weird optimization in sin+cos, x86 backend

[Robert Dewar]

On 2/3/2012 1:12 PM, Konstantin Vladimirov wrote:
> Hi,
>
> I agree, that this case have no practical value. It was autogenerated
> between other thousands of tests and showed really strange results, so
> I decided to ask. I thought, this value fits double precision range
> and, according to C standard, all double-precision arithmetics must be
> avaliable for it.

Yes, indeed and it was available. There was nothing "really strange"
about the results. The only thing strange was your expectations here :-)
>
> Thanks everybody for explanation, I will constrain trig function
> arguments, according to "x is separable with x+pi/4" rule. It seems,
> everything works inside this range.

Yes, it is a good idea to only generate useful tests when you
are autogenerating, otherwise you will get garbage in garbage out :-)
>
> ---
> With best regards, Konstantin
>
> On Fri, Feb 3, 2012 at 7:13 PM, Robert Dewar<dewar@adacore.com>  wrote:
>> On 2/3/2012 10:01 AM, Michael Matz wrote:
>>
>>> No normal math library supports such an extreme range, even basic
>>> identities (like cos^2+sin^2=1) aren't retained with such inputs.
>>
>>
>> I agree: the program is complete nonsense. It would be useful to know
>> what the intent was.
>>>
>>>
>>>
>>> Ciao,
>>> Michael.
>>
>>