Add the GPU rigid body pipeline from https://github.com/erwincoumans/experiments as a Bullet 3.x preview for Bullet 2.80

Extras/RigidBodyGpuPipeline/opencl/opengl_interop/btStopwatch.cpp

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+/*
+Stopwatch for timing and profiling for the Bullet Physics Library, http://bulletphysics.org
+Copyright (c) 2003-2011 Erwin Coumans
+
+This software is provided 'as-is', without any express or implied warranty.
+In no event will the authors be held liable for any damages arising from the use of this software.
+Permission is granted to anyone to use this software for any purpose, 
+including commercial applications, and to alter it and redistribute it freely, 
+subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "btStopwatch.h"
+
+
+#ifdef __CELLOS_LV2__
+#include <sys/sys_time.h>
+#include <sys/time_util.h>
+#include <stdio.h>
+#endif
+
+#if defined (SUNOS) || defined (__SUNOS__) 
+#include <stdio.h> 
+#endif
+
+#if defined(WIN32) || defined(_WIN32)
+
+#define BT_USE_WINDOWS_TIMERS
+#define WIN32_LEAN_AND_MEAN
+#define NOWINRES
+#define NOMCX
+#define NOIME 
+
+#ifdef _XBOX
+	#include <Xtl.h>
+#else //_XBOX
+	#include <windows.h>
+#endif //_XBOX
+
+#include <time.h>
+
+
+#else //_WIN32
+#include <sys/time.h>
+#endif //_WIN32
+
+#define mymin(a,b) (a > b ? a : b)
+
+struct btStopwatchData
+{
+
+#ifdef BT_USE_WINDOWS_TIMERS
+	LARGE_INTEGER mClockFrequency;
+	DWORD mStartTick;
+	LONGLONG mPrevElapsedTime;
+	LARGE_INTEGER mStartTime;
+#else
+#ifdef __CELLOS_LV2__
+	uint64_t	mStartTime;
+#else
+	struct timeval mStartTime;
+#endif
+#endif //__CELLOS_LV2__
+
+};
+
+
+btStopwatch::btStopwatch()
+{
+	m_data = new btStopwatchData;
+#ifdef BT_USE_WINDOWS_TIMERS
+	QueryPerformanceFrequency(&m_data->mClockFrequency);
+#endif
+	reset();
+}
+
+btStopwatch::~btStopwatch()
+{
+	delete m_data;
+}
+
+btStopwatch::btStopwatch(const btStopwatch& other)
+{
+	m_data = new btStopwatchData;
+	*m_data = *other.m_data;
+}
+
+btStopwatch& btStopwatch::operator=(const btStopwatch& other)
+{
+	*m_data = *other.m_data;
+	return *this;
+}
+
+
+	/// Resets the initial reference time.
+void btStopwatch::reset()
+{
+#ifdef BT_USE_WINDOWS_TIMERS
+	QueryPerformanceCounter(&m_data->mStartTime);
+	m_data->mStartTick = GetTickCount();
+	m_data->mPrevElapsedTime = 0;
+#else
+#ifdef __CELLOS_LV2__
+
+	typedef uint64_t  ClockSize;
+	ClockSize newTime;
+	//__asm __volatile__( "mftb %0" : "=r" (newTime) : : "memory");
+	SYS_TIMEBASE_GET( newTime );
+	m_data->mStartTime = newTime;
+#else
+	gettimeofday(&m_data->mStartTime, 0);
+#endif
+#endif
+}
+
+/// Returns the time in ms since the last call to reset or since 
+/// the btStopwatch was created.
+float btStopwatch::getTimeMilliseconds()
+{
+	return getTimeMicroseconds()/1000.f;
+}
+
+	/// Returns the time in us since the last call to reset or since 
+	/// the stopwatch was created.
+unsigned long int btStopwatch::getTimeMicroseconds()
+{
+#ifdef BT_USE_WINDOWS_TIMERS
+		LARGE_INTEGER currentTime;
+		QueryPerformanceCounter(&currentTime);
+		LONGLONG elapsedTime = currentTime.QuadPart - m_data->mStartTime.QuadPart;
+
+		// Compute the number of millisecond ticks elapsed.
+		unsigned long msecTicks = (unsigned long)(1000 * elapsedTime / m_data->mClockFrequency.QuadPart);
+
+		// Check for unexpected leaps in the Win32 performance counter.  
+		// (This is caused by unexpected data across the PCI to ISA 
+		// bridge, aka south bridge.  See Microsoft KB274323.)
+		unsigned long elapsedTicks = GetTickCount() - m_data->mStartTick;
+		signed long msecOff = (signed long)(msecTicks - elapsedTicks);
+		if (msecOff < -100 || msecOff > 100)
+		{
+			// Adjust the starting time forwards.
+			LONGLONG msecAdjustment = mymin(msecOff * 
+				m_data->mClockFrequency.QuadPart / 1000, elapsedTime - 
+				m_data->mPrevElapsedTime);
+			m_data->mStartTime.QuadPart += msecAdjustment;
+			elapsedTime -= msecAdjustment;
+		}
+
+		// Store the current elapsed time for adjustments next time.
+		m_data->mPrevElapsedTime = elapsedTime;
+
+		// Convert to microseconds.
+		unsigned long usecTicks = (unsigned long)(1000000 * elapsedTime / 
+			m_data->mClockFrequency.QuadPart);
+
+		return usecTicks;
+#else
+
+#ifdef __CELLOS_LV2__
+		uint64_t freq=sys_time_get_timebase_frequency();
+		double dFreq=((double) freq)/ 1000000.0;
+		typedef uint64_t  ClockSize;
+		ClockSize newTime;
+		//__asm __volatile__( "mftb %0" : "=r" (newTime) : : "memory");
+		SYS_TIMEBASE_GET( newTime );
+
+		return (unsigned long int)((double(newTime-m_data->mStartTime)) / dFreq);
+#else
+
+		struct timeval currentTime;
+		gettimeofday(&currentTime, 0);
+		return (currentTime.tv_sec - m_data->mStartTime.tv_sec) * 1000000 + (currentTime.tv_usec - m_data->mStartTime.tv_usec);
+#endif//__CELLOS_LV2__
+#endif 
+}
+
+
+