[llvm-commits] [patch] Change how we handle mandatory unwind tables

[Rafael Ávila de Espíndola]

>> nil = implementation defined?
>> nounwind = ?
>> ehframes = always generate
>> ehframes + nounwuind = don't generate
>
> No. It is:
>
> nil = Needs an eh frame because an exception might pass by.
> nounwind = No need for a eh frame
> ehframe = Needs an eh frame because the ABI says so and because an
> exception might pass by.
> ehframe + nounwind = Needs an eh frame because the ABI says so.
>
> Optimizations can add nounwind. This allows an invoke to become a call
> for example. If the FE added ehframe, we still get the eh table. If it
> did not, adding nounwind removes the only reason why we had an eh table
> and it is not generated.

Thanks for suggesting the table btw. I will add it to the comments.

I think a good summary of why we should add ehframe is that with it the 
compiler knows *why* it needs to produce an eh table. That way 
optimizations can manipulate exceptions and the compiler still knows if 
an eh table is needed or not.

Cheers,
Rafael