[Bug tree-optimization/107114] [13 Regression] Failure to discover range results in bogus warning

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107114

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P4                          |P3
           Keywords|                            |missed-optimization
   Target Milestone|---                         |13.0

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jeffrey A. Law from comment #4)
> I'll double check, but IIRC we throw away the loop structures at the end of
> DOM and they're supposed to be rebuilt (which appears to be happening as we
> re-construct LCSSA).

If you elide a loop it gets removed by fixup but we never fully re-build
loops.  Eliding a loop might have removed a stmt based on which undefined
behavior on overflow we could have derived an upper bound for the outer loop.
But you really have to sit down and see why we are no longer deriving
number of iterations [upper bound].