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