NetBSD/sys/lib/libkern/arch/ns32k/strcmp.S

130 lines
3.0 KiB
ArmAsm

/*
* Written by Randy Hyde, 1993
* Public domain.
*/
#include <machine/asm.h>
#if defined(LIBC_SCCS)
RCSID("$NetBSD: strcmp.S,v 1.1 1996/11/07 07:36:25 matthias Exp $")
#endif
/*
* int
* strcmp (const char *s1, const char *s2)
* compare strings s1 and s2.
*/
ENTRY(strcmp)
enter [r3,r4,r5],0
movd B_ARG1,r1
movd B_ARG0,r2
/*
* First begin by seeing if we can doubleword align the
* pointers. The following code only aligns the pointer in R1.
* If the L.O. two bits of R2 do not match, it's going to run
* slower but there is nothing we can do about that. Better to
* have at least one of them double word aligned rather than
* neither.
*/
movqd 3,r3
andd r1,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 0(r1),0(r2) ; bne 8f ; cmpqb 0,0(r1) ; beq 9f
cmpb 1(r1),1(r2) ; bne 8f ; cmpqb 0,1(r1) ; beq 9f
cmpb 2(r1),2(r2) ; bne 8f ; cmpqb 0,2(r1) ; beq 9f
addqd 3,r1
addqd 3,r2
br 5f
.align 2,0xa2
3: cmpb 0(r1),0(r2) ; bne 8f ; cmpqb 0,0(r1) ; beq 9f
cmpb 1(r1),1(r2) ; bne 8f ; cmpqb 0,1(r1) ; beq 9f
addqd 2,r1
addqd 2,r2
br 5f
.align 2,0xa2
4: cmpb 0(r1),0(r2) ; bne 8f ; cmpqb 0,0(r1) ; beq 9f
addqd 1,r1
addqd 1,r2
/*
* Okay, when we get down here R1 points at a double word
* algined source block of bytes, R2 points at another block of
* bytes (typically, though not always double word aligned).
* 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,r3 /* Magic number to use */
movd 0x80808080,r4 /* Another magic number. */
movd 0(r1),r5 /* Get 1st double word. */
movd r5,r0 /* Save for storage later. */
subd r3,r0 /* Gets borrow if byte = 0. */
bicd r5,r0 /* Clear original bits. */
andd r4,r0 /* See if borrow occurred. */
cmpqd 0,r0
bne 1f /* If this DWORD contained a 0. */
.align 2,0xa2
0: movd 4(r1),r0 /* Get next 4 bytes to process */
cmpd r5,0(r2) /* Compare prev four bytes. */
bne 1f
addqd 4,r1
addqd 4,r2
movd r0,r5 /* Save for storage if no zeros. */
subd r3,r0
bicd r5,r0
andd r4,r0
cmpqd 0,r0
beq 0b
/*
* At this point either the strings are not equal or
* they contain a zero byte. Check them.
*/
1: cmpb 0(r1),0(r2) ; bne 8f ; cmpqb 0,0(r1) ; beq 9f
cmpb 1(r1),1(r2) ; bne 8f ; cmpqb 0,1(r1) ; beq 9f
cmpb 2(r1),2(r2) ; bne 8f ; cmpqb 0,2(r1) ; beq 9f
cmpb 3(r1),3(r2) ; bne 8f
9: movqd 0,r0
exit [r3,r4,r5]
ret 0
8: blo 0f /* Operands were reversed on cmp. */
movqd -1,r0 /* It's >, so return one. */
exit [r3,r4,r5]
ret 0
0: movqd 1,r0 /* It's <, so return -1. */
exit [r3,r4,r5]
ret 0