From 2c24c61da56cb530102c4b5c4e1dca057badf02d Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Sat, 16 Nov 2024 09:11:52 +0100
Subject: [PATCH] perf: `first_100_primes` moved to the static storage

---
 src/core/include/mp-units/ext/prime.h | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/core/include/mp-units/ext/prime.h b/src/core/include/mp-units/ext/prime.h
index 1206dc7e7..a5a8f1068 100644
--- a/src/core/include/mp-units/ext/prime.h
+++ b/src/core/include/mp-units/ext/prime.h
@@ -38,6 +38,7 @@ import std;
 #include <numeric>
 #include <optional>
 #include <tuple>
+#include <version>
 #endif
 #endif
 
@@ -441,9 +442,20 @@ constexpr auto get_first_of(const Rng& rng, UnaryFunction f)
   return get_first_of(begin(rng), end(rng), f);
 }
 
+#if __cpp_constexpr < 202211L
+template<std::size_t N>
+struct first_n_primes_impl {
+  static constexpr auto value = first_n_primes<N>();
+};
+#endif
+
 [[nodiscard]] consteval std::uintmax_t find_first_factor(std::uintmax_t n)
 {
-  constexpr auto first_100_primes = first_n_primes<100>();
+#if __cpp_constexpr >= 202211L
+  static constexpr auto first_100_primes = first_n_primes<100>();
+#else
+  constexpr auto first_100_primes = first_n_primes_impl<100>::value;
+#endif
 
   for (const auto& p : first_100_primes) {
     if (n % p == 0u) {