For atomics metadata, we can make data race analysis more efficient by
entirely ignoring functions that include memory accesses but which only
access non-escaping (non-shared) and/or non-mutable memory. Such
functions will not be considered to be covered by "atomics" metadata,
resulting in the following benefits:
1. reduces "covered" metadata; and
2. allows data race analysis to skip such functions.
Reviewed By: dvyukov
Differential Revision: https://reviews.llvm.org/D143159
