97 lines
3.8 KiB
ArmAsm
97 lines
3.8 KiB
ArmAsm
/* $NetBSD: random.S,v 1.6 2010/09/07 20:35:50 pooka Exp $ */
|
|
|
|
/*-
|
|
* Copyright (c) 1998 The NetBSD Foundation, Inc.
|
|
* All rights reserved.
|
|
*
|
|
* This code is derived from software contributed to The NetBSD Foundation
|
|
* by Charles M. Hannum.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
/*
|
|
* Copyright (c) 1990,1993 The Regents of the University of California.
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that: (1) source code distributions
|
|
* retain the above copyright notice and this paragraph in its entirety, (2)
|
|
* distributions including binary code include the above copyright notice and
|
|
* this paragraph in its entirety in the documentation or other materials
|
|
* provided with the distribution, and (3) all advertising materials mentioning
|
|
* features or use of this software display the following acknowledgement:
|
|
* ``This product includes software developed by the University of California,
|
|
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
|
|
* the University nor the names of its contributors may be used to endorse
|
|
* or promote products derived from this software without specific prior
|
|
* written permission.
|
|
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
|
|
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
|
|
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
|
|
*
|
|
* Here is a very good random number generator. This implementation is
|
|
* based on ``Two Fast Implementations of the "Minimal Standard" Random
|
|
* Number Generator'', David G. Carta, Communications of the ACM, Jan 1990,
|
|
* Vol 33 No 1. Do NOT modify this code unless you have a very thorough
|
|
* understanding of the algorithm. It's trickier than you think. If
|
|
* you do change it, make sure that its 10,000'th invocation returns
|
|
* 1043618065.
|
|
*
|
|
* Here is easier-to-decipher pseudocode:
|
|
*
|
|
* p = (16807*seed)<30:0> # e.g., the low 31 bits of the product
|
|
* q = (16807*seed)<62:31> # e.g., the high 31 bits starting at bit 32
|
|
* if (p + q < 2^31)
|
|
* seed = p + q
|
|
* else
|
|
* seed = ((p + q) & (2^31 - 1)) + 1
|
|
* return (seed);
|
|
*
|
|
* The result is in (0,2^31), e.g., it's always positive.
|
|
*/
|
|
#include <machine/asm.h>
|
|
|
|
.data
|
|
randseed:
|
|
.long 1
|
|
.text
|
|
ENTRY(random)
|
|
movl $16807,%eax
|
|
PIC_PROLOGUE
|
|
imull PIC_GOTOFF(randseed)
|
|
PIC_EPILOGUE
|
|
shld $1,%eax,%edx
|
|
andl $0x7fffffff,%eax
|
|
addl %edx,%eax
|
|
js neg
|
|
PIC_PROLOGUE
|
|
movl %eax,PIC_GOTOFF(randseed)
|
|
PIC_EPILOGUE
|
|
ret
|
|
neg:
|
|
subl $0x7fffffff,%eax
|
|
PIC_PROLOGUE
|
|
movl %eax,PIC_GOTOFF(randseed)
|
|
PIC_EPILOGUE
|
|
ret
|