RFR: 8332268: C2: Add missing optimizations for UDivI/L and UModI/L and unify the shared logic with the signed nodes [v3]

[Tobias Hartmann]

On Mon, 25 Nov 2024 14:49:14 GMT, theoweidmannoracle <duke at openjdk.org> wrote:

>> Yeah, it is a trade-off. I think this here is small enough to just change it now in the same RFE. But if you prefer to do it in a separate RFE, that's fine too for me.
>
> If I make these changes here now, I need to come up with tests for these uncasts, which will probably take me a while (I have no experience with this yet and I can't tell how long it might take me) and the PR will stall in the meantime. If I open a follow-up RFE, I can take a look at this independently and this PR, whose main intention was to take over the main applicable optimizations from the signed to unsigned can be merged already. So as @eme64 says, it's a trade-off between creating the perfect PR now or getting some good changes in and then making refinements in the same area in a later, follow-up PR.

Drive-by comment: Such uncast optimizations are definitely non-trivial changes as they tend to trigger other issues by allowing subgraphs to be folded that would otherwise not be folded. So let's make sure we have proper tests for this. In my opinion, putting some of this work into a separate RFE is perfectly fine.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22061#discussion_r1856762430