[PATCH] D25485: [x86] use 'neg' for negation of bool

[Sanjay Patel via llvm-commits]

spatel added a comment.

In https://reviews.llvm.org/D25485#569404, @spatel wrote:

> Looking closer at the SystemZ regression test differences, we have more instructions with the LegalizeDAG patch, so I think that target is missing a pattern ( cc'ing @uweigand  and @jonpa ).


On 2nd thought, this is a missing combine for all targets:

  define i32 @topbit(i32 %x) {
    %sra = ashr i32 %x, 31
    %neg = sub i32 0, %sra
    ret i32 %neg
  }

Should be simplified to:

  %neg = lshr i32 %x, 31


https://reviews.llvm.org/D25485