cscg22-gearboy

CSCG 2022 Challenge 'Gearboy'
git clone https://git.sinitax.com/sinitax/cscg22-gearboy
Log | Files | Refs | sfeed.txt

s_scalbn.c (2374B)

      1/* @(#)s_scalbn.c 5.1 93/09/24 */
      2/*
      3 * ====================================================
      4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      5 *
      6 * Developed at SunPro, a Sun Microsystems, Inc. business.
      7 * Permission to use, copy, modify, and distribute this
      8 * software is freely granted, provided that this notice
      9 * is preserved.
     10 * ====================================================
     11 */
     12
     13#if defined(LIBM_SCCS) && !defined(lint)
     14static const char rcsid[] =
     15    "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $";
     16#endif
     17
     18/*
     19 * scalbn (double x, int n)
     20 * scalbn(x,n) returns x* 2**n  computed by  exponent
     21 * manipulation rather than by actually performing an
     22 * exponentiation or a multiplication.
     23 */
     24
     25#include "math_libm.h"
     26#include "math_private.h"
     27
     28libm_hidden_proto(copysign)
     29#ifdef __STDC__
     30     static const double
     31#else
     32     static double
     33#endif
     34       two54 = 1.80143985094819840000e+16,      /* 0x43500000, 0x00000000 */
     35         twom54 = 5.55111512312578270212e-17,   /* 0x3C900000, 0x00000000 */
     36         huge_val = 1.0e+300, tiny = 1.0e-300;
     37
     38libm_hidden_proto(scalbn)
     39#ifdef __STDC__
     40     double scalbn(double x, int n)
     41#else
     42     double scalbn(x, n)
     43     double x;
     44     int n;
     45#endif
     46{
     47    int32_t k, hx, lx;
     48    EXTRACT_WORDS(hx, lx, x);
     49    k = (hx & 0x7ff00000) >> 20;        /* extract exponent */
     50    if (k == 0) {               /* 0 or subnormal x */
     51        if ((lx | (hx & 0x7fffffff)) == 0)
     52            return x;           /* +-0 */
     53        x *= two54;
     54        GET_HIGH_WORD(hx, x);
     55        k = ((hx & 0x7ff00000) >> 20) - 54;
     56        if (n < -50000)
     57            return tiny * x;    /* underflow */
     58    }
     59    if (k == 0x7ff)
     60        return x + x;           /* NaN or Inf */
     61    k = k + n;
     62    if (k > 0x7fe)
     63        return huge_val * copysign(huge_val, x);        /* overflow  */
     64    if (k > 0) {                /* normal result */
     65        SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
     66        return x;
     67    }
     68    if (k <= -54) {
     69        if (n > 50000)          /* in case integer overflow in n+k */
     70            return huge_val * copysign(huge_val, x);    /* overflow */
     71        else
     72            return tiny * copysign(tiny, x);    /* underflow */
     73    }
     74    k += 54;                    /* subnormal result */
     75    SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
     76    return x * twom54;
     77}
     78
     79libm_hidden_def(scalbn)