RFR: 8217869: Add count_leading_zeros utility

[Tobias Hartmann]

Hi Claes,

looks good to me too.

Best regards,
Tobias

On 28.01.19 10:36, Nils Eliasson wrote:
> A very welcome improvement.
> 
> Thank you Claes!
> 
> Reviewed,
> 
> // Nils
> 
> On 2019-01-28 10:34, Claes Redestad wrote:
>> Hi,
>>
>> adding a count_leading_zeros implementation using compiler intrinsics
>> means a straightforward optimization of RegMask::find_highest_bit. For
>> platforms lacking intrinsic support a more efficient algorithm is
>> implemented.
>>
>> Adding a 64-bit version would be straightforward, but let's do that
>> when we need it.
>>
>> Bug:    https://bugs.openjdk.java.net/browse/JDK-8217869
>> Webrev: http://cr.openjdk.java.net/~redestad/8217869/open.00/
>>
>> Testing: tier1-3
>>
>> The xlc changes are untested, so it'd be much appreciated if someone
>> can run the test on that platform.
>>
>> Thanks!
>>
>> /Claes