[Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q;

[gcc-bugzilla at contacts dot eelis.net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64450

            Bug ID: 64450
           Summary: Optimize   0>=p-q   to   q>=p   for char*p,*q;
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc-bugzilla at contacts dot eelis.net

Created attachment 34365
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34365&action=edit
Testcase

It was noticed that Boost's iterator_facade incurred a performance penalty
(while it should ideally be zero-overhead), which results from the fact that
GCC does not optimize   0>=p-q  to  q>=p  for char*p,*q;. See attachment.

This probably applies to > and < and <= as well.