What to do with gmp wasm fixes

[Sylvain Henry]

Hi Cheng,

Couldn't the changes be upstreamed into libgmp directly? Other projects 
may benefit from being able to compile libgmp into wasm. Or are the 
changes specific to GHC?

 > - Send a PR to gmp-tarballs, including our patch (doesn't alter 
behavior on native archs) and the updated tarball build script

I'm not sure if it's still the case, but in the past we applied some 
patches to gmp before building it (to use fPIC and to remove the docs). 
So it should be possible to do it for wasm.

 > - Give up gmp completely, only support native bignum for wasm32.

That's the solution we will use for the JS backend. For wasm, it would 
be great to compare performance between both native and gmp ghc-bignum 
backends. libgmp uses some asm code when it is directly compiled to 
x86-64 asm for example and afaict passing through wasm will make it use 
less optimized codes. It may make the gmp backend less relevant: only 
benchmarks will tell. I would ensure that everything works with 
ghc-bignum's native backend before worrying about using gmp.

Cheers,
Sylvain


On 20/05/2022 13:43, Cheng Shao wrote:
> Hi all,
>
> The ghc wasm32-wasi build needs to patch gmp. Currently, our working
> branch uses a fork of gmp-tarballs that includes the patch into the
> tarball, but at some point we need to upstream it. What's the best way
> to add these fixes?
>
> - Send a PR to gmp-tarballs, including our patch (doesn't alter
> behavior on native archs) and the updated tarball build script
> - Don't touch gmp-tarballs, use "system" gmp, so the wasm32-wasi gmp
> build process is decoupled from ghc build
> - Give up gmp completely, only support native bignum for wasm32.
>
> Cheers.
> Cheng
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