[clang] [llvm] [WebAssembly] Implement an alternative translation for -wasm-enable-sjlj (PR #84137)

[Sam Clegg via cfe-commits]

sbc100 wrote:

> > In terms of getting this landed and tested, I wonder which path we should take:
> > 
> > 1. Land this now, without tests, then update emscripten then come back and flip the default, at which point the existing tests will get updated.
> > 2. Duplicate/update the the existing tests to tests both modes, then delete those changes once we flip the default.
> > 
> > Personally I think I'd be happy with (1) since this is a behind and experimental flag.
> > What do others think? @aheejin ?
> 
> Come to think of it, should we even introduce this experimental option? Adding `if (NewOption) ... else ...` everywhere makes the code complicated. Can we just do
> 
> 1. Add library functions in emscripten

So you think it should be possible to have both old and new versions supported in emscripten at the same time?    If that works that would be great.  Do you want to send and emscripten PR?  And link to it here?   If we can confirm that all tests pass then I agree it would be great to do this in a single LLVM change.

> 2. Replace the current logic in LLVM with new code. (Without `if`~`else`). Tests can be updated with this.
> 3. Remove old library functions in emscripten.
>    ?



https://github.com/llvm/llvm-project/pull/84137