coollang-2020-fs VS llvm-project

Looks interesting.

Once I saw it's a Czech university course using F#, I knew Tomáš Petříček would be the lecturer :)

A couple years back, I wrote a compiler of tiny-ish scala subset in F# (the code is imperative, though)[1]

[1]: https://github.com/mykolav/coollang-2020-fs

The repo is on github: https://github.com/mykolav/coollang-2020-fs

Go to the project's repository to explore the source code.

You might find [CS 6120: Advanced Compilers: The Self-Guided Online Course][1] interesting. I'm slowly working through it, but basically its focus is intermediate representations, optimizations, etc. A link to the course was on the first page of HN some time ago.

Also -- and you knew it was coming -- I've written a [toy-compiler of a Scala subset][2] myself :)

I'm new to F# and writing compilers, so I'm sure the code is full of rookie mistakes. Still, it works and does generate assembly and executables for Linux and Windows.

[1]: https://www.cs.cornell.edu/courses/cs6120/2020fa/self-guided...

[2]: https://github.com/mykolav/coollang-2020-fs

See

https://github.com/llvm/llvm-project/issues/88344

https://fortran-lang.discourse.group/t/flang-new-how-to-forc...

You can never mistake type_declaration with an identifier, otherwise the program will not work. Aside from that constraint, you are free to name them whatever you like, there is no one standard, and each parser has it own naming conventions, unless you are planning to use something like LLVM. If you are interested, you can see examples of naming in different language parsers in the AST Explorer.

> There is one way to make the LLVM JIT compiler more usable, but I fear it’s going to take years to be implemented: being able to cache and reuse compiled queries.

Actually, it's implemented in LLVM for years :) https://github.com/llvm/llvm-project/commit/a98546ebcd2a692e...

> It's true, this was a CVE in Rust and not a CVE in C++, but only because C++ doesn't regard the issue as a problem at all. The problem definitely exists in C++, but it's not acknowledged as a problem, let alone fixed.

Can you find a link that substantiates your claim? You're throwing out some heavy accusations here that don't seem to match reality at all.

Case in point, this was fixed in both major C++ libraries:

https://github.com/gcc-mirror/gcc/commit/ebf6175464768983a2d...

https://github.com/llvm/llvm-project/commit/4f67a909902d8ab9...

So what C++ community refused to regard this as an issue and refused to fix it? Where is your supporting evidence for your claims?

For everyone else looking for the magic in this almost 7k lines monster, look at line 6610 [1].

[1] https://github.com/llvm/llvm-project/blob/8ec28af8eaff5acd0d...

Through value tracking. It's actually LLVM that does this, GCC probably does it as well, so in theory explicit bounds checks in regular C code would also be removed by the compiler.

How it works exactly I don't know, and apparently it's so complex that it requires over 9000 lines of C++ to express:

https://github.com/llvm/llvm-project/blob/main/llvm/lib/Anal...

https://github.com/llvm/llvm-project/blob/main/flang/docs/F2...

• Go • Rust • Lua • pure C (sans C++) • 6502 assembly • WebAssembly • compiler backends, like LLVM or Cranelift

Compilers also may even spill data to stack from memory, even when the original location is still available, as can be seen in this issue: https://github.com/llvm/llvm-project/issues/53348

I vaguely remember that spilling like this could allow high-end CPUs to use something similar to register renaming, i.e. stack locations like [rsp + 96] could be stay in a physical registers during function execution (high-end CPUs often have more physical registers, than logical ones), but could find good references whether such optimization exists in practice or not.

Unfortunately, I think more often than note it causes performance regressions and in some cases it may even cause unnecessary stack spilling of sensitive data: https://github.com/rust-lang/rust/issues/88930#issuecomment-...