builtin setjmp

["M R Swami Reddy" <MR.Swami.Reddy@xxxxxxx>]

Hello,
I am using the gcc with libstdc++. In this, optabs.c use the 
_builtin_setjmp function.
Could you please let me know, from where (ie from C libs or gcc sources) 
this builtin_setjmp
definition  will be observed?

Thanks
Swami