[LLVMdev] Conditions that cause Clang refuse inlining a function

[David Blaikie]

There are lots of reasons a compiler will choose not to inline a function
(inlining, while usually a win for performance is a time/space tradeoff, so
often a compiler will try not to make a function 'too large' by inlining
too many functions into it - it will simply so at some threshold)

In any case, if the correctness of your program depends on the function
being inlined, you can use the always_inline attribute.
On Sep 4, 2014 5:46 AM, "David Sela" <sela.david at gmail.com> wrote:

> Hi Anton,
> Thanks for the answer.
>
> The link you provided doesn't answer the question. It lists the ways to
> overcome the linking error if the inline was not successful.
> The only condition that is found there to make the compiler not inline is "when
> compiling without optimization".
>
> I asked the question in the forum because I think that this info is not
> documented and most chances that the people that know the code inside-out
> will know the answer.
>
> Thanks,
> David
>
>
>
> On Thu, Sep 4, 2014 at 3:30 PM, Anton Korobeynikov <
> anton at korobeynikov.info> wrote:
>
>> Hello
>>
>> First of all, such a question definitely belongs to cfe-dev, not llvmdev.
>>
>> Next, 'inline' is certainly a hint, and the full the answer is a first
>> entry here: http://clang.llvm.org/compatibility.html#inline
>>
>> On Thu, Sep 4, 2014 at 3:42 PM, David Sela <sela.david at gmail.com> wrote:
>> > Hi,
>> >
>> > I want to have some functions in my code inline so I use the inline
>> keyword:
>> >
>> > inline void foo() {}
>> >
>> > On some functions the compiler inlines the function but it fails to do
>> so on
>> > other functions and thus I get a linkage error:
>> >
>> > error: undefined reference to 'foo'
>> >
>> > What are the conditions that make the compiler refuse inline?
>> >
>> > Thanks,
>> > David
>> >
>> > p.s. I know that there are ways to pass compilation and let the compiler
>> > decide if to inline like using __attribute__((always_inline)) but I must
>> > have the function inline.
>> >
>> > _______________________________________________
>> > LLVM Developers mailing list
>> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >
>>
>>
>>
>> --
>> With best regards, Anton Korobeynikov
>> Faculty of Mathematics and Mechanics, Saint Petersburg State University
>>
>
>
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