http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-11 15:58:41 UTC --- (In reply to comment #8) > Created attachment 29637 [details] > gcc48-pr53265.patch > > Untested patch. Not sure about the warning wording, plus no idea how to call > the warning option (-Wnum-loop-iterations, -Wundefined-behavior-in-loop, > something else?), whether to enable it by default, or just for -Wall. > A bigger issue is that I see multiple warnings for the same stmts, despite the > guard in loop structure, because apparently the same loop is represented by > different loop structures during the optimizations. Yeah, before the tree loop optimization pipeline loops are not preserved ... (easy to change, apart from code missing to inline a loop tree). Eventually use gimple_no_warning on the stmt? Supposedly not very reliable either. I think with your patch you also fail to warn for bounds discovered by discover_iteration_bound_by_body_walk or maybe_lower_iteration_bound. That said, I'd expected you warn from within record_niter_bound. Btw, after number_of_latch_executions () its return value is cached in loop->nb_iterations, no need to pass around another value.
