[PATCH] D125232: [riscv] Fix data flow for VSETVLI insertion

[Philip Reames via Phabricator via llvm-commits]

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After staring at some generated code for a while, I'm becoming less sure the switch from optimistic to conservative dataflow in this patch is a good idea.  I want to give that some more thought, and try separating out only the re-visit logic.

In the meantime, I posted a tactical fix for a miscompile in the current workaround: https://reviews.llvm.org/D125408

Now that the two mutation bugs (PHI, and scalar op) have landed, I think we're approaching correct.  We need the tactical fix just posted, but I think once that lands, this review can be reframed as a code quality issue which no longer influences correctness.

I think we still want something like this.  Our other option would be to investigate scheduling corrections at more optimal places.  I'm going to give that a bit of thought, but my initial reaction is "yuck".


Repository:
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  https://reviews.llvm.org/D125232/new/

https://reviews.llvm.org/D125232