1 /*
2 * ====================================================
3 * Copyright (C) 1998,2002 by Red Hat Inc. All rights reserved.
4 *
5 * Permission to use, copy, modify, and distribute this
6 * software is freely granted, provided that this notice
7 * is preserved.
8 * ====================================================
9 */
10
11 #if !defined(_SOFT_FLOAT)
12
13 /*
14 Fast version of exp using Intel float instructions.
15
16 double _f_exp (double x);
17
18 Function computes e ** x. The following special cases exist:
19 1. if x is 0.0 ==> return 1.0
20 2. if x is infinity ==> return infinity
21 3. if x is -infinity ==> return 0.0
22 4. if x is NaN ==> return x
23 There is no error checking or setting of errno.
24 */
25
26
27 #include <math.h>
28 #include <ieeefp.h>
29 #include "f_math.h"
30
_f_exp(double x)31 double _f_exp (double x)
32 {
33 if (check_finite(x))
34 {
35 double result;
36 asm ("fldl2e; fmulp; fld %%st; frndint; fsub %%st,%%st(1); fxch;" \
37 "fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1); fmulp" :
38 "=t"(result) : "0"(x));
39 return result;
40 }
41 else if (x == -infinity())
42 return 0.0;
43
44 return x;
45 }
46
47 #endif
48