I was very surprised that GCC could optimize NEON SIMD intrinsics. After spending hours trying to optimize my vector code, trying to get the spacing between register dependencies right to reduce stalls, breaking long reduction operations into intermediate results, messing with LLVM-MCA, etc., I realized that I just couldn’t beat the compiler. It was doing its best to allocate registers and reorder instructions to keep the pipeline filled.

I don’t think it always did the best job and saw a bunch of register spills I thought were unnecessary, but I couldn’t justify the time and effort to do it in assembly…