[PATCH] D76024: [MachineLICM] Let targets decide to hoist cheap instructions

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

I'm not sure what, exactly, is specific to Cortex-M here.  Copies between int and SIMD registers aren't really cheaper on other CPUs, relatively speaking.  I don't really like adding a new target hook without a better justification for why Cortex-M is different from other targets; having target-specific codepaths is going to make it harder for anyone to make improvements here in the future.

Maybe we should revisit the assumption that copies are cheap, in MachineLICMBase::IsCheapInstruction?  Or maybe we should revisit the assumption that we should avoid hoisting cheap instructions?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76024/new/

https://reviews.llvm.org/D76024