https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104356
--- Comment #40 from rguenther at suse dot de <rguenther at suse dot de> --- On Thu, 3 Feb 2022, amacleod at redhat dot com wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104356 > > --- Comment #37 from Andrew Macleod <amacleod at redhat dot com> --- > (In reply to Jakub Jelinek from comment #35) > > I meant something like: > > return Z / X; > > > and there evrp does with -O2 -gnatp optimize away the division. > > Though that is likely the X / boolean_range_Y case which you've disabled. > > In any case, I think you want to hear from Andrew/Aldy where exactly does > > VRP/ranger assume UB on integer division by zero. > > That divide is remove by the simplifier because it determines that X has a > range of [0,1] and I believe the simplifer chooses to ignore the 0 under > various circumstances. > > As for ranger, range-ops will return UNDEFINED for the range if x is known to > be [0,0]. This can be propagated around, and depending on how it ends up > being > used as to what happens with it. I think that's OK as outgoing range (on the non-exceptional path - on the exeptional path the result isn't computed). That just may not be used to simplify the stmt producing the range itself of course.
