[LLVMdev] a question about constant fold for fdiv

[Jeff Cohen]

Jeff Cohen wrote:
> Reid Spencer wrote:
>> On Thu, 2007-03-22 at 15:50 -0700, leo han wrote:
>>   
>>> Hello, I have a question about the constant folding for fdiv instructions. 
>>> For the instruction "fdiv double 0.0, 0.0", the folded result is inf. I 
>>> think this should be nan. Can anyone tell me why it is not nan?
>>>     
>>
>> I think the specification says that it is "undefined" so any value will
>> do. inf is just as undefined as nan.
>>
>> Reid.
>
> In IEEE Std 754-1985, subclause 7.2- Division by Zero, it says:
>
> /"If the divisor is zero and the dividend is a finite nonzero number, 
> then the division by zero shall be signaled. The result, when no trap 
> occurs, shall be a correctly signed (infinity symbol)(6.3)."
>
> /So LLVM is correct (assuming it handles signs correctly).

Never mind... only applies if a non-zero number is being divided by zero.
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