https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113660
--- Comment #1 from Alexandre Oliva <aoliva at gcc dot gnu.org> --- There's nothing specific about -fharden-control-flow-redundancy here, FWIW. ISTM that it just adds enough EH-related stuff to the function that an EH note gets attached to the impossible asm, a stmt then insn at the end of a block. Then, when vregs realizes that the asm has impossible constraints, it deletes it, and that loses the REG_EH_REGION note attached to it, which triggers the error. I'm not sure what the correct behavior would be, but presumably the note would have to be preserved/moved, or not required.
