[Bug middle-end/106534] [13 Regression][gcn] ICE 'verify_ssa failed' / 'error: definition in block 18 does not dominate use in block 19' during libgfortran bootstrap

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106534

--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Created attachment 53416
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53416&action=edit
Reduced testcase - fails with cc1 -O2 inp.i

Reduced inputfile attached.

Full code has the full ICE output:

src/gcc-mainline/libgfortran/io/unit.c: In function 'get_gfc_unit':
gcc-mainline/libgfortran/io/unit.c:326:1: error: definition in block 18 does
not dominate use in block 19
  326 | get_gfc_unit (int n, int do_create)
      | ^~~~~~~~~~~~
for SSA_NAME: p_47 in statement:
p_30 = PHI <p_47(19), p_47(38)>
PHI argument
p_47
for PHI node
p_30 = PHI <p_47(19), p_47(38)>
during GIMPLE pass: phiopt
gcc-mainline/libgfortran/io/unit.c:326:1: internal compiler error: verify_ssa
failed
0x11699ff verify_ssa(bool, bool)
        gcc-mainline/gcc/tree-ssa.cc:1211
0xe4e6dd execute_function_todo
        gcc-mainline/gcc/passes.cc:2098
0xe4eb7b execute_todo
        gcc-mainline/gcc/passes.cc:2145