RFR: 8351833: Unexpected increase in live nodes when splitting Phis through MergeMems in PhiNode::Ideal [v3]

[Daniel Lundén]

On Mon, 14 Apr 2025 09:08:04 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>> Yes, for sure interesting. Let us create a separate RFE to investigate.
>
> I had a closer look at the example and found that the generation of large amounts of cold code is due to two factors:
> 1. (excessive?) use of `@ForceInline` in [StringConcatHelper](https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/lang/StringConcatHelper.java) and 
> 2.  generation of fast/path idioms for constructs within the cold inlined code (allocations in particular). 
> 
> For 1. we should evaluate whether forced inlining in  `StringConcatHelper` is warranted (in terms of cost/benefits). For 2., I filed [JDK-8354509](https://bugs.openjdk.org/browse/JDK-8354509).

Thanks for filing [JDK-8354509](https://bugs.openjdk.org/browse/JDK-8354509). Should we file an RFE for 1. as well?

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PR Review Comment: https://git.openjdk.org/jdk/pull/24325#discussion_r2044013312