[Bug fortran/95939] New: ice with -O3 in compute_live_loop_exits

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95939

            Bug ID: 95939
           Summary: ice with -O3 in compute_live_loop_exits
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

Recent gcc trunk gfortran compiler does this:

$ /home/dcb/gcc/results/bin/gfortran -c -O3 ./gfortran.dg/graphite/pr42285.f90
during GIMPLE pass: vect
./gfortran.dg/graphite/pr42285.f90:3:0:

    3 | SUBROUTINE EFGRDM(NCF,NFRG,G,RTRMS,GM,IOPT,K1)
      | 
internal compiler error: in compute_live_loop_exits, at
tree-ssa-loop-manip.c:247
0x6d94fd compute_live_loop_exits
        ../../trunk.git/gcc/tree-ssa-loop-manip.c:247
0x6d94fd add_exit_phis_var
        ../../trunk.git/gcc/tree-ssa-loop-manip.c:334
0x6d94fd add_exit_phis
        ../../trunk.git/gcc/tree-ssa-loop-manip.c:356
0x6d94fd rewrite_into_loop_closed_ssa_1(bitmap_head*, unsigned int, int, loop*)
        ../../trunk.git/gcc/tree-ssa-loop-manip.c:678

This seems to have gone wrong sometime between date 20200624
and 20200625.

It is often worthwhile to run all the Fortran code in the testsuite 
through the compiler with -O3 or -O3 -march=native.