Integrated: 8305203: Simplify trimming operation in Region::Ideal

[Xin Liu]

On Thu, 30 Mar 2023 05:26:08 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.~~(we can't measure any change of compilation time, so there's no point to simplify it)
> 
> 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.

This pull request has now been integrated.

Changeset: 82e8b033
Author:    Xin Liu <xliu at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/82e8b0332b5313dda26688c49434837374d233d6
Stats:     28 lines in 1 file changed: 7 ins; 10 del; 11 mod

8305203: Simplify trimming operation in Region::Ideal

Reviewed-by: thartmann, kvn

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PR: https://git.openjdk.org/jdk/pull/13238