QBE – a new compiler back end

QBE aims to be a pure C embeddable backend that provides 70% of the performance of advanced compilers in 10% of the code. Its small size serves both its aspirations of correctness and our ability to understand, fix, and improve it. It also serves its users by providing trivial integration and great flexibility.

http://c9x.me/compile/

Another wart is that it's already larger than TCC (which supports 4 target CPUs and gcc asm intrinsics).

I was gonna call you out on that but I think you're actually right. QBE is ``less than 8 kloc'', while the main logic of TCC is like 4-5 kloc. Also, doesn't TCC retarget by just having you recompile the whole thing but with a different target (no 'plug-and-play')?
Still, TCC also has its set of issues (register alloc..?, only few warnings etc.); I've also noticed problems when passing/returning structs...
I still use it as my 'main' (read: hobby) compiler, though.