By "workable" I meant something more modest, say, successfully compiling SQLite, something that CCC fails to do unless you stretch the meaning of success (it seems the problem may have to do with register allocation, but I would say that register allocation is pretty much the only interesting job a C compiler does).

As to the Linux kernel, you're right that a compiler that can successfully compile it is likely to be bigger, but we don't know that CCC is able to do it, either. What we do know is that (when using the gcc linker and assembler) people were able to boot the RISC-V kernel in qemu. That's something for sure, but not enough to call it a successfuly compilation.

TCC did several years ago. It could boot Linux from source in under 10 seconds. It's wasn't that big of a C compiler. It's in the 50,000 lines of code range.