sysdeps/ieee754/flt-32/s_scalblnf.c

   1 /* s_scalbnf.c -- float version of s_scalbn.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #include <math.h>
  17 #include <math_private.h>
  18
  19 static const float
  20 two25   =  3.355443200e+07,     /* 0x4c000000 */
  21 twom25  =  2.9802322388e-08,    /* 0x33000000 */
  22 huge   = 1.0e+30,
  23 tiny   = 1.0e-30;
  24
  25 float
  26 __scalblnf (float x, long int n)
  27 {
  28         int32_t k,ix;
  29         GET_FLOAT_WORD(ix,x);
  30         k = (ix&0x7f800000)>>23;                /* extract exponent */
  31         if (__builtin_expect(k==0, 0)) {        /* 0 or subnormal x */
  32             if ((ix&0x7fffffff)==0) return x; /* +-0 */
  33             x *= two25;
  34             GET_FLOAT_WORD(ix,x);
  35             k = ((ix&0x7f800000)>>23) - 25;
  36             }
  37         if (__builtin_expect(k==0xff, 0)) return x+x;   /* NaN or Inf */
  38         if (__builtin_expect(n< -50000, 0))
  39           return tiny*copysignf(tiny,x);        /*underflow*/
  40         if (__builtin_expect(n> 50000 || k+n > 0xfe, 0))
  41           return huge*copysignf(huge,x); /* overflow  */
  42         /* Now k and n are bounded we know that k = k+n does not
  43            overflow.  */
  44         k = k+n;
  45         if (__builtin_expect(k > 0, 1))         /* normal result */
  46             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
  47         if (k <= -25)
  48             return tiny*copysignf(tiny,x);      /*underflow*/
  49         k += 25;                                /* subnormal result */
  50         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
  51         return x*twom25;
  52 }