https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82683
--- Comment #10 from Segher Boessenkool <segher at gcc dot gnu.org> --- reg-notes.def says /* The value in REG dies in this insn (i.e., it is not needed past this insn). If REG is set in this insn, the REG_DEAD note may, but need not, be omitted. */ REG_NOTE (DEAD) so the notes should have gone to insn 20 here, not insn 21 (which is a new r83). Or deleted altogether.