Implement workaround for Windows versions which do not support XSAVE.

Fixes CRT math routines using FMA instructions from causing illegal instructions.

Source/Core/Common/Common.vcxproj

@@ -125,6 +125,7 @@
     <ClCompile Include="x64CPUDetect.cpp" />
     <ClCompile Include="x64Emitter.cpp" />
     <ClCompile Include="x64FPURoundMode.cpp" />
+    <ClCompile Include="XSaveWorkaround.cpp" />
   </ItemGroup>
   <ItemGroup>
     <Text Include="CMakeLists.txt" />

Source/Core/Common/Common.vcxproj.filters

@@ -103,6 +103,7 @@
       <Filter>Logging</Filter>
     </ClCompile>
     <ClCompile Include="stdafx.cpp" />
+    <ClCompile Include="XSaveWorkaround.cpp" />
   </ItemGroup>
   <ItemGroup>
     <Text Include="CMakeLists.txt" />

Source/Core/Common/XSaveWorkaround.cpp

@@ -0,0 +1,40 @@
+// Copyright 2013 Dolphin Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+
+#if defined(_WIN32) && defined(_ARCH_64)
+
+#include <math.h>
+#include <Windows.h>
+
+// This puts the rest of this translation unit into a segment which is
+// initialized by the CRT *before* any of the other code (including C++
+// static initializers).
+#pragma warning(disable : 4075)
+#pragma init_seg(".CRT$XCB")
+
+struct EnableXSaveWorkaround
+{
+	EnableXSaveWorkaround()
+	{
+		// Some Windows environments may have hardware support for AVX/FMA,
+		// but the OS does not support it. The CRT math library does not support
+		// this scenario, so we have to manually tell it not to use FMA3
+		// instructions.
+
+		// The API name is somewhat misleading - we're testing for OS support
+		// here.
+		if (!IsProcessorFeaturePresent(PF_XSAVE_ENABLED))
+		{
+			_set_FMA3_enable(0);
+		}
+	}
+};
+
+static EnableXSaveWorkaround enableXSaveWorkaround;
+
+// N.B. Any code after this will still be in the .CRT$XCB segment. Please just
+// do not append any code here unless it is intended to be executed before
+// static initializers.
+
+#endif