[all-commits] [llvm/llvm-project] 4010a7: Reapply [InstCombine] Support switch in phi to con...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4010a7a5d0ea21374f3dcab85aa26a9804e1c35d
      https://github.com/llvm/llvm-project/commit/4010a7a5d0ea21374f3dcab85aa26a9804e1c35d
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2022-03-17 (Thu, 17 Mar 2022)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
    M llvm/test/Transforms/InstCombine/simple_phi_condition.ll

  Log Message:
  -----------
  Reapply [InstCombine] Support switch in phi to cond fold

Reapply with an explicit check for multi-edges, as the expected
behavior of multi-edge dominance is unclear (D120811).

-----

For conditional branches, we know the value is i1 0 or i1 1 along
the outgoing edges. For switches we can apply exactly the same
optimization, just with the known values determined by the switch
cases.