STORE_JUMP
STORE_JUMP (jump, b, laststart);
STORE_JUMP (maybe_pop_jump, b, laststart - 3);
STORE_JUMP (jump_past_alt, fixup_alt_jump, b - 1);
STORE_JUMP (jump_past_alt, fixup_alt_jump, b);
STORE_JUMP (jump_past_alt, fixup_alt_jump, b);