Compilers and languages have had a very long time to work on autovectorizing existing code for SIMD (54 years since ILLIAC, 25+ since SPARC VIS and MMX from Int

Compilers and languages have had a very long time to work on autovectorizing existing code for SIMD (54 years since ILLIAC, 25+ since SPARC VIS and MMX from Intel in 1994/1997). It mostly doesn't work for C/C++. The language has to support it, other optimization opportunities will be constantly blocked by lack information and/or restrictive specified semantics of operations. The potential of transparent SIMD use by compilers has apparently stayed marginal enough that no mainstream application languages in all that time have updated towards facilitating it.