lib/i386/em/em_fef8.s

   1 .sect .text; .sect .rom; .sect .data; .sect .bss
   2 .define .fef8
   3
   4         .sect .text
   5 .fef8:
   6                                 ! this could be simpler, if only the
   7                                 ! fxtract instruction was emulated properly
   8         mov     bx,sp
   9         mov     ax,12(bx)
  10         and     ax,0x7ff00000
  11         je      1f              ! zero exponent
  12         shr     ax,20
  13         sub     ax,1022
  14         mov     cx,ax           ! exponent in cx
  15         mov     ax,12(bx)
  16         and     ax,0x800fffff
  17         or      ax,0x3fe00000   ! load -1 exponent
  18         mov     dx,8(bx)
  19         mov     bx,4(bx)
  20         mov     4(bx),dx
  21         mov     8(bx),ax
  22         mov     (bx),cx
  23         ret
  24 1:                              ! we get here on zero exp
  25         mov     ax,12(bx)
  26         and     ax,0xfffff
  27         or      ax,8(bx)
  28         jne     1f              ! zero result
  29         mov     bx,4(bx)
  30         mov     (bx),ax
  31         mov     4(bx),ax
  32         mov     8(bx),ax
  33         ret
  34 1:                              ! otherwise unnormalized number
  35         mov     cx,12(bx)
  36         and     cx,0x800fffff
  37         mov     dx,cx
  38         and     cx,0x80000000
  39         mov     ax,-1021
  40 2:
  41         test    dx,0x100000
  42         jne     1f
  43         dec     ax
  44         shl     8(bx),1
  45         rcl     dx,1
  46         or      dx,cx
  47         jmp     2b
  48 1:
  49         and     dx,0x800fffff
  50         or      dx,0x3fe00000   ! load -1 exponent
  51         mov     cx,8(bx)
  52         mov     bx,4(bx)
  53         mov     (bx),ax
  54         mov     8(bx),dx
  55         mov     4(bx),cx
  56         ret