Thread safety analysis: Consider global variables in scope
Instead of just mutex members we also consider mutex globals.
Unsurprisingly they are always in scope. Now the paper [1] says that
> The scope of a class member is assumed to be its enclosing class,
> while the scope of a global variable is the translation unit in
> which it is defined.
But I don't think we should limit this to TUs where a definition is
available - a declaration is enough to acquire the mutex, and if a mutex
is really limited in scope to a translation unit, it should probably be
only declared there.
The previous attempt in
9dcc82f34ea was causing false positives because
I wrongly assumed that LiteralPtrs were always globals, which they are
not. This should be fixed now.
[1] https://static.googleusercontent.com/media/research.google.com/en/us/pubs/archive/42958.pdf
Fixes PR46354.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D84604