[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#1090588, @yamauchi wrote:

> In https://reviews.llvm.org/D46336#1089012, @lebedev.ri wrote:
>
> > Having looked through https://reviews.llvm.org/D45842, i find this differential rather more complex.
> >  Maybe instcombine shouldn't be doing this..
> >
> > It would be interesting to know which of these testcase *aren't* handled by https://reviews.llvm.org/D45842.
>
>
> Input:
>
>   define i1 @bit-check-combine1(i32 %a, i32 %b) {
>   entry:
>     %0 = and i32 %a, 1
>     %1 = icmp eq i32 %0, 0
>     %2 = and i32 %a, 2
>     %3 = icmp eq i32 %2, 0
>     %4 = and i32 %a, 4
>     %5 = icmp eq i32 %4, 0
>     %6 = and i32 %b, 8
>     %7 = icmp eq i32 %6, 0
>     %8 = and i32 %b, 16
>     %9 = icmp eq i32 %8, 0
>     %10 = and i32 %b, 32
>     %11 = icmp eq i32 %10, 0
>     %12 = and i1 %1, %3
>     %13 = and i1 %12, %5
>     %14 = and i1 %13, %7
>     %15 = and i1 %14, %9
>     %16 = and i1 %15, %11
>     ret i1 %16
>   }
>
>
> ...
>
> After -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 %3, %2
>     %5 = icmp eq i32 %4, 0
>     ret i1 %5
>   }
>


.. and if you run `-reassociate -instcombine` once more?


Repository:
  rL LLVM

https://reviews.llvm.org/D46336