sysdeps/libm-i387/e_exp.S

   1 /*
   2  * Written by J.T. Conklin <jtc@netbsd.org>.
   3  * Public domain.
   4  */
   5
   6 #include <machine/asm.h>
   7
   8 RCSID("$NetBSD: e_exp.S,v 1.4 1995/05/08 23:47:04 jtc Exp $")
   9
  10 /* e^x = 2^(x * log2(e)) */
  11 ENTRY(__ieee754_exp)
  12         fldl    4(%esp)
  13         fxam
  14         fstsw   %ax
  15         sahf
  16         jnc     .LnoInf
  17         jp      .LisInf
  18 .LnoInf:
  19         fldl2e
  20         fmulp                           /* x * log2(e) */
  21         fstl    %st(1)
  22         frndint                         /* int(x * log2(e)) */
  23         fstl    %st(2)
  24         fsubrp                          /* fract(x * log2(e)) */
  25         f2xm1                           /* 2^(fract(x * log2(e))) - 1 */
  26         fld1
  27         faddp                           /* 2^(fract(x * log2(e))) */
  28         fscale                          /* e^x */
  29         ret
  30
  31 .LisInf:
  32         andb    $2, %ah
  33         jz      .LpInf
  34         fldz
  35 .LpInf: ret