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0 pointspbohun3mo ago0 comments

As far as I know, only Go uses Go's back end because it was specifically designed for Go. But the architecture is such that it makes it trivial for Go to cross compile for any OS and architecture. This is something that LLVM cannot do. You have to compile a new compiler for every OS and arch combo you wish to compile to.

You could imagine creating a modified Go assembler that is more generic and not tied to Go's ABI that could accomplish the same effect as LLVM. However, it'd probably be better to create a project like that from scratch, because most of Go's optimizations happen before reaching the assembler stage.

It would probably be best to have the intermediate language that QBE has and transform that into "intermediate assembly" (IA) very similar to Go's assembly. That way the IL stage could contain nearly all the optimization passes, and the IA stage would focus on code generation that would translate to any OS/arch combo.

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nicoburns3mo ago

> As far as I know, only Go uses Go's back end because it was specifically designed for Go. But the architecture is such that it makes it trivial for Go to cross compile for any OS and architecture. This is something that LLVM cannot do. You have to compile a new compiler for every OS and arch combo you wish to compile to.

I don't think that's true. Zig have a cross-compiler (that also compiles C and C++) based on LLVM. I believe LLVM (unlike gcc) is inherently a cross-compiler, and it's mostly just shipping header files for every platform that `zig cc` is adding.

LeFantome3mo ago

I do not have enough knowledge to say anything bad about LLVM. As an "amateur" compiler writer, it did confuse me a bit though.

What I will say is that it seem popular to start with LLVM and then move away from it. Zig is doign that. Rust is heading in the direction perhaps with Cranelift. It feels that, if LLVM had completely nailed its mission, these kinds of projects would be less common.

It is also notable that the Dragonegg project to bring GCC languages to LLVM died but we have multiple projects porting Rust to GCC.

account423mo ago

Even Clang can cross-compile from one compiler binary - whats missing is bundling the "platform SDK" for all targets like Zig does.

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