[libc++] Make views::iota aware of __int128 (#167869)

Fixes #167991

Author: philnik777

libcxx/docs/ReleaseNotes/22.rst

@@ -114,5 +114,8 @@ ABI Affecting Changes
   potentially inheriting from the types they wrap. At this point in time we are not aware of any ABI changes caused by
   this.
 
+- ``ranges::iota_view`` is now aware of ``__int128``. This causes ``iota_view::difference_type`` to change from
+  ``long long`` to ``__int128`` in some cases.
+
 Build System Changes
 --------------------

libcxx/include/__ranges/iota_view.h

@@ -58,11 +58,17 @@ struct __get_wider_signed {
       return type_identity<int>{};
     else if constexpr (sizeof(_Int) < sizeof(long))
       return type_identity<long>{};
-    else
+    else if constexpr (sizeof(_Int) < sizeof(long long))
       return type_identity<long long>{};
-
-    static_assert(
-        sizeof(_Int) <= sizeof(long long), "Found integer-like type that is bigger than largest integer like type.");
+#  if _LIBCPP_HAS_INT128
+    else if constexpr (sizeof(_Int) <= sizeof(__int128))
+      return type_identity<__int128>{};
+#  else
+    else if constexpr (sizeof(_Int) <= sizeof(long long))
+      return type_identity<long long>{};
+#  endif
+    else
+      static_assert(false, "Found integer-like type that is bigger than the largest integer like type.");
   }
 
   using type = typename decltype(__call())::type;

libcxx/test/std/ranges/range.factories/range.iota.view/indices.pass.cpp

@@ -21,7 +21,6 @@
 #include <vector>
 
 #include "test_macros.h"
-#define TEST_HAS_NO_INT128 // Size cannot be larger than 64 bits
 #include "type_algorithms.h"
 
 #include "types.h"

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

@@ -106,7 +106,12 @@ 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(std::is_signed_v<Iter::difference_type>);
+#ifdef TEST_HAS_NO_INT128
     LIBCPP_STATIC_ASSERT(std::same_as<Iter::difference_type, long long>);
+#else
+    LIBCPP_STATIC_ASSERT(std::same_as<Iter::difference_type,
+                                      std::conditional_t<sizeof(long) == sizeof(long long), __int128, long long>>);
+#endif
   }
   {
     const std::ranges::iota_view<long long> io(0);
@@ -118,7 +123,11 @@ void test() {
     // https://eel.is/c++draft/range.iota.view#1.3
     static_assert(sizeof(Iter::difference_type) >= sizeof(long long));
     static_assert(std::is_signed_v<Iter::difference_type>);
+#ifdef TEST_HAS_NO_INT128
     LIBCPP_STATIC_ASSERT(std::same_as<Iter::difference_type, long long>);
+#else
+    LIBCPP_STATIC_ASSERT(std::same_as<Iter::difference_type, __int128>);
+#endif
   }
   {
     const std::ranges::iota_view<Decrementable> io;