[Sema] Don't use dyn_cast to detect an AtomicType

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

2 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index a64932b1c71..23a6fc3c4cd 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -6100,7 +6100,7 @@ static void DiagnoseOutOfRangeComparison(Sema &S, BinaryOperator *E,
   // TODO: Investigate using GetExprRange() to get tighter bounds
   // on the bit ranges.
   QualType OtherT = Other->getType();
-  if (const AtomicType *AT = dyn_cast<AtomicType>(OtherT))
+  if (const auto *AT = OtherT->getAs<AtomicType>())
     OtherT = AT->getValueType();
   IntRange OtherRange = IntRange::forValueOfType(S.Context, OtherT);
   unsigned OtherWidth = OtherRange.Width;
diff --git a/clang/test/Sema/atomic-compare.c b/clang/test/Sema/atomic-compare.c
index 2eed0912602..01eb8200472 100644
--- a/clang/test/Sema/atomic-compare.c
+++ b/clang/test/Sema/atomic-compare.c
@@ -19,3 +19,8 @@ void f(_Atomic(int) a, _Atomic(int) b) {
   if (!a > b)     {} // no warning
   if (!a > -1)    {} // expected-warning {{comparison of constant -1 with boolean expression is always true}}
 }
+
+typedef _Atomic(int) Ty;
+void PR23638(Ty *a) {
+  if (*a == 1) {} // no warning
+}