sysdeps/x86_64/fpu/e_logl.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: $")
  12
  13
  14 #ifdef __ELF__
  15         .section .rodata
  16 #else
  17         .text
  18 #endif
  19         .align ALIGNARG(4)
  20         ASM_TYPE_DIRECTIVE(one,@object)
  21 one:    .double 1.0
  22         ASM_SIZE_DIRECTIVE(one)
  23         /* It is not important that this constant is precise.  It is only
  24            a value which is known to be on the safe side for using the
  25            fyl2xp1 instruction.  */
  26         ASM_TYPE_DIRECTIVE(limit,@object)
  27 limit:  .double 0.29
  28         ASM_SIZE_DIRECTIVE(limit)
  29
  30
  31 #ifdef PIC
  32 #define MO(op) op##(%rip)
  33 #else
  34 #define MO(op) op
  35 #endif
  36
  37         .text
  38 ENTRY(__ieee754_logl)
  39         fldln2                  // log(2)
  40         fldt    8(%rsp)         // x : log(2)
  41         fxam
  42         fnstsw
  43         fld     %st             // x : x : log(2)
  44         testb   $1, %ah
  45         jnz     3f              // in case x is NaN or +-Inf
  46 4:      fsubl   MO(one)         // x-1 : x : log(2)
  47         fld     %st             // x-1 : x-1 : x : log(2)
  48         fabs                    // |x-1| : x-1 : x : log(2)
  49         fcompl  MO(limit)       // x-1 : x : log(2)
  50         fnstsw                  // x-1 : x : log(2)
  51         andb    $0x45, %ah
  52         jz      2f
  53         fstp    %st(1)          // x-1 : log(2)
  54         fyl2xp1                 // log(x)
  55         ret
  56
  57 2:      fstp    %st(0)          // x : log(2)
  58         fyl2x                   // log(x)
  59         ret
  60
  61 3:      testb   $4, %ah
  62         jnz     4b              // in case x is +-Inf
  63         fstp    %st(1)
  64         fstp    %st(1)
  65         ret
  66 END (__ieee754_logl)