Macro rustc_data_structures::parallel

macro_rules! parallel {
    (impl $fblock:tt [$($c:tt,)*] [$block:tt $(, $rest:tt)*]) => { ... };
    (impl $fblock:tt [$($blocks:tt,)*] []) => { ... };
    ($fblock:tt, $($blocks:tt),*) => { ... };
}

Runs a list of blocks in parallel. The first block is executed immediately on the current thread. Use that for the longest running block.