HostCPU.cc

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#include "HostCPU.hh"
#include "openmsx.hh"
#include <cassert>
#ifdef _MSC_VER
#include <intrin.h>
#endif

namespace HostCPU {

// Initially assume no CPU feature support
bool mmxFlag  = false;
bool sseFlag  = false;
bool sse2Flag = false;

/*static*/ // to avoid 'unsused static function' compiler warning on x86_64
void setFeatures(unsigned features)
{
        const unsigned CPUID_FEATURE_MMX  = 0x00800000;
        const unsigned CPUID_FEATURE_SSE  = 0x02000000;
        const unsigned CPUID_FEATURE_SSE2 = 0x04000000;

        mmxFlag  = (features & CPUID_FEATURE_MMX)  != 0;
        sseFlag  = (features & CPUID_FEATURE_SSE)  != 0;
        sse2Flag = (features & CPUID_FEATURE_SSE2) != 0;
}

void init()
{
        #ifdef __x86_64
        // X86_64 machines always have mmx, sse, sse2
        mmxFlag  = true;
        sseFlag  = true;
        sse2Flag = true;
        #elif ASM_X86_32
        #ifdef _MSC_VER
        unsigned hasCPUID;
        __asm {
                // Load EFLAGS into EAX
                pushfd
                pop             eax
                // Save current value.
                mov             ecx,eax
                // Toggle bit 21.
                xor             eax,200000h
                // Load EAX into EFLAGS.
                push    eax
                popfd
                // Load EFLAGS into EAX.
                pushfd
                pop             eax
                // Did bit 21 change?
                xor             eax,ecx
                and             eax,200000h
                mov             hasCPUID,eax
        }
        if (hasCPUID) {
                int cpuInfo[4];
                __cpuid(cpuInfo, 0);
                if (cpuInfo[0] >= 1) {
                        __cpuid(cpuInfo, 1);
                        setFeatures(cpuInfo[3]);
                }
        }
        #else
                // Note: On Mac OS X, EBX is in use by the OS,
                //       so we have to restore it.
                // Is CPUID instruction supported?
                unsigned hasCPUID;
                asm (
                        // Load EFLAGS into EAX.
                        "pushfl;"
                        "popl   %%eax;"
                        // Save current value.
                        "movl   %%eax,%%ecx;"
                        // Toggle bit 21.
                        "xorl   $0x200000, %%eax;"
                        // Load EAX into EFLAGS.
                        "pushl  %%eax;"
                        "popfl;"
                        // Load EFLAGS into EAX.
                        "pushfl;"
                        "popl   %%eax;"
                        // Did bit 21 change?
                        "xor    %%ecx, %%eax;"
                        "andl   $0x200000, %%eax;"
                        : "=a" (hasCPUID) // 0
                        : // no input
                        : "ecx"
                        );
                if (hasCPUID) {
                        // Which CPUID calls are supported?
                        unsigned highest;
                        asm (
                                "pushl  %%ebx;"
                                "cpuid;"
                                "popl   %%ebx;"
                                : "=a" (highest) // 0
                                : "0" (0) // 1: function
                                : "ecx", "edx"
                        );
                        if (highest >= 1) {
                                // Get features flags.
                                unsigned features;
                                asm (
                                        "pushl  %%ebx;"
                                        "cpuid;"
                                        "popl   %%ebx;"
                                        : "=d" (features) // 0
                                        : "a" (1) // 1: function
                                        : "ecx"
                                );
                                setFeatures(features);
                        }
                }
        #endif
        #endif

        PRT_DEBUG("MMX:  " << mmxFlag);
        PRT_DEBUG("SSE:  " << sseFlag);
        PRT_DEBUG("SSE2: " << sse2Flag);

        if (hasSSE2()) { assert(hasMMX() && hasSSE()); }
        if (hasSSE())  { assert(hasMMX()); }
}

} // namespace openmsx