minix/lib/ack/i386/em/disconnected/em_fef8.s

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.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