compiler/stdc/math/s_logbl.c

   1 /*
   2  * From: @(#)s_ilogb.c 5.1 93/09/24
   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 #include <float.h>
  14 #include <limits.h>
  15 #include "math.h"
  16 #include "fpmath.h"
  17 #include "math_private.h"
  18
  19 long double
  20 logbl(long double x)
  21 {
  22         union IEEEl2bits u;
  23         unsigned long m;
  24         int b;
  25
  26         u.e = x;
  27         if (u.bits.exp == 0) {
  28                 if ((u.bits.manl | u.bits.manh) == 0) { /* x == 0 */
  29                         u.bits.sign = 1;
  30                         return (1.0L / u.e);
  31                 }
  32                 /* denormalized */
  33                 if (u.bits.manh == 0) {
  34                         m = 1lu << (LDBL_MANL_SIZE - 1);
  35                         for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1)
  36                                 b++;
  37                 } else {
  38                         m = 1lu << (LDBL_MANH_SIZE - 1);
  39                         for (b = 0; !(u.bits.manh & m); m >>= 1)
  40                                 b++;
  41                 }
  42 #ifdef LDBL_IMPLICIT_NBIT
  43                 b++;
  44 #endif
  45                 return ((long double)(LDBL_MIN_EXP - b - 1));
  46         }
  47         if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1)       /* normal */
  48                 return ((long double)(u.bits.exp - LDBL_MAX_EXP + 1));
  49         else                                            /* +/- inf or nan */
  50                 return (x * x);
  51 }