The Free On-line Dictionary of Computing (30 December 2018):

peephole optimisation
peephole optimization

    A kind of low-level code optimisation that
   considers only a few adjacent machine code instructions at a
   time and looks for certain combinations which can be replaced
   with more efficient sequences.  E.g.

   	ADD R0, #1
   	ADD R0, #1

   (add one to register R0) could be replaced by

   	ADD R0, #2

   as long as there were no jumps to the second instruction.

   (2008-11-17)