RFR: 8360192: C2: Make the type of count leading/trailing zero nodes more precise [v12]

[Qizheng Xing]

On Tue, 19 Aug 2025 13:54:31 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Qizheng Xing has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add more constant folding tests for CLZ/CTZ
>
> src/hotspot/share/opto/countbitsnode.cpp line 47:
> 
>> 45:     if (x >> 30 == 0) { n +=  2; x <<=  2; }
>> 46:     n -= x >> 31;
>> 47:     return TypeInt::make(n);
> 
> Is there already a test that covers all the cases that constant fold here? Just to make sure we do not get regressions here.

Added in IR test `TestCountBitsRange.java`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25928#discussion_r2329682681