[Bug rtl-optimization/81791] New: [8 Regression] ICE in cfg_layout_redirect_edge_and_branch, at cfgrtl.c:4422

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81791

            Bug ID: 81791
           Summary: [8 Regression] ICE in
                    cfg_layout_redirect_edge_and_branch, at cfgrtl.c:4422
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
  Target Milestone: ---

Starting from r250360, we probably exposed a latent bug:

$ g++ /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/opt/pr47355.C -O2 
-fmodulo-sched
during RTL pass: sms
/home/marxin/Programming/gcc/gcc/testsuite/g++.dg/opt/pr47355.C: In function
‘void foo()’:
/home/marxin/Programming/gcc/gcc/testsuite/g++.dg/opt/pr47355.C:39:1: internal
compiler error: in cfg_layout_redirect_edge_and_branch, at cfgrtl.c:4422
 }
 ^
0x95cb2e cfg_layout_redirect_edge_and_branch
        ../../gcc/cfgrtl.c:4422
0x95cb58 cfg_layout_redirect_edge_and_branch_force
        ../../gcc/cfgrtl.c:4432
0x9475c3 redirect_edge_and_branch_force(edge_def*, basic_block_def*)
        ../../gcc/cfghooks.c:474
0x9481c9 make_forwarder_block(basic_block_def*, bool (*)(edge_def*), void
(*)(basic_block_def*))
        ../../gcc/cfghooks.c:892
0x9558f3 create_preheader(loop*, int)
        ../../gcc/cfgloopmanip.c:1534
0x955b3e create_preheaders(int)
        ../../gcc/cfgloopmanip.c:1585
0xbf55de apply_loop_flags
        ../../gcc/loop-init.c:64
0xbf60bc loop_optimizer_init(unsigned int)
        ../../gcc/loop-init.c:123
0x1589322 sms_schedule
        ../../gcc/modulo-sched.c:1351
0x1589322 execute
        ../../gcc/modulo-sched.c:3342