[PATCH] Added InstCombine transform for pattern "(A ^ B) | ((~A) ^ B) -> True".

[David Majnemer]

I don't think we need to do anything here, running reassociate before instcombine cleans things up.
  $ cat t.ll
  define i32 @test14(i32 %x, i32 %y) {
    %nega = xor i32 %x, -1
    %xor = xor i32 %nega, %y
    %xor1 = xor i32 %x, %y
    %or = or i32 %xor, %xor1
    ret i32 %or
  }

  define i32 @test15(i32 %x, i32 %y) {
    %xor = xor i32 %x, %y
    %nega = xor i32 %x, -1
    %xor1 = xor i32 %nega, %y
    %or = or i32 %xor, %xor1
    ret i32 %or
  }

  $ ~/llvm/Debug+Asserts/bin/opt -reassociate -instcombine t.ll -o - -S
  ; ModuleID = 't.ll'

  define i32 @test14(i32 %x, i32 %y) {
    ret i32 -1
  }

  define i32 @test15(i32 %x, i32 %y) {
    ret i32 -1
  }

http://reviews.llvm.org/D4691