Auto merge of #52672 - ljedrz:unstable_sorts, r=<try>

Prefer sort_unstable*() over sort*()

Since `sort_unstable` is considered typically faster than the regular `sort` ([benchmarks](#40601 (comment))), it might be a good idea to check for potential wins in the compiler.

src/librustc/hir/lowering.rs

@@ -4803,6 +4803,6 @@ fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {
     // Sorting by span ensures that we get things in order within a
     // file, and also puts the files in a sensible order.
     let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
-    body_ids.sort_by_key(|b| bodies[b].value.span);
+    body_ids.sort_unstable_by_key(|b| bodies[b].value.span);
     body_ids
 }

src/librustc/hir/pat_util.rs

@@ -157,7 +157,7 @@ impl hir::Pat {
             }
             true
         });
-        variants.sort();
+        variants.sort_unstable();
         variants.dedup();
         variants
     }

src/librustc/infer/error_reporting/mod.rs

@@ -434,7 +434,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         };
 
         // sort the errors by span, for better error message stability.
-        errors.sort_by_key(|u| match *u {
+        errors.sort_unstable_by_key(|u| match *u {
             RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(),
             RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
             RegionResolutionError::SubSupConflict(ref rvo, _, _, _, _) => rvo.span(),

src/librustc/infer/lexical_region_resolve/mod.rs

@@ -568,8 +568,8 @@ impl<'cx, 'gcx, 'tcx> LexicalResolver<'cx, 'gcx, 'tcx> {
                 _ => 2,
             }
         }
-        lower_bounds.sort_by_key(region_order_key);
-        upper_bounds.sort_by_key(region_order_key);
+        lower_bounds.sort_unstable_by_key(region_order_key);
+        upper_bounds.sort_unstable_by_key(region_order_key);
 
         for lower_bound in &lower_bounds {
             for upper_bound in &upper_bounds {

src/librustc/middle/resolve_lifetime.rs

@@ -1426,7 +1426,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             .collect();
 
         // ensure that we issue lints in a repeatable order
-        def_ids.sort_by_key(|&def_id| self.tcx.def_path_hash(def_id));
+        def_ids.sort_unstable_by_key(|&def_id| self.tcx.def_path_hash(def_id));
 
         for def_id in def_ids {
             debug!(

src/librustc/session/code_stats.rs

@@ -100,7 +100,7 @@ impl CodeStats {
 
         // Primary sort: large-to-small.
         // Secondary sort: description (dictionary order)
-        sorted.sort_by(|info1, info2| {
+        sorted.sort_unstable_by(|info1, info2| {
             // (reversing cmp order to get large-to-small ordering)
             match info2.overall_size.cmp(&info1.overall_size) {
                 Ordering::Equal => info1.type_description.cmp(&info2.type_description),
@@ -151,7 +151,7 @@ impl CodeStats {
 
                 // We want to print fields by increasing offset.
                 let mut fields = fields.clone();
-                fields.sort_by_key(|f| f.offset);
+                fields.sort_unstable_by_key(|f| f.offset);
 
                 for field in fields.iter() {
                     let FieldInfo { ref name, offset, size, align } = *field;

src/librustc/session/config.rs

@@ -2401,7 +2401,7 @@ mod dep_tracking {
             impl DepTrackingHash for Vec<$t> {
                 fn hash(&self, hasher: &mut DefaultHasher, error_format: ErrorOutputType) {
                     let mut elems: Vec<&$t> = self.iter().collect();
-                    elems.sort();
+                    elems.sort_unstable();
                     Hash::hash(&elems.len(), hasher);
                     for (index, elem) in elems.iter().enumerate() {
                         Hash::hash(&index, hasher);

src/librustc/ty/layout.rs

@@ -288,15 +288,15 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
                 match kind {
                     StructKind::AlwaysSized |
                     StructKind::MaybeUnsized => {
-                        optimizing.sort_by_key(|&x| {
+                        optimizing.sort_unstable_by_key(|&x| {
                             // Place ZSTs first to avoid "interesting offsets",
                             // especially with only one or two non-ZST fields.
                             let f = &fields[x as usize];
                             (!f.is_zst(), cmp::Reverse(field_align(f)))
                         });
                     }
                     StructKind::Prefixed(..) => {
-                        optimizing.sort_by_key(|&x| field_align(&fields[x as usize]));
+                        optimizing.sort_unstable_by_key(|&x| field_align(&fields[x as usize]));
                     }
                 }
             }

src/librustc/util/time_graph.rs

@@ -127,7 +127,7 @@ impl TimeGraph {
         let mut threads: Vec<PerThread> =
             table.values().map(|data| data.clone()).collect();
 
-        threads.sort_by_key(|timeline| timeline.timings[0].start);
+        threads.sort_unstable_by_key(|timeline| timeline.timings[0].start);
 
         let earliest_instant = threads[0].timings[0].start;
         let latest_instant = threads.iter()

src/librustc_codegen_llvm/back/write.rs

@@ -1923,7 +1923,7 @@ fn start_executing_work(tcx: TyCtxt,
         // Regardless of what order these modules completed in, report them to
         // the backend in the same order every time to ensure that we're handing
         // out deterministic results.
-        compiled_modules.sort_by(|a, b| a.name.cmp(&b.name));
+        compiled_modules.sort_unstable_by(|a, b| a.name.cmp(&b.name));
 
         let compiled_metadata_module = compiled_metadata_module
             .expect("Metadata module not compiled?");

src/librustc_codegen_llvm/base.rs

@@ -925,7 +925,7 @@ pub fn codegen_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         println!("n_inlines: {}", all_stats.n_inlines);
         println!("n_closures: {}", all_stats.n_closures);
         println!("fn stats:");
-        all_stats.fn_stats.sort_by_key(|&(_, insns)| insns);
+        all_stats.fn_stats.sort_unstable_by_key(|&(_, insns)| insns);
         for &(ref name, insns) in all_stats.fn_stats.iter() {
             println!("{} insns, {}", insns, *name);
         }
@@ -1037,7 +1037,7 @@ fn collect_and_partition_mono_items<'a, 'tcx>(
                 output.push_str(" @@");
                 let mut empty = Vec::new();
                 let cgus = item_to_cgus.get_mut(i).unwrap_or(&mut empty);
-                cgus.as_mut_slice().sort_by_key(|&(ref name, _)| name.clone());
+                cgus.as_mut_slice().sort_unstable_by_key(|&(ref name, _)| name.clone());
                 cgus.dedup();
                 for &(ref cgu_name, (linkage, _)) in cgus.iter() {
                     output.push_str(" ");
@@ -1065,7 +1065,7 @@ fn collect_and_partition_mono_items<'a, 'tcx>(
             })
             .collect();
 
-        item_keys.sort();
+        item_keys.sort_unstable();
 
         for item in item_keys {
             println!("MONO_ITEM {}", item);

src/librustc_driver/driver.rs

@@ -1003,7 +1003,7 @@ where
             .iter()
             .cloned()
             .collect();
-        missing_fragment_specifiers.sort();
+        missing_fragment_specifiers.sort_unstable();
         for span in missing_fragment_specifiers {
             let lint = lint::builtin::MISSING_FRAGMENT_SPECIFIER;
             let msg = "missing fragment specifier";
@@ -1530,7 +1530,7 @@ pub fn collect_crate_types(session: &Session, attrs: &[ast::Attribute]) -> Vec<c
                 session,
             ));
         }
-        base.sort();
+        base.sort_unstable();
         base.dedup();
     }
 
@@ -1562,7 +1562,7 @@ pub fn compute_crate_disambiguator(session: &Session) -> CrateDisambiguator {
     let mut metadata = session.opts.cg.metadata.clone();
     // We don't want the crate_disambiguator to dependent on the order
     // -C metadata arguments, so sort them:
-    metadata.sort();
+    metadata.sort_unstable();
     // Every distinct -C metadata value is only incorporated once:
     metadata.dedup();
 

src/librustc_driver/lib.rs

@@ -1051,7 +1051,7 @@ impl RustcDefaultCalls {
             match *req {
                 TargetList => {
                     let mut targets = rustc_target::spec::get_targets().collect::<Vec<String>>();
-                    targets.sort();
+                    targets.sort_unstable();
                     println!("{}", targets.join("\n"));
                 },
                 Sysroot => println!("{}", sess.sysroot().display()),
@@ -1117,7 +1117,7 @@ impl RustcDefaultCalls {
                         });
                     }
 
-                    cfgs.sort();
+                    cfgs.sort_unstable();
                     for cfg in cfgs {
                         println!("{}", cfg);
                     }
@@ -1229,8 +1229,8 @@ Available lint options:
     fn sort_lint_groups(lints: Vec<(&'static str, Vec<lint::LintId>, bool)>)
                         -> Vec<(&'static str, Vec<lint::LintId>)> {
         let mut lints: Vec<_> = lints.into_iter().map(|(x, y, _)| (x, y)).collect();
-        lints.sort_by(|&(x, _): &(&'static str, Vec<lint::LintId>),
-                       &(y, _): &(&'static str, Vec<lint::LintId>)| {
+        lints.sort_unstable_by(|&(x, _): &(&'static str, Vec<lint::LintId>),
+                                &(y, _): &(&'static str, Vec<lint::LintId>)| {
             x.cmp(y)
         });
         lints

src/librustc_driver/profile/trace.rs

@@ -208,8 +208,8 @@ pub fn write_counts(count_file: &mut File, counts: &mut HashMap<String,QueryMetr
     for (ref cons, ref qm) in counts.iter() {
         data.push((cons.clone(), qm.count.clone(), qm.dur_total.clone(), qm.dur_self.clone()));
     };
-    data.sort_by(|&(_,_,_,self1),&(_,_,_,self2)|
-                 if self1 > self2 { Ordering::Less } else { Ordering::Greater } );
+    data.sort_unstable_by(|&(_,_,_,self1),&(_,_,_,self2)|
+                          if self1 > self2 { Ordering::Less } else { Ordering::Greater } );
     for (cons, count, dur_total, dur_self) in data {
         write!(count_file, "{}, {}, {}, {}\n",
                cons, count,

src/librustc_errors/emitter.rs

@@ -196,7 +196,7 @@ impl EmitterWriter {
                         line_index,
                         annotations: vec![ann],
                     });
-                    slot.lines.sort();
+                    slot.lines.sort_unstable();
                     return;
                 }
             }
@@ -265,7 +265,7 @@ impl EmitterWriter {
         }
 
         // Find overlapping multiline annotations, put them at different depths
-        multiline_annotations.sort_by(|a, b| {
+        multiline_annotations.sort_unstable_by(|a, b| {
             (a.1.line_start, a.1.line_end).cmp(&(b.1.line_start, b.1.line_end))
         });
         for item in multiline_annotations.clone() {
@@ -403,7 +403,7 @@ impl EmitterWriter {
         // otherwise the lines would end up needing to go over a message.
 
         let mut annotations = line.annotations.clone();
-        annotations.sort_by(|a,b| b.start_col.cmp(&a.start_col));
+        annotations.sort_unstable_by(|a,b| b.start_col.cmp(&a.start_col));
 
         // First, figure out where each label will be positioned.
         //
@@ -681,7 +681,7 @@ impl EmitterWriter {
         //   | |  |
         //   | |  something about `foo`
         //   | something about `fn foo()`
-        annotations_position.sort_by(|a, b| {
+        annotations_position.sort_unstable_by(|a, b| {
             // Decreasing order
             a.1.len().cmp(&b.1.len()).reverse()
         });

src/librustc_errors/lib.rs

@@ -155,7 +155,7 @@ impl CodeSuggestion {
         self.substitutions.iter().cloned().map(|mut substitution| {
             // Assumption: all spans are in the same file, and all spans
             // are disjoint. Sort in ascending order.
-            substitution.parts.sort_by_key(|part| part.span.lo());
+            substitution.parts.sort_unstable_by_key(|part| part.span.lo());
 
             // Find the bounding span.
             let lo = substitution.parts.iter().map(|part| part.span.lo()).min().unwrap();
@@ -618,7 +618,7 @@ impl Handler {
                                              })
                                              .collect::<Vec<_>>();
             if !error_codes.is_empty() {
-                error_codes.sort();
+                error_codes.sort_unstable();
                 if error_codes.len() > 1 {
                     let limit = if error_codes.len() > 9 { 9 } else { error_codes.len() };
                     self.failure(&format!("Some errors occurred: {}{}",

src/librustc_metadata/cstore_impl.rs

@@ -356,7 +356,7 @@ pub fn provide<'tcx>(providers: &mut Providers<'tcx>) {
             // we believe that libstd is consistently assigned crate
             // num 1, so it should be enough to resolve #46112.
             let mut crates: Vec<CrateNum> = (*tcx.crates()).clone();
-            crates.sort();
+            crates.sort_unstable();
 
             for &cnum in crates.iter() {
                 // Ignore crates without a corresponding local `extern crate` item.

src/librustc_metadata/encoder.rs

@@ -1438,7 +1438,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
             })
             .collect::<Vec<_>>();
 
-        deps.sort_by_key(|&(cnum, _)| cnum);
+        deps.sort_unstable_by_key(|&(cnum, _)| cnum);
 
         {
             // Sanity-check the crate numbers

src/librustc_mir/borrow_check/move_errors.rs

@@ -324,7 +324,7 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
                         }
                     }
 
-                    binds_to.sort();
+                    binds_to.sort_unstable();
                     binds_to.dedup();
                     for local in binds_to {
                         let bind_to = &self.mir.local_decls[local];
@@ -344,7 +344,7 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
             GroupedMoveError::MovesFromPattern { mut binds_to, .. } => {
                 // Suggest ref, since there might be a move in
                 // another match arm
-                binds_to.sort();
+                binds_to.sort_unstable();
                 binds_to.dedup();
                 for local in binds_to {
                     let bind_to = &self.mir.local_decls[local];

src/librustc_mir/borrow_check/nll/region_infer/dump_mir.rs

@@ -77,7 +77,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
 
         let mut constraints: Vec<_> = self.constraints.iter().collect();
-        constraints.sort();
+        constraints.sort_unstable();
         for constraint in &constraints {
             let OutlivesConstraint {
                 sup,

src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs

@@ -227,7 +227,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         debug!("report_error: categorized_path={:?}", categorized_path);
 
         // Find what appears to be the most interesting path to report to the user.
-        categorized_path.sort_by(|p0, p1| p0.0.cmp(&p1.0));
+        categorized_path.sort_unstable_by(|p0, p1| p0.0.cmp(&p1.0));
         debug!("report_error: sorted_path={:?}", categorized_path);
 
         // Get a span

src/librustc_mir/borrow_check/nll/region_infer/mod.rs

@@ -418,7 +418,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         debug!("propagate_constraints: constraints={:#?}", {
             let mut constraints: Vec<_> = self.constraints.iter().collect();
-            constraints.sort();
+            constraints.sort_unstable();
             constraints
         });
 

src/librustc_mir/build/matches/mod.rs

@@ -192,7 +192,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             let source_info = self.source_info(span);
 
             let mut otherwise = otherwise;
-            otherwise.sort();
+            otherwise.sort_unstable();
             otherwise.dedup(); // variant switches can introduce duplicate target blocks
             for block in otherwise {
                 self.cfg.terminate(block, source_info, TerminatorKind::Unreachable);
@@ -644,7 +644,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                              -> BasicBlock
     {
         let source_info = self.source_info(span);
-        otherwise.sort();
+        otherwise.sort_unstable();
         otherwise.dedup(); // variant switches can introduce duplicate target blocks
         if otherwise.len() == 1 {
             otherwise[0]

src/librustc_mir/interpret/memory.rs

@@ -408,7 +408,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
             return;
         }
         use std::fmt::Write;
-        allocs.sort();
+        allocs.sort_unstable();
         allocs.dedup();
         let mut allocs_to_print = VecDeque::from(allocs);
         let mut allocs_seen = FxHashSet::default();

src/librustc_mir/monomorphize/mod.rs

@@ -29,7 +29,7 @@ pub fn assert_symbols_are_distinct<'a, 'tcx, I>(tcx: TyCtxt<'a, 'tcx, 'tcx>, mon
         (mono_item, mono_item.symbol_name(tcx))
     }).collect();
 
-    (&mut symbols[..]).sort_by(|&(_, ref sym1), &(_, ref sym2)|{
+    (&mut symbols[..]).sort_unstable_by(|&(_, ref sym1), &(_, ref sym2)|{
         sym1.cmp(sym2)
     });
 

src/librustc_mir/monomorphize/partitioning.rs

@@ -262,7 +262,7 @@ pub fn partition<'a, 'tcx, I>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         internalization_candidates: _,
     } = post_inlining;
 
-    result.sort_by(|cgu1, cgu2| {
+    result.sort_unstable_by(|cgu1, cgu2| {
         cgu1.name().cmp(cgu2.name())
     });
 
@@ -502,7 +502,7 @@ fn merge_codegen_units<'tcx>(initial_partitioning: &mut PreInliningPartitioning<
     // smallest into each other) we're sure to start off with a deterministic
     // order (sorted by name). This'll mean that if two cgus have the same size
     // the stable sort below will keep everything nice and deterministic.
-    codegen_units.sort_by_key(|cgu| cgu.name().clone());
+    codegen_units.sort_unstable_by_key(|cgu| cgu.name().clone());
 
     // Merge the two smallest codegen units until the target size is reached.
     while codegen_units.len() > target_cgu_count {

src/librustc_mir/transform/check_unsafety.rs

@@ -501,7 +501,7 @@ pub fn check_unsafety<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
     }
 
     let mut unsafe_blocks: Vec<_> = unsafe_blocks.into_iter().collect();
-    unsafe_blocks.sort();
+    unsafe_blocks.sort_unstable();
     let used_unsafe: FxHashSet<_> = unsafe_blocks.iter()
         .flat_map(|&&(id, used)| if used { Some(id) } else { None })
         .collect();

src/librustc_mir/util/patch.rs

@@ -156,7 +156,7 @@ impl<'tcx> MirPatch<'tcx> {
         }
 
         let mut new_statements = self.new_statements;
-        new_statements.sort_by(|u,v| u.0.cmp(&v.0));
+        new_statements.sort_unstable_by(|u,v| u.0.cmp(&v.0));
 
         let mut delta = 0;
         let mut last_bb = START_BLOCK;