LLVM-MOS is an out-of-tree Clang and LLVM backend for the MOS Technology 6502, the CPU behind the NES, Atari 2600/8-bit, BBC Micro, Commodore 64, and many more beloved devices. LLVM-MOS converts freestanding C/C++ into fairly efficient 6502 machine code, despite the 6502’s limited and heterogeneous registers, lack of stack-relative addressing modes, and 256-byte stack. This talk will explore the grab-bag of tricks that hoodwinked LLVM into supporting an almost 50-year-old architecture: "imaginary" registers, instruction set regularization, whole-program static stack allocation, and, of course, lots and lots of pseudo-instructions.