[Bug tree-optimization/53265] Warn when undefined behavior implies smaller iteration count

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265

--- Comment #12 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2013-03-11 16:49:25 UTC ---
(In reply to comment #10)
> (In reply to comment #8)
> > Not sure about the warning wording
> 
> What about (... "iteration %E invokes undefined behavior", max)?
> 
> > plus no idea how to call the warning option (-Wnum-loop-iterations, 
> > -Wundefined-behavior-in-loop, something else?)
> 
> Can it be -Waggressive-loop-optimizations to follow existing pairs of
> -{W,fno-}strict-{aliasing,overflow} for the recently added
> -fno-aggressive-loop-optimizations?

I think these two are very good suggestions. Thanks, Alexander.

And if this gets implemented for 4.8, I think it will make the new loop
optimizations much safer to use and, hence, much more useful.