RFR: 8366361: C2 SuperWord: rename VTransformNode::set_req -> init_req, analogue to Node::init_req [v2]

[Christian Hagedorn]

On Mon, 1 Sep 2025 07:08:56 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> I'm working on cost-modeling, and am integrating some smaller changes from this proof-of-concept PR:
>> https://github.com/openjdk/jdk/pull/20964
>> [See plan overfiew.](https://bugs.openjdk.org/browse/JDK-8340093)
>> 
>> This is a pure refactoring - no change in behaviour. I'm presenting it like this because it will make reviews easier.
>> 
>> The current implementation of `VTransformNode::set_req` has `init_req` semantics, it verifies that the corresponding input is still nullptr. We should thus rename it. It will also free up the "set_req" name for later use in VTransform optimizations, where we want to modify the graph.
>> 
>> See `VTransformReductionVectorNode::optimize_move_non_strict_order_reductions_out_of_loop` in the proof-of-concept PR.
>> 
>> FYI: this PR is dependent on https://github.com/openjdk/jdk/pull/26987. I'll rebase once that one is integrated. We can still already review, so that the process is a little faster later on. (I have more small changes coming, but separating makes them more reviewable.)
>
> Emanuel Peter has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:
> 
>  - Merge branch 'master' into JDK-8366361-vtn-init_req
>  - JDK-8366361
>  - For Christian: use phase->intcon instead
>  - Update src/hotspot/share/opto/vtransform.hpp
>    
>    Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>
>  - JDK-8366357

Marked as reviewed by chagedorn (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk/pull/26991#pullrequestreview-3172354981