How to easily identify that a FUNCTION_DECL is a lambda

[Richard Biener]

On July 16, 2018 4:30:42 PM GMT+02:00, Nathan Sidwell <nathan@acm.org> wrote:
>On 07/16/2018 03:23 AM, Martin Liška wrote:
>> Hi.
>> 
>> For purpose of --coverage I would like to distinguish lambda
>functions
>> among DECL_ARTIFICIAL functions. Currently, cp-tree.h provides macro:
>> 
>> /* Test if FUNCTION_DECL is a lambda function.  */
>> #define LAMBDA_FUNCTION_P(FNDECL)				\
>>    (DECL_DECLARES_FUNCTION_P (FNDECL)				\
>>     && DECL_OVERLOADED_OPERATOR_P (FNDECL)			\
>>     && DECL_OVERLOADED_OPERATOR_IS (FNDECL, CALL_EXPR)		\
>>     && LAMBDA_TYPE_P (CP_DECL_CONTEXT (FNDECL)))
>> 
>> That's FE-specific function that probably should not be called from
>> middle-end. Any idea how to distinguish lambdas?
>
>You're going to need a language hook.  Lambda fns are just regular 
>member fns outside the front-end.  Make the hook more than 
>'lambda_fn_p', so it can extend to other exciting C++ features. 
>Perhaps 
>something like:
>
>enum synthetic_fn_kind {
>   sfk_none,
>   sfk_cxx_lambda,
>};
>synthetic_fn_kind (*categorize_artificial_fn) (tree decl);
>
>We'll have to expose the union of FE's such sythetic fns to the middle 
>end, but at least not how the FE distinguishes them.
>
>Hm, but isn't this info lost if we're in LTO at this point?  Not sure
>if 
>we'll need to propagate this through the LTO streaming.  I guess that's
>
>a later bug to handle though.

Just use a spare bit in function_decl, then we can simply stream it. 

Richard. 

>nathan