[PATCH] AArch64: Improve SVE memcpy and memmove

[Wilco Dijkstra]

Improve SVE memcpy/memmove by copying 2 vectors if the size is small enough.
This improves performance of random memcpy by ~9% on Neoverse V1, and
memcpy/memmove of 33-64 bytes become ~16% faster.

Passes regress, OK for commit?

---

diff --git a/sysdeps/aarch64/multiarch/memcpy_sve.S b/sysdeps/aarch64/multiarch/memcpy_sve.S
index f4dc214f60bf25e818eb6b8de2d4093ad0c886e1..d11be6a44301af4bfd7fa4900555b769dc58d34d 100644
--- a/sysdeps/aarch64/multiarch/memcpy_sve.S
+++ b/sysdeps/aarch64/multiarch/memcpy_sve.S
@@ -67,14 +67,15 @@ ENTRY (__memcpy_sve)
 
 	cmp	count, 128
 	b.hi	L(copy_long)
-	cmp	count, 32
+	cntb	vlen
+	cmp	count, vlen, lsl 1
 	b.hi	L(copy32_128)
-
 	whilelo p0.b, xzr, count
-	cntb	vlen
-	tbnz	vlen, 4, L(vlen128)
-	ld1b	z0.b, p0/z, [src]
-	st1b	z0.b, p0, [dstin]
+	whilelo p1.b, vlen, count
+	ld1b	z0.b, p0/z, [src, 0, mul vl]
+	ld1b	z1.b, p1/z, [src, 1, mul vl]
+	st1b	z0.b, p0, [dstin, 0, mul vl]
+	st1b	z1.b, p1, [dstin, 1, mul vl]
 	ret
 
 	/* Medium copies: 33..128 bytes.  */
@@ -102,14 +103,6 @@ L(copy96):
 	stp	C_q, D_q, [dstend, -32]
 	ret
 
-L(vlen128):
-	whilelo p1.b, vlen, count
-	ld1b	z0.b, p0/z, [src, 0, mul vl]
-	ld1b	z1.b, p1/z, [src, 1, mul vl]
-	st1b	z0.b, p0, [dstin, 0, mul vl]
-	st1b	z1.b, p1, [dstin, 1, mul vl]
-	ret
-
 	.p2align 4
 	/* Copy more than 128 bytes.  */
 L(copy_long):
@@ -158,14 +151,15 @@ ENTRY (__memmove_sve)
 
 	cmp	count, 128
 	b.hi	L(move_long)
-	cmp	count, 32
+	cntb	vlen
+	cmp	count, vlen, lsl 1
 	b.hi	L(copy32_128)
-
 	whilelo p0.b, xzr, count
-	cntb	vlen
-	tbnz	vlen, 4, L(vlen128)
-	ld1b	z0.b, p0/z, [src]
-	st1b	z0.b, p0, [dstin]
+	whilelo p1.b, vlen, count
+	ld1b	z0.b, p0/z, [src, 0, mul vl]
+	ld1b	z1.b, p1/z, [src, 1, mul vl]
+	st1b	z0.b, p0, [dstin, 0, mul vl]
+	st1b	z1.b, p1, [dstin, 1, mul vl]
 	ret
 
 	.p2align 4