- aarch64 backend
- STDC: thread local, VLAs, complex, long double, atomics
- test on non-GNU and non-linux POSIX systems (alpine, various BSDs)
- DWARF debug information
- implement GNU extensions: __attribute__, __builtin_*, ...
- compiler optimizations:
    - dead store/load optimization,
    - inlining
    - loop inversion
    - instruction scheduling
    - better regalloc spilling heuristics

- testing on real world codebases