[llvm] [InstCombine] Remove AllOnes fallbacks in getMaskedTypeForICmpPair() (PR #104941)

[Nikita Popov via llvm-commits]

nikic wrote:

Another test case:
```llvm
define i1 @test2(i64 %a) {
  %cmp1 = icmp ne i64 %a, 0
  %a.mask = and i64 %a, 9223372036854775807
  %cmp2 = icmp eq i64 %a.mask, 0
  %and = and i1 %cmp1, %cmp2 
  ret i1 %and 
}

define i1 @test2(i64 %a) {
  %and = icmp eq i64 %a, -9223372036854775808
  ret i1 %and
}
```

https://github.com/llvm/llvm-project/pull/104941