Zlib-rs is faster than C

I found out I already know Rust:

        unsafe {
            let x_tmp0 = _mm_clmulepi64_si128(xmm_crc0, crc_fold, 0x10);
            xmm_crc0 = _mm_clmulepi64_si128(xmm_crc0, crc_fold, 0x01);
            xmm_crc1 = _mm_xor_si128(xmm_crc1, x_tmp0);
            xmm_crc1 = _mm_xor_si128(xmm_crc1, xmm_crc0);

Kidding aside, I thought the purpose of Rust was for safety but the keyword unsafe is sprinkled liberally throughout this library. At what point does it really stop mattering if this is C or Rust?

Presumably with inline assembly both languages can emit what is effectively the same machine code. Is the Rust compiler a better optimizing compiler than C compilers?

The usual answer is: You only need to verify the unsafe blocks, not every block. Though 'unsafe' in Rust is actually even less safe than regular C, if a bit more predictable, so there's a crossover point where you really shouldn't have bothered.

The Rust compiler is indeed better than the C one, largely because of having more information and doing full-program optimisation. A `vec_foo = vec_foo.into_iter().map(...).collect::Vec<foo>`, for example, isn't going to do any bounds checks or allocate.