is it allowed to use musttail on llvm.coro.resume?

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1

It makes sense that you would be able to do this:

%save1 = llvm.coro.save()

%unused = musttail call llvm.coro.resume(%some_handle)

%x = llvm.coro.suspend()
…

But the docs for musttail say:

The call must immediately precede a ret instruction, or a pointer bitcast followed by a ret instruction.

Should this be amended to allow a musttail to be followed by llvm.coro.suspend() ?

Regards,
Andrew

2

Just found this in CoroSplit.cpp:

// Add musttail to any resume instructions that is immediately followed by a
// suspend (i.e. ret). We do this even in -O0 to support guaranteed tail call
// for symmetrical coroutine control transfer (C++ Coroutines TS extension).
// This transformation is done only in the resume part of the coroutine that has
// identical signature and calling convention as the coro.resume call.
static void addMustTailToCoroResumes(Function &F) {