LXR linux/arch/ia64/lib/carta

   1/*
   2 * Fast, simple, yet decent quality random number generator based on
   3 * a paper by David G. Carta ("Two Fast Implementations of the
   4 * `Minimal Standard' Random Number Generator," Communications of the
   5 * ACM, January, 1990).
   6 *
   7 * Copyright (C) 2002 Hewlett-Packard Co
   8 *      David Mosberger-Tang <davidm@hpl.hp.com>
   9 */
  10
  11#include <asm/asmmacro.h>
  12
  13#define a       r2
  14#define m       r3
  15#define lo      r8
  16#define hi      r9
  17#define t0      r16
  18#define t1      r17
  19#define seed    r32
  20
  21GLOBAL_ENTRY(carta_random32)
  22        movl    a = (16807 << 16) | 16807
  23        ;;
  24        pmpyshr2.u t0 = a, seed, 0
  25        pmpyshr2.u t1 = a, seed, 16
  26        ;;
  27        unpack2.l t0 = t1, t0
  28        dep     m = -1, r0, 0, 31
  29        ;;
  30        zxt4    lo = t0
  31        shr.u   hi = t0, 32
  32        ;;
  33        dep     t0 = 0, hi, 15, 49      // t0 = (hi & 0x7fff)
  34        ;;
  35        shl     t0 = t0, 16             // t0 = (hi & 0x7fff) << 16
  36        shr     t1 = hi, 15             // t1 = (hi >> 15)
  37        ;;
  38        add     lo = lo, t0
  39        ;;
  40        cmp.gtu p6, p0 = lo, m
  41        ;;
  42(p6)    and     lo = lo, m
  43        ;;
  44(p6)    add     lo = 1, lo
  45        ;;
  46        add     lo = lo, t1
  47        ;;
  48        cmp.gtu p6, p0 = lo, m
  49        ;;
  50(p6)    and     lo = lo, m
  51        ;;
  52(p6)    add     lo = 1, lo
  53        br.ret.sptk.many rp
  54END(carta_random32)
  55