Build Your Own WebAssembly Compiler

https://www.infoq.com/presentations/webassembly-compiler/

by simonpure • 7 years ago

144 19 7 years ago

Here's Colin's blog post with code and diagrams inline: https://blog.scottlogic.com/2019/05/17/webassembly-compiler....

I found Colin's posts real helpful when writing some WebAssembly by hand for the first few days of Advent of Code: https://observablehq.com/collection/@ballingt/advent-of-wasm

catpolice• 7 years ago

Last year I decided to write a WASM-targeting compiler in Javascript, completely by hand. The idea was to compile a vaguely C-like toy language to WASM without any external dependencies.

Part of the motivation was that while I've written many simple parsers, I mostly used parser generators with BNF grammars and I didn't feel like I had a good sense of how the code I ended up generating actually worked for something with complex syntax and semantics. I felt like I was writing specs for a parser, rather than writing a parser. And I didn't have a huge amount of experience with code generation.

My toy language has vaguely C-like syntax with block scope and infix operators with various precedences, so it was a bit more complicated than JSON, but I ended up using something like Pratt parsing/Precedence Climbing (see https://www.oilshell.org/blog/2017/03/31.html) and wrote the whole thing in a way that's - hopefully - pretty easy to read for folks interested in wrapping their head around parsing complex syntax (e.g. with scope and name resolution). The lexer, parser and language definition ended up being about 1000 lines of JS (counting some pretty extensive comments).

Code generation is pretty straightforward once you have an AST.

Any JS programmers that are interested in really getting into the nitty-gritty of writing your own parser/compiler should check it out. The source is here: https://github.com/j-s-n/WebBS.

If you want to play around with the language and inspect the generated ASTs and WASM bytecode, there's an interactive IDE with example code here: https://j-s-n.github.io/WebBS/index.html#splash

vchak1• 7 years ago

I found this one pretty interesting. https://maierfelix.github.io/mini-c/

ridiculous_fish3• 7 years ago

Are there any fast ways to run wasm on systems that forbid creating new executable pages? A high performance interpreter?

vbezhenar2• 7 years ago

What system do you mean? iOS supports wasm AFAIK.

jimmcslim• 7 years ago

Mobile Safari may support WASM, but I think the GP is suggesting that a native iOS app would not be permitted to load, compile, and execute a WebAssembly module.

ridiculous_fish3• 7 years ago

Not iOS but it's an interesting thought experiment: if you wanted to build a fast WASM implementation for iOS, how would yo do it?

maxgraey• 7 years ago

check this one: https://github.com/wasm3/wasm3

ridiculous_fish3• 7 years ago

Nice find, only 4.5x slower is nothing to sneeze at. I doubt that WASM is optimal for interpretation and you could probably gain another 2x through a bytecode compilation target optimized for interpreting.

ryohey• 7 years ago

Here’s my wasm parser/runtime written in TypeScript, for instance. https://github.com/ryohey/ts-wasm-runtime

6nf• 7 years ago

My self hosted compiler: https://github.com/PierreRossouw/wats

Aardappel• 7 years ago

Documentation on how Lobster's Wasm-backend works, which contains plenty of useful info for anyone making their own backend: http://aardappel.github.io/lobster/implementation_wasm.html

pjmlp• 7 years ago

Cool, thanks for sharing.

Build Your Own WebAssembly Compiler

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