This function is called by the __atomic_is_lock_free() builtin if the value
cannot be resolved to true at compile time. Lack of this function is
causing the non-lockfree atomics tests in libc++ to not be run (see D91911)
This function is also added in D85044, but that review also adds support
for using lock-free atomics in more cases, whereas this is a minimal change
that just adds __atomic_is_lock_free() for the implementation of atomic.c.
Reviewed By: ldionne
Differential Revision: https://reviews.llvm.org/D92302
The macOS name mangling adds another underscore. Therefore, on macOS
the __atomic_* functions are actually ___atomic_* in libcompiler_rt.dylib.
To handle this case, prepend the asm() argument with __USER_LABEL_PREFIX__
in the same way that atomic.c does.
Reviewed By: ldionne
Differential Revision: https://reviews.llvm.org/D92833
Adds some simple sanity checks that the support functions for the atomic
builtins do the right thing. This doesn't test concurrency and memory model
issues.
Differential Revision: https://reviews.llvm.org/D86278
Alex Richardson