/* Optimized strchr implementation for PowerPC.

   Copyright (C) 1997-2018 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>

/* See strlen.s for comments on how this works.  */

/* char * [r3] strchr (const char *s [r3] , int c [r4] )  */

ENTRY (strchr)

#define rTMP1	r0

#define rRTN	r3	/* outgoing result */

#define rSTR	r8	/* current word pointer */

#define rCHR	r4	/* byte we're looking for, spread over the whole word */

#define rWORD	r5	/* the current word */

#define rCLZB	rCHR	/* leading zero byte count */

#define rFEFE	r6	/* constant 0xfefefeff (-0x01010101) */

#define r7F7F	r7	/* constant 0x7f7f7f7f */

#define rTMP2	r9

#define rIGN	r10	/* number of bits we should ignore in the first word */

#define rMASK	r11	/* mask with the bits to ignore set to 0 */

#define rTMP3	r12

#define rTMP4	rIGN

#define rTMP5	rMASK

	rlwimi	rCHR, rCHR, 8, 16, 23

	li	rMASK, -1

	rlwimi	rCHR, rCHR, 16, 0, 15

	rlwinm	rIGN, rRTN, 3, 27, 28

	lis	rFEFE, -0x101

	lis	r7F7F, 0x7f7f

	clrrwi	rSTR, rRTN, 2

	addi	rFEFE, rFEFE, -0x101

	addi	r7F7F, r7F7F, 0x7f7f

/* Test the first (partial?) word.  */

	lwz	rWORD, 0(rSTR)

#ifdef __LITTLE_ENDIAN__

	slw	rMASK, rMASK, rIGN

#else

	srw	rMASK, rMASK, rIGN

#endif

	orc	rWORD, rWORD, rMASK

	add	rTMP1, rFEFE, rWORD

	nor	rTMP2, r7F7F, rWORD

	and.	rTMP4, rTMP1, rTMP2

	xor	rTMP3, rCHR, rWORD

	orc	rTMP3, rTMP3, rMASK

	b	L(loopentry)

/* The loop.  */

L(loop):

	lwzu	rWORD, 4(rSTR)

	and.	rTMP5, rTMP1, rTMP2

/* Test for 0.	*/

	add	rTMP1, rFEFE, rWORD /* x - 0x01010101.  */

	nor	rTMP2, r7F7F, rWORD /* ~(x | 0x7f7f7f7f) == ~x & 0x80808080.  */

	bne	L(foundit)

	and.	rTMP4, rTMP1, rTMP2 /* (x - 0x01010101) & ~x & 0x80808080.  */

/* Start test for the bytes we're looking for.  */

	xor	rTMP3, rCHR, rWORD

L(loopentry):

	add	rTMP1, rFEFE, rTMP3

	nor	rTMP2, r7F7F, rTMP3

	beq	L(loop)

/* There is a zero byte in the word, but may also be a matching byte (either

   before or after the zero byte).  In fact, we may be looking for a

   zero byte, in which case we return a match.  */

	and.	rTMP5, rTMP1, rTMP2

	li	rRTN, 0

	beqlr

/* At this point:

   rTMP5 bytes are 0x80 for each match of c, 0 otherwise.

   rTMP4 bytes are 0x80 for each match of 0, 0 otherwise.

   But there may be false matches in the next most significant byte from

   a true match due to carries.  This means we need to recalculate the

   matches using a longer method for big-endian.  */

#ifdef __LITTLE_ENDIAN__

	addi	rTMP1, rTMP5, -1

	andc	rTMP1, rTMP1, rTMP5

	cntlzw	rCLZB, rTMP1

	addi	rTMP2, rTMP4, -1

	andc	rTMP2, rTMP2, rTMP4

	cmplw	rTMP1, rTMP2

	bgtlr

	subfic	rCLZB, rCLZB, 32-7

#else

/* I think we could reduce this by two instructions by keeping the "nor"

   results from the loop for reuse here.  See strlen.S tail.  Similarly

   one instruction could be pruned from L(foundit).  */

	and	rFEFE, r7F7F, rWORD

	or	rTMP5, r7F7F, rWORD

	and	rTMP1, r7F7F, rTMP3

	or	rTMP4, r7F7F, rTMP3

	add	rFEFE, rFEFE, r7F7F

	add	rTMP1, rTMP1, r7F7F

	nor	rWORD, rTMP5, rFEFE

	nor	rTMP2, rTMP4, rTMP1

	cntlzw	rCLZB, rTMP2

	cmplw	rWORD, rTMP2

	bgtlr

#endif

	srwi	rCLZB, rCLZB, 3

	add	rRTN, rSTR, rCLZB

	blr

L(foundit):

#ifdef __LITTLE_ENDIAN__

	addi	rTMP1, rTMP5, -1

	andc	rTMP1, rTMP1, rTMP5

	cntlzw	rCLZB, rTMP1

	subfic	rCLZB, rCLZB, 32-7-32

	srawi	rCLZB, rCLZB, 3

#else

	and	rTMP1, r7F7F, rTMP3

	or	rTMP4, r7F7F, rTMP3

	add	rTMP1, rTMP1, r7F7F

	nor	rTMP2, rTMP4, rTMP1

	cntlzw	rCLZB, rTMP2

	subi	rSTR, rSTR, 4

	srwi	rCLZB, rCLZB, 3

#endif

	add	rRTN, rSTR, rCLZB

	blr

END (strchr)

weak_alias (strchr, index)

libc_hidden_builtin_def (strchr)