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
18static const float
19two25 = 3.355443200e+07, /* 0x4c000000 */
20twom25 = 2.9802322388e-08, /* 0x33000000 */
21huge = 1.0e+30,
22tiny = 1.0e-30;
23
24float
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}
52

source code of glibc/sysdeps/ieee754/flt-32/s_scalbnf.c