libstdc++: Implement std::philox_engine for targets without __int128

This moves the __detail::_Select_uint_least_t<N>::type class to
namespace scope and extends it with more 128-bit arithmetic operations,
implemented in terms of uint64_t.

Now std::philox_engine can use _Select_uint_least_t<w*2>::type instead
of __uint128_t, so that it works on targets without 128-bit integers.
This also means that targets that do support __uint128_t only use it
when actually necessary, so that we use uint64_t when generating a
32-bit result (e.g. with std::philox4x32).

libstdc++-v3/ChangeLog:

	* include/bits/random.h [!__SIZEOF_INT128__] (__rand_uint128):
	Refactor and rename _Select_uint_least_t<128>::type to a new
	class. Make all members constexpr. Add new member functions for
	additional arithmetic and bitwise operations, and comparisons.
	(__detail::_Select_uint_least_t<>::type): Define as an alias of
	__rand_uint128.
	* include/bits/random.tcc (philox_engine::_M_mulhi): Use
	_Select_uint_least_t<w*2>::type instead of __uint128_t.
	(philox_engine::_M_transition): Likewise.
	* include/bits/version.def (philox_engine): Remove extra_cond.
	* include/bits/version.h: Regenerate.
	* testsuite/26_numerics/random/philox4x32.cc: Remove
	dg-require-cpp-feature-test directive.
	* testsuite/26_numerics/random/philox4x64.cc: Likewise.
	* testsuite/26_numerics/random/philox_engine/cons/copy.cc:
	Likewise.
	* testsuite/26_numerics/random/philox_engine/cons/default.cc:
	Likewise.
	* testsuite/26_numerics/random/philox_engine/cons/seed.cc:
	Likewise.
	* testsuite/26_numerics/random/philox_engine/operators/equal.cc:
	Likewise.
	* testsuite/26_numerics/random/philox_engine/operators/serialize.cc:
	Likewise.
	* testsuite/26_numerics/random/philox_engine/requirements/constants.cc:
	Likewise.
	* testsuite/26_numerics/random/philox_engine/requirements/typedefs.cc:
	Likewise.

Co-authored-by: Jakub Jelinek <[email protected]>
Reviewed-by: Tomasz Kamiński <[email protected]>

Author: jwakely

libstdc++-v3/include/bits/random.h

@@ -915,9 +915,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     philox_engine<_UIntType, __w, __n, __r, __consts...>::
     _S_mulhi(_UIntType __a, _UIntType __b)
     {
-      const __uint128_t __num =
-	  static_cast<__uint128_t>(__a) * static_cast<__uint128_t>(__b);
-      return static_cast<_UIntType>((__num >> __w) & max());
+      using __type = typename __detail::_Select_uint_least_t<__w * 2>::type;
+      const __type __num = static_cast<__type>(__a) * __b;
+      return static_cast<_UIntType>(__num >> __w) & max();
     }
 
   template<typename _UIntType, size_t __w, size_t __n, size_t __r,
@@ -938,33 +938,34 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       if (_M_i != __n)
 	return;
 
+      using __type = typename __detail::_Select_uint_least_t<__w * 2>::type;
+
       _M_philox();
       if constexpr (__n == 4)
 	{
-	  __uint128_t __uh =
-	    (static_cast<__uint128_t>(_M_x[1]) << __w)
-		  | (static_cast<__uint128_t>(_M_x[0]) + 1);
-	  __uint128_t __lh =
-	    ((static_cast<__uint128_t>(_M_x[3]) << __w)
-		  | (_M_x[2]));
-	  __uint128_t __bigMask =
-	    (static_cast<__uint128_t>(1) << ((2 * __w) - 1))
-		  | ((static_cast<__uint128_t>(1) << ((2 * __w) - 1)) - 1);
+	  __type __uh
+	    = (static_cast<__type>(_M_x[1]) << __w)
+		| (static_cast<__type>(_M_x[0]) + 1);
+	  __type __lh
+	    = (static_cast<__type>(_M_x[3]) << __w)
+		| static_cast<__type>(_M_x[2]);
+	  __type __bigMask
+	    = ~__type(0) >> ((sizeof(__type) * __CHAR_BIT__) - (__w * 2));
 	  if ((__uh & __bigMask) == 0)
 	    {
 	      ++__lh;
 	      __uh = 0;
 	    }
-	  _M_x[0] = __uh & max();
-	  _M_x[1] = (__uh >> (__w)) & max();
-	  _M_x[2] = __lh & max();
-	  _M_x[3] = (__lh >> (__w)) & max();
+	  _M_x[0] = static_cast<_UIntType>(__uh & max());
+	  _M_x[1] = static_cast<_UIntType>((__uh >> (__w)) & max());
+	  _M_x[2] = static_cast<_UIntType>(__lh & max());
+	  _M_x[3] = static_cast<_UIntType>((__lh >> (__w)) & max());
 	}
       else
 	{
-	  __uint128_t __num =
-		  (static_cast<__uint128_t>(_M_x[1]) << __w)
-		  | (static_cast<__uint128_t>(_M_x[0]) + 1);
+	  __type __num =
+		  (static_cast<__type>(_M_x[1]) << __w)
+		  | (static_cast<__type>(_M_x[0]) + 1);
 	  _M_x[0] = __num & max();
 	  _M_x[1] = (__num >> __w) & max();
 	}

libstdc++-v3/include/bits/random.tcc

@@ -2241,7 +2241,6 @@ ftms = {
   values = {
     v = 202406;
     cxxmin = 26;
-    extra_cond = "__SIZEOF_INT128__";
   };
 };
 

libstdc++-v3/include/bits/version.def

@@ -2507,7 +2507,7 @@
 #undef __glibcxx_want_constexpr_exceptions
 
 #if !defined(__cpp_lib_philox_engine)
-# if (__cplusplus >  202302L) && (__SIZEOF_INT128__)
+# if (__cplusplus >  202302L)
 #  define __glibcxx_philox_engine 202406L
 #  if defined(__glibcxx_want_all) || defined(__glibcxx_want_philox_engine)
 #   define __cpp_lib_philox_engine 202406L

libstdc++-v3/include/bits/version.h

@@ -1,5 +1,4 @@
 // { dg-do run { target c++26 } }
-// { dg-require-cpp-feature-test __cpp_lib_philox_engine }
 
 // N5014 29.5.6 Engines and engine adaptors with predefined parameters
 

libstdc++-v3/testsuite/26_numerics/random/philox4x32.cc

@@ -1,5 +1,4 @@
 // { dg-do run { target c++26 } }
-// { dg-require-cpp-feature-test __cpp_lib_philox_engine }
 
 // N5014 29.5.6 Engines and engine adaptors with predefined parameters
 

libstdc++-v3/testsuite/26_numerics/random/philox4x64.cc

@@ -1,5 +1,4 @@
 // { dg-do run { target c++26 } }
-// { dg-require-cpp-feature-test __cpp_lib_philox_engine }
 
 // N5014 29.5.4 Random Number Engine Class Templates
 // N5014 29.5.4.5 Class Template philox_engine

libstdc++-v3/testsuite/26_numerics/random/philox_engine/cons/copy.cc

@@ -1,5 +1,4 @@
 // { dg-do run { target c++26 } }
-// { dg-require-cpp-feature-test __cpp_lib_philox_engine }
 
 // N5014 29.5.4.5 Class Template philox_engine
 

libstdc++-v3/testsuite/26_numerics/random/philox_engine/cons/default.cc

@@ -1,5 +1,4 @@
 // { dg-do run { target c++26 } }
-// { dg-require-cpp-feature-test __cpp_lib_philox_engine }
 
 #include <random>
 #include <testsuite_hooks.h>

libstdc++-v3/testsuite/26_numerics/random/philox_engine/cons/seed.cc

@@ -1,5 +1,4 @@
 // { dg-do run { target c++26 } }
-// { dg-require-cpp-feature-test __cpp_lib_philox_engine }
 
 // N5014 29.5.4.5 Class Template philox_engine