Get the SH2 dynarec working (x86/x64)

[inactive123]

I think one of the main stumbling blocks right now with the Yabause core is that we have to fall back on the SH2 interpreter instead of using the dynarec.

I believe PIC compliance issues are still a problem with the x86/x86_x64 dynarec as it is right now. Once this is fixed, I believe we could finally build yabause with the dynarec working.

@nayslayer I hope you will be able to research this. I am already putting down $50 towards this purpose.

Ideally this could be used for Kronos as well, which is another Yabause fork - you can find the repo for that one here -

[inactive123]

Added this bounty here starting at $50 -

https://www.bountysource.com/issues/64699532-get-the-sh2-dynarec-working-x86-x64

@nayslayer You could consider this a separate stepping stone bounty to see if the Yabause dynarec approach is feasible for Beetle Saturn.

[nayslayer]

@twinaphex Hey there. I've skimmed the relevant (assembly) code and it's indeed not PIC-compliant. I guess you've tried to build the x64 dynarec and it failed to link, am I right? I'll work on fixing that next. To skip the tedious work of adding (%rip) after every constant name I'll have to switch to the modern yasm (or otherwise nasm) assembler instead of the (hideous and obsolete) gnu as - hope you don't mind that too much.

[barbudreadmon]

The kronos libretro port is now a branch of this repo, and the cached interpreter method it is using might be the same performance-wise and better compatibility-wise.

[barbudreadmon]

@twinaphex @nayslayer There is a JIT interpreter in latest yabause sources (with arm, aarch64, x86 & x86_64 backends it seems), i tried enabling it in d951f40 but it just crashes for some reason (it's built by default upstream so i would expect it's supposed to work ?). Maybe someone would like to take a look.

Also tagging @d356, the author of this JIT, maybe he'll want to help

[rcaridade145]

@barbudreadmon That compiler is based on Play! Codegen and afaik it does not support sh2 Yabause#320 . Just DSP and others. Perhaps there has been some fix between 2016 and now to the codegen lib. What was the error?

[barbudreadmon]

Here is the error :

../sh2_jit.cpp:2739: void recompile_and_exec(SH2_struct*): Assertion `(context->jit.pc & 0xfff00000) == 0' failed.

This jit was added as a SH-2 cpu core in b12a74d, and also seems to be built by default, are you sure it's not supposed to work ?

[rcaridade145]

@barbudreadmon I just remember reading that it was not ready for prime time. That work was all after the 0.9.15 release . So probably it is a work in progress, at least for the SH2.