ARMv8 in RPi4?

Thank-you, Richard.

I know that I'm a bit of a dinosaur these days, but since my baptism in hands-on computing 50 years ago this year, assembler on a PDP11/20, my interest is in low level control of a processor with no other software present and the Pi4 with its 64 bit processing and (virtually) unlimited addressing capability seems to me to be the answer to a maiden's prayer.

To that end I'm keen to know after browsing the ARMv8 docummentation what other aspects are not implemented on the RPi4.

(Yes, I've touched on this repeatedly in this group in the past, but with many other interests, it's been a case of putting off today what can be put off until tomorrow! :-) )

The C language, which I have used over many years as a real-time embedded softy has certain incorrectnesses (wrong precedences between logical and relational operations, and the stacking of procedure parameters in the wrong order to enable printf to work) and part of my interest is in language development which started in that same 50 year history with the formative work leading to SWEPSPEED and CUTLASS in the CEGB at Portishead SSD.