-Winfinite-recursion confused by some tautological expressions

[AaronBallman]

Consider code like:

void func1(int i) {
  if (i || !i)
    func1(i);
}

void func2(int i) {
  if (i > 0 || i <= 0)
    func2(i);
}

Clang correctly diagnoses func2() as being recursive along all paths, but it mysteriously does not diagnose func1(). (https://godbolt.org/z/Ks3Wvdf8W)

Surprisingly, we don't seem to catch i || !i as being a tautological comparison, so it's possible that's a related issue (https://godbolt.org/z/hs9Ehrbss).

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[hazohelet]

I'll work on this. We can also add i && !i as a tautological comparison.

[hazohelet]

Proposed fix: https://reviews.llvm.org/D152093