49 lines
827 B
ArmAsm
Executable file
49 lines
827 B
ArmAsm
Executable file
.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
|