[clang][Interp] Implement IntegralAP::comp (#67954)

Author: tbaederr

clang/lib/AST/Interp/IntegralAP.h

@@ -210,7 +210,6 @@ template <bool Signed> class IntegralAP final {
   }
 
   static bool comp(IntegralAP A, IntegralAP *R) {
-    assert(false);
     *R = IntegralAP(~A.V);
     return false;
   }

clang/test/AST/Interp/literals.cpp

@@ -52,6 +52,9 @@ namespace i128 {
   constexpr int128_t Two = (int128_t)1 << 1ul;
   static_assert(Two == 2, "");
 
+  constexpr uint128_t AllOnes = ~static_cast<uint128_t>(0);
+  static_assert(AllOnes == static_cast<uint128_t>(-1), "");
+
 #if __cplusplus >= 201402L
   template <typename T>
   constexpr T CastFrom(__int128_t A) {