RFR: 8345287: C2: live in computation is broken

[Roland Westrelin]

On Mon, 2 Dec 2024 10:08:30 GMT, Damon Fenacci <dfenacci at openjdk.org> wrote:

> Well spotted! I've just got one doubt: do we actually need that `if (!lo->is_empty())` at all?

It's a performance optimization from https://bugs.openjdk.org/browse/JDK-8234003
Otherwise the iterator code will look for the next element in the set which is done by iterating over an array that can be large even when the set is empty.
8234003 introduced the bug here.

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PR Comment: https://git.openjdk.org/jdk/pull/22473#issuecomment-2511388535