Peephole optimization

Peephole optimization is an optimization technique performed on a small set of compiler-generated instructions, known as a peephole or window, that involves replacing the instructions with a logically equivalent set that has better performance.

For example:

  • Instead of pushing a register onto the stack and then immediately popping the value back into the register, remove both instructions
  • Instead of multiplying x by 2, do x << 1
  • Instead of multiplying a floating point register by 8, add 3 to the floating point register's exponent

The term peephole optimization was introduced by William Marshall McKeeman in 1965.

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