Fix misalignment of conditional invertible requirement counts

Author: Azoy

include/swift/ABI/GenericContext.h

@@ -696,7 +696,7 @@ class TrailingGenericContextObjects<TargetSelf<Runtime>,
     if (!asSelf()->hasConditionalInvertedProtocols())
       return 0;
 
-    return countBitsUsed(getConditionalInvertedProtocols().rawBits());
+    return __builtin_popcount(getConditionalInvertedProtocols().rawBits());
   }
 
   size_t numTrailingObjects(

lib/IRGen/GenMeta.cpp

@@ -1334,6 +1334,13 @@ namespace {
             B.addPlaceholderWithSize(IGM.Int16Ty));
       }
 
+      // The conditional invertible protocol set is alone as a 16 bit slot, so
+      // an even amount of conditional invertible protocols will cause an uneven
+      // alignment.
+      if ((numProtocols & 1) == 0) {
+        B.addInt16(0);
+      }
+
       // Emit the generic requirements for the conditional conformance
       // to each invertible protocol.
       auto nominal = cast<NominalTypeDecl>(Type);