add optimized aarch64 memcpy and memset

these are based on the ARM optimized-routines repository v20.05
(ef907c7a799a), with macro dependencies flattened out and memmove code
removed from memcpy. this change is somewhat unfortunate since having
the branch for memmove support in the large n case of memcpy is the
performance-optimal and size-optimal way to do both, but it makes
memcpy alone (static-linked) about 40% larger and suggests a policy
that use of memcpy as memmove is supported.

tabs used for alignment have also been replaced with spaces.

COPYRIGHT

@@ -131,6 +131,9 @@ The ARM memcpy code (src/string/arm/memcpy.S) is Copyright © 2008
 The Android Open Source Project and is licensed under a two-clause BSD
 license. It was taken from Bionic libc, used on Android.
 
+The AArch64 memcpy and memset code (src/string/aarch64/*) are
+Copyright © 1999-2019, Arm Limited.
+
 The implementation of DES for crypt (src/crypt/crypt_des.c) is
 Copyright © 1994 David Burren. It is licensed under a BSD license.
 

src/string/aarch64/memcpy.S

@@ -0,0 +1,186 @@
+/*
+ * memcpy - copy memory area
+ *
+ * Copyright (c) 2012-2020, Arm Limited.
+ * SPDX-License-Identifier: MIT
+ */
+
+/* Assumptions:
+ *
+ * ARMv8-a, AArch64, unaligned accesses.
+ *
+ */
+
+#define dstin   x0
+#define src     x1
+#define count   x2
+#define dst     x3
+#define srcend  x4
+#define dstend  x5
+#define A_l     x6
+#define A_lw    w6
+#define A_h     x7
+#define B_l     x8
+#define B_lw    w8
+#define B_h     x9
+#define C_l     x10
+#define C_lw    w10
+#define C_h     x11
+#define D_l     x12
+#define D_h     x13
+#define E_l     x14
+#define E_h     x15
+#define F_l     x16
+#define F_h     x17
+#define G_l     count
+#define G_h     dst
+#define H_l     src
+#define H_h     srcend
+#define tmp1    x14
+
+/* This implementation of memcpy uses unaligned accesses and branchless
+   sequences to keep the code small, simple and improve performance.
+
+   Copies are split into 3 main cases: small copies of up to 32 bytes, medium
+   copies of up to 128 bytes, and large copies.  The overhead of the overlap
+   check is negligible since it is only required for large copies.
+
+   Large copies use a software pipelined loop processing 64 bytes per iteration.
+   The destination pointer is 16-byte aligned to minimize unaligned accesses.
+   The loop tail is handled by always copying 64 bytes from the end.
+*/
+
+.global memcpy
+.type memcpy,%function
+memcpy:
+	add     srcend, src, count
+	add     dstend, dstin, count
+	cmp     count, 128
+	b.hi    .Lcopy_long
+	cmp     count, 32
+	b.hi    .Lcopy32_128
+
+	/* Small copies: 0..32 bytes.  */
+	cmp     count, 16
+	b.lo    .Lcopy16
+	ldp     A_l, A_h, [src]
+	ldp     D_l, D_h, [srcend, -16]
+	stp     A_l, A_h, [dstin]
+	stp     D_l, D_h, [dstend, -16]
+	ret
+
+	/* Copy 8-15 bytes.  */
+.Lcopy16:
+	tbz     count, 3, .Lcopy8
+	ldr     A_l, [src]
+	ldr     A_h, [srcend, -8]
+	str     A_l, [dstin]
+	str     A_h, [dstend, -8]
+	ret
+
+	.p2align 3
+	/* Copy 4-7 bytes.  */
+.Lcopy8:
+	tbz     count, 2, .Lcopy4
+	ldr     A_lw, [src]
+	ldr     B_lw, [srcend, -4]
+	str     A_lw, [dstin]
+	str     B_lw, [dstend, -4]
+	ret
+
+	/* Copy 0..3 bytes using a branchless sequence.  */
+.Lcopy4:
+	cbz     count, .Lcopy0
+	lsr     tmp1, count, 1
+	ldrb    A_lw, [src]
+	ldrb    C_lw, [srcend, -1]
+	ldrb    B_lw, [src, tmp1]
+	strb    A_lw, [dstin]
+	strb    B_lw, [dstin, tmp1]
+	strb    C_lw, [dstend, -1]
+.Lcopy0:
+	ret
+
+	.p2align 4
+	/* Medium copies: 33..128 bytes.  */
+.Lcopy32_128:
+	ldp     A_l, A_h, [src]
+	ldp     B_l, B_h, [src, 16]
+	ldp     C_l, C_h, [srcend, -32]
+	ldp     D_l, D_h, [srcend, -16]
+	cmp     count, 64
+	b.hi    .Lcopy128
+	stp     A_l, A_h, [dstin]
+	stp     B_l, B_h, [dstin, 16]
+	stp     C_l, C_h, [dstend, -32]
+	stp     D_l, D_h, [dstend, -16]
+	ret
+
+	.p2align 4
+	/* Copy 65..128 bytes.  */
+.Lcopy128:
+	ldp     E_l, E_h, [src, 32]
+	ldp     F_l, F_h, [src, 48]
+	cmp     count, 96
+	b.ls    .Lcopy96
+	ldp     G_l, G_h, [srcend, -64]
+	ldp     H_l, H_h, [srcend, -48]
+	stp     G_l, G_h, [dstend, -64]
+	stp     H_l, H_h, [dstend, -48]
+.Lcopy96:
+	stp     A_l, A_h, [dstin]
+	stp     B_l, B_h, [dstin, 16]
+	stp     E_l, E_h, [dstin, 32]
+	stp     F_l, F_h, [dstin, 48]
+	stp     C_l, C_h, [dstend, -32]
+	stp     D_l, D_h, [dstend, -16]
+	ret
+
+	.p2align 4
+	/* Copy more than 128 bytes.  */
+.Lcopy_long:
+
+	/* Copy 16 bytes and then align dst to 16-byte alignment.  */
+
+	ldp     D_l, D_h, [src]
+	and     tmp1, dstin, 15
+	bic     dst, dstin, 15
+	sub     src, src, tmp1
+	add     count, count, tmp1      /* Count is now 16 too large.  */
+	ldp     A_l, A_h, [src, 16]
+	stp     D_l, D_h, [dstin]
+	ldp     B_l, B_h, [src, 32]
+	ldp     C_l, C_h, [src, 48]
+	ldp     D_l, D_h, [src, 64]!
+	subs    count, count, 128 + 16  /* Test and readjust count.  */
+	b.ls    .Lcopy64_from_end
+
+.Lloop64:
+	stp     A_l, A_h, [dst, 16]
+	ldp     A_l, A_h, [src, 16]
+	stp     B_l, B_h, [dst, 32]
+	ldp     B_l, B_h, [src, 32]
+	stp     C_l, C_h, [dst, 48]
+	ldp     C_l, C_h, [src, 48]
+	stp     D_l, D_h, [dst, 64]!
+	ldp     D_l, D_h, [src, 64]!
+	subs    count, count, 64
+	b.hi    .Lloop64
+
+	/* Write the last iteration and copy 64 bytes from the end.  */
+.Lcopy64_from_end:
+	ldp     E_l, E_h, [srcend, -64]
+	stp     A_l, A_h, [dst, 16]
+	ldp     A_l, A_h, [srcend, -48]
+	stp     B_l, B_h, [dst, 32]
+	ldp     B_l, B_h, [srcend, -32]
+	stp     C_l, C_h, [dst, 48]
+	ldp     C_l, C_h, [srcend, -16]
+	stp     D_l, D_h, [dst, 64]
+	stp     E_l, E_h, [dstend, -64]
+	stp     A_l, A_h, [dstend, -48]
+	stp     B_l, B_h, [dstend, -32]
+	stp     C_l, C_h, [dstend, -16]
+	ret
+
+.size memcpy,.-memcpy

src/string/aarch64/memset.S

@@ -0,0 +1,115 @@
+/*
+ * memset - fill memory with a constant byte
+ *
+ * Copyright (c) 2012-2020, Arm Limited.
+ * SPDX-License-Identifier: MIT
+ */
+
+/* Assumptions:
+ *
+ * ARMv8-a, AArch64, Advanced SIMD, unaligned accesses.
+ *
+ */
+
+#define dstin   x0
+#define val     x1
+#define valw    w1
+#define count   x2
+#define dst     x3
+#define dstend  x4
+#define zva_val x5
+
+.global memset
+.type memset,%function
+memset:
+
+	dup     v0.16B, valw
+	add     dstend, dstin, count
+
+	cmp     count, 96
+	b.hi    .Lset_long
+	cmp     count, 16
+	b.hs    .Lset_medium
+	mov     val, v0.D[0]
+
+	/* Set 0..15 bytes.  */
+	tbz     count, 3, 1f
+	str     val, [dstin]
+	str     val, [dstend, -8]
+	ret
+	nop
+1:      tbz     count, 2, 2f
+	str     valw, [dstin]
+	str     valw, [dstend, -4]
+	ret
+2:      cbz     count, 3f
+	strb    valw, [dstin]
+	tbz     count, 1, 3f
+	strh    valw, [dstend, -2]
+3:      ret
+
+	/* Set 17..96 bytes.  */
+.Lset_medium:
+	str     q0, [dstin]
+	tbnz    count, 6, .Lset96
+	str     q0, [dstend, -16]
+	tbz     count, 5, 1f
+	str     q0, [dstin, 16]
+	str     q0, [dstend, -32]
+1:      ret
+
+	.p2align 4
+	/* Set 64..96 bytes.  Write 64 bytes from the start and
+	   32 bytes from the end.  */
+.Lset96:
+	str     q0, [dstin, 16]
+	stp     q0, q0, [dstin, 32]
+	stp     q0, q0, [dstend, -32]
+	ret
+
+	.p2align 4
+.Lset_long:
+	and     valw, valw, 255
+	bic     dst, dstin, 15
+	str     q0, [dstin]
+	cmp     count, 160
+	ccmp    valw, 0, 0, hs
+	b.ne    .Lno_zva
+
+#ifndef SKIP_ZVA_CHECK
+	mrs     zva_val, dczid_el0
+	and     zva_val, zva_val, 31
+	cmp     zva_val, 4              /* ZVA size is 64 bytes.  */
+	b.ne    .Lno_zva
+#endif
+	str     q0, [dst, 16]
+	stp     q0, q0, [dst, 32]
+	bic     dst, dst, 63
+	sub     count, dstend, dst      /* Count is now 64 too large.  */
+	sub     count, count, 128       /* Adjust count and bias for loop.  */
+
+	.p2align 4
+.Lzva_loop:
+	add     dst, dst, 64
+	dc      zva, dst
+	subs    count, count, 64
+	b.hi    .Lzva_loop
+	stp     q0, q0, [dstend, -64]
+	stp     q0, q0, [dstend, -32]
+	ret
+
+.Lno_zva:
+	sub     count, dstend, dst      /* Count is 16 too large.  */
+	sub     dst, dst, 16            /* Dst is biased by -32.  */
+	sub     count, count, 64 + 16   /* Adjust count and bias for loop.  */
+.Lno_zva_loop:
+	stp     q0, q0, [dst, 32]
+	stp     q0, q0, [dst, 64]!
+	subs    count, count, 64
+	b.hi    .Lno_zva_loop
+	stp     q0, q0, [dstend, -64]
+	stp     q0, q0, [dstend, -32]
+	ret
+
+.size memset,.-memset
+