code: func compareReplaceInline(s1, s2 string, old, new byte) int {
  	// TODO(stevvooe): We are missing an optimization when the s1 and s2 have
  	// the exact same slice header. It will make the code unsafe but can
  	// provide some extra performance.
  
  	l := len(s1)
  	if len(s2) < l {
  		l = len(s2)
  	}
  
  	for i := 0; i < l; i++ {
  		c1, c2 := s1[i], s2[i]
  		if c1 == old {
  			c1 = new
  		}
  
  		if c2 == old {
  			c2 = new
  		}
  
  		if c1 < c2 {
  			return -1
  		}
  
  		if c1 > c2 {
  			return +1
  		}
  	}
  
  	if len(s1) < len(s2) {
  		return -1
  	}
  
  	if len(s1) > len(s2) {
  		return +1
  	}
  
  	return 0
  }
docs: // compareReplaceInline modifies runtime.cmpstring to replace old with new
  // during a byte-wise comparison.