Hi. I tried this code:

const COUNT : usize = 40000; fn main () { let mut vol_buffer = [ 0u64; COUNT ]; let mut input = unsafe { std::ptr::read_volatile(&mut vol_buffer) }; input[0] = 42; eprintln!("{:?}", input[0]); }

Expected results:

Relatively quick compilation of a program that prints 42.

Actual results:

rustc took 45 seconds on my really rather fast laptop (and also uses a great deal of memory). The compiled binary works as epected.

Changing the value of COUNT shows the following (with an earlier rustc, but the newly-updated one is about as slow):

10000 1.74s
20000 5.9s
30000 20s
40000 46s

I haven't waited for completion of any larger values. In my original version I had COUNT = a million; I killed rustc after some minutes and about 2G of RAM use.

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rustc --version --verbose:

binary: rustc commit-hash: 346aec9b02f3c74f3fce97fd6bda24709d220e49 commit-date: 2020-07-11 host: x86_64-unknown-linux-gnu release: 1.46.0-nightly LLVM version: 10.0