[clang][Interp] Handle __unaligned in alignof expressions

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -1084,6 +1084,9 @@ static CharUnits AlignOfType(QualType T, const ASTContext &ASTCtx,
   if (const auto *Ref = T->getAs<ReferenceType>())
     T = Ref->getPointeeType();
 
+  if (T.getQualifiers().hasUnaligned())
+    return CharUnits::One();
+
   // __alignof is defined to return the preferred alignment.
   // Before 8, clang returned the preferred alignment for alignof and
   // _Alignof as well.

clang/test/AST/Interp/ms.cpp

@@ -6,3 +6,5 @@
 
 /// Used to assert because the two parameters to _rotl do not have the same type.
 static_assert(_rotl(0x01, 5) == 32);
+
+static_assert(alignof(__unaligned int) == 1, "");