diff options
Diffstat (limited to 'lib/libc/alpha/string/bzero.S')
-rw-r--r-- | lib/libc/alpha/string/bzero.S | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/lib/libc/alpha/string/bzero.S b/lib/libc/alpha/string/bzero.S new file mode 100644 index 0000000..9897344 --- /dev/null +++ b/lib/libc/alpha/string/bzero.S @@ -0,0 +1,110 @@ +/* $NetBSD: bzero.S,v 1.2 1996/10/17 03:08:12 cgd Exp $ */ + +/* + * Copyright (c) 1995 Carnegie-Mellon University. + * All rights reserved. + * + * Author: Trevor Blackwell + * + * Permission to use, copy, modify and distribute this software and + * its documentation is hereby granted, provided that both the copyright + * notice and this permission notice appear in all copies of the + * software, derivative works or modified versions, and any portions + * thereof, and that both notices appear in supporting documentation. + * + * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" + * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND + * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. + * + * Carnegie Mellon requests users of this software to return to + * + * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU + * School of Computer Science + * Carnegie Mellon University + * Pittsburgh PA 15213-3890 + * + * any improvements or extensions that they make and grant Carnegie the + * rights to redistribute these changes. + */ + +#include <machine/asm.h> + +LEAF(bzero,2) + ble a1,bzero_done + bic a1,63,t3 /* t3 is # bytes to do 64 bytes at a time */ + + /* If nothing in first word, ignore it */ + subq zero,a0,t0 + and t0,7,t0 /* t0 = (0-size)%8 */ + beq t0,bzero_nostart1 + + cmpult a1,t0,t1 /* if size > size%8 goto noshort */ + beq t1,bzero_noshort + + /* + * The whole thing is less than a word. + * Mask off 1..7 bytes, and finish. + */ + ldq_u t2,0(a0) + lda t0,-1(zero) /* t0=-1 */ + mskql t0,a1,t0 /* Get ff in bytes (a0%8)..((a0+a1-1)%8) */ + insql t0,a0,t0 + bic t2,t0,t2 /* zero those bytes in word */ + stq_u t2,0(a0) + RET + +bzero_noshort: + /* Handle the first partial word */ + ldq_u t2,0(a0) + subq a1,t0,a1 + mskql t2,a0,t2 /* zero bytes (a0%8)..7 in word */ + stq_u t2,0(a0) + + addq a0,t0,a0 /* round a0 up to next word */ + bic a1,63,t3 /* recalc t3 (# bytes to do 64 bytes at a + time) */ + +bzero_nostart1: + /* + * Loop, zeroing 64 bytes at a time + */ + beq t3,bzero_lp_done +bzero_lp: + stq zero,0(a0) + stq zero,8(a0) + stq zero,16(a0) + stq zero,24(a0) + subq t3,64,t3 + stq zero,32(a0) + stq zero,40(a0) + stq zero,48(a0) + stq zero,56(a0) + addq a0,64,a0 + bne t3,bzero_lp + +bzero_lp_done: + /* + * Handle the last 0..7 words. + * We mask off the low bits, so we don't need an extra + * compare instruction for the loop (just a bne. heh-heh) + */ + and a1,0x38,t4 + beq t4,bzero_finish_lp_done +bzero_finish_lp: + stq zero,0(a0) + subq t4,8,t4 + addq a0,8,a0 + bne t4,bzero_finish_lp + + /* Do the last partial word */ +bzero_finish_lp_done: + and a1,7,t5 /* 0..7 bytes left */ + beq t5,bzero_done /* mskqh won't change t0 if t5==0, but I + don't want to touch, say, a new VM page */ + ldq t0,0(a0) + mskqh t0,t5,t0 + stq t0,0(a0) +bzero_done: + RET + + END(bzero) |