mmx_ssesupport.h

该源码程序实现了intel MMX16位的底层控制功能,在vc环境下完成的。

// MMX_SSESupport.h

#pragma once

#define _MMX_FEATURE_BIT        0x00800000      // bit 23
#define _SSE_FEATURE_BIT        0x02000000      // bit 25

// Unnamed namespace is used instead of static function (new C++ standard).
// Basically, this function should be included to only one cpp file
// in the project to test MMX/SSE support when the program starts. 
// If it is included to more than one file, namespace prevents linker error.

namespace
{
    // Test MMX and SSE support using code fragments
    // from Visual Studio CPUID sample
    void TestFeatures(bool* pbMMX,              // [out] true - MMX is supported
                      bool* pbSSE)              // [out] true - SSE is supported
    {
        *pbMMX = false;
        *pbSSE = false;

        unsigned int dwFeature = 0;

        // test processor support
        __try 
        {
            _asm 
            {
                mov eax, 1
                cpuid
                mov dwFeature, edx      // this value defines support for MMX, SSE ...
            }
        }
        __except (EXCEPTION_EXECUTE_HANDLER) 
        {
            return;         // cpuid is not supported; MMX and SSE are not supported
        }

        if (dwFeature & _MMX_FEATURE_BIT )  // processor supports MMX
        {
            // test OS support for MMX
            __try 
            {
                _asm
                {
                    pxor mm0, mm0           // executing any MMX instruction
                    emms
                }

                *pbMMX = true;
            }
            __except (EXCEPTION_EXECUTE_HANDLER) 
            {
            }
        }

        if (dwFeature & _SSE_FEATURE_BIT )  // processor supports SSE
        {
            // test OS support for SSE
            __try 
            {
                _asm
                {
                    xorps xmm0, xmm0        // executing any SSE instruction
                }

                *pbSSE = true;
            }
            __except (EXCEPTION_EXECUTE_HANDLER) 
            {
            }
        }
    }
};