RFR: 8360192: C2: Make the type of count leading/trailing zero nodes more precise [v7]

[Chen Liang]

On Wed, 6 Aug 2025 12:38:28 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Qizheng Xing has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains nine additional commits since the last revision:
>> 
>>  - Merge branch 'master' into enhance-clz-type
>>  - Add checks for results of all test methods
>>  - Replace `isa_*` with `is_*` and add checks for `Type::BOTTOM`
>>  - Merge branch 'master' into enhance-clz-type
>>  - Move `TestCountBitsRange` to `compiler.c2.gvn`
>>  - Fix null checks
>>  - Narrow type bound
>>  - Use `BitsPerX` constant instead of `sizeof`
>>  - Make the type of count leading/trailing zero nodes more precise
>
> src/hotspot/share/opto/countbitsnode.cpp line 57:
> 
>> 55: 
>> 56:   // If the input is BOTTOM, the result is the local BOTTOM.
>> 57:   if (t == Type::BOTTOM) {
> 
> `t` should not be `Type::BOTTOM`, please remove this case.

Maybe convert to an assert?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25928#discussion_r2257319939