https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97926
--- Comment #2 from acsawdey at gcc dot gnu.org --- patch_jump_insn() is running into a land mine -- the insn before modification is invalid: (gdb) p insn_invalid_p(insn, true) $4 = 1 (gdb) pr insn (jump_insn 18 17 114 6 (set (pc) (if_then_else (unle (reg:CCFP 131) (const_int 0 [0])) (label_ref 21) (pc))) "../../gcc/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-11.c":9:10 -1 (nil) -> 21) So verify_changes() fails because the same insn with a different label_ref inserted is also invalid.