[Bug tree-optimization/77498] New: [7 regression] Performance drop after r239414 on spec2000/172mgrid

[ysrumyan at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77498

            Bug ID: 77498
           Summary: [7 regression] Performance drop after r239414 on
                    spec2000/172mgrid
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ysrumyan at gmail dot com
  Target Milestone: ---

We noticed significant regression after
https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=239414
I attached simple routine to reproduce. We can see that register pressure is 2x
higher with this patch after pre. The regression is worse for 32-bit mode.