Add an inline_wasm! macro or make inline_asm! work on wasm targets

[fitzgen]

For my use cases, this would have been nice, but not strictly necessary. I expect it will eventually become higher priority for someone.

[est31]

Can you explain what this macro should do? Inline assembly in the form of wabt?

[fitzgen]

I was imagining writing WAT inline.

[pepyakin]

Hm, should be possible with wabt-rs and https://github.com/dtolnay/proc-macro-hack

[koute]

Technically you don't even need procedural macros; you could use a normal macro to generate a __inline_wasm("...your code here") call in your code and then just replace it when postprocessing your .wasm file. (This is in fact how stdweb's js! macro works on wasm32-unknown-unknown.)

Ideally I think that something like that should be supported by Rust's (currently unstable) asm! though.

[pepyakin]

Always thought that js! works as proc-macro, nice to know!

[est31]

@fitzgen I see, that would be quite nice indeed.

Ideally I think that something like that should be supported by Rust's (currently unstable) asm! though.

The asm! macro seems to do something on the wasm target, I've only tried out whether compilation errors or we run into llvm assertions or something... nothing of that kind! So maybe it actually is functional already. But generally the intention is I think that the asm syntax is the same over all targets, see this latest proposal.

[isislovecruft]

I'd also be interested in inline web assembly, to use as a corollary to what the test::black_box() (in libtest) function does, but for wasm32 targets, i.e. as a way to disable optimisations.

[ashleygwilliams]

we probably want to track this in a way that's different than an issue on this repo. going to close (but please reopen if i am incorrect and also apologies!)