The under the hood stuff like true 256 bit registers, branch prediction, cache, etc, all is below the machine code level as other people have pointed out. The compiler doesn't know about it.
>What about if the binary runs on a different CPU, will the compiler include feature checks and multiple code versions?
This is referred to as multiple/dynamic code paths and it needs to be supported by the processor microarchitecture and compiler. afaik only the Intel Compiler and Intel processors support it with the <code>-ax</code> compilation flag.
In general you should pick a minimum architecture for your applications, since it will be forward compatible.