[Bug tree-optimization/72712] New: Tenfold compile time regression

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72712

            Bug ID: 72712
           Summary: Tenfold compile time regression
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
                CC: law at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

Created attachment 39025
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39025&action=edit
Testcase

Since revision r236831, the -O2 compilation time of the attached
testcase went from 17 seconds to 250 seconds on my desktop (-O3 went
from 19 to 284).  Just compile with

~/gcc/bisect/inst/bin/gfortran -c -o o2.o -O2  pr.f90

to see for yourself.

I have extracted the testcase from a benchmark which has a number of
similar functions and I was never patient enough to wait for it to
finish compilation (the script running the suite always kills
compilation as running too long too).