How to Reliably Detect SSE3 Support in C ?

Checking for SSE3 Support in C

Your provided code snippet utilizes the __cpuid instruction to determine if the CPU supports the SSE3 instruction set. However, you've encountered limitations with using IsProcessorFeaturePresent() on Windows XP. Here's a more comprehensive approach to detecting SSE3 support:

#include <intrin.h>

bool CheckSSE3()
{
    int cpuInfo[4];
    int cpuidCount;

    // Get the number of valid info IDs
    __cpuid(cpuInfo, 0);
    cpuidCount = cpuInfo[0];

    // Check for SSE3 support if the CPU has at least one info ID
    if (cpuidCount >= 1)
    {
        __cpuid(cpuInfo, 1);
        bool sse3Support = (cpuInfo[2] & 0x1);
        return sse3Support;
    }

    return false;
}

Optimized Approach

For enhanced performance, consider the following:

1. Use intrinsics: Directly access the __cpuid instruction using intrinsics like _mm_lfence, _mm_sfence, and _mm_mfence.
2. Cache the result: Store the SSE3 support state in a static variable after the initial check to avoid multiple CPUID calls.
3. Define your own macros or functions: Create convenient definitions or functions to simplify SSE3 support checks throughout your codebase.

Additional Considerations

Note that checking for CPU support is not sufficient. For proper SSE3 operation, you may also require operating system support, depending on the OS and its configuration.

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