[Bug middle-end/78463] New: pure/const functions are assumed not to trap

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78463

            Bug ID: 78463
           Summary: pure/const functions are assumed not to trap
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, wrong-code
          Severity: enhancement
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
                CC: hubicka at gcc dot gnu.org, jakub at gcc dot gnu.org
  Target Milestone: ---

PR70586 shows that pure/const functions are assumed not to trap (EH / throw is
captured separately already).  This makes them fail the has-side-effects check
which can lead to wrong-code issues (see that PR).

We need a more fine-grained analysis (and IPA propagation) of what functions
may do (trap, invoke undefined overflow, use FP math, etc.) to ask the right
questions from optimizations (and enable more optimizations).