RFR: 8305203: Simplify trimming operation in Region::Ideal [v2]

[Xin Liu]

On Mon, 3 Apr 2023 19:42:42 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> This patch improves how Region::Ideal trims unreachable paths. 
>> 
>> 1. Don't restart from beginning. Trimming doesn't change the DU-chain.
>> 2. Replace DFIterator with DFIterator_Fast. The later is a raw pointer in release build.
>> 3. Don't call add_users_to_worklist(this) repeatly.
>> 4. Reduce its strength from add_users_to_worklist to
>>    add_users_to_worklist0 because RegionNode has no special logic.
>> 
>> This patch also includes a cosmetic change: rename n to 'use' inside of the loop.
>> Otherwise, we would overshadow Node* n = in(i). Nothing wrong but harder to read.
>
> Xin Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update coding style according to reviewer's feedback.

hi, @vnkozlov 
Could you take a look this PR? thanks.

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PR Comment: https://git.openjdk.org/jdk/pull/13238#issuecomment-1501979313