Function simd_enabled 

pub fn simd_enabled() -> bool

LOGOS_SIMD=1 opts a recognized PURE ELEMENT-WISE MAP region (Oracle-proven in-bounds, unit-stride, no loop-carried scalar — see crate::vectorize::recognize_elementwise_map) into a 2-wide packed-double loop. DEFAULT OFF: the bit-identical differential gate must certify it before promotion, and no current benchmark exercises a float map. Read once.