RFR: 8275202: C2: optimize out more redundant conditions

[Roland Westrelin]

On Mon, 29 Jan 2024 22:36:27 GMT, Joshua Cao <duke at openjdk.org> wrote:

> It won't be as powerful as the fixed point optimization that is proposed in this PR, but it is sufficient to cover the case mentioned in the JBS issue and would have less compile time overhead.

I think it would do a lot less so in my opinion, it's worth pursuing the fixed point optimization. The main reason it has such an overhead in the current patch is that it's run too often (every time there's a loop opts pass). There are corner cases that were hard to handled otherwise (and cause the compiler to crash). I've been working on a new version of the patch where the pass is run only once or twice (and found ways to handle the corner cases that were problematic). It's not ready yet.

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PR Comment: https://git.openjdk.org/jdk/pull/14586#issuecomment-1917133085