RFR: 8335006: C2 SuperWord: add JMH benchmark VectorLoadToStoreForwarding.java

[Emanuel Peter]

On Tue, 25 Jun 2024 14:30:50 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> I'm committing the benchmark mentioned in my blog article:
>> https://eme64.github.io/blog/2024/06/24/Auto-Vectorization-and-Store-to-Load-Forwarding.html
>> 
>> These are the numbers I got on my machine. Read the blog for a full analysis.
>> ![image](https://github.com/openjdk/jdk/assets/32593061/28ba310d-1f7e-4c5c-ae0e-1f38e6214603)
>> 
>> **Quick summary:**
>> We see that vectorization is only beneficial for `OFFSET = 0, 1, 2, 4, 8, 16`, at least with the current SuperWord implementation. The regression for `OFFSET = 3 `is especially stark.
>> 
>> The effect that explains the slowdown of vectorization for the other cases is failed store-to-load-forwarding.
>> 
>> I ran it like this on my machine:
>> `make test TEST="micro:vm.compiler.VectorLoadToStoreForwarding" CONF=linux-x64`
>
> Good.

Thanks for the reviews @vnkozlov @shipilev @sviswa7 !

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PR Comment: https://git.openjdk.org/jdk/pull/19880#issuecomment-2191815080