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