/* Optimized strcmp implementation for Power7 using 'cmpb' instruction

   Copyright (C) 2014-2018 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/>.  */

/* The optimization is achieved here through cmpb instruction.

   8byte aligned strings are processed with double word comparision

   and unaligned strings are handled effectively with loop unrolling

   technique  */

#include <sysdep.h>

#ifndef STRCMP

# define STRCMP strcmp

#endif

/* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4])  */

	.machine	power7

ENTRY_TOCLESS (STRCMP, 4)

	CALL_MCOUNT 2

	or r9, r3, r4

	rldicl. r10, r9, 0, 61	/* are s1 and s2 8 byte aligned..?  */

	bne cr0, L(process_unaligned_bytes)

	li	r5, 0

	.align 4

/* process input parameters on double word aligned boundary  */

L(unrollDword):

	ld	r8,0(r3)

	ld	r10,0(r4)

	cmpb	r7,r8,r5

	cmpdi	cr7,r7,0

	mr	r9,r7

	bne 	cr7,L(null_found)

	cmpld	cr7,r8,r10

	bne	cr7,L(different)

	ld	r8,8(r3)

	ld	r10,8(r4)

	cmpb	r7,r8,r5

	cmpdi	cr7,r7,0

	mr	r9,r7

	bne 	cr7,L(null_found)

	cmpld	cr7,r8,r10

	bne	cr7,L(different)

	ld	r8,16(r3)

	ld	r10,16(r4)

	cmpb	r7,r8,r5

	cmpdi	cr7,r7,0

	mr	r9,r7

	bne 	cr7,L(null_found)

	cmpld	cr7,r8,r10

	bne	cr7,L(different)

	ld	r8,24(r3)

	ld	r10,24(r4)

	cmpb	r7,r8,r5

	cmpdi	cr7,r7,0

	mr	r9,r7

	bne 	cr7,L(null_found)

	cmpld	cr7,r8,r10

	bne	cr7,L(different)

	addi r3, r3, 32

	addi r4, r4, 32

	beq cr7, L(unrollDword)

	.align 4

L(null_found):

#ifdef __LITTLE_ENDIAN__

	neg	r7,r9

	and	r9,r9,r7

	li	r7,-1

	cntlzd	r9,r9

	subfic	r9,r9,71

	sld	r9,r7,r9

#else

	cntlzd	r9,r9

	li	r7,-1

	addi	r9,r9,8

	srd	r9,r7,r9

#endif

	or	r8,r8,r9

	or	r10,r10,r9

L(different):

	cmpb	r9,r8,r10

#ifdef __LITTLE_ENDIAN__

	addi	r7,r9,1

	andc	r9,r7,r9

	cntlzd	r9,r9

	subfic	r9,r9,63

#else

	not	r9,r9

	cntlzd	r9,r9

	subfic	r9,r9,56

#endif

	srd	r3,r8,r9

	srd	r10,r10,r9

	rldicl	r10,r10,0,56

	rldicl	r3,r3,0,56

	subf	r3,r10,r3

	blr

	.align 4

L(process_unaligned_bytes):

	lbz r9, 0(r3)		/* load byte from s1  */

	lbz r10, 0(r4)		/* load byte from s2  */

	cmpdi cr7, r9, 0	/* compare *s1 with NULL  */

	beq cr7, L(diffOfNULL)	/* if *s1 is NULL , return *s1 - *s2  */

	cmplw cr7, r9, r10	/* compare *s1 and *s2  */

	bne cr7, L(ComputeDiff)	/* branch to compute difference and return  */

	lbz r9, 1(r3)		/* load next byte from s1  */

	lbz r10, 1(r4)		/* load next byte from s2  */

	cmpdi cr7, r9, 0	/* compare *s1 with NULL  */

	beq cr7, L(diffOfNULL)	/* if *s1 is NULL , return *s1 - *s2  */

	cmplw cr7, r9, r10	/* compare *s1 and *s2  */

	bne cr7, L(ComputeDiff)	/* branch to compute difference and return  */

	lbz r9, 2(r3)		/* unroll 3rd byte here  */

	lbz r10, 2(r4)

	cmpdi cr7, r9, 0

	beq cr7, L(diffOfNULL)

	cmplw cr7, r9, r10

	bne 7, L(ComputeDiff)

	lbz r9, 3(r3)		/* unroll 4th byte now  */

	lbz r10, 3(r4)

	addi r3, r3, 4		/* increment s1 by unroll factor  */

	cmpdi cr7, r9, 0

	cmplw cr6, 9, r10

	beq cr7, L(diffOfNULL)

	addi r4, r4, 4		/* increment s2 by unroll factor  */

	beq cr6, L(process_unaligned_bytes)	/* unroll byte processing  */

	.align 4

L(ComputeDiff):

	extsw r9, r9

	subf r10, r10, r9	/* compute s1 - s2  */

	extsw r3, r10

	blr			/* return  */

	.align 4

L(diffOfNULL):

	li r9, 0

	subf r10, r10, r9	/* compute s1 - s2  */

	extsw r3, r10		/* sign extend result  */

	blr			/* return  */

END (STRCMP)

libc_hidden_builtin_def (strcmp)