strcmp.s

mips架构的bootloader,99左右的版本 但源代码现在没人更新了

/*************************************************************
 * File: lib/strcmp.s
 * Purpose: Part of C runtime library
 * Author: Phil Bunce ([e-mail])
 * Revision History:
 *	970304	Start of revision history
 */

/* Note that the Algorithmics assembler generates 6 warnings for this
 * file.  This is because the assembler considers the load instructions
 * are not save in the delay slot of a branch.  You can safely ignore 
 * the warnings.  
 */

#include <regdef.h>

#ifdef TEST
#define strcmp xstrcmp
#endif

/*
** Loop unrolled four times
*/

	.globl	strcmp
	.ent	strcmp
strcmp:
	.set noreorder

	# main loop
1:	lbu	t0, (a0)
	lbu	t1, (a1)
	beq	t0, zero, 2f	# brif end of string
	 lbu	t2, 1(a0)
	bne	t0, t1, 2f	# brif bytes not equal
	 lbu	t3, 1(a1)
	beq	t2, zero, 3f	# brif end of string
	 lbu	t4, 2(a0)
	bne	t2, t3, 3f	# brif bytes not equal
	 lbu	t5, 2(a1)
	beq	t4, zero, 4f	# brif end of string
	 lbu	t6, 3(a0)
	bne	t4, t5, 4f	# brif bytes not equal
	 lbu	t7, 3(a1)
	beq	t6, zero, 5f	# brif end of string
	 addu	a0, 4
	beq	t6, t7, 1b	# brif bytes equal
	 addu	a1, 4
5:	j	ra
	 subu	v0, t6, t7

2:	j	ra
	 subu	v0, t0, t1
3:	j	ra
	 subu	v0, t2, t3
4:	j	ra
	 subu	v0, t4, t5

	.set reorder
	.end	strcmp