> On 2015-Oct-13, at 09:55, Aaron Ballman <[email protected]> wrote:
>
> aaron.ballman added a comment.
>
> In http://reviews.llvm.org/D12922#265452, @ahatanak wrote:
>
>> I think there are a couple of things that have to be discussed:
>>
>> 1. Name of the attribute: Should it be "notail" or "notailcall"? Perhaps it
>> should be named something like "nodirecttail" to indicate it is used to
>> block direct calls, but not indirect calls?
>
>
> The attribute prevents tail calls from the call site, not for the function
> itself. "notail", at least to me, implies that the function definition itself
> will not have TCO; it does not imply that callers will be affected. Perhaps
> "not_tail_called" or "disable_tail_calls"? It's a hard concept to get across
> in a small identifier.
Note that LLVM has an IR-level attribute called "disabletailcails" that implies
that the function definition itself will not have TCO.
I like notailcall because of its relation to noinline. They're both structured
like "no<someverb>", and both apply to what callers can do.
I don't really have a strong opinion though, just sharing those thoughts.
>
> Also, I would like to see a test that shows always_inline, notail also gets
> diagnosed as mutually exclusive, and a test that the right thing happens with
> a C++ spelling on a member function.
>
> ~Aaron
>
>
> ================
> Comment at: include/clang/Basic/AttrDocs.td:1619
> @@ +1618,3 @@
> + let Content = [{
> +Tail call optimization is not performed on direct calls to a function marked
> ``notail``.
> + }];
> ----------------
> It would be good to clarify what you mean by direct calls, as not all of the
> readers are going to understand that easily. Perhaps a simple code example
> showing a call to the function, and a call to the same function through a
> function pointer, with comments showing which one has TCO.
>
> You should also call out that it is mutually exclusive with always_inline.
>
> ================
> Comment at: lib/Sema/SemaDeclAttr.cpp:1705
> @@ +1704,3 @@
> +static void handleNoTailAttr(Sema &S, Decl *D, const AttributeList &Attr) {
> + if (checkAttrMutualExclusion<AlwaysInlineAttr>(S, D, Attr))
> + return;
> ----------------
> Missing the same check in the always_inline attribute handler.
>
>
> http://reviews.llvm.org/D12922
>
>
>
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