Backport from mainline

    Backport from mainline
        2012-07-31  Andrey Belevantsev  <abel@ispras.ru>
        PR target/53975

        * sel-sched-ir.c (has_dependence_note_reg_use): Clarify comment.
        Revert
        2011-08-04  Sergey Grechanik  <mouseentity@ispras.ru>
        * sel-sched-ir.c (has_dependence_note_reg_use): Call ds_full_merge
        only if producer writes to the register given by regno.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_7-branch@192497 138bc75d-0d04-0410-961f-82ee72b054a4