From c9b01b1d6996962ef4b330b7c458f4f6971d4768 Mon Sep 17 00:00:00 2001
From: Erik Hofman <erik@ehofman.com>
Date: Fri, 16 Dec 2016 10:50:24 +0100
Subject: [PATCH] Enable SSE and SSE2 by default

---
 CMakeLists.txt                | 16 +++++++++++++++
 CMakeModules/DetectArch.cmake | 37 +++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 CMakeModules/DetectArch.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index afef3bceb..ada9241cb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -168,6 +168,7 @@ option(SYSTEM_FLITE      "Set to ON to build Flightgear with the system's Flite
 option(SYSTEM_HTS_ENGINE "Set to ON to build Flightgear with the system's HTS Engine library" ${SYSTEM_HTS_ENGINE_DEFAULT})
 option(FG_NIGHTLY        "Set to ON to mark this as a nightly build" OFF)
 option(ENABLE_DEV_WARNINGS "Set to ON to include developer-warnings" OFF)
+option(ENABLE_SIMD       "Enable SSE/SSE2 support for x86 compilers" ON)
 
 # additional utilities
 option(ENABLE_FGELEV     "Set to ON to build the fgelev application (default)" ON)
@@ -184,6 +185,8 @@ option(ENABLE_FLITE      "Set to ON to build the Flite text-to-speech module" ON
 option(ENABLE_QT         "Set to ON to build the internal Qt launcher" ON)
 option(ENABLE_TRAFFIC    "Set to ON to build the external traffic generator modules" ON)
 
+include (DetectArch)
+
 # when building an OSG with commit 15ec7e2ae7a8b983ecc44e1ce7363a9a9fa7da95
 # applied, we can use better link options
 option(OSG_FSTREAM_EXPORT_FIXED "Set to ON if the osgDB fstream export patch is applied" OFF)
@@ -332,9 +335,16 @@ endif(ENABLE_RTI)
 if(CMAKE_COMPILER_IS_GNUCXX)
     set(WARNING_FLAGS_CXX "-Wall")
     set(WARNING_FLAGS_C   "-Wall")
+
     if (CMAKE_VERSION VERSION_LESS 3.1)
        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
     endif()
+
+    if(ENABLE_SIMD)
+      if (X86 OR X86_64)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse3 -mfpmath=sse")
+      endif()
+    endif()
 endif(CMAKE_COMPILER_IS_GNUCXX)
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" )
@@ -356,6 +366,12 @@ if(WIN32)
 
     if(MSVC)
         set(MSVC_FLAGS "-DNOMINMAX -D_USE_MATH_DEFINES -D_CRT_SECURE_NO_WARNINGS -D_SCL_SECURE_NO_WARNINGS -D__CRT_NONSTDC_NO_WARNINGS /MP")
+        if(ENABLE_SIMD)
+          if (X86 OR X86_64)
+            set(MSVC_FLAGS "${MSVC_FLAGS} /arch:SSE /arch:SSE2 /Ox")
+          endif()
+        endif()
+
         if (NOT OSG_FSTREAM_EXPORT_FIXED AND ${MSVC_VERSION} GREATER 1599)
           message(STATUS "For better linking performance, use OSG with fixed fstream header")
           # needed to avoid link errors on multiply-defined standard C++
diff --git a/CMakeModules/DetectArch.cmake b/CMakeModules/DetectArch.cmake
new file mode 100644
index 000000000..33849d1a5
--- /dev/null
+++ b/CMakeModules/DetectArch.cmake
@@ -0,0 +1,37 @@
+IF(CMAKE_SYSTEM_PROCESSOR MATCHES amd64.*|x86_64.* OR CMAKE_GENERATOR MATCHES "Visual Studio.*Win64")
+  IF(CMAKE_C_FLAGS MATCHES -m32 OR CMAKE_CXX_FLAGS MATCHES -m32)
+    SET(X86 1)
+  ELSE(CMAKE_C_FLAGS MATCHES -m32 OR CMAKE_CXX_FLAGS MATCHES -m32)
+    SET(X86_64 1)
+  ENDIF(CMAKE_C_FLAGS MATCHES -m32 OR CMAKE_CXX_FLAGS MATCHES -m32)
+ELSEIF(CMAKE_SYSTEM_PROCESSOR MATCHES i686.*|i386.*|x86.* OR WIN32)
+  IF(CMAKE_C_FLAGS MATCHES -m64 OR CMAKE_CXX_FLAGS MATCHES -m64)
+    SET(X86_64 1)
+  ELSE(CMAKE_C_FLAGS MATCHES -m64 OR CMAKE_CXX_FLAGS MATCHES -m64)
+    SET(X86 1)
+  ENDIF(CMAKE_C_FLAGS MATCHES -m64 OR CMAKE_CXX_FLAGS MATCHES -m64)
+ELSEIF(CMAKE_SYSTEM_PROCESSOR MATCHES arm.* AND CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    SET(ARM 1)
+ELSEIF(CMAKE_SYSTEM_PROCESSOR MATCHES mips)
+    SET(MIPS 1)
+ENDIF()
+
+IF ("${CMAKE_C_COMPILER_ID}" STREQUAL "Clang")
+  # using Clang
+  SET(CLANG 1)
+ELSEIF ("${CMAKE_C_COMPILER_ID}" STREQUAL "TinyCC")
+  # using TinyCC
+  SET(TINYCC 1)
+ELSEIF ("${CMAKE_C_COMPILER_ID}" STREQUAL "GNU")
+  # using GCC
+  SET(GCC 1)
+ELSEIF ("${CMAKE_C_COMPILER_ID}" STREQUAL "Intel")
+  # using Intel C++
+  SET(INTELCC 1)
+ELSEIF ("${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC")
+  # using Visual Studio C++
+  SET(MSVC 1)
+ELSEIF ("${CMAKE_C_COMPILER_ID}" STREQUAL "MIPSpro")
+  # using SGI MIPSpro
+  SET(MIPSPRO 1)
+ENDIF()