Enable __int128_t as difference type in counting_iterator (#6487)

Fixes #6485

Author: miscco

libcudacxx/include/cuda/__iterator/counting_iterator.h

@@ -41,6 +41,7 @@
 #include <cuda/std/__ranges/enable_borrowed_range.h>
 #include <cuda/std/__ranges/movable_box.h>
 #include <cuda/std/__ranges/view_interface.h>
+#include <cuda/std/__type_traits/always_false.h>
 #include <cuda/std/__type_traits/conditional.h>
 #include <cuda/std/__type_traits/enable_if.h>
 #include <cuda/std/__type_traits/is_constructible.h>
@@ -79,13 +80,21 @@ struct __get_wider_signed
     {
       return ::cuda::std::type_identity<long>{};
     }
-    else
+#if _CCCL_HAS_INT128()
+    else if constexpr (sizeof(_Int) < sizeof(long long))
     {
       return ::cuda::std::type_identity<long long>{};
     }
-
-    static_assert(sizeof(_Int) <= sizeof(long long),
-                  "Found integer-like type that is bigger than largest integer like type.");
+    else // if constexpr (sizeof(_Int) < sizeof(__int128_t))
+    {
+      return ::cuda::std::type_identity<__int128_t>{};
+    }
+#else // ^^^ _CCCL_HAS_INT128() ^^^ / vvv !_CCCL_HAS_INT128() vvv
+    else // if constexpr (sizeof(_Int) < sizeof(long long))
+    {
+      return ::cuda::std::type_identity<long long>{};
+    }
+#endif // _CCCL_HAS_INT128()
     _CCCL_UNREACHABLE();
   }
 

libcudacxx/test/libcudacxx/cuda/iterators/counting_iterator/iterator_traits.compile.pass.cpp

@@ -142,6 +142,12 @@ _CCCL_CONCEPT HasIteratorCategory =
 template <template <class...> class Traits>
 __host__ __device__ void test()
 {
+#if _CCCL_HAS_INT128()
+  using widest_integer = __int128_t;
+#else // ^^^ _CCCL_HAS_INT128() ^^^ / vvv !_CCCL_HAS_INT128() vvv
+  using widest_integer = long long;
+#endif // !_CCCL_HAS_INT128()
+
   {
     using Iter       = cuda::counting_iterator<char>;
     using IterTraits = Traits<Iter>;
@@ -189,7 +195,7 @@ __host__ __device__ void test()
     // Same as below, if there is no type larger than long, we can just use that.
     static_assert(sizeof(typename IterTraits::difference_type) >= sizeof(long));
     static_assert(cuda::std::is_signed_v<typename IterTraits::difference_type>);
-    static_assert(cuda::std::same_as<typename IterTraits::difference_type, long long>);
+    static_assert(cuda::std::same_as<typename IterTraits::difference_type, widest_integer>);
     static_assert(cuda::std::random_access_iterator<Iter>);
     static_assert(cuda::std::__has_random_access_traversal<Iter>);
   }
@@ -202,7 +208,7 @@ __host__ __device__ void test()
     // https://eel.is/c++draft/range.iota.view#1.3
     static_assert(sizeof(typename IterTraits::difference_type) >= sizeof(long long));
     static_assert(cuda::std::is_signed_v<typename IterTraits::difference_type>);
-    static_assert(cuda::std::same_as<typename IterTraits::difference_type, long long>);
+    static_assert(cuda::std::same_as<typename IterTraits::difference_type, widest_integer>);
     static_assert(cuda::std::random_access_iterator<Iter>);
     static_assert(cuda::std::__has_random_access_traversal<Iter>);
   }

libcudacxx/test/libcudacxx/cuda/iterators/counting_iterator/member_typedefs.compile.pass.cpp

@@ -108,6 +108,11 @@ _CCCL_CONCEPT HasIteratorCategory =
 
 __host__ __device__ void test()
 {
+#if _CCCL_HAS_INT128()
+  using widest_integer = __int128_t;
+#else // ^^^ _CCCL_HAS_INT128() ^^^ / vvv !_CCCL_HAS_INT128() vvv
+  using widest_integer = long long;
+#endif // !_CCCL_HAS_INT128()
   {
     using Iter = cuda::counting_iterator<char>;
     static_assert(cuda::std::same_as<Iter::iterator_concept, cuda::std::random_access_iterator_tag>);
@@ -155,7 +160,7 @@ __host__ __device__ void test()
     // Same as below, if there is no type larger than long, we can just use that.
     static_assert(sizeof(Iter::difference_type) >= sizeof(long));
     static_assert(cuda::std::is_signed_v<Iter::difference_type>);
-    static_assert(cuda::std::same_as<Iter::difference_type, long long>);
+    static_assert(cuda::std::same_as<Iter::difference_type, widest_integer>);
     static_assert(cuda::std::random_access_iterator<Iter>);
     static_assert(cuda::std::is_trivially_copyable_v<Iter>);
   }
@@ -168,7 +173,7 @@ __host__ __device__ void test()
     // https://eel.is/c++draft/range.iota.view#1.3
     static_assert(sizeof(Iter::difference_type) >= sizeof(long long));
     static_assert(cuda::std::is_signed_v<Iter::difference_type>);
-    static_assert(cuda::std::same_as<Iter::difference_type, long long>);
+    static_assert(cuda::std::same_as<Iter::difference_type, widest_integer>);
     static_assert(cuda::std::random_access_iterator<Iter>);
     static_assert(cuda::std::is_trivially_copyable_v<Iter>);
   }

libcudacxx/test/libcudacxx/std/ranges/range.factories/range.iota.view/iterator/member_typedefs.compile.pass.cpp

@@ -107,6 +107,12 @@ _CCCL_CONCEPT HasIteratorCategory =
 
 __host__ __device__ void test()
 {
+#if _CCCL_HAS_INT128()
+  using widest_integer = __int128_t;
+#else // ^^^ _CCCL_HAS_INT128() ^^^ / vvv !_CCCL_HAS_INT128() vvv
+  using widest_integer = long long;
+#endif // !_CCCL_HAS_INT128()
+
   {
     const cuda::std::ranges::iota_view<char> io(0);
     using Iter = decltype(io.begin());
@@ -155,7 +161,7 @@ __host__ __device__ void test()
     // Same as below, if there is no type larger than long, we can just use that.
     static_assert(sizeof(Iter::difference_type) >= sizeof(long));
     static_assert(cuda::std::is_signed_v<Iter::difference_type>);
-    static_assert(cuda::std::same_as<Iter::difference_type, long long>);
+    static_assert(cuda::std::same_as<Iter::difference_type, widest_integer>);
     unused(io);
   }
   {
@@ -168,7 +174,7 @@ __host__ __device__ void test()
     // https://eel.is/c++draft/range.iota.view#1.3
     static_assert(sizeof(Iter::difference_type) >= sizeof(long long));
     static_assert(cuda::std::is_signed_v<Iter::difference_type>);
-    static_assert(cuda::std::same_as<Iter::difference_type, long long>);
+    static_assert(cuda::std::same_as<Iter::difference_type, widest_integer>);
     unused(io);
   }
   {