RFR: 8343629: More MergeStore benchmark

[Emanuel Peter]

On Wed, 23 Oct 2024 07:03:33 GMT, Shaojin Wen <swen at openjdk.org> wrote:

> 1. Added the putBytes4 benchmark, which corresponds to StringBuilder appendNull
> 2. Optimized the putChars4/setInt/setLong series of benchmarks to reduce extra overhead and more accurately reflect performance differences.

> ```java
> "null".getBytes(0, 4, bytes4, off);
> ```
>   
> Is it possible to do MergeStore in this scenario?

I don't know. What do the logs say? And what does it currently compile down to, i.e. what assembly instructions?

Otherwise I think this update seems reasonable.

It would be nice if you could do some summary / explanation: which cases do still not optimize, and why?

For that, it would be helpful if you had a run with, and one without `MergeStores` enabled - then we can easily compare the performance!

You can find an example of how to do that easily here:
https://github.com/openjdk/jdk/pull/19970/files#diff-9072c369f5b541ef9fca3ad8320aa59e88cc72f203c03da58100b1d111ffc324R746-R749

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PR Comment: https://git.openjdk.org/jdk/pull/21659#issuecomment-2458877595
PR Comment: https://git.openjdk.org/jdk/pull/21659#issuecomment-2458878368
PR Comment: https://git.openjdk.org/jdk/pull/21659#issuecomment-2458880901
PR Comment: https://git.openjdk.org/jdk/pull/21659#issuecomment-2458883551