NetBSD/lib/libc/arch/ns32k/string/strchr.S

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/* $NetBSD: strchr.S,v 1.3 1998/04/03 22:58:09 matthias Exp $ */
/*
* Written by Matthias Pfaller, 1996
* Public domain.
*/
#include <machine/asm.h>
#if defined(LIBC_SCCS)
RCSID("$NetBSD: strchr.S,v 1.3 1998/04/03 22:58:09 matthias Exp $")
# if defined(INDEX)
RCSID("$Masqueraded: as index $")
# endif
#endif
#if !defined(INDEX)
/*
* char *
* strchr (const char *s, int c)
* locate the first occurrence of c in the string s.
*/
KENTRY(strchr, 8)
#else
/*
* char *
* index (const char *s, int c)
* locate the first occurrence of c in the string s.
*/
KENTRY(index, 8)
#endif
enter [r3,r4,r5],0
movd B_ARG0,r0
movzbd B_ARG1,r1
movd 0x01010101,r5
muld r1,r5
/*
* First begin by seeing if we can doubleword align the
* pointer. The following code only aligns the pointer in r0.
*/
movqd 3,r3
andd r0,r3
0: casew 1f(pc)[r3:w]
1: .word 5f-0b
.word 2f-0b
.word 3f-0b
.word 4f-0b
.align 2,0xa2
2: cmpb r5,0(r0) ; beq 6f ; cmpqb 0,0(r0) ; beq notfound
cmpb r5,1(r0) ; beq 7f ; cmpqb 0,1(r0) ; beq notfound
cmpb r5,2(r0) ; beq 8f ; cmpqb 0,2(r0) ; beq notfound
addqd 3,r0
br 5f
.align 2,0xa2
3: cmpb r5,0(r0) ; beq 6f ; cmpqb 0,0(r0) ; beq notfound
cmpb r5,1(r0) ; beq 7f ; cmpqb 0,1(r0) ; beq notfound
addqd 2,r0
br 5f
.align 2,0xa2
4: cmpb r5,0(r0) ; beq 6f ; cmpqb 0,0(r0) ; beq notfound
addqd 1,r0
/*
* Okay, when we get down here R0 points at a double word
* algined source block of bytes.
* This guy processes four bytes at a time and checks for the
* zero terminating byte amongst the bytes in the double word.
* This algorithm is de to Dave Rand.
*
* Sneaky test for zero amongst four bytes:
*
* xxyyzztt
* -01010101
* ---------
* aabbccdd
* bic xxyyzztt
* ---------
* eeffgghh ee=0x80 if xx=0, ff=0x80 if yy=0, etc.
*
* This whole result will be zero if there
* was no zero byte, it will be non-zero if
* there is a zero byte present.
*/
5: movd 0x01010101,r2 /* Magic number to use */
movd 0x80808080,r3 /* Another magic number. */
addqd -4,r0
.align 2,0xa2
0: movd 4(r0),r1 /* Get next double word. */
addd 4,r0 /* Advance pointer */
movd r1,r4 /* Save for storage later. */
subd r2,r1 /* Gets borrow if byte = 0. */
bicd r4,r1 /* Clear original bits. */
andd r3,r1 /* See if borrow occurred. */
cmpqd 0,r1
bne 1f /* See if this DWORD contained a 0. */
xord r5,r4 /* Convert any 'c' to 0. */
movd r4,r1
subd r2,r1
bicd r4,r1
andd r3,r1
cmpqd 0,r1
beq 0b
/*
* At this point, r0 points at a double word which
* contains a zero byte or c.
*/
1: cmpb r5,0(r0) ; beq 6f ; cmpqb 0,0(r0) ; beq notfound
cmpb r5,1(r0) ; beq 7f ; cmpqb 0,1(r0) ; beq notfound
cmpb r5,2(r0) ; beq 8f ; cmpqb 0,2(r0) ; beq notfound
cmpb r5,3(r0) ; beq 9f
notfound:
movqd 0,r0
exit [r3,r4,r5]
ret ARGS
6: exit [r3,r4,r5]
ret ARGS
7: addqd 1,r0
exit [r3,r4,r5]
ret ARGS
8: addqd 2,r0
exit [r3,r4,r5]
ret ARGS
9: addqd 3,r0
exit [r3,r4,r5]
ret ARGS