lib/libm/src/s_scalbnf.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 <sys/cdefs.h>
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_scalbnf.c,v 1.12 2013/05/20 19:40:09 joerg Exp $");
  19 #endif
  20
  21 #include "namespace.h"
  22 #include "math.h"
  23 #include "math_private.h"
  24
  25 #ifndef _LP64
  26 __strong_alias(_scalbnf, _scalblnf)
  27 #endif
  28 __weak_alias(scalbnf, _scalbnf)
  29 __weak_alias(scalblnf, _scalblnf)
  30 __weak_alias(ldexpf, _scalbnf)
  31
  32 static const float
  33 two25   =  0x1.0p25,    /* 0x4c000000 */
  34 twom25  =  0x1.0p-25,   /* 0x33000000 */
  35 huge   = 1.0e+30,
  36 tiny   = 1.0e-30;
  37
  38 #ifdef _LP64
  39 float
  40 scalbnf(float x, int n)
  41 {
  42         return scalblnf(x, n);
  43 }
  44 #endif
  45
  46 float
  47 scalblnf(float x, long n)
  48 {
  49         int32_t k,ix;
  50         GET_FLOAT_WORD(ix,x);
  51         k = (ix&0x7f800000)>>23;                /* extract exponent */
  52         if (k==0) {                             /* 0 or subnormal x */
  53             if ((ix&0x7fffffff)==0) return x; /* +-0 */
  54             x *= two25;
  55             GET_FLOAT_WORD(ix,x);
  56             k = ((ix&0x7f800000)>>23) - 25;
  57             if (n< -50000) return tiny*x;       /*underflow*/
  58             }
  59         if (k==0xff) return x+x;                /* NaN or Inf */
  60         k = k+n;
  61         if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
  62         if (k > 0)                              /* normal result */
  63             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
  64         if (k <= -25) {
  65             if (n > 50000)      /* in case integer overflow in n+k */
  66                 return huge*copysignf(huge,x);  /*overflow*/
  67             else return tiny*copysignf(tiny,x); /*underflow*/
  68         }
  69         k += 25;                                /* subnormal result */
  70         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
  71         return x*twom25;
  72 }