C# non SIMD (naive non optimized version) is in the same ballbark as other similar GC languages. Nim version is not some naive version also and seem rather specially crafted so it can be vectorized and still looses to C# SIMD.
Nim 1672
Julia 3012
D 3479
C# (SIMD) 5853
C# 8919
It's direct translation of formula, using `mod` rather `x = -x`.
*Rather comparing numbers << 1. **No blank/comment lines. As cloc and similar tools count.
Although arguably these flags are more reasonable than allowing the use of -march=native.
Also consider the inherent advantage popular languages have: you don't need to break out to a completely niche language, while achieving high performance. Saying this, this microbenchmark is naive and does not showcase realistic bottlenecks applications would face like how well-optimized standard library and popular frameworks are, whether the compiler deals with complexity and abstractions well, whether there are issues with multi-threaded scaling, etc etc. You can tell this by performance of dynamically typed languages - since all data is defined in scope of a single function, the compiler needs to do very little work and can hide the true cost of using something like Lua (LuaJIT).
Agree with the rest of your comment.
I don't see these flags in Nim compilation config. The only extra option used is "-march=native"[0].
[0] https://github.com/niklas-heer/speed-comparison/blob/9681e8e...