[Bug tree-optimization/79663] New: r244815 causes 10% regression for spec1k/172.mgrid on AArch64

[amker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79663

            Bug ID: 79663
           Summary: r244815 causes 10% regression for spec1k/172.mgrid on
                    AArch64
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amker at gcc dot gnu.org
  Target Milestone: ---

Change @r244815 causes 10% regression for spec1k/172.mgrid on AArch64.  Hot
loop in resid_ is unrolled by factor=2 now in predcom, which causes bad IVOPT
and increased register pressure.
Mine.