1/*
2 * Public domain.
3 */
4
5#include <machine/asm.h>
6#include <i386-math-asm.h>
7#include <libm-alias-finite.h>
8
9DEFINE_DBL_MIN
10
11#ifdef PIC
12# define MO(op) op##@GOTOFF(%ecx)
13#else
14# define MO(op) op
15#endif
16
17 .text
18ENTRY(__ieee754_exp2)
19#ifdef PIC
20 LOAD_PIC_REG (cx)
21#endif
22 fldl 4(%esp)
23/* I added the following ugly construct because exp(+-Inf) resulted
24 in NaN. The ugliness results from the bright minds at Intel.
25 For the i686 the code can be written better.
26 -- drepper@cygnus.com. */
27 fxam /* Is NaN or +-Inf? */
28 fstsw %ax
29 movb $0x45, %dh
30 andb %ah, %dh
31 cmpb $0x05, %dh
32 je 1f /* Is +-Inf, jump. */
33 fld %st
34 frndint /* int(x) */
35 fsubr %st,%st(1) /* fract(x) */
36 fxch
37 f2xm1 /* 2^(fract(x)) - 1 */
38 fld1
39 faddp /* 2^(fract(x)) */
40 fscale /* e^x */
41 fstp %st(1)
42 DBL_NARROW_EVAL_UFLOW_NONNEG_NAN
43 ret
44
451: testl $0x200, %eax /* Test sign. */
46 jz 2f /* If positive, jump. */
47 fstp %st
48 fldz /* Set result to 0. */
492: ret
50END (__ieee754_exp2)
51libm_alias_finite (__ieee754_exp2, __exp2)
52

source code of glibc/sysdeps/i386/fpu/e_exp2.S