sysdeps/x86_64/fpu/s_log1pl.S

   1 /*
   2  * Written by J.T. Conklin <jtc@netbsd.org>.
   3  * Public domain.
   4  *
   5  * Adapted for `long double' by Ulrich Drepper <drepper@cygnus.com>.
   6  * Adapted for x86-64 by Andreas Jaeger <aj@suse.de>.
   7  */
   8
   9 #include <machine/asm.h>
  10
  11 RCSID("$NetBSD: s_log1p.S,v 1.7 1995/05/09 00:10:58 jtc Exp $")
  12
  13 #ifdef __ELF__
  14         .section .rodata
  15 #else
  16         .text
  17 #endif
  18         .align ALIGNARG(4)
  19         /* The fyl2xp1 can only be used for values in
  20                 -1 + sqrt(2) / 2 <= x <= 1 - sqrt(2) / 2
  21            0.29 is a safe value.
  22         */
  23 limit:  .tfloat 0.29
  24         /* Please note:  we use a double value here.  Since 1.0 has
  25            an exact representation this does not effect the accuracy
  26            but it helps to optimize the code.  */
  27 one:    .double 1.0
  28
  29 /*
  30  * Use the fyl2xp1 function when the argument is in the range -0.29 to 0.29,
  31  * otherwise fyl2x with the needed extra computation.
  32  */
  33 #ifdef PIC
  34 #define MO(op) op##(%rip)
  35 #else
  36 #define MO(op) op
  37 #endif
  38
  39         .text
  40 ENTRY(__log1pl)
  41         fldln2
  42
  43         fldt    8(%rsp)
  44
  45         fxam
  46         fnstsw
  47         fld     %st
  48         andb    $1,%ah
  49         jnz     3f              // in case x is NaN or ±Inf
  50 4:
  51         fabs
  52         fldt    MO(limit)
  53         fcompp
  54         fnstsw
  55         andb    $1,%ah
  56         jz      2f
  57
  58         faddl   MO(one)
  59         fyl2x
  60         ret
  61
  62 2:      fyl2xp1
  63         ret
  64
  65 3:      jp      4b              // in case x is ±Inf
  66         fstp    %st(1)
  67         fstp    %st(1)
  68         ret
  69
  70 END (__log1pl)
  71 weak_alias (__log1pl, log1pl)