I had some trouble porting to QEMU 4. It works but the exec/sec decrease drammatically.
For example, on tcpdump exec/sec are dropped from ~1650 to ~60.
I can't figure out why this happens and if someone will find why please tag me.

As a note for the future, I didn' use the QEMU helpers cause a patched version of tcg_gen_callN (tcg_gen_afl_maybe_log_call) that only generates calls to afl_maybe_log is faster. It avoids an hashtable lookup for flags and sizemask (I hardcoded them) and many operations related to arguments preparation will be simplified by the compiler.