usr/src/lib/libc/mips/string/bzero.s

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Ralph Campbell.
 *
 * %sccs.include.redist.c%
 */

#include <machine/machAsmDefs.h>

#if defined(LIBC_SCCS) && !defined(lint)
        ASMSTR("@(#)bzero.s     8.1 (Berkeley) %G%")
#endif /* LIBC_SCCS and not lint */

/* bzero(s1, n) */

LEAF(bzero)
        .set    noreorder
        blt     a1, 12, smallclr        # small amount to clear?
        subu    a3, zero, a0            # compute # bytes to word align address
        and     a3, a3, 3
        beq     a3, zero, 1f            # skip if word aligned
        subu    a1, a1, a3              # subtract from remaining count
        swr     zero, 0(a0)             # clear 1, 2, or 3 bytes to align
        addu    a0, a0, a3
1:
        and     v0, a1, 3               # compute number of words left
        subu    a3, a1, v0
        move    a1, v0
        addu    a3, a3, a0              # compute ending address
2:
        addu    a0, a0, 4               # clear words
        bne     a0, a3, 2b              #   unrolling loop doesnt help
        sw      zero, -4(a0)            #   since we are limited by memory speed
smallclr:
        ble     a1, zero, 2f
        addu    a3, a1, a0              # compute ending address
1:
        addu    a0, a0, 1               # clear bytes
        bne     a0, a3, 1b
        sb      zero, -1(a0)
2:
        j       ra
        nop
END(bzero)