btCpuFeatureUtility.h

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#ifndef BT_CPU_UTILITY_H
#define BT_CPU_UTILITY_H
 
#include "LinearMath/btScalar.h"
 
#include <string.h>  //memset
#ifdef USE_SIMD
#include <emmintrin.h>
#ifdef BT_ALLOW_SSE4
#include <intrin.h>
#endif  //BT_ALLOW_SSE4
#endif  //USE_SIMD
 
#if defined BT_USE_NEON
#define ARM_NEON_GCC_COMPATIBILITY 1
#include <arm_neon.h>
#include <sys/types.h>
#include <sys/sysctl.h>  //for sysctlbyname
#endif                   //BT_USE_NEON
 
class btCpuFeatureUtility
{
public:
        enum btCpuFeature
        {
                CPU_FEATURE_FMA3 = 1,
                CPU_FEATURE_SSE4_1 = 2,
                CPU_FEATURE_NEON_HPFP = 4
        };
 
        static int getCpuFeatures()
        {
                static int capabilities = 0;
                static bool testedCapabilities = false;
                if (0 != testedCapabilities)
                {
                        return capabilities;
                }
 
#ifdef BT_USE_NEON
                {
                        uint32_t hasFeature = 0;
                        size_t featureSize = sizeof(hasFeature);
                        int err = sysctlbyname("hw.optional.neon_hpfp", &hasFeature, &featureSize, NULL, 0);
                        if (0 == err && hasFeature)
                                capabilities |= CPU_FEATURE_NEON_HPFP;
                }
#endif  //BT_USE_NEON
 
#ifdef BT_ALLOW_SSE4
                {
                        int cpuInfo[4];
                        memset(cpuInfo, 0, sizeof(cpuInfo));
                        unsigned long long sseExt = 0;
                        __cpuid(cpuInfo, 1);
 
                        bool osUsesXSAVE_XRSTORE = cpuInfo[2] & (1 << 27) || false;
                        bool cpuAVXSuport = cpuInfo[2] & (1 << 28) || false;
 
                        if (osUsesXSAVE_XRSTORE && cpuAVXSuport)
                        {
                                sseExt = _xgetbv(0);
                        }
                        const int OSXSAVEFlag = (1UL << 27);
                        const int AVXFlag = ((1UL << 28) | OSXSAVEFlag);
                        const int FMAFlag = ((1UL << 12) | AVXFlag | OSXSAVEFlag);
                        if ((cpuInfo[2] & FMAFlag) == FMAFlag && (sseExt & 6) == 6)
                        {
                                capabilities |= btCpuFeatureUtility::CPU_FEATURE_FMA3;
                        }
 
                        const int SSE41Flag = (1 << 19);
                        if (cpuInfo[2] & SSE41Flag)
                        {
                                capabilities |= btCpuFeatureUtility::CPU_FEATURE_SSE4_1;
                        }
                }
#endif  //BT_ALLOW_SSE4
 
                testedCapabilities = true;
                return capabilities;
        }
};
 
#endif  //BT_CPU_UTILITY_H