[thirdparty/glibc.git] / sysdeps / arm / armv6 / strrchr.S

/* strrchr -- find the last occurence of C in a nul-terminated string
   Copyright (C) 2013-2017 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 (strrchr)
	@ r0 = start of string
	@ r1 = character to match
	@ returns NULL for no match, or a pointer to the match

	mov	r3, r0
	mov	r0, #0
	uxtb	r1, r1

	@ Loop a few times until we're aligned.
	tst	r3, #7
	beq	2f
1:	sfi_breg r3, \
	ldrb	r2, [\B], #1
	cmp	r2, r1			@ Find the character
	it	eq
	subeq	r0, r3, #1
	cmp	r2, #0			@ Find EOS
	it	eq
	bxeq	lr
	tst	r3, #7			@ Find the aligment point
	bne	1b

	@ So now we're aligned.  Now we actually need a stack frame.
2:	push	{ r4, r5, r6, r7 }
	cfi_adjust_cfa_offset (16)
	cfi_rel_offset (r4, 0)
	cfi_rel_offset (r5, 4)
	cfi_rel_offset (r6, 8)
	cfi_rel_offset (r7, 12)

	orr	r1, r1, r1, lsl #8	@ Replicate C to all bytes
#ifdef ARCH_HAS_T2
	movw	ip, #0x0101
	movt	ip, #0x0101
#else
	ldr	ip, =0x01010101
#endif
	orr	r1, r1, r1, lsl #16
	mov	r2, #0			@ No found bits yet

	@ Loop searching for EOS and C, 8 bytes at a time.
	@ Any time we find a match in a word, we copy the address of
	@ the word to r0, and the found bits to r2.
3:	sfi_breg r3, \
	ldrd	r4, r5, [\B], #8
	@ 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.
	uqsub8	r6, ip, r4		@ Find EOS
	uqsub8	r7, ip, r5
	eor	r4, r4, r1		@ Convert C bytes to 0
	eor	r5, r5, r1
	uqsub8	r4, ip, r4		@ Find C
	uqsub8	r5, ip, r5
	cmp	r6, #0			@ Found EOS, first word
	bne	4f
	cmp	r4, #0			@ Handle C, first word
	itt	ne
	subne	r0, r3, #8
	movne	r2, r4
	cmp	r7, #0			@ Found EOS, second word
	bne	5f
	cmp	r5, #0			@ Handle C, second word
	itt	ne
	subne	r0, r3, #4
	movne	r2, r5
	b	3b

	@ Found EOS in second word; fold to first word.
5:	add	r3, r3, #4		@ Dec pointer to 2nd word, with below
	mov	r4, r5			@ Overwrite first word C found
	mov	r6, r7			@ Overwrite first word EOS found

	@ Found EOS.  Zap found C after EOS.
4:	sub	r3, r3, #8		@ Decrement pointer to first word
#ifdef __ARMEB__
	@ Byte swap to be congruent with LE, which is easier from here on.
	rev	r6, r6			@ Byte swap found EOS,
	rev	r4, r4			@ ... this found C
	rev	r2, r2			@ ... prev found C
#endif
	sub	r7, r6, #1		@ Toggle EOS lsb and below
	eor	r6, r6, r7		@ All bits below and including lsb
	ands	r4, r4, r6		@ Zap C above EOS
	itt	ne
	movne	r2, r4			@ Copy to result, if still non-zero
	movne	r0, r3

	pop	{ r4, r5, r6, r7 }
	cfi_adjust_cfa_offset (-16)
	cfi_restore (r4)
	cfi_restore (r5)
	cfi_restore (r6)
	cfi_restore (r7)

	@ Adjust the result pointer if we found a word containing C.
	cmp	r2, #0
	clz	r2, r2			@ Find the bit offset of the last C
	itt	ne
	rsbne	r2, r2, #32		@ Convert to a count from the right
	addne	r0, r0, r2, lsr #3	@ Convert to byte offset and add.
	bx	lr

END (strrchr)

weak_alias (strrchr, rindex)
libc_hidden_builtin_def (strrchr)
Commit	Line	Data
f5ad94e0	1	/* strrchr -- find the last occurence of C in a nul-terminated string
bfff8b1b	2	Copyright (C) 2013-2017 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 (strrchr)
	25	@ r0 = start of string
	26	@ r1 = character to match
	27	@ returns NULL for no match, or a pointer to the match
	28
	29	mov r3, r0
	30	mov r0, #0
	31	uxtb r1, r1
	32
	33	@ Loop a few times until we're aligned.
	34	tst r3, #7
	35	beq 2f
a7ac7522 RM	36	1: sfi_breg r3, \
a7ac7522 RM	37	ldrb r2, [\B], #1
f5ad94e0 RH	38	cmp r2, r1 @ Find the character
	39	it eq
	40	subeq r0, r3, #1
	41	cmp r2, #0 @ Find EOS
	42	it eq
	43	bxeq lr
	44	tst r3, #7 @ Find the aligment point
	45	bne 1b
	46
	47	@ So now we're aligned. Now we actually need a stack frame.
	48	2: push { r4, r5, r6, r7 }
	49	cfi_adjust_cfa_offset (16)
	50	cfi_rel_offset (r4, 0)
	51	cfi_rel_offset (r5, 4)
	52	cfi_rel_offset (r6, 8)
	53	cfi_rel_offset (r7, 12)
	54
	55	orr r1, r1, r1, lsl #8 @ Replicate C to all bytes
	56	#ifdef ARCH_HAS_T2
	57	movw ip, #0x0101
	58	movt ip, #0x0101
	59	#else
	60	ldr ip, =0x01010101
	61	#endif
	62	orr r1, r1, r1, lsl #16
	63	mov r2, #0 @ No found bits yet
	64
	65	@ Loop searching for EOS and C, 8 bytes at a time.
	66	@ Any time we find a match in a word, we copy the address of
	67	@ the word to r0, and the found bits to r2.
a7ac7522 RM	68	3: sfi_breg r3, \
a7ac7522 RM	69	ldrd r4, r5, [\B], #8
f5ad94e0 RH	70	@ Subtracting (unsigned saturating) from 1 means result of 1 for
	71	@ any byte that was originally zero and 0 otherwise. Therefore
	72	@ we consider the lsb of each byte the "found" bit.
	73	uqsub8 r6, ip, r4 @ Find EOS
	74	uqsub8 r7, ip, r5
	75	eor r4, r4, r1 @ Convert C bytes to 0
	76	eor r5, r5, r1
	77	uqsub8 r4, ip, r4 @ Find C
	78	uqsub8 r5, ip, r5
	79	cmp r6, #0 @ Found EOS, first word
	80	bne 4f
	81	cmp r4, #0 @ Handle C, first word
	82	itt ne
	83	subne r0, r3, #8
	84	movne r2, r4
	85	cmp r7, #0 @ Found EOS, second word
	86	bne 5f
	87	cmp r5, #0 @ Handle C, second word
	88	itt ne
	89	subne r0, r3, #4
	90	movne r2, r5
	91	b 3b
	92
	93	@ Found EOS in second word; fold to first word.
	94	5: add r3, r3, #4 @ Dec pointer to 2nd word, with below
	95	mov r4, r5 @ Overwrite first word C found
	96	mov r6, r7 @ Overwrite first word EOS found
	97
	98	@ Found EOS. Zap found C after EOS.
	99	4: sub r3, r3, #8 @ Decrement pointer to first word
	100	#ifdef __ARMEB__
	101	@ Byte swap to be congruent with LE, which is easier from here on.
	102	rev r6, r6 @ Byte swap found EOS,
	103	rev r4, r4 @ ... this found C
	104	rev r2, r2 @ ... prev found C
	105	#endif
	106	sub r7, r6, #1 @ Toggle EOS lsb and below
	107	eor r6, r6, r7 @ All bits below and including lsb
	108	ands r4, r4, r6 @ Zap C above EOS
	109	itt ne
	110	movne r2, r4 @ Copy to result, if still non-zero
	111	movne r0, r3
	112
	113	pop { r4, r5, r6, r7 }
	114	cfi_adjust_cfa_offset (-16)
	115	cfi_restore (r4)
	116	cfi_restore (r5)
	117	cfi_restore (r6)
	118	cfi_restore (r7)
	119
	120	@ Adjust the result pointer if we found a word containing C.
	121	cmp r2, #0
	122	clz r2, r2 @ Find the bit offset of the last C
	123	itt ne
	124	rsbne r2, r2, #32 @ Convert to a count from the right
	125	addne r0, r0, r2, lsr #3 @ Convert to byte offset and add.
	126	bx lr
	127
	128	END (strrchr)
	129
	130	weak_alias (strrchr, rindex)
	131	libc_hidden_builtin_def (strrchr)