fix PR68976: only add loop close phi for names defined in loop

fix PR68976: only add loop close phi for names defined in loop

        * graphite-isl-ast-to-gimple.c: Fix comment.
        * graphite-scop-detection.c (defined_in_loop_p): New.
        (canonicalize_loop_closed_ssa): Do not add close phi nodes for SSA
        names defined in loop.

gcc/testsuite

        * gcc.dg/graphite/pr68976.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@232658 138bc75d-0d04-0410-961f-82ee72b054a4