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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/ia64/lib/carta_random.S
10817 views
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/*

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 * Fast, simple, yet decent quality random number generator based on

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 * a paper by David G. Carta ("Two Fast Implementations of the

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 * `Minimal Standard' Random Number Generator," Communications of the

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 * ACM, January, 1990).

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 *

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 * Copyright (C) 2002 Hewlett-Packard Co

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 *	David Mosberger-Tang <[email protected]>

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 */

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#include <asm/asmmacro.h>

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#define a	r2

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#define m	r3

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#define lo	r8

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#define hi	r9

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#define t0	r16

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#define t1	r17

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#define	seed	r32

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GLOBAL_ENTRY(carta_random32)

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	movl	a = (16807 << 16) | 16807

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	;;

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	pmpyshr2.u t0 = a, seed, 0

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	pmpyshr2.u t1 = a, seed, 16

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	;;

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	unpack2.l t0 = t1, t0

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	dep	m = -1, r0, 0, 31

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	;;

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	zxt4	lo = t0

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	shr.u	hi = t0, 32

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	;;

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	dep	t0 = 0, hi, 15, 49	// t0 = (hi & 0x7fff)

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	;;

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	shl	t0 = t0, 16		// t0 = (hi & 0x7fff) << 16

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	shr	t1 = hi, 15		// t1 = (hi >> 15)

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	;;

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	add	lo = lo, t0

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	;;

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	cmp.gtu	p6, p0 = lo, m

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	;;

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(p6)	and	lo = lo, m

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	;;

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(p6)	add	lo = 1, lo

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	;;

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	add	lo = lo, t1

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	;;

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	cmp.gtu p6, p0 = lo, m

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	;;

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(p6)	and	lo = lo, m

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	;;

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(p6)	add	lo = 1, lo

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	br.ret.sptk.many rp

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END(carta_random32)

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