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