[PATCH] D129793: [LSR] Allow already invariant operand for ICmpZero matching

[Philip Reames via Phabricator via llvm-commits]

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The ICmpZero matching is checking to see if the expression is loop invariant per SCEV and expandable.  This allows expressions inside the loop which can be made loop invariant to be seamlessly expanded, but is overly conservative for expressions which already *are* loop invariant.

As a simple justification for why this is correct, consider a loop invariant urem as RHS vs an alternate function with that same urem wrapped inside a helper call.  Why would it be legal to match the later, but not the former?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129793

Files:
  llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
  llvm/test/CodeGen/RISCV/rvv/sink-splat-operands.ll
  llvm/test/Transforms/LoopStrengthReduce/RISCV/icmp-zero.ll

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