[cfe-dev] [RFC] Per-callsite inline intrinsics

[Piotr Padlewski via cfe-dev]

What is the semantics of calling function with __builtin_always_inline that
is marked with __attribute__ ((noinline)) ?
It seems reasonable to me that call site attributes should be stronger than
global attributes.

In general SGTM.

wt., 4 wrz 2018 o 12:32 Jakub Kuderski via cfe-dev <cfe-dev at lists.llvm.org>
napisał(a):

>  they seem like very surgical tools for controlling inlining, and so
>> applying them to a family of functions is perhaps unwise -- and the case
>> where the builtin is applied to a call in some instantiations and to a
>> built-in operator in others does not immediately seem like a primary
>> concern to me
>>
> Having seen a lot of library and game engine code with FORCE_INLINE stuck
> on dozens functions, I'd eventually expect it to become an issue for some
> people. However, I think it would be easier to start simple and issue
> errors in any case where these intrinsics don't make sense, and relax it
> later if there's a real need.
>
> (Are there also macro scenarios where you anticipate it being unknown
>> whether the operand is a function call?)
>>
> Arthur O'Dwyer pointed that out in the code review -- one example could be
> sqrt being a function call or a builtin call. Another thing that comes to
> my mind is `min` from windows.h.
>
>
> On Tue, Sep 4, 2018 at 11:53 AM Jon Chesterfield via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> This is a good idea. I've been working around the absence of this by
>> writing wrapper functions tagged with the corresponding metadata.
>>
>> I don't know clang well enough to review the implementation, but if it
>> ships, I'll use it. Whatever the syntax.
>>
>> Thanks
>>
>>
>> Hi folks,
>>>
>>> TL;DR: I propose to add 3 new C/C++ intrinsics for controlling inlining
>>> at
>>> callsite:
>>> * __builtin_no_inline(Foo()) -- prevents the call to Foo() from being
>>> inlined at that particular callsite.
>>> * __builtin_always_inline(Foo()) -- inlines this call to Foo(), if
>>> possible.
>>> * __builtin_flatten_inline(Foo()) -- inlines this call to Foo() and
>>> (transitively) everything called within Foo’s body.
>>>
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