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Zig's Incremental Compilation Internals

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Re: Zig's Incremental Compilation Internals

#7
Zig's toolchain work is continually impressive. While I still don't plan to write software in it, given that I believe memory safety is table stakes, all of this stuff is very, very good. Before the incremental work, it was the toolchain and cross-compiler work. The toolchain stuff has continually been fantastic. I'm very curious to see what they come up with next!

> Semantic analysis is the most difficult part of the compiler to handle incrementally. Perhaps unsurprisingly then, this is where language design starts to matter a lot: while I am pretty confident that most modern languages could support incremental compilation similar to how we do, certain design decisions can make that much more difficult. Zig has had its design tweaked over the years (sometimes controversially) specifically so that it is easier to support fast incremental compilation.

This is something I wish that we had done with Rust. It is impossible to do all of the things at once, though, and we already had a tremendous amount of things to do. This is also part of the "when do you ship 1.0" tradeoff; for our goals with the language, 2015 was the right moment to launch, but if had a few more years to bake things, maybe we could have made compile times way faster. Software engineering is hard.

Re: Zig's Incremental Compilation Internals

#8

Zig's toolchain work is continually impressive. While I still don't plan to write software in it, given that I believe memory safety is table stakes, all of this stuff is very, very good. Before the incremental work, it was the toolchain and cross-compiler work. The toolchain stuff has continually been fantastic. I'm very curious to see what they come up with next! > Semantic analysis is the most difficult part of th…

The thing with rust is that you get safety with slow compilation, it's a tradeoff.

Zig doesn't have the same safety guarantees, it's on the dev to use safe coding patterns, so the tradeoff for safety is discipline or experience.

Re: Zig's Incremental Compilation Internals

#9
post #8

Zig's toolchain work is continually impressive. While I still don't plan to write software in it, given that I believe memory safety is table stakes, all of this stuff is very, very good. Before the incremental work, it was the toolchain and cross-compiler work. The toolchain stuff has continually been fantastic. I'm very curious to see what they come up with next! > Semantic analysis is the most difficult part of th…

The thing with rust is that you get safety with slow compilation, it's a tradeoff. Zig doesn't have the same safety guarantees, it's on the dev to use safe coding patterns, so the tradeoff for safety is discipline or experience.

Rust's safety checks have basically nothing to do with its slow compile times. This is something that sounds intuitive but is just completely incorrect.

In particular, Rust made several good design decisions around this stuff that keeps those checks fast, like keeping checks local rather than being global.

Re: Zig's Incremental Compilation Internals

#10
post #2

Does this work for release builds or just debug builds now?

It only works with our self-hosted code generation backends (the main one being for x86_64), which right now don't have any optimisation passes. It's planned that they will in future, but that's a long-term goal. Also, any optimisations which propagate information between functions (the most obvious and important one is inlining) are more-or-less incompatible with incremental compilation (I touch on this in the post IIRC), so once this does work it'll probably still be limited to a subset of optimisations.

TL;DR: only debug builds for now, could extend to release builds once we have our own optimisation passes one day, but some optimisations will still be inapplicable.

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