/* strrchr -- find the last occurence of C in a nul-terminated string

   Copyright (C) 2013-2018 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:	ldrb	r2, [r3], #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:	ldrd	r4, r5, [r3], #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)