An AtomicType might be hidden behind arbitrary levels of typedefs.
getAs<> will reliably walk through the sugar to get the underlying
AtomicType.
This fixes PR23638.
llvm-svn: 238083
This fixes a couple of asserts when analyzing comparisons involving
C11 atomics that were uncovered by r205608 when we extended the
applicability of -Wtautological-constant-out-of-range-compare.
llvm-svn: 213573