//--------------------------------------------------------------------------
// Rob Wyatt for Game Developer/Gamasutra April 1999
//--------------------------------------------------------------------------
#include "Windows.h"
#include "Detect.h"
#include "KNI.h"

//--------------------------------------------------------------------------
CDetect::CDetect
(
)
: SIMDPresent(false),OSSupport(false),OSExceptions(false),DetectStatus(true),
  SerialPresent(false)
//---------------------------
{
    //
    // First detect the presence of the new SIMD instructions
    //
    __try
    {
        SIMDPresent = DetectFeatureBit(25);
    }
    __except(EXCEPTION_EXECUTE_HANDLER)
    {
        DetectStatus = false;
    }

    // We do not have SIMD so there is no point in continuing.
    if (!SIMDPresent)
        return;

    //
    // Check for OS support
    //
    __try
    {
        _asm
        {
            //Execute a Streaming SIMD instruction and see if an
            //exception occurs. If the exception is an unknown
            //op-code then SIMD is not supported by the OS.
            ADDPS(_XMM0,_XMM1)
        }
        OSSupport = true;
    }
    __except(EXCEPTION_EXECUTE_HANDLER)
    {
        if (_exception_code() != STATUS_ILLEGAL_INSTRUCTION)
        {
            DetectStatus = false;
        }
    }

    //
    // Detect the exception support
    //
    OSExceptions = DetectExceptionSupport();

    //
    // Check if a serial number is present
    //
    __try
    {
        SerialPresent = DetectFeatureBit(18);
    }
    __except(EXCEPTION_EXECUTE_HANDLER)
    {
        DetectStatus = false;
    }

    //
    // Now if the serial number bit is set then try to read it
    // but trap any possible exceptions just in case
    //
    if (SerialPresent)
    {
        __try
        {
            ReadSerialNumber(SerialNumber);
        }
        __except(EXCEPTION_EXECUTE_HANDLER)
        {
            DetectStatus = false;
            SerialPresent = false;
        }
    }
}



//--------------------------------------------------------------------------
bool CDetect::DetectExceptionSupport
(
)
//---------------------------
{
    bool    exception_support = true;

    float   test_val[4] = {1.0f, 1.0f, 1.0f, 1.0f};
    DWORD   control;
    DWORD   control_original;

    __try
    {
        _asm
        {
            // Enable divide by zero exceptions by clearing
            // bit 9 in the SIMD control register.
            push    ebp
            lea     ebp,control
            STMXCSR
            mov     eax, DWORD PTR [ebp]
            and     DWORD PTR [ebp], 0fffffdffh
            LDMXCSR
            pop     ebp
            mov     control_original, eax

            // clear XMM0, all bits being 0 is 0.0 in floating point
            lea     eax,test_val
            XORPS   (_XMM0,_XMM0)
            MOVUPS  (_XMM1,EAX_PTR)
            DIVPS   (_XMM1,_XMM0)
        }
    }
    __except(EXCEPTION_EXECUTE_HANDLER) 
    {
        // The divide by zero above has caused an illegal instruction
        // exception so the OS must not support SIMD exceptions.
        if (_exception_code() == STATUS_ILLEGAL_INSTRUCTION)
        {
            exception_support = false;
        }
    }

    //
    // Put the original SIMD register back
    //
    _asm
    {    
        push    ebp
        lea     ebp,control_original
        LDMXCSR
        pop     ebp
    }

    return exception_support;
}


//--------------------------------------------------------------------------
bool CDetect::DetectFeatureBit
(
    DWORD   bit
)
//---------------------------
{
    bool    found;
    DWORD   test_bit = 1<<bit;

    _asm
    {
        pushfd
        pop     eax             // get EFLAGS into eax
        mov     ebx,eax         // kep a copy
        xor     eax,0x200000    // toggle CPUID bit
        push    eax
        popfd                   // set new EFLAGS
        pushfd
        pop     eax             // EFLAGS back into eax
        xor     eax,ebx         // have we changed the ID bit?
        je      NO_FEATURE
        // we could toggle the bit so CPUID is present
        mov     eax,1
        cpuid                   // get processor features
        test    edx,test_bit    // check the required bit
        jz      NO_FEATURE
        mov     found,1    
        jmp     DONE
NO_FEATURE:
        mov     found,0
DONE:
    }

    return found;
}



//------------------------------------------------------------------------------
// Only call this once you have determined that the serial number feature
// is present.
void CDetect::ReadSerialNumber
(
    DWORD*  serial
)
//---------------------------
{
    DWORD   t,m,b;
    
    _asm
    {
        mov     eax,1
        cpuid
        mov     t,eax       // top 32 bits are the processor signature bits

        mov     eax,3
        cpuid
        mov     m,edx
        mov     b,ecx
    }

    // copy the locals into the pointer variables passed in
    serial[SN_BOTTOM] = b;
    serial[SN_MIDDLE] = m;
    serial[SN_TOP] = t;
}