Update __is_unsigned builtin to match the Standard.

Updates __is_unsigned to have the same behavior as the standard
specifies. This is in line with 511dbd8, which applied the same change
to __is_signed.

Refs D67897.

Differential Revision: https://reviews.llvm.org/D98104

clang/docs/LanguageExtensions.rst

@@ -1194,7 +1194,9 @@ The following type trait primitives are supported by Clang. Those traits marked
 * ``__is_sealed`` (Microsoft):
   Synonym for ``__is_final``.
 * ``__is_signed`` (C++, Embarcadero):
-  Returns false for enumeration types, and returns true for floating-point types. Note, before Clang 10, returned true for enumeration types if the underlying type was signed, and returned false for floating-point types.
+  Returns false for enumeration types, and returns true for floating-point
+  types. Note, before Clang 10, returned true for enumeration types if the
+  underlying type was signed, and returned false for floating-point types.
 * ``__is_standard_layout`` (C++, GNU, Microsoft, Embarcadero)
 * ``__is_trivial`` (C++, GNU, Microsoft, Embarcadero)
 * ``__is_trivially_assignable`` (C++, GNU, Microsoft)
@@ -1202,10 +1204,9 @@ The following type trait primitives are supported by Clang. Those traits marked
 * ``__is_trivially_copyable`` (C++, GNU, Microsoft)
 * ``__is_trivially_destructible`` (C++, MSVC 2013)
 * ``__is_union`` (C++, GNU, Microsoft, Embarcadero)
-* ``__is_unsigned`` (C++, Embarcadero)
-  Note that this currently returns true for enumeration types if the underlying
-  type is unsigned, in violation of the requirements for ``std::is_unsigned``.
-  This behavior is likely to change in a future version of Clang.
+* ``__is_unsigned`` (C++, Embarcadero):
+  Returns false for enumeration types. Note, before Clang 13, returned true for
+  enumeration types if the underlying type was unsigned.
 * ``__is_void`` (C++, Embarcadero)
 * ``__is_volatile`` (C++, Embarcadero)
 * ``__reference_binds_to_temporary(T, U)`` (Clang):  Determines whether a

clang/lib/Sema/SemaExprCXX.cpp

@@ -4856,9 +4856,11 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
   case UTT_IsSigned:
     // Enum types should always return false.
     // Floating points should always return true.
-    return !T->isEnumeralType() && (T->isFloatingType() || T->isSignedIntegerType());
+    return T->isFloatingType() ||
+           (T->isSignedIntegerType() && !T->isEnumeralType());
   case UTT_IsUnsigned:
-    return T->isUnsignedIntegerType();
+    // Enum types should always return false.
+    return T->isUnsignedIntegerType() && !T->isEnumeralType();
 
     // Type trait expressions which query classes regarding their construction,
     // destruction, and copying. Rather than being based directly on the

clang/test/SemaCXX/type-traits.cpp

@@ -13,6 +13,7 @@ typedef NonPOD NonPODArMB[10][2];
 // PODs
 enum Enum { EV };
 enum SignedEnum : signed int { };
+enum UnsignedEnum : unsigned int { };
 struct POD { Enum e; int i; float f; NonPOD* p; };
 struct Empty {};
 struct IncompleteStruct;
@@ -1440,6 +1441,7 @@ void is_signed()
   int t25[F(__is_signed(IntArNB))];
   int t26[F(__is_signed(Union))];
   int t27[F(__is_signed(UnionAr))];
+  int t28[F(__is_signed(UnsignedEnum))];
 }
 
 void is_unsigned()
@@ -1450,7 +1452,6 @@ void is_unsigned()
   int t04[T(__is_unsigned(unsigned int))];
   int t05[T(__is_unsigned(unsigned long))];
   int t06[T(__is_unsigned(unsigned long long))];
-  int t07[T(__is_unsigned(Enum))];
 
   int t10[F(__is_unsigned(void))];
   int t11[F(__is_unsigned(cvoid))];
@@ -1468,6 +1469,9 @@ void is_unsigned()
   int t24[F(__is_unsigned(Derives))];
   int t25[F(__is_unsigned(ClassType))];
   int t26[F(__is_unsigned(IntArNB))];
+  int t27[F(__is_unsigned(Enum))];
+  int t28[F(__is_unsigned(UnsignedEnum))];
+  int t29[F(__is_unsigned(SignedEnum))];
 }
 
 typedef Int& IntRef;