libc/arch-arm64/generic/bionic/memmove.S

/* Copyright (c) 2014, Linaro Limited
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
       * Redistributions of source code must retain the above copyright
         notice, this list of conditions and the following disclaimer.
       * Redistributions in binary form must reproduce the above copyright
         notice, this list of conditions and the following disclaimer in the
         documentation and/or other materials provided with the distribution.
       * Neither the name of the Linaro nor the
         names of its contributors may be used to endorse or promote products
         derived from this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/* Assumptions:
 *
 * ARMv8-a, AArch64
 * Unaligned accesses
 * wchar_t is 4 bytes
 */

#include <private/bionic_asm.h>

/* Parameters and result.  */
#ifdef BCOPY
#define origdstin	x1
#define origsrc	x0
#endif
#define dstin	x0
#define src	x1
#define count	x2
#define tmp1	x3
#define tmp1w	w3
#define tmp2	x4
#define tmp2w	w4
#define tmp3	x5
#define tmp3w	w5
#define dst	x6

#define A_l	x7
#define A_h	x8
#define B_l	x9
#define B_h	x10
#define C_l	x11
#define C_h	x12
#define D_l	x13
#define D_h	x14

#ifdef BCOPY
ENTRY(bcopy)
	/* Swap src and dst so that a branch to memcpy doesn't cause issues. */
	mov	tmp1, origsrc
	mov	origsrc, origdstin
	mov	origdstin, tmp1
#elif defined(WMEMMOVE)
ENTRY(wmemmove)
	lsl	count, count, #2
#else
ENTRY(memmove)
#endif
	cmp	dstin, src
	b.lo	.Ldownwards
	add	tmp1, src, count
	cmp	dstin, tmp1
	b.hs	memcpy		/* No overlap.  */

	/* Upwards move with potential overlap.
	 * Need to move from the tail backwards.  SRC and DST point one
	 * byte beyond the remaining data to move.  */
	add	dst, dstin, count
	add	src, src, count
	cmp	count, #64
	b.ge	.Lmov_not_short_up

	/* Deal with small moves quickly by dropping straight into the
	 * exit block.  */
.Ltail63up:
	/* Move up to 48 bytes of data.  At this point we only need the
	 * bottom 6 bits of count to be accurate.  */
	ands	tmp1, count, #0x30
	b.eq	.Ltail15up
	sub	dst, dst, tmp1
	sub	src, src, tmp1
	cmp	tmp1w, #0x20
	b.eq	1f
	b.lt	2f
	ldp	A_l, A_h, [src, #32]
	stp	A_l, A_h, [dst, #32]
1:
	ldp	A_l, A_h, [src, #16]
	stp	A_l, A_h, [dst, #16]
2:
	ldp	A_l, A_h, [src]
	stp	A_l, A_h, [dst]
.Ltail15up:
	/* Move up to 15 bytes of data.  Does not assume additional data
	 * being moved.  */
	tbz	count, #3, 1f
	ldr	tmp1, [src, #-8]!
	str	tmp1, [dst, #-8]!
1:
	tbz	count, #2, 1f
	ldr	tmp1w, [src, #-4]!
	str	tmp1w, [dst, #-4]!
1:
	tbz	count, #1, 1f
	ldrh	tmp1w, [src, #-2]!
	strh	tmp1w, [dst, #-2]!
1:
	tbz	count, #0, 1f
	ldrb	tmp1w, [src, #-1]
	strb	tmp1w, [dst, #-1]
1:
	ret

.Lmov_not_short_up:
	/* We don't much care about the alignment of DST, but we want SRC
	 * to be 128-bit (16 byte) aligned so that we don't cross cache line
	 * boundaries on both loads and stores.  */
	ands	tmp2, src, #15		/* Bytes to reach alignment.  */
	b.eq	2f
	sub	count, count, tmp2
	/* Move enough data to reach alignment; unlike memcpy, we have to
	 * be aware of the overlap, which means we can't move data twice.  */
	tbz	tmp2, #3, 1f
	ldr	tmp1, [src, #-8]!
	str	tmp1, [dst, #-8]!
1:
	tbz	tmp2, #2, 1f
	ldr	tmp1w, [src, #-4]!
	str	tmp1w, [dst, #-4]!
1:
	tbz	tmp2, #1, 1f
	ldrh	tmp1w, [src, #-2]!
	strh	tmp1w, [dst, #-2]!
1:
	tbz	tmp2, #0, 1f
	ldrb	tmp1w, [src, #-1]!
	strb	tmp1w, [dst, #-1]!
1:

	/* There may be less than 63 bytes to go now.  */
	cmp	count, #63
	b.le	.Ltail63up
2:
	subs	count, count, #128
	b.ge	.Lmov_body_large_up
	/* Less than 128 bytes to move, so handle 64 here and then jump
	 * to the tail.  */
	ldp	A_l, A_h, [src, #-64]!
	ldp	B_l, B_h, [src, #16]
	ldp	C_l, C_h, [src, #32]
	ldp	D_l, D_h, [src, #48]
	stp	A_l, A_h, [dst, #-64]!
	stp	B_l, B_h, [dst, #16]
	stp	C_l, C_h, [dst, #32]
	stp	D_l, D_h, [dst, #48]
	tst	count, #0x3f
	b.ne	.Ltail63up
	ret

	/* Critical loop.  Start at a new Icache line boundary.  Assuming
	 * 64 bytes per line this ensures the entire loop is in one line.  */
	.p2align 6
.Lmov_body_large_up:
	/* There are at least 128 bytes to move.  */
	ldp	A_l, A_h, [src, #-16]
	ldp	B_l, B_h, [src, #-32]
	ldp	C_l, C_h, [src, #-48]
	ldp	D_l, D_h, [src, #-64]!
1:
	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.ge	1b
	stp	A_l, A_h, [dst, #-16]
	stp	B_l, B_h, [dst, #-32]
	stp	C_l, C_h, [dst, #-48]
	stp	D_l, D_h, [dst, #-64]!
	tst	count, #0x3f
	b.ne	.Ltail63up
	ret


.Ldownwards:
	/* For a downwards move we can safely use memcpy provided that
	 * DST is more than 16 bytes away from SRC.  */
	sub	tmp1, src, #16
	cmp	dstin, tmp1
	b.ls	memcpy		/* May overlap, but not critically.  */

	mov	dst, dstin	/* Preserve DSTIN for return value.  */
	cmp	count, #64
	b.ge	.Lmov_not_short_down

	/* Deal with small moves quickly by dropping straight into the
	 * exit block.  */
.Ltail63down:
	/* Move up to 48 bytes of data.  At this point we only need the
	 * bottom 6 bits of count to be accurate.  */
	ands	tmp1, count, #0x30
	b.eq	.Ltail15down
	add	dst, dst, tmp1
	add	src, src, tmp1
	cmp	tmp1w, #0x20
	b.eq	1f
	b.lt	2f
	ldp	A_l, A_h, [src, #-48]
	stp	A_l, A_h, [dst, #-48]
1:
	ldp	A_l, A_h, [src, #-32]
	stp	A_l, A_h, [dst, #-32]
2:
	ldp	A_l, A_h, [src, #-16]
	stp	A_l, A_h, [dst, #-16]
.Ltail15down:
	/* Move up to 15 bytes of data.  Does not assume additional data
	   being moved.  */
	tbz	count, #3, 1f
	ldr	tmp1, [src], #8
	str	tmp1, [dst], #8
1:
	tbz	count, #2, 1f
	ldr	tmp1w, [src], #4
	str	tmp1w, [dst], #4
1:
	tbz	count, #1, 1f
	ldrh	tmp1w, [src], #2
	strh	tmp1w, [dst], #2
1:
	tbz	count, #0, 1f
	ldrb	tmp1w, [src]
	strb	tmp1w, [dst]
1:
	ret

.Lmov_not_short_down:
	/* We don't much care about the alignment of DST, but we want SRC
	 * to be 128-bit (16 byte) aligned so that we don't cross cache line
	 * boundaries on both loads and stores.  */
	neg	tmp2, src
	ands	tmp2, tmp2, #15		/* Bytes to reach alignment.  */
	b.eq	2f
	sub	count, count, tmp2
	/* Move enough data to reach alignment; unlike memcpy, we have to
	 * be aware of the overlap, which means we can't move data twice.  */
	tbz	tmp2, #3, 1f
	ldr	tmp1, [src], #8
	str	tmp1, [dst], #8
1:
	tbz	tmp2, #2, 1f
	ldr	tmp1w, [src], #4
	str	tmp1w, [dst], #4
1:
	tbz	tmp2, #1, 1f
	ldrh	tmp1w, [src], #2
	strh	tmp1w, [dst], #2
1:
	tbz	tmp2, #0, 1f
	ldrb	tmp1w, [src], #1
	strb	tmp1w, [dst], #1
1:

	/* There may be less than 63 bytes to go now.  */
	cmp	count, #63
	b.le	.Ltail63down
2:
	subs	count, count, #128
	b.ge	.Lmov_body_large_down
	/* Less than 128 bytes to move, so handle 64 here and then jump
	 * to the tail.  */
	ldp	A_l, A_h, [src]
	ldp	B_l, B_h, [src, #16]
	ldp	C_l, C_h, [src, #32]
	ldp	D_l, D_h, [src, #48]
	stp	A_l, A_h, [dst]
	stp	B_l, B_h, [dst, #16]
	stp	C_l, C_h, [dst, #32]
	stp	D_l, D_h, [dst, #48]
	tst	count, #0x3f
	add	src, src, #64
	add	dst, dst, #64
	b.ne	.Ltail63down
	ret

	/* Critical loop.  Start at a new cache line boundary.  Assuming
	 * 64 bytes per line this ensures the entire loop is in one line.  */
	.p2align 6
.Lmov_body_large_down:
	/* There are at least 128 bytes to move.  */
	ldp	A_l, A_h, [src, #0]
	sub	dst, dst, #16		/* Pre-bias.  */
	ldp	B_l, B_h, [src, #16]
	ldp	C_l, C_h, [src, #32]
	ldp	D_l, D_h, [src, #48]!	/* src += 64 - Pre-bias.  */
1:
	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.ge	1b
	stp	A_l, A_h, [dst, #16]
	stp	B_l, B_h, [dst, #32]
	stp	C_l, C_h, [dst, #48]
	stp	D_l, D_h, [dst, #64]
	add	src, src, #16
	add	dst, dst, #64 + 16
	tst	count, #0x3f
	b.ne	.Ltail63down
	ret
#ifdef BCOPY
END(bcopy)
#elif defined(WMEMMOVE)
END(wmemmove)
#else
END(memmove)
#endif