8373731: C2: Missed optimization opportunity for AddI

[hgqxjj]

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This change fixes a missed optimization in C2 IGVN where Add/Sub cancellation patterns such as x + (y - x) and (x - y) + y are not eliminated after an upstream rewrite exposes the cancellation opportunity. The root cause is that input edge rewiring on a SubI/SubL does not reliably re-enqueue its AddI/AddL users.

To address this, the change enqueues the relevant AddI/AddL users when the corresponding SubI/SubL node is processed in PhaseIterGVN::subsume_node(), where the graph has already been rewired. Only Add users matching the cancellation shape are enqueued to keep the worklist impact minimal.

Test: GHA

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Issue

• JDK-8373731: C2: Missed optimization opportunity for AddI (Enhancement - P4)

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