Compiler refactor: replace Control Flow Graphs with builders

[Akuli]

A builder defines how to do somewhat elementary things, e.g. a function/method call, conditional branch, or an equals comparison. Then a new file ast_to_builder.jou recurses over the AST and calls methods of the builder accordingly.

For now, there is only one builder, which builds LLVM IR. The idea is to later build a special, intentionally very limited "Jou IR" to solve #566.

Also, I really hated how the old CFG's worked. They were very similar to LLVM IR, but much shittier.

TODO:

• get CI green
• document this
• resolve # TODO: rename to AstToBuilder
• resolve # TODO: add error message for this, or dynamic size?
• resolve # TODO: https://github.com/Akuli/jou/issues/683
• resolve # TODO: tell llvm, if we know a function is noreturn ?
• resolve # TODO: useful, but doesn't belong here
• resolve # TODO: Everything named legacy_llvm14_cast can be removed once we drop LLVM 14 support
• resolve # TODO: which casts are necessary on LLVM 14 and which are not?
• resolve # TODO: method to find field
• resolve # TODO: do we need is_main_file?
• resolve # TODO: delete id
• resolve # TODO: delete double pointer

[Akuli]

Not gonna resolve all TODOs. This PR already deletes more TODOs than it adds.

[Akuli]

Don't know why the CI is failing now, and I cannot reproduce it locally. Maybe I'll fix finish this PR some other day :)

[Akuli]

I set up an awful Windows VM to debug this. (It is awful for various reasons.) This seems like a stack overflow bug.

I am adding debug prints to examples/aoc2024/day22/part2.jou, and running it with ../../../jou.exe -O0 part2.jou. It stops mid-way along a long loop, exits with status 1, and prints no error. Like this:

But if I add a dummy variable foo: byte[10000] on the stack, it stops earlier:

I think the problem is that the new builder is allocating stack space in the loop, instead of doing it before the loop and then reusing the stack variables. I'm glad the test setup is good enough to catch this :)

[Akuli]

Apparently using -o and then double-clicking the executable gives a better error message on Windows.

Due to my terrible VM setup, I cannot copy/paste or copy files from the VM, so anyone else reading this will be stuck with Finnish screenshots. Oops :)

[Akuli]

It is a stack overflow https://stackoverflow.com/a/76892354

I wonder if there's a way to better report this kind of errors to the Jou programmer when not using -o.

[Akuli]

It worked!!!! :)