[Reflection] Reject BuiltinTypeDescriptors with non-power-of-two alignments.

rdar://problem/56784375

Author: mikeash

stdlib/public/Reflection/TypeRefBuilder.cpp

@@ -253,12 +253,18 @@ TypeRefBuilder::getBuiltinTypeInfo(const TypeRef *TR) {
 
   for (auto Info : ReflectionInfos) {
     for (auto BuiltinTypeDescriptor : Info.Builtin) {
-      if (BuiltinTypeDescriptor->getAlignment() <= 0)
-        continue;
       if (BuiltinTypeDescriptor->Stride <= 0)
         continue;
       if (!BuiltinTypeDescriptor->hasMangledTypeName())
         continue;
+
+      auto Alignment = BuiltinTypeDescriptor->getAlignment();
+      if (Alignment <= 0)
+        continue;
+      // Reject any alignment that's not a power of two.
+      if (Alignment & (Alignment - 1))
+        continue;
+
       auto CandidateMangledName =
         readTypeRef(BuiltinTypeDescriptor, BuiltinTypeDescriptor->TypeName);
       if (!reflectionNameMatches(CandidateMangledName, MangledName))