cpu.cpp

一款C++小游戏的源代码

#include <stdio.h>
#include <string.h>
#include "gl.h"

extern CPUInfo cpu = { 
	"NoVendorName",
	0, 0,
	false,
	false,
	false,
	false };

//  Checks whether the cpuid instruction is available.
// return:     0: not supported     1: supported
static int IsCpuidSupported( void )
{
	int result;
	_asm{
		pushfd;                    /* get extended flags */
		pop eax;
		mov ebx, eax;         	/* save current flags */
		xor eax, 0x200000;     	/* toggle bit 21 */
		push eax;	               /* put new flags on stack */
		popfd;                     /* flags updated now in flags */
		pushfd;                    /* get extended flags */
		pop eax;
		xor ebx, eax;         /* if bit 21 r/w then supports cpuid */
		jz nocpuid;
		mov result, 1;
		jmp iscpuid_end;
	nocpuid:
		mov result, 0;
	iscpuid_end:
	}

   return result;
}

#define CPUID __asm _emit 0x0F _asm _emit 0xA2

static void GetCpuidInfo(long cpuid_levels, long *eax, long *ebx, long *ecx, long *edx)
{ 
	int a, b, c, d;
	
	__asm{
		mov eax, cpuid_levels
		CPUID;
		mov a, eax
		mov b, ebx
		mov c, ecx
		mov d, edx;
	}

	*eax = a;
	*ebx = b;
	*ecx = c;
	*edx = d;
}

#undef CPUID

//Returns TRUE if this is a Cyrix processor.
static int IsCyrix( void )
{
	int result;

	__asm{
		xor ax, ax;
		sahf;                      /* bit 1 is always 1 in flags */
		mov ax, 5;
		mov bx, 2;
		div bl;                    /* this does not change flags */
		lahf;                      /* get flags */
		cmp ah, 2;                 /* check for change in flags */
		jne notcyrix;              /* flags changed not Cyrix */
		mov result, 1;                /* TRUE Cyrix CPU */
		jmp iscyrix_end;
	notcyrix:
		mov result, 0;                /* FALSE NON-Cyrix CPU */
	iscyrix_end:
	}

   return result;
}

// Returns TRUE if the CPU has floating point hardware.
static int IsFpu( void )
{
	int result;

	__asm{
		fninit;
		mov eax, 0x5a5a;
		fnstsw ax;
		cmp eax, 0;
		jne nofpu;
		mov result, 1;
		jmp isfpu_end;
	nofpu:
		mov result, 0;
	isfpu_end:
	}
	return result;
}

void CheckCPU( void )
{// I'm only concern about whether this CPU is Pentium-class+ 
// whether MMX and 3dnow are supported.

	long cpuid_levels;
	long eax0, ebx0, ecx0, edx0;
	
	if( IsCpuidSupported() ){
		cpu.cpuid = true;
		eax0 = ebx0 = ecx0 = 0;
		GetCpuidInfo( 0, &eax0, &ebx0, &ecx0, &edx0 );
		*(long*)(&cpu.vendor[0]) = ebx0;
		*(long*)(&cpu.vendor[4]) = edx0;
		*(long*)(&cpu.vendor[8]) = ecx0;
		cpu.vendor[12] = '\0';
		cpuid_levels = eax0;
		//printf( "%s ", cpu.vendor );
		
		if( cpuid_levels != 0 ){
			eax0 = ebx0 = ecx0 = edx0 = 0;
			GetCpuidInfo( 1, &eax0, &ebx0, &ecx0, &edx0 );
			cpu.family = ( eax0 & 0xf00 ) >> 8;
			cpu.model = ( eax0 & 0xf0 ) >> 4;
			cpu.fpu = ( edx0 & 1 ? true : false );
			cpu.mmx = ( edx0 & 0x800000 ? true : false );
			//printf( "CPU family:%d, model:%d\n", cpu.family, cpu.model );
			//if( cpu.mmx )
			//	printf( "%s ", "MMX" );
		}
		
		GetCpuidInfo( 0x80000000, &eax0, &ebx0, &ecx0, &edx0 );
		if( eax0 & 0x80000000 ){
			GetCpuidInfo( 0x80000001, &eax0, &ebx0, &ecx0, &edx0 );
			cpu._3dnow = ( edx0 & 0x80000000 ? true : false );
			//if( cpu._3dnow )
				//printf( "%s ", "3DNow!" );
		}
		if( IsCyrix() )
			cpu.model = 14;
	}
	else{
	// If this CPU does not support instruction CPUID, 
	// I just look it as x486.
		cpu.family = 4;
		cpu.fpu = IsFpu();
	}
}