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Use an Arc to share caches between clones.

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This commit is contained in:
Camille GILLOT 2025-06-15 14:16:11 +00:00 • committed by Camille Gillot
parent bd06903cd1
commit 42ff1089ed
1 changed files with 13 additions and 4 deletions
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17
compiler/rustc_middle/src/mir/basic_blocks.rs
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@ -1,4 +1,4 @@
use std::sync::OnceLock;
use std::sync::{Arc, OnceLock};
use rustc_data_structures::graph;
use rustc_data_structures::graph::dominators::{Dominators, dominators};
@ -14,7 +14,8 @@ use crate::mir::{BasicBlock, BasicBlockData, START_BLOCK};
#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
pub struct BasicBlocks<'tcx> {
basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
cache: Cache,
/// Use an `Arc` so we can share the cache when we clone the MIR body, as borrowck does.
cache: Arc<Cache>,
}
// Typically 95%+ of basic blocks have 4 or fewer predecessors.
@ -38,9 +39,10 @@ struct Cache {
impl<'tcx> BasicBlocks<'tcx> {
#[inline]
pub fn new(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
BasicBlocks { basic_blocks, cache: Cache::default() }
BasicBlocks { basic_blocks, cache: Arc::new(Cache::default()) }
}
#[inline]
pub fn dominators(&self) -> &Dominators<BasicBlock> {
self.cache.dominators.get_or_init(|| dominators(self))
}
@ -104,7 +106,14 @@ impl<'tcx> BasicBlocks<'tcx> {
/// All other methods that allow you to mutate the basic blocks also call this method
/// themselves, thereby avoiding any risk of accidentally cache invalidation.
pub fn invalidate_cfg_cache(&mut self) {
self.cache = Cache::default();
if let Some(cache) = Arc::get_mut(&mut self.cache) {
// If we only have a single reference to this cache, clear it.
*cache = Cache::default();
} else {
// If we have several references to this cache, overwrite the pointer itself so other
// users can continue to use their (valid) cache.
self.cache = Arc::new(Cache::default());
}
}
}