random.S revision 1.3.32.1
1 1.3.32.1 yamt /* $NetBSD: random.S,v 1.3.32.1 2007/02/26 09:11:25 yamt Exp $ */ 2 1.3.32.1 yamt 3 1.3.32.1 yamt /* 4 1.3.32.1 yamt * Copyright (c) 1994 Ludd, University of Lule}, Sweden. All rights reserved. 5 1.3.32.1 yamt * 6 1.3.32.1 yamt * Redistribution and use in source and binary forms, with or without 7 1.3.32.1 yamt * modification, are permitted provided that the following conditions 8 1.3.32.1 yamt * are met: 9 1.3.32.1 yamt * 1. Redistributions of source code must retain the above copyright 10 1.3.32.1 yamt * notice, this list of conditions and the following disclaimer. 11 1.3.32.1 yamt * 2. Redistributions in binary form must reproduce the above copyright 12 1.3.32.1 yamt * notice, this list of conditions and the following disclaimer in the 13 1.3.32.1 yamt * documentation and/or other materials provided with the distribution. 14 1.3.32.1 yamt * 3. The name of the author may not be used to endorse or promote products 15 1.3.32.1 yamt * derived from this software without specific prior written permission 16 1.3.32.1 yamt * 17 1.3.32.1 yamt * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 1.3.32.1 yamt * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 1.3.32.1 yamt * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 1.3.32.1 yamt * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 1.3.32.1 yamt * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 1.3.32.1 yamt * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 1.3.32.1 yamt * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 1.3.32.1 yamt * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 1.3.32.1 yamt * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 1.3.32.1 yamt * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 1.3.32.1 yamt */ 28 1.1 mycroft 29 1.1 mycroft /* 30 1.1 mycroft * Copyright (c) 1990,1993 The Regents of the University of California. 31 1.1 mycroft * All rights reserved. 32 1.1 mycroft * 33 1.1 mycroft * Redistribution and use in source and binary forms, with or without 34 1.1 mycroft * modification, are permitted provided that: (1) source code distributions 35 1.1 mycroft * retain the above copyright notice and this paragraph in its entirety, (2) 36 1.1 mycroft * distributions including binary code include the above copyright notice and 37 1.1 mycroft * this paragraph in its entirety in the documentation or other materials 38 1.1 mycroft * provided with the distribution, and (3) all advertising materials mentioning 39 1.1 mycroft * features or use of this software display the following acknowledgement: 40 1.1 mycroft * ``This product includes software developed by the University of California, 41 1.1 mycroft * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 42 1.1 mycroft * the University nor the names of its contributors may be used to endorse 43 1.1 mycroft * or promote products derived from this software without specific prior 44 1.1 mycroft * written permission. 45 1.1 mycroft * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 46 1.1 mycroft * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 47 1.1 mycroft * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 48 1.1 mycroft * 49 1.1 mycroft * Here is a very good random number generator. This implementation is 50 1.1 mycroft * based on ``Two Fast Implementations of the "Minimal Standard" Random 51 1.1 mycroft * Number Generator'', David G. Carta, Communications of the ACM, Jan 1990, 52 1.1 mycroft * Vol 33 No 1. Do NOT modify this code unless you have a very thorough 53 1.1 mycroft * understanding of the algorithm. It's trickier than you think. If 54 1.1 mycroft * you do change it, make sure that its 10,000'th invocation returns 55 1.1 mycroft * 1043618065. 56 1.1 mycroft * 57 1.1 mycroft * Here is easier-to-decipher pseudocode: 58 1.1 mycroft * 59 1.1 mycroft * p = (16807*seed)<30:0> # e.g., the low 31 bits of the product 60 1.1 mycroft * q = (16807*seed)<62:31> # e.g., the high 31 bits starting at bit 32 61 1.1 mycroft * if (p + q < 2^31) 62 1.1 mycroft * seed = p + q 63 1.1 mycroft * else 64 1.1 mycroft * seed = ((p + q) & (2^31 - 1)) + 1 65 1.1 mycroft * return (seed); 66 1.1 mycroft * 67 1.1 mycroft * The result is in (0,2^31), e.g., it's always positive. 68 1.1 mycroft */ 69 1.1 mycroft 70 1.2 matt #include <machine/asm.h> 71 1.2 matt 72 1.1 mycroft .data 73 1.1 mycroft randseed: 74 1.1 mycroft .long 1 75 1.2 matt 76 1.2 matt ENTRY(random, 0) 77 1.3 matt movl $16807,%r0 78 1.1 mycroft 79 1.3 matt movl randseed,%r1 # %r2=16807*loword(randseed) 80 1.3 matt bicl3 $0xffff0000,%r1,%r2 81 1.3 matt mull2 %r0,%r2 82 1.3 matt ashl $-16,%r1,%r1 # %r1=16807*hiword(randseed) 83 1.3 matt bicl2 $0xffff0000,%r1 84 1.3 matt mull2 %r0,%r1 85 1.3 matt bicl3 $0xffff0000,%r2,%r0 86 1.3 matt ashl $-16,%r2,%r2 # %r1+=(%r2>>16) 87 1.3 matt bicl2 $0xffff0000,%r2 88 1.3 matt addl2 %r2,%r1 89 1.3 matt ashl $16,%r1,%r2 # %r0|=%r1<<16 90 1.3 matt bisl2 %r2,%r0 91 1.3 matt ashl $-16,%r1,%r1 # %r1=%r1>>16 92 1.3 matt 93 1.3 matt ashl $1,%r1,%r1 94 1.3 matt movl %r0,%r2 95 1.3 matt rotl $1,%r0,%r0 96 1.3 matt bicl2 $0xfffffffe,%r0 97 1.3 matt bisl2 %r0,%r1 98 1.3 matt movl %r2,%r0 99 1.3 matt bicl2 $0x80000000,%r0 100 1.3 matt addl2 %r1,%r0 101 1.1 mycroft bgeq L1 102 1.3 matt subl2 $0x7fffffff,%r0 103 1.3 matt L1: movl %r0,randseed 104 1.1 mycroft ret 105
Indexes created Sun Sep 21 20:09:37 GMT 2025