https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42108
--- Comment #63 from Richard Biener <rguenth at gcc dot gnu.org> --- Created attachment 34239 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34239&action=edit LIM patch This is a patch to loop invariant motion I was playing with to use range information to move a stmt up to a place where we can determine the range information is still correct. Unfortunately for the testcase this doesn't allow moving the division at all and we are lucky that we have range information at all because of the fortran frontend casting 'n' to unsigned before dividing by it. Another possibility is to (finally) teach LIM to hoist code which conditional execution status needs to be preserved by guarding the hoisted code with that conditional code. Thus hoist a / b as either b != 0 ? a / b : 0(?) or as <execution condition> ? a / b : 0. Where for this case the condition of execution is probably more complex than testing the denominator for zero (thus testing the condition under which we have to preserve execution). Followup optimizations then eventually can get rid of that condition.
