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/*
* Written by J.T. Conklin <jtc@netbsd.org>.
* Public domain.
*/
#include <machine/asm.h>
RCSID("$NetBSD: e_exp.S,v 1.4 1995/05/08 23:47:04 jtc Exp $")
/* e^x = 2^(x * log2(e)) */
ENTRY(__ieee754_exp)
fldl 4(%esp)
/* I added the following ugly construct because exp(+-Inf) resulted
in NaN. The ugliness results from the bright minds at Intel.
For the i686 the code can be written better.
-- drepper@cygnus.com. */
fxam /* Is NaN or +-Inf? */
fstsw %ax
sahf
jnc .LnoInfNaN /* No, jump. */
jp .LisInf /* Is +-Inf, jump. */
.LnoInfNaN:
fldl2e
fmulp /* x * log2(e) */
fstl %st(1)
frndint /* int(x * log2(e)) */
fstl %st(2)
fsubrp /* fract(x * log2(e)) */
f2xm1 /* 2^(fract(x * log2(e))) - 1 */
fld1
faddp /* 2^(fract(x * log2(e))) */
fscale /* e^x */
fstp %st(1)
ret
.LisInf:
andb $2, %ah /* Test sign. */
jz .LpInf /* If positive, jump. */
fldz /* Set result to 0. */
.LpInf: ret
END (__ieee754_exp)
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