dschuff added a comment.
Otherwise it looks good to me, although @majnemer would know more about the
subtleties of what IR actually gets generated.
================
Comment at: lib/CodeGen/CGCleanup.h:630
static const EHPersonality MSVC_CxxFrameHandler3;
+ static const EHPersonality GNU_Wasm_CPlusCPlus;
----------------
aheejin wrote:
> dschuff wrote:
> > We might consider having 2 personalities: one for use with builtin
> > exceptions, and other for emulated exceptions? I'm imagining that with this
> > style of IR we might be able to do emulated exceptions better than we have
> > for emscripten today. We don't have to think about that now, but maybe the
> > name of the personality might reflect it: e.g. `GNU_Wasm_CPlusPlus_Native`
> > (or builtin) vs `GNU_Wasm_CPlusPlus_Emulated` (or external).
> (We talked in person :) ) I'll think about it. But I guess we can change the
> name once we start implementing that feature?
Sounds good. BTW this should actually be `GNU_Wasm_CPlusPlus` instead of
`GNU_Wasm_CPlusCPlus`
================
Comment at: lib/CodeGen/CGException.cpp:1534
+ // In case of wasm personality, we need to pass the exception value to
+ // __clang_call_terminate function.
+ if (getLangOpts().CPlusPlus &&
----------------
aheejin wrote:
> dschuff wrote:
> > Why?
> Not strictly necessarily, because we can modify libcxxabi to our liking. I
> was trying to keep the same behavior as Itanium-style libcxxabi. The
> `__clang_call_terminate` function that's called when an EH cleanup throws is
> as follows:
> ```
> ; Function Attrs: noinline noreturn nounwind
>
> define linkonce_odr hidden void @__clang_call_terminate(i8*) #6 comdat {
>
> %2 = call i8* @__cxa_begin_catch(i8* %0) #2
>
> call void @_ZSt9terminatev() #8
>
> unreachable
>
> }
> ```
>
> So it calls `__cxa_begin_catch` on the exception value before calling
> `std::terminate`. We can change this behavior for wasm if we want, and I
> guess we need some proxy object in case of a foreign exception, but anyway I
> was trying to keep the behavior the same unless there's any reason not to.
Oh I see, we are deviating from MSVC behavior to be more like itanium here.
Makes sense.
================
Comment at: lib/CodeGen/CGException.cpp:1541
+ }
llvm::CallInst *terminateCall =
+ CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
----------------
Should this be in an else block? No need to emit it after we emit the call to
`__clang_call_terminate`
Repository:
rC Clang
https://reviews.llvm.org/D44931
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