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Comment by ameliaquining | Hacker News Reader

I don't think the controversy about Wasm's structured control flow has anything to do with any of this? It's not actually difficult to target Wasm in codegen; I've never heard of any real-world compiler project complaining that this was a major burden. ABI concerns are at a different level.

Most low-level IRs don't do structured control flow because most low-level IRs don't need to be translatable to verified-safe machine code in a single fast pass, whereas for WebAssembly that's a core design requirement.

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http://troubles.md/posts/why-do-we-need-the-relooper-algorit... has a more detailed version of this argument: if WebAssembly had used a CFG as the basis for its control flow, it would have been easier to compile to and easier to efficiently execute/translate while maintaining safety, and maybe GCC would have released a WebAssembly backend by now.

The author alleges that the real reason WebAssembly uses loop/block is because that's how V8 worked internally at the time and Google didn't want to go to the trouble of implementing something different. But more recently V8 has started moving towards CFGs ( https://v8.dev/blog/leaving-the-sea-of-nodes ) so maybe there's hope in the future.

I'm familiar with that post. However, it doesn't include a convincing argument that a CFG interchange format wouldn't have performance costs for Wasm runtimes; it just handwavingly asserts this. It blames Google because Google is a popular villain, but the other three browser vendors (this was before Edge adopted Chromium), all of which initially used different Wasm runtime architectures from Google and from one another, were also in favor of structured control flow, and I assume they knew what they were talking about. Once you get past the conspiracy theory, it's clear that the real issue is just that the author disagrees with the Wasm committee's decision to trade off convenience for compiler writers in order to make things work better for runtimes.

More to the point, none of this has anything to do with ABI.

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