AFAIK SIMD accelerated cipher implementations already mostly do it. For example, AES-NI based implementations of AES-128 and AES-192 keep round keys in XMM regi

AFAIK SIMD accelerated cipher implementations already mostly do it. For example, AES-NI based implementations of AES-128 and AES-192 keep round keys in XMM registers without reloading them during processing of blocks.