here are some built-in functions about atomic operations in the documentation[https://github.com/llvm/llvm-project/blob/a3e6e624c71d60509c84e13ea3ee96c0acde65c3/clang/docs/LanguageExtensions.rst]:
__c11_atomic_init
__c11_atomic_thread_fence
__c11_atomic_store
__c11_atomic_load
__c11_atomic_exchange
__c11_atomic_compare_exchange_strong
__c11_atomic_compare_exchange_weak
__c11_atomic_fetch_add
......
I want to look at the source code implemented by Clang? Their implementation may be in a source file, but I did not find it.