[Bug tree-optimization/127195] [17 Regression] ice in flow_bb_inside_loop_p at cfgloop.cc:846

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127195

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot 
gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2026-09-03
     Ever confirmed|0                           |1

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
With the reduced testcase I get (with checking enabled) and just -O3:

during GIMPLE pass: vect
t.c: In function ‘enhance’:
t.c:11:6: internal compiler error: Segmentation fault
   11 | void enhance() {
      |      ^~~~~~~
0x2a4315f internal_error(char const*, ...)
        ../../gcc/gcc/diagnostic-global-context.cc:787
0x129500f crash_signal
        ../../gcc/gcc/toplev.cc:325
0xc6feb6 flow_bb_inside_loop_p(loop const*, basic_block_def const*)
        ../../gcc/gcc/cfgloop.cc:846
0x1462e88 check_loop_closed_ssa_def
        ../../gcc/gcc/tree-ssa-loop-manip.cc:664
0x1464360 check_loop_closed_ssa_bb
        ../../gcc/gcc/tree-ssa-loop-manip.cc:689
0x14649c6 verify_loop_closed_ssa(bool, loop*)
        ../../gcc/gcc/tree-ssa-loop-manip.cc:714

which shows that SSA form is broken, the use of _6 in _78 = ... has no BB:

(gdb) p debug_immediate_uses_for(def)
_6 : -->4 uses.
_78 = VIEW_CONVERT_EXPR<unsigned char>(_6);
_73 = VIEW_CONVERT_EXPR<unsigned char>(_6);
_52->bold = _6;
_ifc__10 = BIT_INSERT_EXPR <_ifc__8, _6, 0 (1 bits)>;