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

[Christian Hagedorn]

On Thu, 28 Aug 2025 15:30:31 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
> 
> 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.)

Looks good!

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Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26991#pullrequestreview-3167592057