minix/lib/i386/em/em_fef4.s

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ArmAsm
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2005-04-21 16:53:53 +02:00
.sect .text; .sect .rom; .sect .data; .sect .bss
.define .fef4
.sect .text
.fef4:
! this could be simpler, if only the
! fxtract instruction was emulated properly
mov bx,sp
mov ax,8(bx)
and ax,0x7f800000
je 1f ! zero exponent
shr ax,23
sub ax,126
mov cx,ax ! exponent in cx
mov ax,8(bx)
and ax,0x807fffff
or ax,0x3f000000 ! load -1 exponent
mov bx,4(bx)
mov 4(bx),ax
mov (bx),cx
ret
1: ! we get here on zero exp
mov ax,8(bx)
and ax,0x007fffff
jne 1f ! zero result
mov bx,4(bx)
mov (bx),ax
mov 4(bx),ax
ret
1: ! otherwise unnormalized number
mov cx,8(bx)
and cx,0x807fffff
mov dx,cx
and cx,0x80000000
mov ax,-125
2:
test dx,0x800000
jne 1f
dec ax
shl dx,1
or dx,cx
jmp 2b
1:
mov bx,4(bx)
mov (bx),ax
and dx,0x807fffff
or dx,0x3f000000 ! load -1 exponent
mov 4(bx),dx
ret