Auto merge of #108794 - nnethercote:avoid-unnecessary-hashing, r=cjgillot
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`
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commit
150cb38147
10 changed files with 100 additions and 82 deletions
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@ -464,8 +464,10 @@ pub fn lower_to_hir(tcx: TyCtxt<'_>, (): ()) -> hir::Crate<'_> {
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rustc_span::hygiene::clear_syntax_context_map();
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}
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let hir_hash = compute_hir_hash(tcx, &owners);
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hir::Crate { owners, hir_hash }
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// Don't hash unless necessary, because it's expensive.
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let opt_hir_hash =
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if tcx.sess.needs_crate_hash() { Some(compute_hir_hash(tcx, &owners)) } else { None };
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hir::Crate { owners, opt_hir_hash }
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}
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#[derive(Copy, Clone, PartialEq, Debug)]
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@ -658,42 +660,33 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
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bodies.sort_by_key(|(k, _)| *k);
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let bodies = SortedMap::from_presorted_elements(bodies);
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let (hash_including_bodies, hash_without_bodies) = self.hash_owner(node, &bodies);
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let (nodes, parenting) =
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index::index_hir(self.tcx.sess, &*self.tcx.definitions_untracked(), node, &bodies);
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let nodes = hir::OwnerNodes { hash_including_bodies, hash_without_bodies, nodes, bodies };
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let attrs = {
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let hash = self.tcx.with_stable_hashing_context(|mut hcx| {
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// Don't hash unless necessary, because it's expensive.
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let (opt_hash_including_bodies, attrs_hash) = if self.tcx.sess.needs_crate_hash() {
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self.tcx.with_stable_hashing_context(|mut hcx| {
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let mut stable_hasher = StableHasher::new();
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hcx.with_hir_bodies(node.def_id(), &bodies, |hcx| {
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node.hash_stable(hcx, &mut stable_hasher)
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});
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let h1 = stable_hasher.finish();
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let mut stable_hasher = StableHasher::new();
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attrs.hash_stable(&mut hcx, &mut stable_hasher);
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stable_hasher.finish()
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});
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hir::AttributeMap { map: attrs, hash }
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let h2 = stable_hasher.finish();
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(Some(h1), Some(h2))
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})
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} else {
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(None, None)
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};
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let (nodes, parenting) =
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index::index_hir(self.tcx.sess, &*self.tcx.definitions_untracked(), node, &bodies);
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let nodes = hir::OwnerNodes { opt_hash_including_bodies, nodes, bodies };
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let attrs = hir::AttributeMap { map: attrs, opt_hash: attrs_hash };
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self.arena.alloc(hir::OwnerInfo { nodes, parenting, attrs, trait_map })
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}
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/// Hash the HIR node twice, one deep and one shallow hash. This allows to differentiate
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/// queries which depend on the full HIR tree and those which only depend on the item signature.
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fn hash_owner(
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&mut self,
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node: hir::OwnerNode<'hir>,
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bodies: &SortedMap<hir::ItemLocalId, &'hir hir::Body<'hir>>,
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) -> (Fingerprint, Fingerprint) {
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self.tcx.with_stable_hashing_context(|mut hcx| {
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let mut stable_hasher = StableHasher::new();
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hcx.with_hir_bodies(node.def_id(), bodies, |hcx| {
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node.hash_stable(hcx, &mut stable_hasher)
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});
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let hash_including_bodies = stable_hasher.finish();
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let mut stable_hasher = StableHasher::new();
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hcx.without_hir_bodies(|hcx| node.hash_stable(hcx, &mut stable_hasher));
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let hash_without_bodies = stable_hasher.finish();
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(hash_including_bodies, hash_without_bodies)
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})
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}
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/// This method allocates a new `HirId` for the given `NodeId` and stores it in
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/// the `LoweringContext`'s `NodeId => HirId` map.
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/// Take care not to call this method if the resulting `HirId` is then not
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