[PATCH] D150803: Add a new `wasm_custom` clang attribute for marking functions.

Wed Jun 21 15:39:56 PDT 2023

brendandahl added inline comments.

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Comment at: clang/include/clang/Basic/AttrDocs.td:5608-5612
+Clang supports the ``__attribute__((wasm_async))``
+attribute for the WebAssembly target. This attribute may be attached to a
+function definition, which indicates the function will be used with JavaScript
+promise integration (JSPI). The attribute will cause the creation of a custom
+section named "async" that contains each wasm_async function's index value.
----------------
aaron.ballman wrote:
> aaron.ballman wrote:
> > This could be my ignorance of web assembly showing, but the docs don't really help me understand when you'd want to use this attribute. Perhaps a link to what JSPI is and a code example would help a little bit? Or is this more of a low-level implementation detail kind of attribute where folks already know the domain?
> Based on the documentation here, I'm wondering why the `annotate` attribute doesn't suffice? That attribute lets you specify custom information to associate with a declaration that then gets lowered such that passes can do whatever they want with the info, which seems to be a more generalized version of what this attribute is.
> 
> (FWIW, I'm back to having basically no idea when you'd use this attribute or what it would be used for, so my thoughts above might make no sense.)
I was considering that, but it would require more machinery in the wasm backend to store all the attribute values in the output. For now we only really need a flag associated with function. I think if we find more uses for the annotations in the future we could replace wasm_custom with it.

Repository:
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  https://reviews.llvm.org/D150803/new/

https://reviews.llvm.org/D150803