[Bug middle-end/66307] New: Partial argument overlapping with itself should try to reuse infrastructure in calls.c

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66307

            Bug ID: 66307
           Summary: Partial argument overlapping with itself should try to
                    reuse infrastructure in calls.c
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---

With r223753 as a fix for PR 65358 we now detect cases where a partial argument
overlaps with itself during a sibcall optimization.

As pointed out by https://gcc.gnu.org/ml/gcc-patches/2015-05/
it would be nice if we could reuse the existing infrastructure that detects
overlap of a partial argument with *other* arguments in the call. This is found
in calls.c (check_sibcall_argument_overlap for example).

This PR is to keep track of that.