[GabrielTFS]

That's the generic implementation - it's not used on most popular architectures (I think the most popular architecture it's used on would be RISC-V or MIPS) because they all have architecture-specific implementations. The implementation running on the average (x86) computer is likely to be https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/x86... (if you have AVX512), https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/x86... (if you have AVX2 and not AVX512) or https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/x86... (if you have neither AVX2 nor AVX512 - rather rare these days)