diff --git a/clang/include/clang/AST/DependenceFlags.h b/clang/include/clang/AST/DependenceFlags.h
--- a/clang/include/clang/AST/DependenceFlags.h
+++ b/clang/include/clang/AST/DependenceFlags.h
@@ -36,7 +36,6 @@
   };
 };
 using ExprDependence = ExprDependenceScope::ExprDependence;
-static constexpr unsigned ExprDependenceBits = 5;
 
 struct TypeDependenceScope {
   enum TypeDependence : uint8_t {
@@ -62,7 +61,6 @@
   };
 };
 using TypeDependence = TypeDependenceScope::TypeDependence;
-static constexpr unsigned TypeDependenceBits = 4;
 
 #define LLVM_COMMON_DEPENDENCE(NAME)                                           \
   struct NAME##Scope {                                                         \
@@ -78,8 +76,7 @@
       LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue=*/Dependent)                    \
     };                                                                         \
   };                                                                           \
-  using NAME = NAME##Scope::NAME;                                              \
-  static constexpr unsigned NAME##Bits = 3;
+  using NAME = NAME##Scope::NAME;
 
 LLVM_COMMON_DEPENDENCE(NestedNameSpecifierDependence)
 LLVM_COMMON_DEPENDENCE(TemplateNameDependence)
diff --git a/clang/include/clang/AST/Stmt.h b/clang/include/clang/AST/Stmt.h
--- a/clang/include/clang/AST/Stmt.h
+++ b/clang/include/clang/AST/Stmt.h
@@ -21,6 +21,7 @@
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/BitmaskEnum.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator.h"
@@ -310,9 +311,9 @@
 
     unsigned ValueKind : 2;
     unsigned ObjectKind : 3;
-    unsigned /*ExprDependence*/ Dependent : ExprDependenceBits;
+    unsigned /*ExprDependence*/ Dependent : llvm::BitWidth<ExprDependence>;
   };
-  enum { NumExprBits = NumStmtBits + 5 + ExprDependenceBits };
+  enum { NumExprBits = NumStmtBits + 5 + llvm::BitWidth<ExprDependence> };
 
   class ConstantExprBitfields {
     friend class ASTStmtReader;
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -1467,7 +1467,7 @@
     unsigned TC : 8;
 
     /// Store information on the type dependency.
-    /*TypeDependence*/ unsigned Dependence : TypeDependenceBits;
+    unsigned Dependence : llvm::BitWidth<TypeDependence>;
 
     /// True if the cache (i.e. the bitfields here starting with
     /// 'Cache') is valid.
@@ -1496,7 +1496,7 @@
       return CachedLocalOrUnnamed;
     }
   };
-  enum { NumTypeBits = 8 + TypeDependenceBits + 6 };
+  enum { NumTypeBits = 8 + llvm::BitWidth<TypeDependence> + 6 };
 
 protected:
   // These classes allow subclasses to somewhat cleanly pack bitfields
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -50,6 +50,7 @@
 #include "clang/Lex/Token.h"
 #include "clang/Serialization/ASTBitCodes.h"
 #include "clang/Serialization/ASTRecordReader.h"
+#include "llvm/ADT/BitmaskEnum.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
@@ -107,7 +108,7 @@
     /// The number of record fields required for the Expr class
     /// itself.
     static const unsigned NumExprFields =
-        NumStmtFields + ExprDependenceBits + 3;
+        NumStmtFields + llvm::BitWidth<ExprDependence> + 3;
 
     /// Read and initialize a ExplicitTemplateArgumentList structure.
     void ReadTemplateKWAndArgsInfo(ASTTemplateKWAndArgsInfo &Args,
diff --git a/llvm/include/llvm/ADT/BitmaskEnum.h b/llvm/include/llvm/ADT/BitmaskEnum.h
--- a/llvm/include/llvm/ADT/BitmaskEnum.h
+++ b/llvm/include/llvm/ADT/BitmaskEnum.h
@@ -94,6 +94,10 @@
   return U;
 }
 
+constexpr unsigned bitWidth(uint64_t Value) {
+  return Value ? 1 + bitWidth(Value >> 1) : 0;
+}
+
 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
 E operator~(E Val) {
   return static_cast<E>(~Underlying(Val) & Mask<E>());
@@ -139,6 +143,10 @@
 
 // Enable bitmask enums in namespace ::llvm and all nested namespaces.
 LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
+template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
+constexpr unsigned BitWidth = BitmaskEnumDetail::bitWidth(uint64_t{
+    static_cast<std::underlying_type_t<E>>(
+        E::LLVM_BITMASK_LARGEST_ENUMERATOR)});
 
 } // namespace llvm