------- Comment #7 from rguenther at suse dot de 2009-05-15 08:44 ------- Subject: Re: [4.3/4.4/4.5 Regression] Number of iterations analysis wrong
On Fri, 15 May 2009, rakdver at gcc dot gnu dot org wrote: > ------- Comment #6 from rakdver at gcc dot gnu dot org 2009-05-15 00:34 > ------- > (In reply to comment #5) > > It is number of iteration analysis that gets it wrong (I suppose it might > > get > > confused by the two exits of the loop?). > > Sort of; # of iterations analysis assumes that pointers never wrap, and uses > this assumption to derive a wrong number of iterations for the first exit > (which is not taken). We had a similar problem before (PR 25985), but I > somehow persuaded myself that this cannot happen with pointers. Ah - it indeed cannot happen, but you need to assume that the offsets in POINTER_PLUS_EXPRs are signed (even though they are unsigned as they are of type sizetype). At least that should be the only "overflow" present in this testcase, no? Richard. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40087
