I initially added the MOS 6502 support by hacking the HC08 backend. It was awful, someone else (Gabriele Gorla) cleaned it up and got it merged to the mainline.

I initially added the MOS 6502 support by hacking the HC08 backend. It was awful, someone else (Gabriele Gorla) cleaned it up and got it merged to the mainline. There are other options these days for optimized 6502, like llvm-mos or Oscar64.