1*1b088eaaSnakayama/* $NetBSD: random.S,v 1.5 2014/03/07 20:23:09 nakayama Exp $ */ 28a66afbcSmycroft 38a66afbcSmycroft/* 48a66afbcSmycroft * Copyright (c) 1990,1993 The Regents of the University of California. 58a66afbcSmycroft * All rights reserved. 68a66afbcSmycroft * 78a66afbcSmycroft * Redistribution and use in source and binary forms, with or without 88a66afbcSmycroft * modification, are permitted provided that: (1) source code distributions 98a66afbcSmycroft * retain the above copyright notice and this paragraph in its entirety, (2) 108a66afbcSmycroft * distributions including binary code include the above copyright notice and 118a66afbcSmycroft * this paragraph in its entirety in the documentation or other materials 128a66afbcSmycroft * provided with the distribution, and (3) all advertising materials mentioning 138a66afbcSmycroft * features or use of this software display the following acknowledgement: 148a66afbcSmycroft * ``This product includes software developed by the University of California, 158a66afbcSmycroft * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 168a66afbcSmycroft * the University nor the names of its contributors may be used to endorse 178a66afbcSmycroft * or promote products derived from this software without specific prior 188a66afbcSmycroft * written permission. 198a66afbcSmycroft * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 208a66afbcSmycroft * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 218a66afbcSmycroft * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 228a66afbcSmycroft * 238a66afbcSmycroft * Here is a very good random number generator. This implementation is 248a66afbcSmycroft * based on ``Two Fast Implementations of the "Minimal Standard" Random 258a66afbcSmycroft * Number Generator'', David G. Carta, Communications of the ACM, Jan 1990, 268a66afbcSmycroft * Vol 33 No 1. Do NOT modify this code unless you have a very thorough 278a66afbcSmycroft * understanding of the algorithm. It's trickier than you think. If 288a66afbcSmycroft * you do change it, make sure that its 10,000'th invocation returns 298a66afbcSmycroft * 1043618065. 308a66afbcSmycroft * 318a66afbcSmycroft * Here is easier-to-decipher pseudocode: 328a66afbcSmycroft * 338a66afbcSmycroft * p = (16807*seed)<30:0> # e.g., the low 31 bits of the product 348a66afbcSmycroft * q = (16807*seed)<62:31> # e.g., the high 31 bits starting at bit 32 358a66afbcSmycroft * if (p + q < 2^31) 368a66afbcSmycroft * seed = p + q 378a66afbcSmycroft * else 388a66afbcSmycroft * seed = ((p + q) & (2^31 - 1)) + 1 398a66afbcSmycroft * return (seed); 408a66afbcSmycroft * 418a66afbcSmycroft * The result is in (0,2^31), e.g., it's always positive. 428a66afbcSmycroft */ 438a66afbcSmycroft#include <machine/asm.h> 448a66afbcSmycroft 458a66afbcSmycroft .data 46*1b088eaaSnakayama .align 4 478a66afbcSmycroftrandseed: 488a66afbcSmycroft .long 1 49cbd549e7Spooka 508a66afbcSmycroft .text 518a66afbcSmycroftENTRY(random) 528a66afbcSmycroft sethi %hi(16807), %o1 538a66afbcSmycroft wr %o1, %lo(16807), %y 544d12bfcdSjoerg#ifdef __PIC__ 55cbd549e7Spooka PIC_PROLOGUE(%o5, %o2) 56cbd549e7Spooka set randseed, %g1 57cbd549e7Spooka ld [%o5 + %g1], %g1 58cbd549e7Spooka ld [%g1], %o0 59c5889d57Spooka#else 608a66afbcSmycroft sethi %hi(randseed), %g1 618a66afbcSmycroft ld [%g1 + %lo(randseed)], %o0 62c5889d57Spooka#endif 638a66afbcSmycroft andcc %g0, 0, %o2 648a66afbcSmycroft mulscc %o2, %o0, %o2 658a66afbcSmycroft mulscc %o2, %o0, %o2 668a66afbcSmycroft mulscc %o2, %o0, %o2 678a66afbcSmycroft mulscc %o2, %o0, %o2 688a66afbcSmycroft mulscc %o2, %o0, %o2 698a66afbcSmycroft mulscc %o2, %o0, %o2 708a66afbcSmycroft mulscc %o2, %o0, %o2 718a66afbcSmycroft mulscc %o2, %o0, %o2 728a66afbcSmycroft mulscc %o2, %o0, %o2 738a66afbcSmycroft mulscc %o2, %o0, %o2 748a66afbcSmycroft mulscc %o2, %o0, %o2 758a66afbcSmycroft mulscc %o2, %o0, %o2 768a66afbcSmycroft mulscc %o2, %o0, %o2 778a66afbcSmycroft mulscc %o2, %o0, %o2 788a66afbcSmycroft mulscc %o2, %o0, %o2 798a66afbcSmycroft mulscc %o2, %g0, %o2 808a66afbcSmycroft rd %y, %o3 818a66afbcSmycroft srl %o2, 16, %o1 828a66afbcSmycroft set 0xffff, %o4 838a66afbcSmycroft and %o4, %o2, %o0 848a66afbcSmycroft sll %o0, 15, %o0 858a66afbcSmycroft srl %o3, 17, %o3 868a66afbcSmycroft or %o3, %o0, %o0 878a66afbcSmycroft addcc %o0, %o1, %o0 888a66afbcSmycroft bneg 1f 898a66afbcSmycroft sethi %hi(0x7fffffff), %o1 908a66afbcSmycroft retl 914d12bfcdSjoerg#ifdef __PIC__ 92cbd549e7Spooka st %o0, [%g1] 93c5889d57Spooka#else 948a66afbcSmycroft st %o0, [%g1 + %lo(randseed)] 95c5889d57Spooka#endif 968a66afbcSmycroft1: 978a66afbcSmycroft or %o1, %lo(0x7fffffff), %o1 988a66afbcSmycroft add %o0, 1, %o0 998a66afbcSmycroft and %o1, %o0, %o0 1008a66afbcSmycroft retl 1014d12bfcdSjoerg#ifdef __PIC__ 102cbd549e7Spooka st %o0, [%g1] 103c5889d57Spooka#else 1048a66afbcSmycroft st %o0, [%g1 + %lo(randseed)] 105c5889d57Spooka#endif 106