dschuff accepted this revision.
dschuff added a comment.
This revision is now accepted and ready to land.

This flag turns on CPU features (i.e. there's one for each new wasm feature 
proposal that has to be feature-detected), so I think this makes sense to be 
consistent with all the others. I could imagine enabling exceptions in the 
frontend but having some kind of emulation in the backend (like we do today for 
emscripten). More generally the semantics `-fno-exceptions` unfortunately 
doesn't exactly match the kind of behavior people typically want because it 
doesn't allow you to compile code that has try/catch/throw at all. In PNaCl and 
emscripten the default behavior is instead to compile that code but to lower it 
away and turn throw into abort. Also IIRC even with `-fno-exceptions` the code 
still has to allow exceptions to propagate which means you end up with invokes 
everywhere instead of calls, so you are still paying most of the costs of 
enabling EH. So that bit is a little bit complex and we'll probably want to 
think a bit more carefully about what options we want to have. But a machine 
flag for enabling the CPU feature makes sense to start.


Repository:
  rC Clang

https://reviews.llvm.org/D43681



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