Integrated: 8373524: C2: no reachable node should have no use

[Roland Westrelin]

On Tue, 16 Dec 2025 10:02:46 GMT, Roland Westrelin <roland at openjdk.org> wrote:

> The failure occurs because `PhiNode::Ideal` uses `set_req` to update
> an input of a `Phi`. That causes the previous input to be disconnected
> but because of the use of `set_req`, the previous input that has no
> use is not enqueued for `igvn` to be reclaimed. The fix is to use
> `set_req_X` instead. I replaced uses of `set_req` with `set_req_X` in
> `PhiNode::Ideal` where I thought it made sense.

This pull request has now been integrated.

Changeset: e72f205a
Author:    Roland Westrelin <roland at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/e72f205ae312b15ebab0cbeedb73bbf86e485251
Stats:     94 lines in 2 files changed: 91 ins; 0 del; 3 mod

8373524: C2: no reachable node should have no use

Reviewed-by: chagedorn, mhaessig

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PR: https://git.openjdk.org/jdk/pull/28841