where is __is_trivial used in type_traits 4.5.1 defined?

[Jonathan Wakely]

On 9 February 2011 11:20, Larry Evans wrote:
> In:
>
> http://gcc.gnu.org/viewcvs/trunk/libstdc%2B%2B-v3/include/std/type_traits?revision=169421&view=markup
>
> on line 625, there's:
>
> : public integral_constant<bool, __is_trivial(_Tp)>
>
> Since _Tp is a type, not a value, I thought
> __is_trivial must be a macro; however, grepping
> the include directory produced nothing:
>
> find . -type f -exec grep __is_trivial {} \; -ls
>    : public integral_constant<bool, __is_trivial(_Tp)>
> 2966263   20 -rw-r--r--   1 evansl   evansl      17946 Aug 25 02:31
> ./type_traits
>
> Where is __is_trivial defined so I can look  at it to
> try and understand why g++ doesn't complain, when compiling
> type_traits, that _Tp is a type and not a value?

It's a compiler intrinsic provided by G++