[PATCH] D140542: [MachineCombiner] Support local strategy for traces

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

I don't see anything wrong with this patch, but I haven't looked at MachineCombiner in a long time, so I'm likely not the best reviewer.

I do want to note a potential alternative - have you looked at using enableAggressiveFMAFusion() in DAGCombiner?
If you flip that switch for RISCV, the `sub3` calculation in the last block would become:

  	fmadd.d	ft1, ft0, fa1, fa0
  	fnmsub.d	fa0, ft0, fa1, ft1

If the fma instruction timing is the same as plain fmul on your target, then is that even better than the 1 fmadd produced on the test here?


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D140542