sysdeps/x86_64/fpu/e_ilogbl.S

   1 /*
   2  * Public domain.
   3  */
   4
   5 #include <machine/asm.h>
   6
   7 ENTRY(__ieee754_ilogbl)
   8         fldt    8(%rsp)
   9 /* I added the following ugly construct because ilogb(+-Inf) is
  10    required to return INT_MAX in ISO C99.
  11    -- jakub@redhat.com.  */
  12         fxam                    /* Is NaN or +-Inf?  */
  13         fstsw   %ax
  14         movb    $0x45, %dh
  15         andb    %ah, %dh
  16         cmpb    $0x05, %dh
  17         je      1f              /* Is +-Inf, jump.  */
  18         cmpb    $0x40, %dh
  19         je      2f              /* Is +-Inf, jump.  */
  20
  21         fxtract
  22         fstp    %st
  23
  24         fistpl  -4(%rsp)
  25         fwait
  26         movl    -4(%rsp),%eax
  27
  28         ret
  29
  30 1:      fstp    %st
  31         movl    $0x7fffffff, %eax
  32         ret
  33 2:      fstp    %st
  34         movl    $0x80000000, %eax       /* FP_ILOGB0  */
  35         ret
  36 END (__ieee754_ilogbl)