glibc/sysdeps/powerpc/strcmp.S

/* Optimized strcmp implementation for PowerPC.
   Copyright (C) 1997, 1999, 2000 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 Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <sysdep.h>

/* See strlen.s for comments on how the end-of-string testing works.  */

EALIGN(strcmp,4,0)
/* int [r3] strcmp (const char *p1 [r3], const char *p2 [r4])  */

/* General register assignments:
   r0:	temporary
   r3:	pointer to previous word in s1
   r4:	pointer to previous word in s2
   r5:	current word from s1
   r6:	current word from s2
   r7:	0xfefefeff
   r8:	0x7f7f7f7f
   r9:	~(word in s1 | 0x7f7f7f7f)  */

/* Register assignments in the prologue:
   r10:	low 2 bits of p2-p1
   r11:	mask to orc with r5/r6  */

	or    r0,r4,r3
	clrlwi. r0,r0,30
	lis   r7,0xfeff
	bne   L(unaligned)

	lwz   r5,0(r3)
	lwz   r6,0(r4)
	lis   r8,0x7f7f
	addi  r7,r7,-0x101
	addi  r8,r8,0x7f7f
	b     L(g1)

L(g0):	lwzu  r5,4(r3)
	bne   cr1,L(different)
	lwzu  r6,4(r4)
L(g1):	add   r0,r7,r5
	nor   r9,r8,r5
	and.  r0,r0,r9
	cmpw  cr1,r5,r6
	beq+  L(g0)
L(endstring):
/* OK. We've hit the end of the string. We need to be careful that
   we don't compare two strings as different because of gunk beyond
   the end of the strings...  */
	and   r0,r8,r5
	beq   cr1,L(equal)
	add   r0,r0,r8
	xor.  r10,r5,r6
	andc  r9,r9,r0
	blt-  L(highbit)
	cntlzw r10,r10
	cntlzw r9,r9
	addi  r9,r9,7
	cmpw  cr1,r9,r10
	sub   r3,r5,r6
	bgelr+ cr1
L(equal):
	li    r3,0
	blr

L(different):
	lwz   r5,-4(r3)
	xor.  r10,r5,r6
	sub   r3,r5,r6
	bgelr+
L(highbit):
	ori   r3,r6,1
	blr


/* Oh well.  In this case, we just do a byte-by-byte comparison.  */
	.align 4
L(unaligned):
	lbz   r5,0(r3)
	lbz   r6,0(r4)
	b     L(u1)

L(u0):	lbzu  r5,1(r3)
	bne-  L(u4)
	lbzu  r6,1(r4)
L(u1):	cmpwi cr1,r5,0
	beq-  cr1,L(u3)
	cmpw  r5,r6
	bne-  L(u3)
	lbzu  r5,1(r3)
	lbzu  r6,1(r4)
	cmpwi cr1,r5,0
	cmpw  r5,r6
	bne+  cr1,L(u0)
L(u3):	sub   r3,r5,r6
	blr
L(u4):	lbz   r5,-1(r3)
	sub   r3,r5,r6
	blr
END(strcmp)