sysdeps/ieee754/flt-32/s_scalbnf.c

   1 /* s_scalbnf.c -- float version of s_scalbn.c.
   2  */
   3
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 #include <math.h>
  16 #include <math_private.h>
  17
  18 static const float
  19 two25   =  3.355443200e+07,     /* 0x4c000000 */
  20 twom25  =  2.9802322388e-08,    /* 0x33000000 */
  21 huge   = 1.0e+30,
  22 tiny   = 1.0e-30;
  23
  24 float
  25 __scalbnf (float x, int n)
  26 {
  27         int32_t k,ix;
  28         GET_FLOAT_WORD(ix,x);
  29         k = (ix&0x7f800000)>>23;                /* extract exponent */
  30         if (__builtin_expect(k==0, 0)) {        /* 0 or subnormal x */
  31             if ((ix&0x7fffffff)==0) return x; /* +-0 */
  32             x *= two25;
  33             GET_FLOAT_WORD(ix,x);
  34             k = ((ix&0x7f800000)>>23) - 25;
  35             }
  36         if (__builtin_expect(k==0xff, 0)) return x+x;   /* NaN or Inf */
  37         if (__builtin_expect(n< -50000, 0))
  38           return tiny*copysignf(tiny,x);        /*underflow*/
  39         if (__builtin_expect(n> 50000 || k+n > 0xfe, 0))
  40           return huge*copysignf(huge,x); /* overflow  */
  41         /* Now k and n are bounded we know that k = k+n does not
  42            overflow.  */
  43         k = k+n;
  44         if (__builtin_expect(k > 0, 1))         /* normal result */
  45             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
  46         if (k <= -25)
  47             return tiny*copysignf(tiny,x);      /*underflow*/
  48         k += 25;                                /* subnormal result */
  49         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
  50         return x*twom25;
  51 }