diff --git a/compiler/rustc_borrowck/src/borrow_set.rs b/compiler/rustc_borrowck/src/borrow_set.rs
index 5bb92a35826..fa0552e012d 100644
--- a/compiler/rustc_borrowck/src/borrow_set.rs
+++ b/compiler/rustc_borrowck/src/borrow_set.rs
@@ -4,7 +4,7 @@ use crate::nll::ToRegionVid;
 use crate::path_utils::allow_two_phase_borrow;
 use crate::place_ext::PlaceExt;
 use crate::BorrowIndex;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::traversal;
 use rustc_middle::mir::visit::{MutatingUseContext, NonUseContext, PlaceContext, Visitor};
@@ -26,10 +26,10 @@ pub struct BorrowSet<'tcx> {
     /// NOTE: a given location may activate more than one borrow in the future
     /// when more general two-phase borrow support is introduced, but for now we
     /// only need to store one borrow index.
-    pub activation_map: FxHashMap<Location, Vec<BorrowIndex>>,
+    pub activation_map: FxIndexMap<Location, Vec<BorrowIndex>>,
 
     /// Map from local to all the borrows on that local.
-    pub local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
+    pub local_map: FxIndexMap<mir::Local, FxIndexSet<BorrowIndex>>,
 
     pub(crate) locals_state_at_exit: LocalsStateAtExit,
 }
@@ -175,8 +175,8 @@ struct GatherBorrows<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     body: &'a Body<'tcx>,
     location_map: FxIndexMap<Location, BorrowData<'tcx>>,
-    activation_map: FxHashMap<Location, Vec<BorrowIndex>>,
-    local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
+    activation_map: FxIndexMap<Location, Vec<BorrowIndex>>,
+    local_map: FxIndexMap<mir::Local, FxIndexSet<BorrowIndex>>,
 
     /// When we encounter a 2-phase borrow statement, it will always
     /// be assigning into a temporary TEMP:
@@ -186,7 +186,7 @@ struct GatherBorrows<'a, 'tcx> {
     /// We add TEMP into this map with `b`, where `b` is the index of
     /// the borrow. When we find a later use of this activation, we
     /// remove from the map (and add to the "tombstone" set below).
-    pending_activations: FxHashMap<mir::Local, BorrowIndex>,
+    pending_activations: FxIndexMap<mir::Local, BorrowIndex>,
 
     locals_state_at_exit: LocalsStateAtExit,
 }
diff --git a/compiler/rustc_borrowck/src/dataflow.rs b/compiler/rustc_borrowck/src/dataflow.rs
index 2821677c537..d2574aa58c2 100644
--- a/compiler/rustc_borrowck/src/dataflow.rs
+++ b/compiler/rustc_borrowck/src/dataflow.rs
@@ -1,6 +1,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::{self, BasicBlock, Body, Location, Place};
 use rustc_middle::ty::RegionVid;
@@ -124,7 +124,7 @@ pub struct Borrows<'a, 'tcx> {
     body: &'a Body<'tcx>,
 
     borrow_set: &'a BorrowSet<'tcx>,
-    borrows_out_of_scope_at_location: FxHashMap<Location, Vec<BorrowIndex>>,
+    borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
 struct StackEntry {
@@ -138,7 +138,7 @@ struct OutOfScopePrecomputer<'a, 'tcx> {
     visit_stack: Vec<StackEntry>,
     body: &'a Body<'tcx>,
     regioncx: &'a RegionInferenceContext<'tcx>,
-    borrows_out_of_scope_at_location: FxHashMap<Location, Vec<BorrowIndex>>,
+    borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
 impl<'a, 'tcx> OutOfScopePrecomputer<'a, 'tcx> {
@@ -148,7 +148,7 @@ impl<'a, 'tcx> OutOfScopePrecomputer<'a, 'tcx> {
             visit_stack: vec![],
             body,
             regioncx,
-            borrows_out_of_scope_at_location: FxHashMap::default(),
+            borrows_out_of_scope_at_location: FxIndexMap::default(),
         }
     }
 }
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index a622a215a2e..f43b611f54e 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -1,7 +1,7 @@
 use either::Either;
 use rustc_const_eval::util::CallKind;
 use rustc_data_structures::captures::Captures;
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{
     struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
 };
@@ -173,7 +173,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
             let mut is_loop_move = false;
             let mut in_pattern = false;
-            let mut seen_spans = FxHashSet::default();
+            let mut seen_spans = FxIndexSet::default();
 
             for move_site in &move_site_vec {
                 let move_out = self.move_data.moves[(*move_site).moi];
@@ -2223,8 +2223,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
         }
 
-        let mut visited = FxHashSet::default();
-        let mut move_locations = FxHashSet::default();
+        let mut visited = FxIndexSet::default();
+        let mut move_locations = FxIndexSet::default();
         let mut reinits = vec![];
         let mut result = vec![];
 
@@ -2351,7 +2351,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let reinits_reachable = reinits
             .into_iter()
             .filter(|reinit| {
-                let mut visited = FxHashSet::default();
+                let mut visited = FxIndexSet::default();
                 let mut stack = vec![*reinit];
                 while let Some(location) = stack.pop() {
                     if !visited.insert(location) {
diff --git a/compiler/rustc_borrowck/src/diagnostics/find_use.rs b/compiler/rustc_borrowck/src/diagnostics/find_use.rs
index 15f42e26cbf..fd1fda2ee4b 100644
--- a/compiler/rustc_borrowck/src/diagnostics/find_use.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/find_use.rs
@@ -9,7 +9,7 @@ use crate::{
     nll::ToRegionVid,
     region_infer::{Cause, RegionInferenceContext},
 };
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_middle::mir::visit::{MirVisitable, PlaceContext, Visitor};
 use rustc_middle::mir::{Body, Local, Location};
 use rustc_middle::ty::{RegionVid, TyCtxt};
@@ -37,7 +37,7 @@ struct UseFinder<'cx, 'tcx> {
 impl<'cx, 'tcx> UseFinder<'cx, 'tcx> {
     fn find(&mut self) -> Option<Cause> {
         let mut queue = VecDeque::new();
-        let mut visited = FxHashSet::default();
+        let mut visited = FxIndexSet::default();
 
         queue.push_back(self.start_point);
         while let Some(p) = queue.pop_front() {
diff --git a/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs b/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
index 1eaf0a2f15c..d5ece57437e 100644
--- a/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
@@ -1,7 +1,7 @@
 //! Contains utilities for generating suggestions for borrowck errors related to unsatisfied
 //! outlives constraints.
 
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::Diagnostic;
 use rustc_middle::ty::RegionVid;
 use smallvec::SmallVec;
@@ -87,7 +87,7 @@ impl OutlivesSuggestionBuilder {
 
         // Keep track of variables that we have already suggested unifying so that we don't print
         // out silly duplicate messages.
-        let mut unified_already = FxHashSet::default();
+        let mut unified_already = FxIndexSet::default();
 
         for (fr, outlived) in &self.constraints_to_add {
             let Some(fr_name) = self.region_vid_to_name(mbcx, *fr) else {
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 115e512a974..0fc3240c560 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -1,6 +1,5 @@
 //! This query borrow-checks the MIR to (further) ensure it is not broken.
 
-#![allow(rustc::potential_query_instability)]
 #![feature(associated_type_bounds)]
 #![feature(box_patterns)]
 #![feature(let_chains)]
@@ -18,7 +17,7 @@ extern crate rustc_middle;
 #[macro_use]
 extern crate tracing;
 
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::dominators::Dominators;
 use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::{Diagnostic, DiagnosticBuilder, DiagnosticMessage, SubdiagnosticMessage};
@@ -404,7 +403,7 @@ fn do_mir_borrowck<'tcx>(
     // Note that this set is expected to be small - only upvars from closures
     // would have a chance of erroneously adding non-user-defined mutable vars
     // to the set.
-    let temporary_used_locals: FxHashSet<Local> = mbcx
+    let temporary_used_locals: FxIndexSet<Local> = mbcx
         .used_mut
         .iter()
         .filter(|&local| !mbcx.body.local_decls[*local].is_user_variable())
@@ -491,7 +490,7 @@ pub struct BodyWithBorrowckFacts<'tcx> {
 
 pub struct BorrowckInferCtxt<'cx, 'tcx> {
     pub(crate) infcx: &'cx InferCtxt<'tcx>,
-    pub(crate) reg_var_to_origin: RefCell<FxHashMap<ty::RegionVid, RegionCtxt>>,
+    pub(crate) reg_var_to_origin: RefCell<FxIndexMap<ty::RegionVid, RegionCtxt>>,
 }
 
 impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
@@ -588,7 +587,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
     /// borrow errors that is handled by the `reservation_error_reported` field as the inclusion
     /// of the `Span` type (while required to mute some errors) stops the muting of the reservation
     /// errors.
-    access_place_error_reported: FxHashSet<(Place<'tcx>, Span)>,
+    access_place_error_reported: FxIndexSet<(Place<'tcx>, Span)>,
     /// This field keeps track of when borrow conflict errors are reported
     /// for reservations, so that we don't report seemingly duplicate
     /// errors for corresponding activations.
@@ -596,17 +595,17 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
     // FIXME: ideally this would be a set of `BorrowIndex`, not `Place`s,
     // but it is currently inconvenient to track down the `BorrowIndex`
     // at the time we detect and report a reservation error.
-    reservation_error_reported: FxHashSet<Place<'tcx>>,
+    reservation_error_reported: FxIndexSet<Place<'tcx>>,
     /// This fields keeps track of the `Span`s that we have
     /// used to report extra information for `FnSelfUse`, to avoid
     /// unnecessarily verbose errors.
-    fn_self_span_reported: FxHashSet<Span>,
+    fn_self_span_reported: FxIndexSet<Span>,
     /// This field keeps track of errors reported in the checking of uninitialized variables,
     /// so that we don't report seemingly duplicate errors.
-    uninitialized_error_reported: FxHashSet<PlaceRef<'tcx>>,
+    uninitialized_error_reported: FxIndexSet<PlaceRef<'tcx>>,
     /// This field keeps track of all the local variables that are declared mut and are mutated.
     /// Used for the warning issued by an unused mutable local variable.
-    used_mut: FxHashSet<Local>,
+    used_mut: FxIndexSet<Local>,
     /// If the function we're checking is a closure, then we'll need to report back the list of
     /// mutable upvars that have been used. This field keeps track of them.
     used_mut_upvars: SmallVec<[Field; 8]>,
@@ -628,7 +627,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
 
     /// Record the region names generated for each region in the given
     /// MIR def so that we can reuse them later in help/error messages.
-    region_names: RefCell<FxHashMap<RegionVid, RegionName>>,
+    region_names: RefCell<FxIndexMap<RegionVid, RegionName>>,
 
     /// The counter for generating new region names.
     next_region_name: RefCell<usize>,
@@ -2329,7 +2328,7 @@ mod error {
         /// same primary span come out in a consistent order.
         buffered_move_errors:
             BTreeMap<Vec<MoveOutIndex>, (PlaceRef<'tcx>, DiagnosticBuilder<'tcx, ErrorGuaranteed>)>,
-        buffered_mut_errors: FxHashMap<Span, (DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)>,
+        buffered_mut_errors: FxIndexMap<Span, (DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)>,
         /// Diagnostics to be reported buffer.
         buffered: Vec<Diagnostic>,
         /// Set to Some if we emit an error during borrowck
diff --git a/compiler/rustc_borrowck/src/member_constraints.rs b/compiler/rustc_borrowck/src/member_constraints.rs
index 4af324f740a..b6c5d4245d7 100644
--- a/compiler/rustc_borrowck/src/member_constraints.rs
+++ b/compiler/rustc_borrowck/src/member_constraints.rs
@@ -1,7 +1,7 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 use rustc_data_structures::captures::Captures;
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_index::vec::IndexVec;
 use rustc_middle::infer::MemberConstraint;
 use rustc_middle::ty::{self, Ty};
@@ -18,7 +18,7 @@ where
 {
     /// Stores the first "member" constraint for a given `R0`. This is an
     /// index into the `constraints` vector below.
-    first_constraints: FxHashMap<R, NllMemberConstraintIndex>,
+    first_constraints: FxIndexMap<R, NllMemberConstraintIndex>,
 
     /// Stores the data about each `R0 member of [R1..Rn]` constraint.
     /// These are organized into a linked list, so each constraint
@@ -132,7 +132,7 @@ where
 
         let MemberConstraintSet { first_constraints, mut constraints, choice_regions } = self;
 
-        let mut first_constraints2 = FxHashMap::default();
+        let mut first_constraints2 = FxIndexMap::default();
         first_constraints2.reserve(first_constraints.len());
 
         for (r1, start1) in first_constraints {
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index e6195de404c..905d8c42b28 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -3,7 +3,7 @@ use std::rc::Rc;
 
 use rustc_data_structures::binary_search_util;
 use rustc_data_structures::frozen::Frozen;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::scc::Sccs;
 use rustc_errors::Diagnostic;
 use rustc_hir::def_id::CRATE_DEF_ID;
@@ -88,7 +88,7 @@ pub struct RegionInferenceContext<'tcx> {
     member_constraints_applied: Vec<AppliedMemberConstraint>,
 
     /// Map universe indexes to information on why we created it.
-    universe_causes: FxHashMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
+    universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
 
     /// Contains the minimum universe of any variable within the same
     /// SCC. We will ensure that no SCC contains values that are not
@@ -263,7 +263,7 @@ fn sccs_info<'cx, 'tcx>(
     debug!(debug_str);
 
     let num_components = sccs.scc_data().ranges().len();
-    let mut components = vec![FxHashSet::default(); num_components];
+    let mut components = vec![FxIndexSet::default(); num_components];
 
     for (reg_var_idx, scc_idx) in sccs.scc_indices().iter().enumerate() {
         let reg_var = ty::RegionVid::from_usize(reg_var_idx);
@@ -295,9 +295,9 @@ fn sccs_info<'cx, 'tcx>(
 
             (ConstraintSccIndex::from_usize(scc_idx), repr)
         })
-        .collect::<FxHashMap<_, _>>();
+        .collect::<FxIndexMap<_, _>>();
 
-    let mut scc_node_to_edges = FxHashMap::default();
+    let mut scc_node_to_edges = FxIndexMap::default();
     for (scc_idx, repr) in components_representatives.iter() {
         let edges_range = sccs.scc_data().ranges()[*scc_idx].clone();
         let edges = &sccs.scc_data().all_successors()[edges_range];
@@ -325,7 +325,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
         outlives_constraints: OutlivesConstraintSet<'tcx>,
         member_constraints_in: MemberConstraintSet<'tcx, RegionVid>,
-        universe_causes: FxHashMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
+        universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
         type_tests: Vec<TypeTest<'tcx>>,
         liveness_constraints: LivenessValues<RegionVid>,
         elements: &Rc<RegionValueElements>,
@@ -522,6 +522,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// outlives `'a` and hence contains R0 and R1.
     fn init_free_and_bound_regions(&mut self) {
         // Update the names (if any)
+        // This iterator has unstable order but we collect it all into an IndexVec
         for (external_name, variable) in self.universal_regions.named_universal_regions() {
             debug!(
                 "init_universal_regions: region {:?} has external name {:?}",
@@ -918,7 +919,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // Sometimes we register equivalent type-tests that would
         // result in basically the exact same error being reported to
         // the user. Avoid that.
-        let mut deduplicate_errors = FxHashSet::default();
+        let mut deduplicate_errors = FxIndexSet::default();
 
         for type_test in &self.type_tests {
             debug!("check_type_test: {:?}", type_test);
@@ -1504,6 +1505,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // the outlives suggestions or the debug output from `#[rustc_regions]` would be
         // duplicated. The polonius subset errors are deduplicated here, while keeping the
         // CFG-location ordering.
+        // We can iterate the HashMap here because the result is sorted afterwards.
+        #[allow(rustc::potential_query_instability)]
         let mut subset_errors: Vec<_> = polonius_output
             .subset_errors
             .iter()
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index c550e37c63e..ec4b2e9d3e4 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -1,4 +1,4 @@
-use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::LocalDefId;
@@ -65,7 +65,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ) -> VecMap<LocalDefId, OpaqueHiddenType<'tcx>> {
         let mut result: VecMap<LocalDefId, OpaqueHiddenType<'tcx>> = VecMap::new();
 
-        let member_constraints: FxHashMap<_, _> = self
+        let member_constraints: FxIndexMap<_, _> = self
             .member_constraints
             .all_indices()
             .map(|ci| (self.member_constraints[ci].key, ci))
@@ -364,7 +364,7 @@ fn check_opaque_type_parameter_valid(
         OpaqueTyOrigin::TyAlias => {}
     }
     let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
-    let mut seen_params: FxHashMap<_, Vec<_>> = FxHashMap::default();
+    let mut seen_params: FxIndexMap<_, Vec<_>> = FxIndexMap::default();
     for (i, arg) in opaque_type_key.substs.iter().enumerate() {
         let arg_is_param = match arg.unpack() {
             GenericArgKind::Type(ty) => matches!(ty.kind(), ty::Param(_)),
diff --git a/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs b/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
index 167f6646096..23a59c12865 100644
--- a/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
+++ b/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
@@ -3,7 +3,7 @@
 use crate::constraints::ConstraintSccIndex;
 use crate::RegionInferenceContext;
 use itertools::Itertools;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::vec_graph::VecGraph;
 use rustc_data_structures::graph::WithSuccessors;
 use rustc_middle::ty::RegionVid;
@@ -14,7 +14,7 @@ pub(crate) struct ReverseSccGraph {
     graph: VecGraph<ConstraintSccIndex>,
     /// For each SCC, the range of `universal_regions` that use that SCC as
     /// their value.
-    scc_regions: FxHashMap<ConstraintSccIndex, Range<usize>>,
+    scc_regions: FxIndexMap<ConstraintSccIndex, Range<usize>>,
     /// All of the universal regions, in grouped so that `scc_regions` can
     /// index into here.
     universal_regions: Vec<RegionVid>,
@@ -26,7 +26,7 @@ impl ReverseSccGraph {
         &'a self,
         scc0: ConstraintSccIndex,
     ) -> impl Iterator<Item = RegionVid> + 'a {
-        let mut duplicates = FxHashSet::default();
+        let mut duplicates = FxIndexSet::default();
         self.graph
             .depth_first_search(scc0)
             .flat_map(move |scc1| {
@@ -55,7 +55,7 @@ impl RegionInferenceContext<'_> {
         paired_scc_regions.sort();
         let universal_regions = paired_scc_regions.iter().map(|&(_, region)| region).collect();
 
-        let mut scc_regions = FxHashMap::default();
+        let mut scc_regions = FxIndexMap::default();
         let mut start = 0;
         for (scc, group) in &paired_scc_regions.into_iter().group_by(|(scc, _)| *scc) {
             let group_size = group.count();
diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index 717020ea5b8..17e702eb8c5 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -19,7 +19,7 @@ use super::{Locations, TypeChecker};
 
 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     /// Check explicit closure signature annotation,
-    /// e.g., `|x: FxHashMap<_, &'static u32>| ...`.
+    /// e.g., `|x: FxIndexMap<_, &'static u32>| ...`.
     #[instrument(skip(self, body), level = "debug")]
     pub(super) fn check_signature_annotation(&mut self, body: &Body<'tcx>) {
         let mir_def_id = body.source.def_id().expect_local();
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
index 473c0596300..a687d3f5352 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
@@ -1,4 +1,4 @@
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_index::bit_set::HybridBitSet;
 use rustc_index::interval::IntervalSet;
 use rustc_infer::infer::canonical::QueryRegionConstraints;
@@ -56,7 +56,7 @@ pub(super) fn trace<'mir, 'tcx>(
         elements,
         local_use_map,
         move_data,
-        drop_data: FxHashMap::default(),
+        drop_data: FxIndexMap::default(),
     };
 
     let mut results = LivenessResults::new(cx);
@@ -85,7 +85,7 @@ struct LivenessContext<'me, 'typeck, 'flow, 'tcx> {
     move_data: &'me MoveData<'tcx>,
 
     /// Cache for the results of `dropck_outlives` query.
-    drop_data: FxHashMap<Ty<'tcx>, DropData<'tcx>>,
+    drop_data: FxIndexMap<Ty<'tcx>, DropData<'tcx>>,
 
     /// Results of dataflow tracking which variables (and paths) have been
     /// initialized.
@@ -185,7 +185,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
     fn add_extra_drop_facts(
         &mut self,
         drop_used: Vec<(Local, Location)>,
-        relevant_live_locals: FxHashSet<Local>,
+        relevant_live_locals: FxIndexSet<Local>,
     ) {
         let locations = IntervalSet::new(self.cx.elements.num_points());
 
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index a49da3da6c0..06c7b8b8f87 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -9,7 +9,7 @@ use either::Either;
 
 use hir::OpaqueTyOrigin;
 use rustc_data_structures::frozen::Frozen;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::vec_map::VecMap;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
@@ -145,7 +145,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
         outlives_constraints: OutlivesConstraintSet::default(),
         member_constraints: MemberConstraintSet::default(),
         type_tests: Vec::default(),
-        universe_causes: FxHashMap::default(),
+        universe_causes: FxIndexMap::default(),
     };
 
     let CreateResult {
@@ -875,7 +875,7 @@ struct TypeChecker<'a, 'tcx> {
     user_type_annotations: &'a CanonicalUserTypeAnnotations<'tcx>,
     region_bound_pairs: &'a RegionBoundPairs<'tcx>,
     implicit_region_bound: ty::Region<'tcx>,
-    reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
+    reported_errors: FxIndexSet<(Ty<'tcx>, Span)>,
     borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
 }
 
@@ -925,7 +925,7 @@ pub(crate) struct MirTypeckRegionConstraints<'tcx> {
 
     pub(crate) member_constraints: MemberConstraintSet<'tcx, RegionVid>,
 
-    pub(crate) universe_causes: FxHashMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
+    pub(crate) universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
 
     pub(crate) type_tests: Vec<TypeTest<'tcx>>,
 }
diff --git a/compiler/rustc_borrowck/src/universal_regions.rs b/compiler/rustc_borrowck/src/universal_regions.rs
index 76d0b875424..68c86051364 100644
--- a/compiler/rustc_borrowck/src/universal_regions.rs
+++ b/compiler/rustc_borrowck/src/universal_regions.rs
@@ -312,6 +312,9 @@ impl<'tcx> UniversalRegions<'tcx> {
     }
 
     /// Gets an iterator over all the early-bound regions that have names.
+    /// Iteration order may be unstable, so this should only be used when
+    /// iteration order doesn't affect anything
+    #[allow(rustc::potential_query_instability)]
     pub fn named_universal_regions<'s>(
         &'s self,
     ) -> impl Iterator<Item = (ty::Region<'tcx>, ty::RegionVid)> + 's {
diff --git a/compiler/rustc_borrowck/src/used_muts.rs b/compiler/rustc_borrowck/src/used_muts.rs
index e297b1230ea..18dbe24d3b8 100644
--- a/compiler/rustc_borrowck/src/used_muts.rs
+++ b/compiler/rustc_borrowck/src/used_muts.rs
@@ -1,6 +1,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::{
     Local, Location, Place, Statement, StatementKind, Terminator, TerminatorKind,
@@ -26,8 +26,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     ///  See #55344 for context.
     pub(crate) fn gather_used_muts(
         &mut self,
-        temporary_used_locals: FxHashSet<Local>,
-        mut never_initialized_mut_locals: FxHashSet<Local>,
+        temporary_used_locals: FxIndexSet<Local>,
+        mut never_initialized_mut_locals: FxIndexSet<Local>,
     ) {
         {
             let mut visitor = GatherUsedMutsVisitor {
@@ -48,8 +48,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 /// MIR visitor for collecting used mutable variables.
 /// The 'visit lifetime represents the duration of the MIR walk.
 struct GatherUsedMutsVisitor<'visit, 'cx, 'tcx> {
-    temporary_used_locals: FxHashSet<Local>,
-    never_initialized_mut_locals: &'visit mut FxHashSet<Local>,
+    temporary_used_locals: FxIndexSet<Local>,
+    never_initialized_mut_locals: &'visit mut FxIndexSet<Local>,
     mbcx: &'visit mut MirBorrowckCtxt<'cx, 'tcx>,
 }