[thirdparty/glibc.git] / ports / sysdeps / arm / armv6 / rawmemchr.S

/* rawmemchr -- find a byte within an unsized memory block.
   Copyright (C) 2013-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library.  If not, see
   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

	.syntax unified
	.text

ENTRY (__rawmemchr)
	@ r0 = start of string
	@ r1 = character to match
	@ returns a pointer to the match, which must be present.
	sfi_breg r0, \
	ldrb	r2, [\B]		@ load first byte asap

	@ To cater to long strings, we want to search through a few
	@ characters until we reach an aligned pointer.  To cater to
	@ small strings, we don't want to start doing word operations
	@ immediately.  The compromise is a maximum of 16 bytes less
	@ whatever is required to end with an aligned pointer.
	@ r3 = number of characters to search in alignment loop
	and	r3, r0, #7
	uxtb	r1, r1
	rsb	r3, r3, #15		@ 16 - 1 peeled loop iteration
	cmp	r2, r1
	it	eq
	bxeq	lr

	@ Loop until we find ...
1:	sfi_breg r0, \
	ldrb	r2, [\B, #1]!
	subs	r3, r3, #1		@ ... the alignment point
	it	ne
	cmpne	r2, r1			@ ... or C
	bne	1b

	@ Disambiguate the exit possibilites above
	cmp	r2, r1			@ Found C
	it	eq
	bxeq	lr
	add	r0, r0, #1

	@ So now we're aligned.
	sfi_breg r0, \
	ldrd	r2, r3, [\B], #8
	orr	r1, r1, r1, lsl #8	@ Replicate C to all bytes
#ifdef ARCH_HAS_T2
	movw	ip, #0x0101
	sfi_pld	r0, #64
	movt	ip, #0x0101
#else
	ldr	ip, =0x01010101
	sfi_pld	r0, #64
#endif
	orr	r1, r1, r1, lsl #16

	@ Loop searching for C, 8 bytes at a time.
	@ Subtracting (unsigned saturating) from 1 means result of 1 for
	@ any byte that was originally zero and 0 otherwise.  Therefore
	@ we consider the lsb of each byte the "found" bit.
2:	eor	r2, r2, r1		@ Convert C bytes to 0
	eor	r3, r3, r1
	uqsub8	r2, ip, r2		@ Find C
	uqsub8	r3, ip, r3
	sfi_pld	r0, #128
	orrs	r3, r3, r2		@ Test both words for found
	it	eq
	sfi_breg r0, \
	ldrdeq	r2, r3, [\B], #8
	beq	2b

	@ Found something.  Disambiguate between first and second words.
	@ Adjust r0 to point to the word containing the match.
	@ Adjust r2 to the found bits for the word containing the match.
	cmp	r2, #0
	sub	r0, r0, #4
	ite	eq
	moveq	r2, r3
	subne	r0, r0, #4

	@ Find the bit-offset of the match within the word.  Note that the
	@ bit result from clz will be 7 higher than "true", but we'll
	@ immediately discard those bits converting to a byte offset.
#ifdef __ARMEL__
	rev	r2, r2			@ For LE, count from the little end
#endif
	clz	r2, r2
	add	r0, r0, r2, lsr #3	@ Adjust the pointer to the found byte
	bx	lr

END (__rawmemchr)

weak_alias (__rawmemchr, rawmemchr)
libc_hidden_def (__rawmemchr)
Commit	Line	Data
f5ad94e0	1	/* rawmemchr -- find a byte within an unsized memory block.
d4697bc9	2	Copyright (C) 2013-2014 Free Software Foundation, Inc.
f5ad94e0 RH	3	This file is part of the GNU C Library.
	4
	5	The GNU C Library is free software; you can redistribute it and/or
	6	modify it under the terms of the GNU Lesser General Public
	7	License as published by the Free Software Foundation; either
	8	version 2.1 of the License, or (at your option) any later version.
	9
	10	The GNU C Library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	Lesser General Public License for more details.
	14
	15	You should have received a copy of the GNU Lesser General Public
	16	License along with the GNU C Library. If not, see
	17	<http://www.gnu.org/licenses/>. */
	18
	19	#include <sysdep.h>
	20
	21	.syntax unified
	22	.text
	23
	24	ENTRY (__rawmemchr)
	25	@ r0 = start of string
	26	@ r1 = character to match
	27	@ returns a pointer to the match, which must be present.
a7ac7522 RM	28	sfi_breg r0, \
a7ac7522 RM	29	ldrb r2, [\B] @ load first byte asap
f5ad94e0 RH	30
	31	@ To cater to long strings, we want to search through a few
	32	@ characters until we reach an aligned pointer. To cater to
	33	@ small strings, we don't want to start doing word operations
	34	@ immediately. The compromise is a maximum of 16 bytes less
	35	@ whatever is required to end with an aligned pointer.
	36	@ r3 = number of characters to search in alignment loop
	37	and r3, r0, #7
	38	uxtb r1, r1
	39	rsb r3, r3, #15 @ 16 - 1 peeled loop iteration
	40	cmp r2, r1
	41	it eq
	42	bxeq lr
	43
	44	@ Loop until we find ...
a7ac7522 RM	45	1: sfi_breg r0, \
a7ac7522 RM	46	ldrb r2, [\B, #1]!
f5ad94e0 RH	47	subs r3, r3, #1 @ ... the alignment point
	48	it ne
	49	cmpne r2, r1 @ ... or C
	50	bne 1b
	51
	52	@ Disambiguate the exit possibilites above
	53	cmp r2, r1 @ Found C
	54	it eq
	55	bxeq lr
	56	add r0, r0, #1
	57
	58	@ So now we're aligned.
a7ac7522 RM	59	sfi_breg r0, \
a7ac7522 RM	60	ldrd r2, r3, [\B], #8
f5ad94e0 RH	61	orr r1, r1, r1, lsl #8 @ Replicate C to all bytes
	62	#ifdef ARCH_HAS_T2
	63	movw ip, #0x0101
a7ac7522	64	sfi_pld r0, #64
f5ad94e0 RH	65	movt ip, #0x0101
	66	#else
	67	ldr ip, =0x01010101
a7ac7522	68	sfi_pld r0, #64
f5ad94e0 RH	69	#endif
	70	orr r1, r1, r1, lsl #16
	71
	72	@ Loop searching for C, 8 bytes at a time.
	73	@ Subtracting (unsigned saturating) from 1 means result of 1 for
	74	@ any byte that was originally zero and 0 otherwise. Therefore
	75	@ we consider the lsb of each byte the "found" bit.
	76	2: eor r2, r2, r1 @ Convert C bytes to 0
	77	eor r3, r3, r1
	78	uqsub8 r2, ip, r2 @ Find C
	79	uqsub8 r3, ip, r3
a7ac7522	80	sfi_pld r0, #128
f5ad94e0 RH	81	orrs r3, r3, r2 @ Test both words for found
f5ad94e0 RH	82	it eq
a7ac7522 RM	83	sfi_breg r0, \
a7ac7522 RM	84	ldrdeq r2, r3, [\B], #8
f5ad94e0 RH	85	beq 2b
	86
	87	@ Found something. Disambiguate between first and second words.
	88	@ Adjust r0 to point to the word containing the match.
	89	@ Adjust r2 to the found bits for the word containing the match.
	90	cmp r2, #0
	91	sub r0, r0, #4
	92	ite eq
	93	moveq r2, r3
	94	subne r0, r0, #4
	95
	96	@ Find the bit-offset of the match within the word. Note that the
	97	@ bit result from clz will be 7 higher than "true", but we'll
	98	@ immediately discard those bits converting to a byte offset.
	99	#ifdef __ARMEL__
	100	rev r2, r2 @ For LE, count from the little end
	101	#endif
	102	clz r2, r2
	103	add r0, r0, r2, lsr #3 @ Adjust the pointer to the found byte
	104	bx lr
	105
	106	END (__rawmemchr)
	107
	108	weak_alias (__rawmemchr, rawmemchr)
	109	libc_hidden_def (__rawmemchr)