RFR(S) 8029302: Performance regression in Math.pow intrinsic

[Niclas Adlertz]

I agree with you.

Kind Regards,
Niclas Adlertz

On 04/17/2014 11:34 PM, Christian Thalinger wrote:
> I’ve said this before (see bug report) and I say it again (last time, I promise):  yes, it is a performance regression in the C2 compiler but a MUCH better place to “fix" this would be in the library.  Cover the common and special cases there and only use the intrinsic for the uncommon cases.
>
> On Apr 17, 2014, at 7:21 AM, David Chase <david.r.chase at oracle.com> wrote:
>
>> As long as we are doing this as a constant-driven transform in the compiler,
>> it might not hurt to also consider the case of x**3.  Cubes are common enough.
>>
>> David
>>
>>
>> On 2014-04-17, at 11:45 AM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>>
>>> Niclas,
>>>
>>> Looking on __ieee754_pow() in sharedRuntimeTrans.cpp and it has other simple cases:
>>>
>>> x**0 = 1
>>> x**1 = x
>>> x**-1  = 1/x
>>> x**0.5 = sqrt(x)
>>>
>>> It would be nice to know which are frequently used and implement them too.
>>>
>>> Also there is check for NaN before all this cases except x**0 = 1:
>>>
>>> /* +-NaN return x+y */
>>>
>>> You need to test that new C2 code produces the same results for NaN values.
>>>
>>> Thanks,
>>> Vladimir
>>
>