RFR: 8287087: C2: perform SLP reduction analysis on-demand [v2]

[Jatin Bhateja]

On Fri, 14 Apr 2023 12:42:46 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> I tried out your suggestion but unfortunately, the bookkeeping code (marking/storing candidate nodes and their predecessors in the tentative reduction chain) became more complex than the simplifications it enabled.

Hi @robcasloz ,  Ok, my concern was that post path detection we have two occurrences of _original_input_ , this can be optimized if we bookkeep node encountered during path detection. Kindly consider attached rough patch which records the nodes during patch detection.  
[reduction_patch.txt](https://github.com/openjdk/jdk/files/11310121/reduction_patch.txt)

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PR Review Comment: https://git.openjdk.org/jdk/pull/13120#discussion_r1175182260