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Re: [PATCH] powerpc: Fix logbl on power7 [BZ# 21280]
On 21/03/2017 17:09, Tulio Magno Quites Machado Filho wrote:
> Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:
>
>> On 20/03/2017 18:02, Tulio Magno Quites Machado Filho wrote:
>>> 1. Fix the results for negative subnormals by ignoring the signal when
>>> normalizing the value.
>>> 2. Fix the output when the high part is a power of 2 and the low part
>>> is a nonzero number with opposite sign. This fix is based on commit
>>> 380bd0fd2418f8988217de950f8b8ff18af0cb2b.
>>
>> It is not a blocker, but based on the complexity of the change and the
>> optimization real case usage, I wonder if it would be better to just remove
>> it and use the default implementation instead.
>
> I tried to do that before fixing these, but the performance difference is
> still around 2x.
I would expect it, but the question is do we really care about the performance
of logbl-ibm128 to maintain a separated implementation for power7+ only?