Loop Invariant Code Motion

f <- function(n) {
  y <- 1
  z <- 1
  a <- vector("numeric", n)
  for (i in seq_len(n)) {
    x <- y + z # invariant line inside the loop (can be taken outside)
    a[i] <- 6 * i + x * x # invariant expression (can be calculated outside)
  }
}

f_opt <- function(n) {
  y <- 1
  z <- 1
  a <- vector("numeric", n)
  x <- y + z # outside of the loop
  t1 <- x * x # new var, and outside of the loop
  for (i in seq_len(n)) {
    a[i] <- 6 * i + t1
  }
}

f_c <- cmpfun(f)
f_opt_c <- cmpfun(f_opt)

n <- 10000
autoplot(microbenchmark(f(n), f_c(n), f_opt(n), f_opt_c(n)))