bjoernager/rust
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Auto merge of #119192 - michaelwoerister:mcp533-push, r=cjgillot

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Replace a number of FxHashMaps/Sets with stable-iteration-order alternatives

This PR replaces almost all of the remaining `FxHashMap`s in query results with either `FxIndexMap` or `UnordMap`. The only case that is missing is the `EffectiveVisibilities` struct which turned out to not be straightforward to transform. Once that is done too, we can remove the `HashStable` implementation from `HashMap`.

The first commit adds the `StableCompare` trait which is a companion trait to `StableOrd`. Some types like `Symbol` can be compared in a cross-session stable way, but their `Ord` implementation is not stable. In such cases, a `StableCompare` implementation can be provided to offer a lightweight way for stable sorting. The more heavyweight option is to sort via `ToStableHashKey`, but then sorting needs to have access to a stable hashing context and `ToStableHashKey` can also be expensive as in the case of `Symbol` where it has to allocate a `String`.

The rest of the commits are rather mechanical and don't overlap, so they are best reviewed individually.

Part of [MCP 533](https://github.com/rust-lang/compiler-team/issues/533).
This commit is contained in:
bors 2024-01-05 19:38:27 +00:00
commit b8c207435c
30 changed files with 256 additions and 147 deletions
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19
compiler/rustc_passes/src/stability.rs
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@ -6,7 +6,8 @@ use rustc_attr::{
self as attr, ConstStability, DeprecatedSince, Stability, StabilityLevel, StableSince,
Unstable, UnstableReason, VERSION_PLACEHOLDER,
};
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::unord::{ExtendUnord, UnordMap, UnordSet};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{LocalDefId, LocalModDefId, CRATE_DEF_ID, LOCAL_CRATE};
@ -923,7 +924,7 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
}
let declared_lang_features = &tcx.features().declared_lang_features;
let mut lang_features = FxHashSet::default();
let mut lang_features = UnordSet::default();
for &(feature, span, since) in declared_lang_features {
if let Some(since) = since {
// Warn if the user has enabled an already-stable lang feature.
@ -980,11 +981,11 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
fn check_features<'tcx>(
tcx: TyCtxt<'tcx>,
remaining_lib_features: &mut FxIndexMap<&Symbol, Span>,
remaining_implications: &mut FxHashMap<Symbol, Symbol>,
remaining_implications: &mut UnordMap<Symbol, Symbol>,
defined_features: &LibFeatures,
all_implications: &FxHashMap<Symbol, Symbol>,
all_implications: &UnordMap<Symbol, Symbol>,
) {
for (feature, since) in defined_features.to_vec() {
for (feature, since) in defined_features.to_sorted_vec() {
if let FeatureStability::AcceptedSince(since) = since
&& let Some(span) = remaining_lib_features.get(&feature)
{
@ -1021,7 +1022,8 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
// `remaining_lib_features`.
let mut all_implications = remaining_implications.clone();
for &cnum in tcx.crates(()) {
all_implications.extend(tcx.stability_implications(cnum));
all_implications
.extend_unord(tcx.stability_implications(cnum).items().map(|(k, v)| (*k, *v)));
}
check_features(
@ -1050,10 +1052,7 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
tcx.dcx().emit_err(errors::UnknownFeature { span, feature: *feature });
}
// We only use the hash map contents to emit errors, and the order of
// emitted errors do not affect query stability.
#[allow(rustc::potential_query_instability)]
for (implied_by, feature) in remaining_implications {
for (&implied_by, &feature) in remaining_implications.to_sorted_stable_ord() {
let local_defined_features = tcx.lib_features(LOCAL_CRATE);
let span = local_defined_features
.stability