[Bug ipa/85103] New: Performance regressions on SPEC with r257582

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85103

            Bug ID: 85103
           Summary: Performance regressions on SPEC with r257582
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pthaugen at gcc dot gnu.org
                CC: dje at gcc dot gnu.org, hubicka at gcc dot gnu.org,
                    marxin at gcc dot gnu.org, segher at kernel dot crashing.org,
                    wschmidt at gcc dot gnu.org
  Target Milestone: ---
              Host: powerpc64-unknown-linux-gnu
            Target: powerpc64-unknown-linux-gnu
             Build: powerpc64-unknown-linux-gnu

r257582 is responsible for a 6% degradation in CPU2000 175.vpr and a 12%
degradation in CPU2006 401.bzip2. Both run on a Power7 box.

Very initial look at profile of bzip2 shows degradation is contained to
mainSort(), which showed a 54% increase in run cycles. Appears one of the calls
to mainGtU() is inlined into mainSort in the slow version, but the drop in
cycle counts on mainGtu is no where close to the increase on mainSort.