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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Fast, simple, yet decent quality random number generator based on
* a paper by David G. Carta ("Two Fast Implementations of the
* `Minimal Standard' Random Number Generator," Communications of the
* ACM, January, 1990).
*
* Copyright (C) 2002 Hewlett-Packard Co
* David Mosberger-Tang <davidm@hpl.hp.com>
*/
#include <asm/asmmacro.h>
#define a r2
#define m r3
#define lo r8
#define hi r9
#define t0 r16
#define t1 r17
#define seed r32
GLOBAL_ENTRY(carta_random32)
movl a = (16807 << 16) | 16807
;;
pmpyshr2.u t0 = a, seed, 0
pmpyshr2.u t1 = a, seed, 16
;;
unpack2.l t0 = t1, t0
dep m = -1, r0, 0, 31
;;
zxt4 lo = t0
shr.u hi = t0, 32
;;
dep t0 = 0, hi, 15, 49 // t0 = (hi & 0x7fff)
;;
shl t0 = t0, 16 // t0 = (hi & 0x7fff) << 16
shr t1 = hi, 15 // t1 = (hi >> 15)
;;
add lo = lo, t0
;;
cmp.gtu p6, p0 = lo, m
;;
(p6) and lo = lo, m
;;
(p6) add lo = 1, lo
;;
add lo = lo, t1
;;
cmp.gtu p6, p0 = lo, m
;;
(p6) and lo = lo, m
;;
(p6) add lo = 1, lo
br.ret.sptk.many rp
END(carta_random32)
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