[PATCH] D46336: [InstCombine] Apply binary operator simplifications to associative/commutative cases.

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In https://reviews.llvm.org/D46336#1090644, @yamauchi wrote:

> After -instcombine -reassociate -instcombine -reassociate -instcombine with https://reviews.llvm.org/D45842
>
>   define i1 @bit-check-combine1(i32 %a, i32 %b) {
>   entry:
>     %0 = and i32 %b, 8
>     %1 = and i32 %a, 7
>     %2 = or i32 %0, %1
>     %3 = and i32 %b, 48
>     %4 = or i32 %2, %3
>     %5 = icmp eq i32 %4, 0
>     ret i1 %5
>   }
>


So it seems https://reviews.llvm.org/D45842 did what it was supposed to, but the instcombine can't fold that down into

  define i1 @bit-check-combine1(i32 %a, i32 %b) {
  entry:
    %0 = and i32 %a, 7
    %1 = and i32 %b, 56
    %2 = or i32 %0, %1
    %3 = icmp eq i32 %2, 0
    ret i1 %3
  }

I'd guess something in instcombine does not use commutative matchers.
(I did not analyse this at all yet, just 'saving' it as one comment)


Repository:
  rL LLVM

https://reviews.llvm.org/D46336