Add emscripten support built against patched 2.0.34 emsdk

[thelamer]

This is an update of toadkings PR here and I cannot take credit for these changes https://github.com/BinBashBanana using toadkings old PR got this all working:
#132

This needs to be built against a specific version of emscripten that has webgl patched.

git clone https://github.com/emscripten-core/emsdk.git
cd emsdk
./emsdk install 2.0.34
./emsdk activate 2.0.34
wget https://raw.githubusercontent.com/BinBashBanana/webretro/master/source/patches/emscripten.patch
patch -u -p0 -i emscripten.patch
source emsdk_env.sh

On the retroarch side should be built without ASYNC flagged as is currently defined here: (can be deleted)
https://github.com/libretro/RetroArch/blob/master/Makefile.emscripten#L61C1-L63C6

And with the additional flags:
-s TOTAL_STACK=268435456 -s TOTAL_MEMORY=536870912 -s FULL_ES3=1 -s MIN_WEBGL_VERSION=2 -s MAX_WEBGL_VERSION=2

The results are very good even on a low end client machine:

n64.mp4

I can rewrite the guards Retroarch side as well but having a viable bc file is the first step.

Let me know if this is possible to mainline I do not have a deep enough understanding of the codebase to see if there are any breaking changes for other ports here, but most of it looks non obtrusive with guards.

[m4xw]

I need to check whatever i merged to my main branches already, most things still reside in emscripten_testing branch iirc

[m4xw]

Gonna start on this soon

[m4xw]

Rebased & Backported some changes onto emscripten_testing branch

[thelamer]

Am I reading this correct that you are working on dynarec in emscripten?
That is one of the biggest pain points of nearly every core, the SIMD extensions lacking. Hoping for a breakthrough.

[m4xw]

Am I reading this correct that you are working on dynarec in emscripten? That is one of the biggest pain points of nearly every core, the SIMD extensions lacking. Hoping for a breakthrough.

Ahead of time tho, I implemented it through cached interpreter for now so i can compile in parts of the game into the core directly.

Also SIMD seems to work decently with this

[m4xw]

-msimd128 -ftree-vectorize -mfpu=neon

[m4xw]

This is progressing quite well, still too many changes to push it all but thought i give a small update

[alec4]

Hi,
i don't know if this is the right place. But i thought i try it and ask.
How does it look? It would be really cool to have this core also as emscrpten port :)!
Thank you!

[m4xw]

Hi, i don't know if this is the right place. But i thought i try it and ask. How does it look? It would be really cool to have this core also as emscrpten port :)! Thank you!

Its looking good, working on getting it on the last toolchain ver next

[m4xw]

Quite a lot has changed since then, performance has also majorly improved, it seems most of the perf issues were audio driver related (and theres a weird stall on IOS on the GPU if fb emulation is off, doesnt happen elsewhere).
So currently just keeping the PR for reference but I am gonna shelve it soon, gonna integrate my local branches soon