Microsoft’s implementation of C standard library routines like `memcpy` is checking for a global flag, and use AVX when available. The flag is initialized on st

Microsoft’s implementation of C standard library routines like `memcpy` is checking for a global flag, and use AVX when available. The flag is initialized on startup by testing the output of `cpuid` instruction. For this reason, most binaries built with modern Visual C++ are technically using AVX instructions even when compiled for SSE only. It doesn’t mean these binaries gonna fail without AVX support, it only means they’re capable of using AVX when available.