[all-commits] [llvm/llvm-project] 8623da: [DAG] visitFREEZE - generalize freeze(op()) -> op(...

Simon Pilgrim via All-commits all-commits at lists.llvm.org
Wed Aug 10 05:13:07 PDT 2022

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8623da5f748bc36fc78fa148fd34332d386533ea
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2022-08-10 (Wed, 10 Aug 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

  Log Message:
  [DAG] visitFREEZE - generalize freeze(op()) -> op(freeze()) to any number of operands

canCreateUndefOrPoison currently only handles unary ops, but we intend to change that soon - this more closely matches the pushFreezeToPreventPoisonFromPropagating behaviour where the freeze is pushed up to a single operand value, as long as all others are guaranteed not to be poison/undef.

However, pushFreezeToPreventPoisonFromPropagating would freeze all uses of the value - whilst this variant requires the frozen value to be only used in the op - we can look at generalize multiple uses later if the need arises.

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