selfie

See also https://github.com/cksystemsteaching/selfie

this sort of exists at https://github.com/cksystemsteaching/selfie (http://selfie.cs.uni-salzburg.at/) > Selfie is a self-contained 64-bit, 12KLOC C implementation of: (...) a tiny (...) subset of C called C Star (C*) (...) to a tiny (...) subset of RISC-V called RISC-U[;] a[n] (...) emulator (...) that executes RISC-U code[;] (...) a (...) hypervisor (...) that provides RISC-U virtual machines so they have a self-hosted instruction set architecture, compiler, and operating system, though the operating system is much simpler than xv6. because the instruction set is a subset of risc-v you can run its code on actual risc-v hardware (or qemu-system-riscv), but presumably you could also design risc-u hardware in verilog that was simpler than a full implementation of rv64i with whatever extensions the hypervisor needs

I think it's because their subset of C [1], which they call C Star (C*), doesn't support the `sizeof` operator. Since Selfie is supposed to be able to compile itself, it seems they've restricted the used grammar to the subset supported by C*. [1]: https://github.com/cksystemsteaching/selfie/blob/50b5fec8378...

From reading the code [1], both aren't needed; the `SIZEOFUINT64 = (uint64_t) ((uint64_t*) SELFIE_URL + 1) - (uint64_t) SELFIE_URL;` statement is the value that always ends up being used (once the library is initialized). An optimizing compiler would likely optimize the calculation away anyway. My guess is that it's predefined at the top simply for clarity and verbosity's sake (remember that this is built for educational purposes). [1]: https://github.com/cksystemsteaching/selfie/blob/5de675a0f08...

According to the GitHub README, selfie's emulator and hypervisor can only support programs in RISC-U, "a tiny and easy-to-teach subset of RISC-V".[1] So... not the full RISC-V ISA. For what it's worth, the selfie compiler can build RISC-U programs for you. Still a really cool project! I've been meaning to learn more about compiler backend development. I usually spend time on the frontend. [1] https://github.com/cksystemsteaching/selfie

From the project’s README [1]: > Selfie is implemented in a single (!) file and kept minimal for simplicity. There is also a simple in-memory linker, a RISC-U disassembler, a garbage collector, L1 instruction and data caches, a profiler, and a debugger with replay as well as minimal operating system support in the form of RISC-V system calls built into the emulator and hypervisor. The garbage collector is conservative and even self-collecting. It may operate as library in the same address space as the mutator and/or as part of the emulator in the address space of the kernel. I was a bit skeptical reading that, but I’m very impressed right now [2] . . . [1]: https://github.com/cksystemsteaching/selfie/blob/5de675a0f08... [2]: https://github.com/cksystemsteaching/selfie/blob/5de675a0f08...

Maybe this is interesting to you as well? https://github.com/cksystemsteaching/selfie

My (tiny) CS department has a pretty nice compilers course, I thought. You work on a single, ~10k LoC file [0] that is written in a subset of C, compiles that subset to RISC-V, and also has a small VM and even a hypervisor for running the code it generates. The only thing is, the video lectures are 8 years old [1]. Though last semester, all lectures were online and anyone could join. Might be the same next spring/summer. You’d have to check the professor’s Twitter account. [0]: https://github.com/cksystemsteaching/selfie [1]: https://vimeopro.com/user12798068/university-of-salzburg-int...

The language is a strict subset of C modulo some small semantical differences that are relevant for bootstrapping, see https://github.com/cksystemsteaching/selfie/blob/master/sema...