[PATCH] D12923: Add support for function attribute "notail"

[Sanjoy Das via llvm-commits]

sanjoy added a comment.

In http://reviews.llvm.org/D12923#247639, @ahatanak wrote:

> No, tail call optimization doesn't have to be disabled on indirect calls.


What if the indirect callee is marked with `notail`?  Isn't the whole point of `notail` that functions marked `notail` won't have tail calls to them?

Perhaps I'm missing something here, so it helps to be concrete -- in the C example I gave, what's the expected behavior of the program if the function pointer passed to `f` via `ptr` is a `notail` function?

I think the `notail` should be on the call instruction, not on the callee; as some sort of "inverse" of `musttail`.  Then we can teach the optimizer to never codegen a `notail` call as a tail call.


http://reviews.llvm.org/D12923