Slower binaries since some days #42935
Description
This could have the same causes of Issue 42808 (i.e. regression due to #42313), or perhaps not.
This small test program solves the Euler problem number 214:
#![feature(step_by)]
fn main() {
fn e214() -> u64 {
const N_MAX: usize = 40_000_000;
const SIZE: usize = N_MAX / 2;
const LEN: u8 = 25;
let mut chain_length = vec![2u8; SIZE];
let mut tot: u64 = 0;
for i in 1 .. SIZE {
// if not prime, then try next one
if chain_length[i] > 2 { continue; }
// p is prime
let p = 2 * i + 1;
// calculate q*2^k = p-1
let mut q = i;
let mut k = 1;
while (q & 1) == 0 {
q /= 2;
k += 1;
}
// calculate cl = chain_length(p)
let cl = chain_length[q / 2] + k;
// add p to tot if the length matches.
if cl == LEN { tot += p as u64; }
// loop over powers of p.
let mut pp = p as u64;
while pp < N_MAX as u64 {
// Loop over multiples of pp.
for j in ((pp / 2) .. SIZE as u64).step_by(pp) {
chain_length[j as usize] += cl - 2;
}
pp *= p as u64;
}
}
tot
}
assert_eq!(e214(), 1_677_366_278_943);
}
On my PC using nightly-2017-06-18-x86_64-pc-windows-gnu it runs in about 0.39 seconds, while using a more recent Nightly, like the current rustc 1.19.0-nightly (78d8416 2017-06-17), it runs in about 0.87 seconds.