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Rollup merge of #89643 - cjgillot:overlap, r=matthewjasper

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Fix inherent impl overlap check.

The current implementation of the overlap check was slightly buggy, and unified the wrong connected component in the `ids.len() <= 1` case. This became visible in another PR which changed the iteration order of items.

r? ``@matthewjasper`` since you reviewed the other PR.
This commit is contained in:
Matthias Krüger 2021-10-11 23:45:46 +02:00 committed by GitHub
commit b80dd9e445
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3 changed files with 65 additions and 45 deletions
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6
compiler/rustc_index/src/vec.rs
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@ -738,6 +738,12 @@ impl<I: Idx, T> IndexVec<I, Option<T>> {
self.ensure_contains_elem(index, || None); self.ensure_contains_elem(index, || None);
self[index].get_or_insert_with(value) self[index].get_or_insert_with(value)
} }
#[inline]
pub fn remove(&mut self, index: I) -> Option<T> {
self.ensure_contains_elem(index, || None);
self[index].take()
}
} }
impl<I: Idx, T: Clone> IndexVec<I, T> { impl<I: Idx, T: Clone> IndexVec<I, T> {

103
compiler/rustc_typeck/src/coherence/inherent_impls_overlap.rs
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@ -3,6 +3,7 @@ use rustc_errors::struct_span_err;
use rustc_hir as hir; use rustc_hir as hir;
use rustc_hir::def_id::DefId; use rustc_hir::def_id::DefId;
use rustc_hir::itemlikevisit::ItemLikeVisitor; use rustc_hir::itemlikevisit::ItemLikeVisitor;
use rustc_index::vec::IndexVec;
use rustc_middle::ty::{self, TyCtxt}; use rustc_middle::ty::{self, TyCtxt};
use rustc_span::Symbol; use rustc_span::Symbol;
use rustc_trait_selection::traits::{self, SkipLeakCheck}; use rustc_trait_selection::traits::{self, SkipLeakCheck};
@ -158,14 +159,18 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
// This is advantageous to running the algorithm over the // This is advantageous to running the algorithm over the
// entire graph when there are many connected regions. // entire graph when there are many connected regions.
rustc_index::newtype_index! {
pub struct RegionId {
ENCODABLE = custom
}
}
struct ConnectedRegion { struct ConnectedRegion {
idents: SmallVec<[Symbol; 8]>, idents: SmallVec<[Symbol; 8]>,
impl_blocks: FxHashSet<usize>, impl_blocks: FxHashSet<usize>,
} }
// Highest connected region id let mut connected_regions: IndexVec<RegionId, _> = Default::default();
let mut highest_region_id = 0; // Reverse map from the Symbol to the connected region id.
let mut connected_region_ids = FxHashMap::default(); let mut connected_region_ids = FxHashMap::default();
let mut connected_regions = FxHashMap::default();
for (i, &(&_impl_def_id, impl_items)) in impls_items.iter().enumerate() { for (i, &(&_impl_def_id, impl_items)) in impls_items.iter().enumerate() {
if impl_items.len() == 0 { if impl_items.len() == 0 {
@ -173,7 +178,7 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
} }
// First obtain a list of existing connected region ids // First obtain a list of existing connected region ids
let mut idents_to_add = SmallVec::<[Symbol; 8]>::new(); let mut idents_to_add = SmallVec::<[Symbol; 8]>::new();
let ids = impl_items let mut ids = impl_items
.in_definition_order() .in_definition_order()
.filter_map(|item| { .filter_map(|item| {
let entry = connected_region_ids.entry(item.ident.name); let entry = connected_region_ids.entry(item.ident.name);
@ -184,62 +189,64 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
None None
} }
}) })
.collect::<FxHashSet<usize>>(); .collect::<SmallVec<[RegionId; 8]>>();
match ids.len() { // Sort the id list so that the algorithm is deterministic
0 | 1 => { ids.sort_unstable();
let id_to_set = if ids.is_empty() { let ids = ids;
// Create a new connected region match &ids[..] {
let region = ConnectedRegion { // Create a new connected region
[] => {
let id_to_set = connected_regions.next_index();
// Update the connected region ids
for ident in &idents_to_add {
connected_region_ids.insert(*ident, id_to_set);
}
connected_regions.insert(
id_to_set,
ConnectedRegion {
idents: idents_to_add, idents: idents_to_add,
impl_blocks: std::iter::once(i).collect(), impl_blocks: std::iter::once(i).collect(),
}; },
connected_regions.insert(highest_region_id, region); );
(highest_region_id, highest_region_id += 1).0 }
} else { // Take the only id inside the list
// Take the only id inside the list &[id_to_set] => {
let id_to_set = *ids.iter().next().unwrap(); let region = connected_regions[id_to_set].as_mut().unwrap();
let region = connected_regions.get_mut(&id_to_set).unwrap(); region.impl_blocks.insert(i);
region.impl_blocks.insert(i); region.idents.extend_from_slice(&idents_to_add);
region.idents.extend_from_slice(&idents_to_add);
id_to_set
};
let (_id, region) = connected_regions.iter().next().unwrap();
// Update the connected region ids // Update the connected region ids
for ident in region.idents.iter() { for ident in &idents_to_add {
connected_region_ids.insert(*ident, id_to_set); connected_region_ids.insert(*ident, id_to_set);
} }
} }
_ => { // We have multiple connected regions to merge.
// We have multiple connected regions to merge. // In the worst case this might add impl blocks
// In the worst case this might add impl blocks // one by one and can thus be O(n^2) in the size
// one by one and can thus be O(n^2) in the size // of the resulting final connected region, but
// of the resulting final connected region, but // this is no issue as the final step to check
// this is no issue as the final step to check // for overlaps runs in O(n^2) as well.
// for overlaps runs in O(n^2) as well. &[id_to_set, ..] => {
let mut region = connected_regions.remove(id_to_set).unwrap();
// Take the smallest id from the list
let id_to_set = *ids.iter().min().unwrap();
// Sort the id list so that the algorithm is deterministic
let mut ids = ids.into_iter().collect::<SmallVec<[usize; 8]>>();
ids.sort_unstable();
let mut region = connected_regions.remove(&id_to_set).unwrap();
region.idents.extend_from_slice(&idents_to_add);
region.impl_blocks.insert(i); region.impl_blocks.insert(i);
region.idents.extend_from_slice(&idents_to_add);
// Update the connected region ids
for ident in &idents_to_add {
connected_region_ids.insert(*ident, id_to_set);
}
// Remove other regions from ids.
for &id in ids.iter() { for &id in ids.iter() {
if id == id_to_set { if id == id_to_set {
continue; continue;
} }
let r = connected_regions.remove(&id).unwrap(); let r = connected_regions.remove(id).unwrap();
// Update the connected region ids
for ident in r.idents.iter() { for ident in r.idents.iter() {
connected_region_ids.insert(*ident, id_to_set); connected_region_ids.insert(*ident, id_to_set);
} }
region.idents.extend_from_slice(&r.idents); region.idents.extend_from_slice(&r.idents);
region.impl_blocks.extend(r.impl_blocks); region.impl_blocks.extend(r.impl_blocks);
} }
connected_regions.insert(id_to_set, region); connected_regions.insert(id_to_set, region);
} }
} }
@ -254,16 +261,22 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
let avg = impls.len() / connected_regions.len(); let avg = impls.len() / connected_regions.len();
let s = connected_regions let s = connected_regions
.iter() .iter()
.map(|r| r.1.impl_blocks.len() as isize - avg as isize) .flatten()
.map(|r| r.impl_blocks.len() as isize - avg as isize)
.map(|v| v.abs() as usize) .map(|v| v.abs() as usize)
.sum::<usize>(); .sum::<usize>();
s / connected_regions.len() s / connected_regions.len()
}, },
connected_regions.iter().map(|r| r.1.impl_blocks.len()).max().unwrap() connected_regions
.iter()
.flatten()
.map(|r| r.impl_blocks.len())
.max()
.unwrap()
); );
// List of connected regions is built. Now, run the overlap check // List of connected regions is built. Now, run the overlap check
// for each pair of impl blocks in the same connected region. // for each pair of impl blocks in the same connected region.
for (_id, region) in connected_regions.into_iter() { for region in connected_regions.into_iter().flatten() {
let mut impl_blocks = let mut impl_blocks =
region.impl_blocks.into_iter().collect::<SmallVec<[usize; 8]>>(); region.impl_blocks.into_iter().collect::<SmallVec<[usize; 8]>>();
impl_blocks.sort_unstable(); impl_blocks.sort_unstable();

1
compiler/rustc_typeck/src/lib.rs
View File

@ -63,6 +63,7 @@ This API is completely unstable and subject to change.
#![feature(in_band_lifetimes)] #![feature(in_band_lifetimes)]
#![feature(is_sorted)] #![feature(is_sorted)]
#![feature(iter_zip)] #![feature(iter_zip)]
#![feature(min_specialization)]
#![feature(nll)] #![feature(nll)]
#![feature(try_blocks)] #![feature(try_blocks)]
#![feature(never_type)] #![feature(never_type)]