diff --git a/include/fstcpp/fstcpp.h b/include/fstcpp/fstcpp.h
index 5eb0c7414..e17b33766 100644
--- a/include/fstcpp/fstcpp.h
+++ b/include/fstcpp/fstcpp.h
@@ -13,6 +13,17 @@
 #include <string>
 // Other libraries' .h files.
 // Your project's .h files.
+#if defined(MSC_VER_) || defined(FORCE_MSC_VER_)
+#	define USE_GCC_INTRINSIC 0
+// Note: we do not support MSVC intrinsic for now
+#	define USE_MSVC_INTRINSIC 0
+#elif defined(__GNUC__) || defined(__clang__)
+#	define USE_GCC_INTRINSIC 1
+#	define USE_MSVC_INTRINSIC 0
+#else
+#	define USE_GCC_INTRINSIC 0
+#	define USE_MSVC_INTRINSIC 0
+#endif
 
 // Remove these when we upgrade to C++20
 #pragma GCC diagnostic ignored "-Wpragmas"
diff --git a/include/fstcpp/fstcpp_assertion.h b/include/fstcpp/fstcpp_assertion.h
index 1f7265b13..e9606f665 100644
--- a/include/fstcpp/fstcpp_assertion.h
+++ b/include/fstcpp/fstcpp_assertion.h
@@ -102,16 +102,12 @@
 
 // Compatibility layer for unreachable code hint
 #if defined(__cplusplus) && __cplusplus >= 202302L
-// Prefer the standard library version if available
 #	include <utility>
 #	define FST_UNREACHABLE std::unreachable()
-#elif defined(__GNUC__) || defined(__clang__)
-// --- GCC / Clang ---
+#elif USE_GCC_INTRINSIC
 #	define FST_UNREACHABLE __builtin_unreachable()
-#elif defined(_MSC_VER)
-// --- MSVC ---
-#	define FST_UNREACHABLE __assume(0)
+// TODO: implement MSVC version
+// #elif USE_MSVC_INTRINSIC
 #else
-// --- Fallback ---
 #	define FST_UNREACHABLE std::abort()
 #endif
diff --git a/include/fstcpp/fstcpp_stream_write_helper.h b/include/fstcpp/fstcpp_stream_write_helper.h
index e3b9158ba..ad2999962 100644
--- a/include/fstcpp/fstcpp_stream_write_helper.h
+++ b/include/fstcpp/fstcpp_stream_write_helper.h
@@ -6,10 +6,10 @@
 #pragma once
 // direct include
 // C system headers
-#ifdef _MSC_VER
-#	include <intrin.h>
-#endif
 // C++ standard library headers
+#if defined(__cplusplus) && __cplusplus >= 202302L
+#	include <bit>
+#endif
 #include <cstdint>
 #include <cstring>
 #include <vector>
@@ -28,22 +28,24 @@ namespace platform {
 // clang-format off
 template <typename U> U to_big_endian(U u) { return u; }
 #else
-#if defined(__GNUC__) || defined(__clang__)
+#if defined(__cplusplus) && __cplusplus >= 202302L
+template <typename U, size_t S>
+U to_big_endian(U u, std::integral_constant<size_t, S>) {
+	return std::byteswap(u);
+}
+#elif USE_GCC_INTRINSIC
 template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 1>) { return u; }
 template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 2>) { return __builtin_bswap16(u); }
 template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 4>) { return __builtin_bswap32(u); }
 template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 8>) { return __builtin_bswap64(u); }
-#elif defined(_MSC_VER) // MSVC
-template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 1>) { return u; }
-template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 2>) { return _byteswap_ushort(u); }
-template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 4>) { return _byteswap_ulong(u); }
-template<typename U> U to_big_endian(U u, std::integral_constant<size_t, 8>) { return _byteswap_uint64(u); }
+// TODO: implement MSVC version
+// #elif USE_MSVC_INTRINSIC
 #else
-template<typename U, size_t S> U to_big_endian(U u, std::integral_constant<size_t, S>) {
-	U ret{ 0 };
+template <typename U, size_t S>
+U to_big_endian(U u, std::integral_constant<size_t, S>) {
+	U ret{0};
 	for (size_t i = 0; i < S; ++i) {
-		ret |= u & 0xff;
-		ret <<= 8;
+		ret = (ret << 8) | (u & 0xff);
 		u >>= 8;
 	}
 	return ret;
diff --git a/include/fstcpp/fstcpp_variable_info.h b/include/fstcpp/fstcpp_variable_info.h
index f707aaaa8..470bb8ef1 100644
--- a/include/fstcpp/fstcpp_variable_info.h
+++ b/include/fstcpp/fstcpp_variable_info.h
@@ -7,10 +7,10 @@
 // direct include
 #include "fstcpp/fstcpp.h"
 // C system headers
-#ifdef _MSC_VER
-#	include <intrin.h>
-#endif
 // C++ standard library headers
+#if defined(__cplusplus) && __cplusplus >= 202002L
+#	include <bit>
+#endif
 #include <algorithm>
 #include <cstdint>
 #include <limits>
@@ -26,19 +26,29 @@ namespace platform {
 
 // Can be replaced with std::bit_width when C++20 is available
 inline uint64_t clog2(uint64_t x) {
-#if defined(__GNUC__) || defined(__clang__)
-	return 64 - __builtin_clzll(x - 1);
-#elif defined(_MSC_VER)  // MSVC
 	if (x <= 1) return 0;
-	unsigned long index;
-	_BitScanReverse64(&index, x - 1);
-	return static_cast<uint64_t>(index + 1);
+#if defined(__cplusplus) && __cplusplus >= 202002L
+	return std::bit_width(x - 1);
+#elif USE_GCC_INTRINSIC
+	return 64 - __builtin_clzll(x - 1);
+// TODO: implement MSVC version
+// #elif USE_MSVC_INTRINSIC
 #else
 	uint64_t r = 0;
-	while (x > 1) {
-		x >>= 1;
-		r++;
-	}
+	x -= 1;
+	auto CheckAndShift = [&](uint64_t shift) {
+		if (x >> shift) {
+			r += shift;
+			x >>= shift;
+		}
+	};
+	CheckAndShift(32);
+	CheckAndShift(16);
+	CheckAndShift(8);
+	CheckAndShift(4);
+	CheckAndShift(2);
+	CheckAndShift(1);
+	r += x;
 	return r;
 #endif
 }