RFR: 8334431: C2 SuperWord: fix performance regression due to store-to-load-forwarding failures [v2]

[Christian Hagedorn]

On Tue, 19 Nov 2024 15:36:32 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Ah, I thought that as long as the starting addresses match, then all platforms will do the optimization when we store more bytes than we load. But that's not the case then? But of course for the analysis we do in Superword, we only assume that exact matches will work.
>
> Yes, exactly. In general the CPU can be smarter, but we assume only exact matches are successes - all others failure if they overlap in any way.

Got it, thanks for the explanation!

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PR Review Comment: https://git.openjdk.org/jdk/pull/21521#discussion_r1848595159