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Auto merge of #107782 - Zoxc:worker-local, r=cjgillot

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Move the WorkerLocal type from the rustc-rayon fork into rustc_data_structures

This PR moves the definition of the `WorkerLocal` type from `rustc-rayon` into `rustc_data_structures`. This is enabled by the introduction of the `Registry` type which allows you to group up threads to be used by `WorkerLocal` which is basically just an array with an per thread index. The `Registry` type mirrors the one in Rayon and each Rayon worker thread is also registered with the new `Registry`. Safety for `WorkerLocal` is ensured by having it keep a reference to the registry and checking on each access that we're still on the group of threads associated with the registry used to construct it.

Accessing a `WorkerLocal` is micro-optimized due to it being hot since it's used for most arena allocations.

Performance is slightly improved for the parallel compiler:
<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check</td><td align="right">1.9992s</td><td align="right">1.9949s</td><td align="right"> -0.21%</td></tr><tr><td>🟣 <b>hyper</b>:check</td><td align="right">0.2977s</td><td align="right">0.2970s</td><td align="right"> -0.22%</td></tr><tr><td>🟣 <b>regex</b>:check</td><td align="right">1.1335s</td><td align="right">1.1315s</td><td align="right"> -0.18%</td></tr><tr><td>🟣 <b>syn</b>:check</td><td align="right">1.8235s</td><td align="right">1.8171s</td><td align="right"> -0.35%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check</td><td align="right">6.9047s</td><td align="right">6.8930s</td><td align="right"> -0.17%</td></tr><tr><td>Total</td><td align="right">12.1586s</td><td align="right">12.1336s</td><td align="right"> -0.21%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">0.9977s</td><td align="right"> -0.23%</td></tr></table>

cc `@SparrowLii`
This commit is contained in:
bors 2023-04-27 17:43:09 +00:00
commit c14882f74e
5 changed files with 198 additions and 66 deletions
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36
compiler/rustc_ast/src/attr/mod.rs
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@ -10,15 +10,10 @@ use crate::tokenstream::{DelimSpan, Spacing, TokenTree};
use crate::tokenstream::{LazyAttrTokenStream, TokenStream};
use crate::util::comments;
use crate::util::literal::escape_string_symbol;
use rustc_data_structures::sync::WorkerLocal;
use rustc_index::bit_set::GrowableBitSet;
use rustc_span::symbol::{sym, Ident, Symbol};
use rustc_span::Span;
use std::cell::Cell;
use std::iter;
#[cfg(debug_assertions)]
use std::ops::BitXor;
#[cfg(debug_assertions)]
use std::sync::atomic::{AtomicU32, Ordering};
use thin_vec::{thin_vec, ThinVec};
@ -40,39 +35,16 @@ impl MarkedAttrs {
}
}
pub struct AttrIdGenerator(WorkerLocal<Cell<u32>>);
#[cfg(debug_assertions)]
static MAX_ATTR_ID: AtomicU32 = AtomicU32::new(u32::MAX);
pub struct AttrIdGenerator(AtomicU32);
impl AttrIdGenerator {
pub fn new() -> Self {
// We use `(index as u32).reverse_bits()` to initialize the
// starting value of AttrId in each worker thread.
// The `index` is the index of the worker thread.
// This ensures that the AttrId generated in each thread is unique.
AttrIdGenerator(WorkerLocal::new(|index| {
let index: u32 = index.try_into().unwrap();
#[cfg(debug_assertions)]
{
let max_id = ((index + 1).next_power_of_two() - 1).bitxor(u32::MAX).reverse_bits();
MAX_ATTR_ID.fetch_min(max_id, Ordering::Release);
}
Cell::new(index.reverse_bits())
}))
AttrIdGenerator(AtomicU32::new(0))
}
pub fn mk_attr_id(&self) -> AttrId {
let id = self.0.get();
// Ensure the assigned attr_id does not overlap the bits
// representing the number of threads.
#[cfg(debug_assertions)]
assert!(id <= MAX_ATTR_ID.load(Ordering::Acquire));
self.0.set(id + 1);
let id = self.0.fetch_add(1, Ordering::Relaxed);
assert!(id != u32::MAX);
AttrId::from_u32(id)
}
}