From 4066443d897cfbaddbe4ae25de92e5850d63e347 Mon Sep 17 00:00:00 2001
From: Beman <bdawes@acm.org>
Date: Thu, 16 May 2013 10:40:18 -0400
Subject: [PATCH] Rework intrinsic.hpp to handle GCC and Clang __builtin_bswap*
 if available. Add test program.

---
 include/boost/endian/detail/intrinsic.hpp | 55 ++++++++++++++++-------
 test/converter_test.cpp                   |  2 +
 test/intrinsic_test.cpp                   | 24 ++++++++++
 3 files changed, 66 insertions(+), 15 deletions(-)
 create mode 100644 test/intrinsic_test.cpp

diff --git a/include/boost/endian/detail/intrinsic.hpp b/include/boost/endian/detail/intrinsic.hpp
index a1a83cf..c98aec0 100644
--- a/include/boost/endian/detail/intrinsic.hpp
+++ b/include/boost/endian/detail/intrinsic.hpp
@@ -1,27 +1,52 @@
-// Copyright (C) 2012 David Stone
-// Distributed under the Boost Software License, Version 1.0.
-// http://www.boost.org/LICENSE_1_0.txt
-//
-// See http://www.boost.org/libs/endian/ for documentation.
+//  endian/detail/intrinsic.hpp  -------------------------------------------------------//
+
+//  Copyright (C) 2012 David Stone
+//  Copyright Beman Dawes 2013
+
+//  Distributed under the Boost Software License, Version 1.0.
+//  http://www.boost.org/LICENSE_1_0.txt
 
 #ifndef BOOST_ENDIAN_INTRINSIC_HPP
 #define BOOST_ENDIAN_INTRINSIC_HPP
 
-#if ((defined __GNUC__ && !defined(__MINGW32__)) || defined __clang__)
-    #include <byteswap.h>
-    #define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2 bswap_16
-    #define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4 bswap_32
-    #define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8 bswap_64
+#ifndef __has_builtin         // Optional of course
+  #define __has_builtin(x) 0  // Compatibility with non-clang compilers
+#endif
+
+#if (defined(__clang__) && __has_builtin(__builtin_bswap16)) \
+  || (defined(__GNUC__ ) && \
+  (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
+# define BOOST_ENDIAN_INTRINSIC_MSG "__builtin_bswap16, etc."
+
+// prior to 4.8, gcc did not provide __builtin_bswap16 on some platforms so we emulate it
+// see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624
+# if defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)
+#   define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) __builtin_bswap16(x)
+# else
+#   define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) __builtin_bswap32((x) << 16)
+# endif
+
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x) __builtin_bswap32(x)
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x) __builtin_bswap64(x)
+
+#elif ((defined __GNUC__ && !defined(__MINGW32__)) || defined(__clang__))
+# define BOOST_ENDIAN_INTRINSIC_MSG "__builtin_bswap_16, etc."
+# include <byteswap.h>
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) bswap_16(x)
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x) bswap_32(x)
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x) bswap_64(x)
 
 #elif defined _MSC_VER
 //  Microsoft documents these as being compatible since Windows 95 and specificly
 //  lists runtime library support since Visual Studio 2003 (aka 7.1).
-    #include <cstdlib>
-    #define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2 _byteswap_ushort
-    #define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4 _byteswap_ulong
-    #define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8 _byteswap_uint64
+# define BOOST_ENDIAN_INTRINSIC_MSG "_byteswap_ushort, etc."
+# include <cstdlib>
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x) _byteswap_ushort(x)
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x) _byteswap_ulong(x)
+# define BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x) _byteswap_uint64(x)
 #else
-    #define BOOST_ENDIAN_NO_INTRINSICS
+# define BOOST_ENDIAN_NO_INTRINSICS
+# define BOOST_ENDIAN_INTRINSIC_MSG "no byte swap intrinsics"
 #endif
 
 #endif // BOOST_ENDIAN_INTRINSIC_HPP
diff --git a/test/converter_test.cpp b/test/converter_test.cpp
index b920e04..76e9bb7 100644
--- a/test/converter_test.cpp
+++ b/test/converter_test.cpp
@@ -239,6 +239,8 @@ namespace
 
 int cpp_main(int, char * [])
 {
+  cout << "byte swap intrinsics: " BOOST_ENDIAN_INTRINSIC_MSG << endl;
+  
   //std::cerr << std::hex;
 
   cout << "int16_t" << endl;
diff --git a/test/intrinsic_test.cpp b/test/intrinsic_test.cpp
new file mode 100644
index 0000000..90a32fb
--- /dev/null
+++ b/test/intrinsic_test.cpp
@@ -0,0 +1,24 @@
+//  Copyright Beman Dawes 2013
+
+//  Distributed under the Boost Software License, Version 1.0.
+//  http://www.boost.org/LICENSE_1_0.txt
+
+#include "intrinsic.hpp"
+#include <iostream>
+#include <cassert>
+#include <cstdint>
+
+int main()
+{
+  std::cout << "BOOST_ENDIAN_INTRINSIC_MSG: " BOOST_ENDIAN_INTRINSIC_MSG << std::endl;
+
+#ifndef BOOST_ENDIAN_NO_INTRINSICS
+  uint16_t x2 = 0x1122U;
+  assert(BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_2(x2) == 0x2211U);
+  uint32_t x4 = 0x11223344UL;
+  assert(BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_4(x4) == 0x44332211UL);
+  uint64_t x8 = 0x1122334455667788U;
+  assert(BOOST_ENDIAN_INTRINSIC_BYTE_SWAP_8(x8) == 0x8877665544332211ULL);
+#endif
+  return 0;
+}