[Bug c/80653] New: Enhancement: better location info for -Wunsafe-loop-optimizations

["egall at gwmail dot gwu.edu" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80653

            Bug ID: 80653
           Summary: Enhancement: better location info for
                    -Wunsafe-loop-optimizations
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: egall at gwmail dot gwu.edu
  Target Milestone: ---

Currently, with a for-loop, -Wunsafe-loop-optimizations points to the "for":

reloc.c: In function 'bfd_generic_get_relocated_section_contents':
reloc.c:6000:7: warning: missed loop optimization, the loop counter may
overflow [-Wunsafe-loop-optimizations]
       for (parent = reloc_vector; (parent != NULL) && (*parent != NULL);
       ^~~

and with a while-loop, it points to the opening parenthesis:

pef.c: In function 'bfd_pef_parse_symbols':
pef.c:893:13: warning: missed loop optimization, the loop counter may overflow
[-Wunsafe-loop-optimizations]
       while (((codepos + 4UL) <= codelen) && (codepos < (size_t)UINT_MAX))
             ^
pef.c:723:13: warning: missed loop optimization, the loop counter may overflow
[-Wunsafe-loop-optimizations]
       while (((pos + 4UL) <= len) && (pos < (size_t)UINT_MAX))
             ^

It'd be more useful if the caret instead pointed to the variable being used as
the loop counter, and/or the point in the loop where it actually overflows