Address @mordante's review comments

- Skip 100 cases for constant evaluation.
- Cite the source of MS UCRT's constants.

Author: frederick-vs-ja

libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge.pass.cpp

@@ -97,13 +97,8 @@ TEST_CONSTEXPR_CXX26 void test(RandSrc& randomness) {
   test_one<Iter>(3, 3, randomness);
   test<Iter>(4, randomness);
   test<Iter>(50, randomness);
-#if defined(_LIBCPP_HARDENING_MODE)
-  if (!TEST_IS_CONSTANT_EVALUATED) // avoid exceeding the constant evaluation step limit
-#endif
-  {
-    test<Iter>(100, randomness);
-  }
   if (!TEST_IS_CONSTANT_EVALUATED) { // avoid exceeding the constant evaluation step limit
+    test<Iter>(100, randomness);
     test<Iter>(1000, randomness);
   }
 }

libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp

@@ -114,13 +114,8 @@ TEST_CONSTEXPR_CXX26 void test(RandSrc& randomness) {
   test<Iter>(4, randomness);
   test<Iter>(20, randomness);
   test<Iter>(50, randomness);
-#if defined(_LIBCPP_HARDENING_MODE)
-  if (!TEST_IS_CONSTANT_EVALUATED) // avoid exceeding the constant evaluation step limit
-#endif
-  {
-    test<Iter>(100, randomness);
-  }
   if (!TEST_IS_CONSTANT_EVALUATED) { // avoid exceeding the constant evaluation step limit
+    test<Iter>(100, randomness);
     test<Iter>(1000, randomness);
   }
 }

libcxx/test/support/constexpr_random.h

@@ -379,7 +379,7 @@ class uniform_int_distribution {
 #endif
 };
 
-class simple_random_generator {
+class simple_random_generator { // A linear congruential generator, using the constants used by MS UCRT.
 private:
   std::uint32_t status_;