https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110324
--- Comment #3 from Tobias Burnus <burnus at gcc dot gnu.org> --- (gdb) p ((enum rtx_code) (x)->code) $3 = DEFINE_COND_EXEC (gdb) p (int)((enum rtx_code) (x)->code) $4 = 172 and hence: (gdb) p rtx_format[172] $6 = 0x4bcda0 "EssV" where we take the index 2 => 's'. The EssV matches the rtl.def entry: DEF_RTL_EXPR(DEFINE_COND_EXEC, "define_cond_exec", "EssV", RTX_EXTRA) Actually, grepping for 'T' I only find: "define_insn", "sEsTV" "define_peephole", "EsTV" "define_insn_and_split", "sEsTsESV" "define_insn_and_rewrite", "sEsTsSV"