[PATCH] D122152: [InstCombine] Fold two select patterns into and-or

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added a comment.

I'm almost afraid to ask - but should we consider supporting this with freeze?

  ----------------------------------------
  define i1 @src(i1 %a, i1 %b, i1 %c) {
    %nota = xor i1 %a, 1
    %cond = or i1 %nota, %c
    %r = select i1 %cond, i1 %a, i1 %b
    ret i1 %r
  }
  =>
  define i1 @tgt(i1 %a, i1 %b, i1 %c) {
    %bf = freeze i1 %b
    %tmp = or i1 %bf, %c
    %r = and i1 %tmp, %a
    ret i1 %r
  }
  Transformation seems to be correct!
  
  
  ----------------------------------------
  define i1 @src(i1 %a, i1 %b, i1 %c) {
    %notc = xor i1 %c, 1
    %cond = and i1 %notc, %b
    %r = select i1 %cond, i1 %a, i1 %b
    ret i1 %r
  }
  =>
  define i1 @tgt(i1 %a, i1 %b, i1 %c) {
    %fa = freeze i1 %a
    %tmp = or i1 %c, %fa
    %r = and i1 %tmp, %b
    ret i1 %r
  }
  Transformation seems to be correct!


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122152/new/

https://reviews.llvm.org/D122152