diff --git a/mlir/include/mlir/IR/Attributes.h b/mlir/include/mlir/IR/Attributes.h
--- a/mlir/include/mlir/IR/Attributes.h
+++ b/mlir/include/mlir/IR/Attributes.h
@@ -1699,7 +1699,7 @@
   static inline mlir::Attribute getFromVoidPointer(void *ptr) {
     return mlir::Attribute::getFromOpaquePointer(ptr);
   }
-  static constexpr int NumLowBitsAvailable = 3;
+  static constexpr int NumLowBitsAvailable = alignof(mlir::Attribute) == 4 ? 2 : 3;
 };
 
 template <>