RFR: 8265940: Enable C2's optimization for Math.pow(x, 0.5) on all platforms [v2]

[Vladimir Kozlov]

On Wed, 28 Apr 2021 23:34:11 GMT, Jie Fu <jiefu at openjdk.org> wrote:

>> Hi all,
>> 
>> I'd like to enable C2's optimization for Math.pow(x, 0.5) on all platforms.
>> 
>> This is fine because:
>>  1) For x86, it will call the assembly stubs.
>>     This opt has already been implemented for x86_64 [1]. 
>>     And the x86_32 version is added in this patch.
>>  2) For non-x86, it will call the shared runtime c code [2], which does the same opt too.
>> 
>> Testing:
>>   - tier1~3 on Linux/{x86_32, x86_64}, no regression
>> 
>> Thanks,
>> Best regards,
>> Jie
>> 
>> 
>> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/macroAssembler_x86_pow.cpp#L838
>> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/runtime/sharedRuntimeTrans.cpp#L497
>
> Jie Fu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comments for why -0.0/0.0 are excluded

Good.

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Marked as reviewed by kvn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3755