cpuid.c

音频编解码库的具体实现,分析流程清晰,编译测试通过

/*CPUID.C*/
#include <windows.h>
#include "defs.h"

#define _MMX_FEATURE_BIT        0x00800000
#define _SSE_FEATURE_BIT        0x02000000
#define _SSE2_FEATURE_BIT        0x04000000

// This bit is set when cpuid is called with
// register set to 80000001h (only applicable to AMD)
#define _3DNOW_FEATURE_BIT      0x80000000


typedef unsigned long    DWORD; 


int G722_IsCPUID()
{
    __try {
        _asm
        {
            xor eax, eax
            cpuid
        }
    } __except ( EXCEPTION_EXECUTE_HANDLER) {
        return 0;
    }
    return 1;
}

int G722_os_support(int feature)
{

    __try
    {
        switch (feature)
        {
        case _CPU_FEATURE_SSE:
            __asm {
                xorps xmm0, xmm0        // __asm _emit 0x0f __asm _emit 0x57 __asm _emit 0xc0
                                        // executing SSE instruction
            }
            break;
        case _CPU_FEATURE_SSE2:
            __asm {
                __asm _emit 0x66 __asm _emit 0x0f __asm _emit 0x57 __asm _emit 0xc0
                                        // xorpd xmm0, xmm0
                                        // executing WNI instruction
            }
            break;
        case _CPU_FEATURE_3DNOW:
            __asm {
                __asm _emit 0x0f __asm _emit 0x0f __asm _emit 0xc0 __asm _emit 0x96 
                                        // pfrcp mm0, mm0
                                        // executing 3Dnow instruction
            }
            break;
        case _CPU_FEATURE_MMX:
            __asm {
                pxor mm0, mm0           // executing MMX instruction
            }
            break;
        }
    } __except (EXCEPTION_EXECUTE_HANDLER) {
        if (_exception_code() == STATUS_ILLEGAL_INSTRUCTION) {
            return (0);
        }
        return (0);
    }
    return 1;
}

int G722_GetCPUID ()
{

    DWORD dwStandard = 0;
    DWORD dwFeature = 0;
    DWORD dwMax = 0;
    DWORD dwExt = 0;
    int feature = 0, os_support = 0;
    union
    {
        char cBuf[12+1];
        struct
        {
            DWORD dw0;
            DWORD dw1;
            DWORD dw2;
        };
    } Ident;

    if (!G722_IsCPUID())
    {
        return 0;
    }

    _asm
    {
        push ebx
        push ecx
        push edx

        // get the vendor string
        xor eax,eax
        cpuid
        mov dwMax,eax
        mov Ident.dw0,ebx
        mov Ident.dw1,edx
        mov Ident.dw2,ecx

        // get the Standard bits
        mov eax,1
        cpuid
        mov dwStandard,eax
        mov dwFeature,edx

        // get AMD-specials
        mov eax,80000000h
        cpuid
        cmp eax,80000000h
        jc notamd
        mov eax,80000001h
        cpuid
        mov dwExt,edx

notamd:
        pop ecx
        pop ebx
        pop edx
    }

    if (dwFeature & _MMX_FEATURE_BIT)
    {
        feature |= _CPU_FEATURE_MMX;
        if (G722_os_support(_CPU_FEATURE_MMX))
            os_support |= _CPU_FEATURE_MMX;
    }
    if (dwExt & _3DNOW_FEATURE_BIT)
    {
        feature |= _CPU_FEATURE_3DNOW;
        if (G722_os_support(_CPU_FEATURE_3DNOW))
            os_support |= _CPU_FEATURE_3DNOW;
    }
    if (dwFeature & _SSE_FEATURE_BIT)
    {
        feature |= _CPU_FEATURE_SSE;
        if (G722_os_support(_CPU_FEATURE_SSE))
            os_support |= _CPU_FEATURE_SSE;
    }
    if (dwFeature & _SSE2_FEATURE_BIT)
    {
        feature |= _CPU_FEATURE_SSE2;
        if (G722_os_support(_CPU_FEATURE_SSE2))
            os_support |= _CPU_FEATURE_SSE2;
    }    
	__asm emms;
	return feature;
}