dst
> -#define E_h	tmp1
> -#define F_l	src
> -#define F_h	count
> -#define G_l	srcend
> -#define G_h	x15
> +#define A_q	q0
> +#define B_q	q1
> +#define C_q	q2
> +#define D_q	q3
> +#define E_q	q4
> +#define F_q	q5
> +#define G_q	q6
>  
>  /* Copies are split into 3 main cases:
>  
> @@ -68,9 +62,9 @@
>     bumping up the small copies up to 32 bytes allows us to do that without
>     cost and also allows us to reduce the size of the prep code before loop64.
>  
> -   All copies are done only via two registers r6 and r7.  This is to ensure
> -   that all loads hit a single hardware prefetcher which can get correctly
> -   trained to prefetch a single stream.
> +   The copy loop uses only one register q0.  This is to ensure that all loads
> +   hit a single hardware prefetcher which can get correctly trained to prefetch
> +   a single stream.
>  
>     The non-temporal stores help optimize cache utilization.  */
>  
> @@ -91,29 +85,29 @@ ENTRY(__memcpy_falkor)
>  	add	srcend, src, count
>  	add	dstend, dstin, count
>  	b.ls	L(copy32)
> -	ldp	A_l, A_h, [src]
> +	ldr	A_q, [src]
>  	cmp	count, 128
> -	stp	A_l, A_h, [dstin]
> +	str	A_q, [dstin]
>  	b.hi	L(copy_long)
>  
>  	/* Medium copies: 33..128 bytes.  */
>  	sub	tmp1, count, 1
> -	ldp	A_l, A_h, [src, 16]
> -	ldp	B_l, B_h, [srcend, -32]
> -	ldp	C_l, C_h, [srcend, -16]
> +	ldr	A_q, [src, 16]
> +	ldr	B_q, [srcend, -32]
> +	ldr	C_q, [srcend, -16]
>  	tbz	tmp1, 6, 1f
> -	ldp	D_l, D_h, [src, 32]
> -	ldp	E_l, E_h, [src, 48]
> -	stp	D_l, D_h, [dstin, 32]
> -	stp	E_l, E_h, [dstin, 48]
> -	ldp	F_l, F_h, [srcend, -64]
> -	ldp	G_l, G_h, [srcend, -48]
> -	stp	F_l, F_h, [dstend, -64]
> -	stp	G_l, G_h, [dstend, -48]
> +	ldr	D_q, [src, 32]
> +	ldr	E_q, [src, 48]
> +	str	D_q, [dstin, 32]
> +	str	E_q, [dstin, 48]
> +	ldr	F_q, [srcend, -64]
> +	ldr	G_q, [srcend, -48]
> +	str	F_q, [dstend, -64]
> +	str	G_q, [dstend, -48]
>  1:
> -	stp	A_l, A_h, [dstin, 16]
> -	stp	B_l, B_h, [dstend, -32]
> -	stp	C_l, C_h, [dstend, -16]
> +	str	A_q, [dstin, 16]
> +	str	B_q, [dstend, -32]
> +	str	C_q, [dstend, -16]
>  	ret
>  
>  	.p2align 4
> @@ -122,44 +116,44 @@ L(copy32):
>  	/* 16-32 */
>  	cmp	count, 16
>  	b.lo	1f
> -	ldp	A_l, A_h, [src]
> -	ldp	B_l, B_h, [srcend, -16]
> -	stp	A_l, A_h, [dstin]
> -	stp	B_l, B_h, [dstend, -16]
> +	ldr	A_q, [src]
> +	ldr	B_q, [srcend, -16]
> +	str	A_q, [dstin]
> +	str	B_q, [dstend, -16]
>  	ret
>  	.p2align 4
>  1:
>  	/* 8-15 */
>  	tbz	count, 3, 1f
> -	ldr	A_l, [src]
> -	ldr	B_l, [srcend, -8]
> -	str	A_l, [dstin]
> -	str	B_l, [dstend, -8]
> +	ldr	A_x, [src]
> +	ldr	B_x, [srcend, -8]
> +	str	A_x, [dstin]
> +	str	B_x, [dstend, -8]
>  	ret
>  	.p2align 4
>  1:
>  	/* 4-7 */
>  	tbz	count, 2, 1f
> -	ldr	A_lw, [src]
> -	ldr	B_lw, [srcend, -4]
> -	str	A_lw, [dstin]
> -	str	B_lw, [dstend, -4]
> +	ldr	A_w, [src]
> +	ldr	B_w, [srcend, -4]
> +	str	A_w, [dstin]
> +	str	B_w, [dstend, -4]
>  	ret
>  	.p2align 4
>  1:
>  	/* 2-3 */
>  	tbz	count, 1, 1f
> -	ldrh	A_lw, [src]
> -	ldrh	B_lw, [srcend, -2]
> -	strh	A_lw, [dstin]
> -	strh	B_lw, [dstend, -2]
> +	ldrh	A_w, [src]
> +	ldrh	B_w, [srcend, -2]
> +	strh	A_w, [dstin]
> +	strh	B_w, [dstend, -2]
>  	ret
>  	.p2align 4
>  1:
>  	/* 0-1 */
>  	tbz	count, 0, 1f
> -	ldrb	A_lw, [src]
> -	strb	A_lw, [dstin]
> +	ldrb	A_w, [src]
> +	strb	A_w, [dstin]
>  1:
>  	ret
>  
> @@ -178,30 +172,29 @@ L(copy_long):
>  	add	count, count, tmp1
>  
>  L(loop64):
> -	ldp	A_l, A_h, [src, 16]!
> -	stnp	A_l, A_h, [dst, 16]
> -	ldp	A_l, A_h, [src, 16]!
> +	ldr	A_q, [src, 16]!
> +	str	A_q, [dst, 16]
> +	ldr	A_q, [src, 16]!
>  	subs	count, count, 64
> -	stnp	A_l, A_h, [dst, 32]
> -	ldp	A_l, A_h, [src, 16]!
> -	stnp	A_l, A_h, [dst, 48]
> -	ldp	A_l, A_h, [src, 16]!
> -	stnp	A_l, A_h, [dst, 64]
> -	add	dst, dst, 64
> +	str	A_q, [dst, 32]
> +	ldr	A_q, [src, 16]!
> +	str	A_q, [dst, 48]
> +	ldr	A_q, [src, 16]!
> +	str	A_q, [dst, 64]!
>  	b.hi	L(loop64)
>  
>  	/* Write the last full set of 64 bytes.  The remainder is at most 64
>  	   bytes, so it is safe to always copy 64 bytes from the end even if
>  	   there is just 1 byte left.  */
>  L(last64):
> -	ldp	A_l, A_h, [srcend, -64]
> -	stnp	A_l, A_h, [dstend, -64]
> -	ldp	B_l, B_h, [srcend, -48]
> -	stnp	B_l, B_h, [dstend, -48]
> -	ldp	C_l, C_h, [srcend, -32]
> -	stnp	C_l, C_h, [dstend, -32]
> -	ldp	D_l, D_h, [srcend, -16]
> -	stnp	D_l, D_h, [dstend, -16]
> +	ldr	E_q, [srcend, -64]
> +	str	E_q, [dstend, -64]
> +	ldr	D_q, [srcend, -48]
> +	str	D_q, [dstend, -48]
> +	ldr	C_q, [srcend, -32]
> +	str	C_q, [dstend, -32]
> +	ldr	B_q, [srcend, -16]
> +	str	B_q, [dstend, -16]
>  	ret
>  
>  END (__memcpy_falkor)
>
Szabolcs Nagy June 29, 2018, 4:28 p.m. | #2
On 29/06/18 11:43, Siddhesh Poyarekar wrote:
> Vector registers perform better than scalar register pairs for copying
> data so prefer them instead.  This results in a time reduction of over
> 50% (i.e. 2x speed improvemnet) for some smaller sizes for memcpy-walk.
> Larger sizes show improvements of around 1% to 2%.  memcpy-random shows
> a very small improvement, in the range of 1-2%.
> 
> 	* sysdeps/aarch64/multiarch/memcpy_falkor.S (__memcpy_falkor):
> 	Use vector registers.

this is ok to commit.

Patch

diff --git a/sysdeps/aarch64/multiarch/memcpy_falkor.S b/sysdeps/aarch64/multiarch/memcpy_falkor.S
index eef1fb02e4..f1e905d34d 100644
--- a/sysdeps/aarch64/multiarch/memcpy_falkor.S
+++ b/sysdeps/aarch64/multiarch/memcpy_falkor.S
@@ -30,25 +30,19 @@ 
 #define dst	x3
 #define srcend	x4
 #define dstend	x5
-#define A_l	x6
-#define A_lw	w6
-#define A_h	x7
-#define A_hw	w7
 #define tmp1	x14
+#define A_x	x6
+#define B_x	x7
+#define A_w	w6
+#define B_w	w7
 
-#define B_l	x8
-#define B_lw	w8
-#define B_h	x9
-#define C_l	x10
-#define C_h	x11
-#define D_l	x12
-#define D_h	x13
-#define E_l	dst
-#define E_h	tmp1
-#define F_l	src
-#define F_h	count
-#define G_l	srcend
-#define G_h	x15
+#define A_q	q0
+#define B_q	q1
+#define C_q	q2
+#define D_q	q3
+#define E_q	q4
+#define F_q	q5
+#define G_q	q6
 
 /* Copies are split into 3 main cases:
 
@@ -68,9 +62,9 @@ 
    bumping up the small copies up to 32 bytes allows us to do that without
    cost and also allows us to reduce the size of the prep code before loop64.
 
-   All copies are done only via two registers r6 and r7.  This is to ensure
-   that all loads hit a single hardware prefetcher which can get correctly
-   trained to prefetch a single stream.
+   The copy loop uses only one register q0.  This is to ensure that all loads
+   hit a single hardware prefetcher which can get correctly trained to prefetch
+   a single stream.
 
    The non-temporal stores help optimize cache utilization.  */
 
@@ -91,29 +85,29 @@  ENTRY(__memcpy_falkor)
 	add	srcend, src, count
 	add	dstend, dstin, count
 	b.ls	L(copy32)
-	ldp	A_l, A_h, [src]
+	ldr	A_q, [src]
 	cmp	count, 128
-	stp	A_l, A_h, [dstin]
+	str	A_q, [dstin]
 	b.hi	L(copy_long)
 
 	/* Medium copies: 33..128 bytes.  */
 	sub	tmp1, count, 1
-	ldp	A_l, A_h, [src, 16]
-	ldp	B_l, B_h, [srcend, -32]
-	ldp	C_l, C_h, [srcend, -16]
+	ldr	A_q, [src, 16]
+	ldr	B_q, [srcend, -32]
+	ldr	C_q, [srcend, -16]
 	tbz	tmp1, 6, 1f
-	ldp	D_l, D_h, [src, 32]
-	ldp	E_l, E_h, [src, 48]
-	stp	D_l, D_h, [dstin, 32]
-	stp	E_l, E_h, [dstin, 48]
-	ldp	F_l, F_h, [srcend, -64]
-	ldp	G_l, G_h, [srcend, -48]
-	stp	F_l, F_h, [dstend, -64]
-	stp	G_l, G_h, [dstend, -48]
+	ldr	D_q, [src, 32]
+	ldr	E_q, [src, 48]
+	str	D_q, [dstin, 32]
+	str	E_q, [dstin, 48]
+	ldr	F_q, [srcend, -64]
+	ldr	G_q, [srcend, -48]
+	str	F_q, [dstend, -64]
+	str	G_q, [dstend, -48]
 1:
-	stp	A_l, A_h, [dstin, 16]
-	stp	B_l, B_h, [dstend, -32]
-	stp	C_l, C_h, [dstend, -16]
+	str	A_q, [dstin, 16]
+	str	B_q, [dstend, -32]
+	str	C_q, [dstend, -16]
 	ret
 
 	.p2align 4
@@ -122,44 +116,44 @@  L(copy32):
 	/* 16-32 */
 	cmp	count, 16
 	b.lo	1f
-	ldp	A_l, A_h, [src]
-	ldp	B_l, B_h, [srcend, -16]
-	stp	A_l, A_h, [dstin]
-	stp	B_l, B_h, [dstend, -16]
+	ldr	A_q, [src]
+	ldr	B_q, [srcend, -16]
+	str	A_q, [dstin]
+	str	B_q, [dstend, -16]
 	ret
 	.p2align 4
 1:
 	/* 8-15 */
 	tbz	count, 3, 1f
-	ldr	A_l, [src]
-	ldr	B_l, [srcend, -8]
-	str	A_l, [dstin]
-	str	B_l, [dstend, -8]
+	ldr	A_x, [src]
+	ldr	B_x, [srcend, -8]
+	str	A_x, [dstin]
+	str	B_x, [dstend, -8]
 	ret
 	.p2align 4
 1:
 	/* 4-7 */
 	tbz	count, 2, 1f
-	ldr	A_lw, [src]
-	ldr	B_lw, [srcend, -4]
-	str	A_lw, [dstin]
-	str	B_lw, [dstend, -4]
+	ldr	A_w, [src]
+	ldr	B_w, [srcend, -4]
+	str	A_w, [dstin]
+	str	B_w, [dstend, -4]
 	ret
 	.p2align 4
 1:
 	/* 2-3 */
 	tbz	count, 1, 1f
-	ldrh	A_lw, [src]
-	ldrh	B_lw, [srcend, -2]
-	strh	A_lw, [dstin]
-	strh	B_lw, [dstend, -2]
+	ldrh	A_w, [src]
+	ldrh	B_w, [srcend, -2]
+	strh	A_w, [dstin]
+	strh	B_w, [dstend, -2]
 	ret
 	.p2align 4
 1:
 	/* 0-1 */
 	tbz	count, 0, 1f
-	ldrb	A_lw, [src]
-	strb	A_lw, [dstin]
+	ldrb	A_w, [src]
+	strb	A_w, [dstin]
 1:
 	ret
 
@@ -178,30 +172,29 @@  L(copy_long):
 	add	count, count, tmp1
 
 L(loop64):
-	ldp	A_l, A_h, [src, 16]!
-	stnp	A_l, A_h, [dst, 16]
-	ldp	A_l, A_h, [src, 16]!
+	ldr	A_q, [src, 16]!
+	str	A_q, [dst, 16]
+	ldr	A_q, [src, 16]!
 	subs	count, count, 64
-	stnp	A_l, A_h, [dst, 32]
-	ldp	A_l, A_h, [src, 16]!
-	stnp	A_l, A_h, [dst, 48]
-	ldp	A_l, A_h, [src, 16]!
-	stnp	A_l, A_h, [dst, 64]
-	add	dst, dst, 64
+	str	A_q, [dst, 32]
+	ldr	A_q, [src, 16]!
+	str	A_q, [dst, 48]
+	ldr	A_q, [src, 16]!
+	str	A_q, [dst, 64]!
 	b.hi	L(loop64)
 
 	/* Write the last full set of 64 bytes.  The remainder is at most 64
 	   bytes, so it is safe to always copy 64 bytes from the end even if
 	   there is just 1 byte left.  */
 L(last64):
-	ldp	A_l, A_h, [srcend, -64]
-	stnp	A_l, A_h, [dstend, -64]
-	ldp	B_l, B_h, [srcend, -48]
-	stnp	B_l, B_h, [dstend, -48]
-	ldp	C_l, C_h, [srcend, -32]
-	stnp	C_l, C_h, [dstend, -32]
-	ldp	D_l, D_h, [srcend, -16]
-	stnp	D_l, D_h, [dstend, -16]
+	ldr	E_q, [srcend, -64]
+	str	E_q, [dstend, -64]
+	ldr	D_q, [srcend, -48]
+	str	D_q, [dstend, -48]
+	ldr	C_q, [srcend, -32]
+	str	C_q, [dstend, -32]
+	ldr	B_q, [srcend, -16]
+	str	B_q, [dstend, -16]
 	ret
 
 END (__memcpy_falkor)