https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90622
Georg-Johann Lay <gjl at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Priority|P3 |P5 Status|UNCONFIRMED |NEW Last reconfirmed| |2019-05-31 Ever confirmed|0 |1 Known to fail| |8.0.1 --- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> --- Confirmed with v8. The built-in folding special-cases if the inserted bit(s) don't change their position and always expands to XOR-AND-XOR. Otherwise it tries to find some better sequence and fails, and finally just prints that BST-BLD.