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/* $OpenBSD: e_exp.S,v 1.5 2005/08/02 11:17:31 espie Exp $ */
/*
* Written by J.T. Conklin <jtc@netbsd.org>.
* Public domain.
*/
#include <machine/asm.h>
/* e^x = 2^(x * log2(e)) */
ENTRY(__ieee754_exp)
subl $8,%esp
fstcw 4(%esp) /* store fpu control word */
movw 4(%esp),%dx
orw $0x0180,%dx
movw %dx,(%esp)
fldcw (%esp) /* load modfied control word */
fldl 12(%esp)
fldl2e
fmulp /* x * log2(e) */
fst %st(1)
frndint /* int(x * log2(e)) */
fxch %st(1)
fsub %st(1),%st /* fract(x * log2(e)) */
f2xm1 /* 2^(fract(x * log2(e))) - 1 */
fld1
faddp /* 2^(fract(x * log2(e))) */
fscale /* e^x */
fstp %st(1)
fldcw 4(%esp) /* restore original control word */
addl $8,%esp
ret
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