source: trunk/minix/lib/i386/em/em_fef8.s@ 20

.sect .text; .sect .rom; .sect .data; .sect .bss
.define .fef8

        .sect .text
.fef8:
                                ! this could be simpler, if only the
                                ! fxtract instruction was emulated properly
        mov     bx,sp
        mov     ax,12(bx)
        and     ax,0x7ff00000
        je      1f              ! zero exponent
        shr     ax,20
        sub     ax,1022
        mov     cx,ax           ! exponent in cx
        mov     ax,12(bx)
        and     ax,0x800fffff
        or      ax,0x3fe00000   ! load -1 exponent
        mov     dx,8(bx)
        mov     bx,4(bx)
        mov     4(bx),dx
        mov     8(bx),ax
        mov     (bx),cx
        ret
1:                              ! we get here on zero exp
        mov     ax,12(bx)
        and     ax,0xfffff
        or      ax,8(bx)
        jne     1f              ! zero result
        mov     bx,4(bx)
        mov     (bx),ax
        mov     4(bx),ax
        mov     8(bx),ax
        ret
1:                              ! otherwise unnormalized number
        mov     cx,12(bx)
        and     cx,0x800fffff
        mov     dx,cx
        and     cx,0x80000000
        mov     ax,-1021
2:
        test    dx,0x100000
        jne     1f
        dec     ax
        shl     8(bx),1
        rcl     dx,1
        or      dx,cx
        jmp     2b
1:
        and     dx,0x800fffff
        or      dx,0x3fe00000   ! load -1 exponent
        mov     cx,8(bx)
        mov     bx,4(bx)
        mov     (bx),ax
        mov     8(bx),dx
        mov     4(bx),cx
        ret