sysdeps/libm-i387/s_exp2l.S

   1 /*
   2  * Written by J.T. Conklin <jtc@netbsd.org>.
   3  * Adapted for exp2 by Ulrich Drepper <drepper@cygnus.com>.
   4  * Public domain.
   5  */
   6
   7 #include <machine/asm.h>
   8
   9 ENTRY(__exp2l)
  10         fldt    4(%esp)
  11 /* I added the following ugly construct because exp(+-Inf) resulted
  12    in NaN.  The ugliness results from the bright minds at Intel.
  13    For the i686 the code can be written better.
  14    -- drepper@cygnus.com.  */
  15         fxam                            /* Is NaN or +-Inf?  */
  16         fstsw   %ax
  17         movb    $0x45, %dh
  18         andb    %ah, %dh
  19         cmpb    $0x05, %dh
  20         je      1f                      /* Is +-Inf, jump.  */
  21         fld     %st
  22         frndint                         /* int(x) */
  23         fsubr   %st,%st(1)              /* fract(x) */
  24         fxch
  25         f2xm1                           /* 2^(fract(x)) - 1 */
  26         fld1
  27         faddp                           /* 2^(fract(x)) */
  28         fscale                          /* e^x */
  29         fstp    %st(1)
  30         ret
  31
  32 1:      testl   $0x200, %eax            /* Test sign.  */
  33         jz      2f                      /* If positive, jump.  */
  34         fstp    %st
  35         fldz                            /* Set result to 0.  */
  36 2:      ret
  37 END (__exp2l)
  38 weak_alias (__exp2l, exp2l)