[Bug tree-optimization/86434] early string folding defeats strlen optimization and -Warray-bounds

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86434

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Are these examples from real-world code?  Because I can create examples where
early folding is necessary as well...

It's really not an easy black-and-white decision.

Consider

void f (int i)
{
  if (__builtin_strlen (&a[i]) != 3 - i)
    {
      ... large code ...
    }
}

void g ()
{
  f (1);
}

where not folding and eliding the conditionaly will prevent inlining from
happening.

The usual "solution" is to do value-range analysis and folding at the same
time - thus avoiding pass inter-dependences by just having a single pass.