From afb5aecfa44b47455428eeeb2830767a89174286 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Mon, 6 Mar 2023 11:35:32 -0800
Subject: [PATCH] Coalesce `_Byteswap_meow` and `byteswap`, follow Standard
 order.

This was introduced by GH 2235. We didn't mention Standard order while
reviewing. It appears that the rationale for separating the helpers from
the Standard function was that this grouped Standard functions together.
---
 stl/inc/bit | 88 ++++++++++++++++++++++++++---------------------------
 1 file changed, 43 insertions(+), 45 deletions(-)

diff --git a/stl/inc/bit b/stl/inc/bit
index b4ecd911d05..56b5753237c 100644
--- a/stl/inc/bit
+++ b/stl/inc/bit
@@ -34,6 +34,49 @@ _NODISCARD constexpr _To bit_cast(const _From& _Val) noexcept {
     return __builtin_bit_cast(_To, _Val);
 }
 
+#if _HAS_CXX23
+_NODISCARD constexpr unsigned short _Byteswap_ushort(const unsigned short _Val) noexcept {
+    if (_STD is_constant_evaluated()) {
+        return static_cast<unsigned short>((_Val << 8) | (_Val >> 8));
+    } else {
+        return _byteswap_ushort(_Val);
+    }
+}
+
+_NODISCARD constexpr unsigned long _Byteswap_ulong(const unsigned long _Val) noexcept {
+    if (_STD is_constant_evaluated()) {
+        return (_Val << 24) | ((_Val << 8) & 0x00FF'0000) | ((_Val >> 8) & 0x0000'FF00) | (_Val >> 24);
+    } else {
+        return _byteswap_ulong(_Val);
+    }
+}
+
+_NODISCARD constexpr unsigned long long _Byteswap_uint64(const unsigned long long _Val) noexcept {
+    if (_STD is_constant_evaluated()) {
+        return (_Val << 56) | ((_Val << 40) & 0x00FF'0000'0000'0000) | ((_Val << 24) & 0x0000'FF00'0000'0000)
+             | ((_Val << 8) & 0x0000'00FF'0000'0000) | ((_Val >> 8) & 0x0000'0000'FF00'0000)
+             | ((_Val >> 24) & 0x0000'0000'00FF'0000) | ((_Val >> 40) & 0x0000'0000'0000'FF00) | (_Val >> 56);
+    } else {
+        return _byteswap_uint64(_Val);
+    }
+}
+
+_EXPORT_STD template <class _Ty, enable_if_t<is_integral_v<_Ty>, int> = 0>
+_NODISCARD constexpr _Ty byteswap(const _Ty _Val) noexcept {
+    if constexpr (sizeof(_Ty) == 1) {
+        return _Val;
+    } else if constexpr (sizeof(_Ty) == 2) {
+        return static_cast<_Ty>(_Byteswap_ushort(static_cast<unsigned short>(_Val)));
+    } else if constexpr (sizeof(_Ty) == 4) {
+        return static_cast<_Ty>(_Byteswap_ulong(static_cast<unsigned long>(_Val)));
+    } else if constexpr (sizeof(_Ty) == 8) {
+        return static_cast<_Ty>(_Byteswap_uint64(static_cast<unsigned long long>(_Val)));
+    } else {
+        static_assert(_Always_false<_Ty>, "Unexpected integer size");
+    }
+}
+#endif // _HAS_CXX23
+
 _EXPORT_STD template <class _Ty, enable_if_t<_Is_standard_unsigned_integer<_Ty>, int> = 0>
 _NODISCARD constexpr int countl_zero(_Ty _Val) noexcept;
 
@@ -261,34 +304,6 @@ _NODISCARD int _Checked_arm_arm64_countl_zero(const _Ty _Val) noexcept {
 }
 #endif // defined(_M_ARM) || defined(_M_ARM64)
 
-#if _HAS_CXX23
-_NODISCARD constexpr unsigned short _Byteswap_ushort(const unsigned short _Val) noexcept {
-    if (_STD is_constant_evaluated()) {
-        return static_cast<unsigned short>((_Val << 8) | (_Val >> 8));
-    } else {
-        return _byteswap_ushort(_Val);
-    }
-}
-
-_NODISCARD constexpr unsigned long _Byteswap_ulong(const unsigned long _Val) noexcept {
-    if (_STD is_constant_evaluated()) {
-        return (_Val << 24) | ((_Val << 8) & 0x00FF'0000) | ((_Val >> 8) & 0x0000'FF00) | (_Val >> 24);
-    } else {
-        return _byteswap_ulong(_Val);
-    }
-}
-
-_NODISCARD constexpr unsigned long long _Byteswap_uint64(const unsigned long long _Val) noexcept {
-    if (_STD is_constant_evaluated()) {
-        return (_Val << 56) | ((_Val << 40) & 0x00FF'0000'0000'0000) | ((_Val << 24) & 0x0000'FF00'0000'0000)
-             | ((_Val << 8) & 0x0000'00FF'0000'0000) | ((_Val >> 8) & 0x0000'0000'FF00'0000)
-             | ((_Val >> 24) & 0x0000'0000'00FF'0000) | ((_Val >> 40) & 0x0000'0000'0000'FF00) | (_Val >> 56);
-    } else {
-        return _byteswap_uint64(_Val);
-    }
-}
-#endif // _HAS_CXX23
-
 _EXPORT_STD template <class _Ty, enable_if_t<_Is_standard_unsigned_integer<_Ty>, int> _Enabled>
 _NODISCARD constexpr int countl_zero(const _Ty _Val) noexcept {
 #if defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
@@ -324,23 +339,6 @@ _NODISCARD constexpr int popcount(const _Ty _Val) noexcept {
     return _Popcount(_Val);
 }
 
-#if _HAS_CXX23
-_EXPORT_STD template <class _Ty, enable_if_t<is_integral_v<_Ty>, int> = 0>
-_NODISCARD constexpr _Ty byteswap(const _Ty _Val) noexcept {
-    if constexpr (sizeof(_Ty) == 1) {
-        return _Val;
-    } else if constexpr (sizeof(_Ty) == 2) {
-        return static_cast<_Ty>(_Byteswap_ushort(static_cast<unsigned short>(_Val)));
-    } else if constexpr (sizeof(_Ty) == 4) {
-        return static_cast<_Ty>(_Byteswap_ulong(static_cast<unsigned long>(_Val)));
-    } else if constexpr (sizeof(_Ty) == 8) {
-        return static_cast<_Ty>(_Byteswap_uint64(static_cast<unsigned long long>(_Val)));
-    } else {
-        static_assert(_Always_false<_Ty>, "Unexpected integer size");
-    }
-}
-#endif // _HAS_CXX23
-
 _EXPORT_STD enum class endian { little = 0, big = 1, native = little };
 
 _STD_END