tcc only supports x86, and is 4-5 times bigger (lines of code) than the plan9 compiler.
Tcc has supported AMD64 and ARM for ages. It produces reasonably fast code, usable as a library, and has many other nice features. Worth looking at again if you last looked when it only supported x86.
Oh, neat, I will. Still, the main advantage of plan9's compiler is its simplicity.