title: instruction to copy lower 32 bits of a register to upper 32 bits
body: <p>Is there a x86 instruction to directly replicate the lower 32 bits of a x86_64 register to upper 32 bits?</p>
  
  <pre>
  Example : rbx -> 0x0123456789ABCDEF
  Resultant rbx -> 0x89ABCDEF89ABCDEF
  </pre>