[Bug other/55031] New: Documentation on RTL GCSE pass is outdated

[amker.cheng at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55031
             Bug #: 55031
           Summary: Documentation on RTL GCSE pass is outdated
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: amker.ch...@gmail.com


Quoting from GCCINT, section "9.5 RTL passes":
"When optimizing for size, GCSE is done using Morel-Renvoise Partial Redundancy
Elimination, with the exception that it does not try to move invariants out of
loops—that is left to the loop optimization pass. If MR PRE GCSE is done, code
hoisting (aka unification) is also done, as well as load motion."

While the pass gate function is as below:

static bool
gate_rtl_pre (void)
{
  return optimize > 0 && flag_gcse
    && !cfun->calls_setjmp
    && optimize_function_for_speed_p (cfun)
    && dbg_cnt (pre);
}

This conflicts with the documentation, which says Morel-Renvoise PRE will be
used when optimizing for size. I think the document is outdated.