RFR: 8265784: [C2] Hoisting of DecodeN leaves MachTemp inputs behind

[Goetz Lindenmaier]

On Thu, 22 Apr 2021 18:58:28 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> PPC64 and s390 have DecodeN implementations which use a MachTemp input. When LCM hoists the DecodeN, the MachTemp nodes reside in the old block, but should get hoisted together with the DecodeN node.
> Same is true for load Base input which exists on s390 for example. Unfortunately, that's just a platform specific MachNode which is not nicely recognizable in LCM.

Hi Martin, 
I think the loop must go before the block->add_inst(val); .
Else you get a cycle within the block.
The MachTemp must be before the node that uses them in the list.
Best regards,
  Goetz.

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PR: https://git.openjdk.java.net/jdk/pull/3637