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Auto merge of #108794 - nnethercote:avoid-unnecessary-hashing, r=cjgillot

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Avoid unnecessary hashing

I noticed some stable hashing being done in a non-incremental build. It turns out that some of this is necessary to compute the crate hash, but some of it is not. Removing the unnecessary hashing is a perf win.

r? `@cjgillot`
This commit is contained in:
bors 2023-03-12 06:48:30 +00:00
commit 150cb38147
10 changed files with 100 additions and 82 deletions
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55
compiler/rustc_ast_lowering/src/lib.rs
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@ -464,8 +464,10 @@ pub fn lower_to_hir(tcx: TyCtxt<'_>, (): ()) -> hir::Crate<'_> {
rustc_span::hygiene::clear_syntax_context_map();
}
let hir_hash = compute_hir_hash(tcx, &owners);
hir::Crate { owners, hir_hash }
// Don't hash unless necessary, because it's expensive.
let opt_hir_hash =
if tcx.sess.needs_crate_hash() { Some(compute_hir_hash(tcx, &owners)) } else { None };
hir::Crate { owners, opt_hir_hash }
}
#[derive(Copy, Clone, PartialEq, Debug)]
@ -658,42 +660,33 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
bodies.sort_by_key(|(k, _)| *k);
let bodies = SortedMap::from_presorted_elements(bodies);
let (hash_including_bodies, hash_without_bodies) = self.hash_owner(node, &bodies);
let (nodes, parenting) =
index::index_hir(self.tcx.sess, &*self.tcx.definitions_untracked(), node, &bodies);
let nodes = hir::OwnerNodes { hash_including_bodies, hash_without_bodies, nodes, bodies };
let attrs = {
let hash = self.tcx.with_stable_hashing_context(|mut hcx| {
// Don't hash unless necessary, because it's expensive.
let (opt_hash_including_bodies, attrs_hash) = if self.tcx.sess.needs_crate_hash() {
self.tcx.with_stable_hashing_context(|mut hcx| {
let mut stable_hasher = StableHasher::new();
hcx.with_hir_bodies(node.def_id(), &bodies, |hcx| {
node.hash_stable(hcx, &mut stable_hasher)
});
let h1 = stable_hasher.finish();
let mut stable_hasher = StableHasher::new();
attrs.hash_stable(&mut hcx, &mut stable_hasher);
stable_hasher.finish()
});
hir::AttributeMap { map: attrs, hash }
let h2 = stable_hasher.finish();
(Some(h1), Some(h2))
})
} else {
(None, None)
};
let (nodes, parenting) =
index::index_hir(self.tcx.sess, &*self.tcx.definitions_untracked(), node, &bodies);
let nodes = hir::OwnerNodes { opt_hash_including_bodies, nodes, bodies };
let attrs = hir::AttributeMap { map: attrs, opt_hash: attrs_hash };
self.arena.alloc(hir::OwnerInfo { nodes, parenting, attrs, trait_map })
}
/// Hash the HIR node twice, one deep and one shallow hash. This allows to differentiate
/// queries which depend on the full HIR tree and those which only depend on the item signature.
fn hash_owner(
&mut self,
node: hir::OwnerNode<'hir>,
bodies: &SortedMap<hir::ItemLocalId, &'hir hir::Body<'hir>>,
) -> (Fingerprint, Fingerprint) {
self.tcx.with_stable_hashing_context(|mut hcx| {
let mut stable_hasher = StableHasher::new();
hcx.with_hir_bodies(node.def_id(), bodies, |hcx| {
node.hash_stable(hcx, &mut stable_hasher)
});
let hash_including_bodies = stable_hasher.finish();
let mut stable_hasher = StableHasher::new();
hcx.without_hir_bodies(|hcx| node.hash_stable(hcx, &mut stable_hasher));
let hash_without_bodies = stable_hasher.finish();
(hash_including_bodies, hash_without_bodies)
})
}
/// This method allocates a new `HirId` for the given `NodeId` and stores it in
/// the `LoweringContext`'s `NodeId => HirId` map.
/// Take care not to call this method if the resulting `HirId` is then not