All modern x86 CPUs do this to some extent. The details changed over the decades, but the basic principle these days is that the CPUs decode the x86 instruction

All modern x86 CPUs do this to some extent. The details changed over the decades, but the basic principle these days is that the CPUs decode the x86 instruction set into a secret, internal only, more orthogonal sequence of instructions. My understanding is that these sequences can be quite long for the more involved CISC operations. And according to the manuals written by Agner Fox, some instructions even have special cases based on their operands to do something equivalent, but much faster. One particular example that I remember is xor ax,ax which is often used to set ax to zero and is a one byte instruction. Modern CPUs don't compute the xor in the ALU, but just rename ax to a register that is set to 0.