Return to bzero.S CVS log

Up to [local] / sys / lib / libkern / arch / alpha

Annotation of sys/lib/libkern/arch/alpha/bzero.S, Revision 1.1.1.1

1.1       nbrk        1: /*     $OpenBSD: bzero.S,v 1.2 1996/10/31 00:43:16 niklas Exp $        */
                      2: /*     $NetBSD: bzero.S,v 1.2 1996/10/17 04:26:24 cgd Exp $    */
                      3:
                      4: /*
                      5:  * Copyright (c) 1995 Carnegie-Mellon University.
                      6:  * All rights reserved.
                      7:  *
                      8:  * Author: Trevor Blackwell
                      9:  *
                     10:  * Permission to use, copy, modify and distribute this software and
                     11:  * its documentation is hereby granted, provided that both the copyright
                     12:  * notice and this permission notice appear in all copies of the
                     13:  * software, derivative works or modified versions, and any portions
                     14:  * thereof, and that both notices appear in supporting documentation.
                     15:  *
                     16:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
                     17:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
                     18:  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
                     19:  *
                     20:  * Carnegie Mellon requests users of this software to return to
                     21:  *
                     22:  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
                     23:  *  School of Computer Science
                     24:  *  Carnegie Mellon University
                     25:  *  Pittsburgh PA 15213-3890
                     26:  *
                     27:  * any improvements or extensions that they make and grant Carnegie the
                     28:  * rights to redistribute these changes.
                     29:  */
                     30:
                     31: #include <machine/asm.h>
                     32:
                     33: LEAF(bzero,2)
                     34:        ble     a1,bzero_done
                     35:        bic     a1,63,t3        /* t3 is # bytes to do 64 bytes at a time */
                     36:
                     37:        /* If nothing in first word, ignore it */
                     38:        subq    zero,a0,t0
                     39:        and     t0,7,t0         /* t0 = (0-size)%8 */
                     40:        beq     t0,bzero_nostart1
                     41:
                     42:        cmpult  a1,t0,t1        /* if size > size%8 goto noshort */
                     43:        beq     t1,bzero_noshort
                     44:
                     45:        /*
                     46:         * The whole thing is less than a word.
                     47:         * Mask off 1..7 bytes, and finish.
                     48:         */
                     49:        ldq_u   t2,0(a0)
                     50:        lda     t0,-1(zero)     /* t0=-1 */
                     51:        mskql   t0,a1,t0        /* Get ff in bytes (a0%8)..((a0+a1-1)%8) */
                     52:        insql   t0,a0,t0
                     53:        bic     t2,t0,t2        /* zero those bytes in word */
                     54:        stq_u   t2,0(a0)
                     55:        RET
                     56:
                     57: bzero_noshort:
                     58:        /* Handle the first partial word */
                     59:        ldq_u   t2,0(a0)
                     60:        subq    a1,t0,a1
                     61:        mskql   t2,a0,t2        /* zero bytes (a0%8)..7 in word */
                     62:        stq_u   t2,0(a0)
                     63:
                     64:        addq    a0,t0,a0        /* round a0 up to next word */
                     65:        bic     a1,63,t3        /* recalc t3 (# bytes to do 64 bytes at a
                     66:                                   time) */
                     67:
                     68: bzero_nostart1:
                     69:        /*
                     70:         * Loop, zeroing 64 bytes at a time
                     71:         */
                     72:        beq     t3,bzero_lp_done
                     73: bzero_lp:
                     74:        stq     zero,0(a0)
                     75:        stq     zero,8(a0)
                     76:        stq     zero,16(a0)
                     77:        stq     zero,24(a0)
                     78:        subq    t3,64,t3
                     79:        stq     zero,32(a0)
                     80:        stq     zero,40(a0)
                     81:        stq     zero,48(a0)
                     82:        stq     zero,56(a0)
                     83:        addq    a0,64,a0
                     84:        bne     t3,bzero_lp
                     85:
                     86: bzero_lp_done:
                     87:        /*
                     88:         * Handle the last 0..7 words.
                     89:         * We mask off the low bits, so we don't need an extra
                     90:         * compare instruction for the loop (just a bne. heh-heh)
                     91:         */
                     92:        and     a1,0x38,t4
                     93:        beq     t4,bzero_finish_lp_done
                     94: bzero_finish_lp:
                     95:        stq     zero,0(a0)
                     96:        subq    t4,8,t4
                     97:        addq    a0,8,a0
                     98:        bne     t4,bzero_finish_lp
                     99:
                    100:        /* Do the last partial word */
                    101: bzero_finish_lp_done:
                    102:        and     a1,7,t5         /* 0..7 bytes left */
                    103:        beq     t5,bzero_done   /* mskqh won't change t0 if t5==0, but I
                    104:                                   don't want to touch, say, a new VM page */
                    105:        ldq     t0,0(a0)
                    106:        mskqh   t0,t5,t0
                    107:        stq     t0,0(a0)
                    108: bzero_done:
                    109:        RET
                    110:
                    111:        END(bzero)