The "OS" (or rather "kernel") was actually the VM which was implemented in microcode and BCPL. The Smalltalk code within the image was completely abstracted away from the physical machine. In today's terms it was rather the "userland", not a full OS.
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It's refreshing to see Oberon getting some love on the Pi. There’s a certain 'engineering elegance' in the Wirthian school of thought that we’ve largely lost in modern systems.
While working on a C++ vector engine optimized for 5M+ documents in very tight RAM (240MB), I often find myself looking back at how Oberon handled resource management. In an era where a 'hello world' app can pull in 100MB of dependencies, the idea of a full OS that is both human-readable and fits into a few megabytes is more relevant than ever.
Rochus, since you’ve worked on the IDE and the kernel: do you think the strictness of Oberon’s type system and its lean philosophy still offers a performance advantage for modern high-density data tasks, or is it primarily an educational 'ideal' at this point?
I don't know. Unfortunately we don't have an Oberon compiler doing similar optimization as e.g. GCC, so we can only speculate. I did measurements some time ago to compare a typical Oberon compiler on x86 with GCC and the performance was roughly equivalent to that of GCC without optimizations (see https://github.com/rochus-keller/Are-we-fast-yet/tree/main/O...). The C++ type system is also pretty strict, and on the other hand it's possible and even unavoidable in the Oberon system 3 to do pointer arithmetics and other things common in C behind the compiler's back (via the SYSTEM module features which are not even type safe). So the original Oberon syntax and semantics is likely not on the sweet spot of systems programming. With my Micron (i.e. Micro Oberon, see https://github.com/rochus-keller/micron/) language currently in development I try for one part to get closer to C in terms of features and performance, but with stricter type safety, and on the other hand it also supports high-level applications e.g. with a garbage collector; the availabiltiy of features is controlled via language levels which are selected on module level. This design can be regarded as a consequence of many years of studying/working with Wirth languages and the Oberon system.
There was a couple of PhD theses at ETH Zurich in the 90s on optimizations for Oberon, as well as SSA support. I haven't looked at your language yet, but depending on how advanced your compiler is, and how similar to Oberon, they might be worth looking up.
I'm only aware of Brandis’s thesis who did optimizations on a subset of Oberon for the PPC architecture. There was also a JIT compiler, but not particularly optimized. OP2 was the prevalent compiler and continued to be extended and used for AOS, and it wasn't optimizing. To really assess whether a given language can achieve higher performance than other languages due to its special design features, we should actually implement it on the same optimizing infrastructure as the other languages (e.g. LLVM) so that both implementations have the same chance to get out the maximum possible benefit. Otherwise there are always alternative explanations for performance differences.
It might have been Brandis' thesis I was primarily thinking about. Of the PhD theses at EHTz on Oberon, I'm also a big fan of Michael Franz' thesis on Semantic Dictionary Encoding, but that only touched on optimization potential as a sidenote. I'm certain there was at least one other paper on optimization, but it might not have been a PhD thesis...
I get the motivation for wanting to use LLVM, but personally I don't like it (and have the luxury of ignoring it since I only do compilers as a hobby...) and prefer to aim for self-hosting whenever I work on a language. But LLVM is of course a perfectly fine choice if your goal doesn't include self-hosting - you get a lot for free.
> This paper has presented a study of a system that
provides code generation and continuous code optimization
as a central system service[…]
> Our results have shown that–because of the profiling feedback loop–object code produced by continuous optimizations is often of a higher quality than can be achieved using static "off-line" compilation. Optimization at runtime, if performed judiciously, can often surpass optimizations performed at compile-time, independent of whether the latter are guided by profiling information or not. Our results have also given evidence that reoptimizing an already running program in response to changes in user behavior can give rise to real performance improvements.
Kistler, Thomas, and Michael Franz. "Continuous program optimization: Design and evaluation." IEEE Transactions on Computers 50, no. 6 (2002). <https://doi.org/10.1109/12.931893>
I don’t like LLVM either, because its size and complexity are simply spiraling out of control, and especially because I consider the IR to be a total design failure. If I use LLVM at all, it would be version 4.0.1 or 3.4 at most. But it is the standard, especially if you want to run tests related to the question the fellow asked above. The alternative would be to build a frontend for GCC, but that is no less complex or time-consuming (and ultimately, you’re still dependent on binutils). However, C on LLVM or GCC should probably be considered the “upper bound” when it comes to how well a program can be optimized, and thus the benchmark for any performance measurement.
> However, C on LLVM or GCC should probably be considered the “upper bound” when it comes to how well a program can be optimized, and thus the benchmark for any performance measurement.
Is it? Isn't it rather the case that C is too low level to express intent and (hence) offer room to optimize? I would expect that a language in which, e.g. matrix multiplication can be natively expressed, could be compiled to more efficient code for such.
I would rather expect, that for compilers which don't optimize well, C is the easiest to produce fairly efficient code for (well, perhaps BCPL would be even easier, but nobody wants to use that these days).
When you call LLVM IR a design failure, do you mean its semantic model (e.g., memory/UB), or its role as a cross-language contract? Is there a specific IR propert that prevents clean mapping from Oberon?
To be fair they also kind of share that opinion, hence why MLIR came to be, first only for AI, nowadays for everything, even C is going to get its own MLIR (ongoing effort).
Is anyone attempting to implement Oberon on LLVM IR? Sounds like a fun project
Threre are at least two projects I'm aware of, but I don't think they are ready yet to make serious measurements or to make optimal use of LLVM (just too big and complex for most people).
That benchmark is a great data point, thanks for sharing. The performance parity with unoptimized GCC makes sense, given how much heavy lifting modern LLVM/GCC backends do for C++.
Your approach with Micron and the 'language levels' is particularly interesting. One of the biggest hurdles I face in C++ with these high-density vector tasks is exactly that: balancing the raw 'unsafe' pointer arithmetic needed for SIMD and custom memory layouts with the safety needed for the rest of the application.
Having those features controlled at the module level (like your Micron levels) sounds like a much cleaner architectural 'contract' than the scattered unsafe blocks or reinterpret_cast mess we often deal with in systems programming. I'll definitely keep an eye on the Micron repository—bridging that gap between Wirth-style safety and C-level performance is something the industry is still clearly struggling with (even with Rust's rise).
you can check also XDS modula2/oberon-2 programming system.
is an optimizing complier
https://github.com/excelsior-oss/xds