Merging upstream version 1.71.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

9 files changed, 299 insertions, 253 deletions

diff --git a/compiler/rustc_monomorphize/Cargo.toml b/compiler/rustc_monomorphize/Cargo.toml
index c8af10576..6d3a3bf90 100644
--- a/compiler/rustc_monomorphize/Cargo.toml
+++ b/compiler/rustc_monomorphize/Cargo.toml
@@ -8,11 +8,11 @@ edition = "2021"
 [dependencies]
 serde = "1"
 serde_json = "1"
-smallvec = { version = "1.8.1", features = [ "union", "may_dangle" ] }
 tracing = "0.1"
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_hir = { path = "../rustc_hir" }
+rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
diff --git a/compiler/rustc_monomorphize/messages.ftl b/compiler/rustc_monomorphize/messages.ftl
index 6cea6a603..fdd47e6f7 100644
--- a/compiler/rustc_monomorphize/messages.ftl
+++ b/compiler/rustc_monomorphize/messages.ftl
@@ -1,32 +1,32 @@
-monomorphize_recursion_limit =
-    reached the recursion limit while instantiating `{$shrunk}`
-    .note = `{$def_path_str}` defined here
-
-monomorphize_written_to_path = the full type name has been written to '{$path}'
-
-monomorphize_type_length_limit = reached the type-length limit while instantiating `{$shrunk}`
-
 monomorphize_consider_type_length_limit =
     consider adding a `#![type_length_limit="{$type_length}"]` attribute to your crate
 
-monomorphize_fatal_error = {$error_message}
-
-monomorphize_unknown_partition_strategy = unknown partitioning strategy
+monomorphize_couldnt_dump_mono_stats =
+    unexpected error occurred while dumping monomorphization stats: {$error}
 
-monomorphize_symbol_already_defined = symbol `{$symbol}` is already defined
+monomorphize_encountered_error_while_instantiating =
+    the above error was encountered while instantiating `{$formatted_item}`
 
-monomorphize_unused_generic_params = item has unused generic parameters
+monomorphize_fatal_error = {$error_message}
 
 monomorphize_large_assignments =
     moving {$size} bytes
     .label = value moved from here
     .note = The current maximum size is {$limit}, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
 
-monomorphize_couldnt_dump_mono_stats =
-    unexpected error occurred while dumping monomorphization stats: {$error}
+monomorphize_recursion_limit =
+    reached the recursion limit while instantiating `{$shrunk}`
+    .note = `{$def_path_str}` defined here
 
-monomorphize_encountered_error_while_instantiating =
-    the above error was encountered while instantiating `{$formatted_item}`
+monomorphize_symbol_already_defined = symbol `{$symbol}` is already defined
+
+monomorphize_type_length_limit = reached the type-length limit while instantiating `{$shrunk}`
 
 monomorphize_unknown_cgu_collection_mode =
     unknown codegen-item collection mode '{$mode}', falling back to 'lazy' mode
+
+monomorphize_unknown_partition_strategy = unknown partitioning strategy
+
+monomorphize_unused_generic_params = item has unused generic parameters
+
+monomorphize_written_to_path = the full type name has been written to '{$path}'
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 7bcff7e07..35b154b7b 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -185,9 +185,9 @@ use rustc_middle::mir::interpret::{ErrorHandled, GlobalAlloc, Scalar};
 use rustc_middle::mir::mono::{InstantiationMode, MonoItem};
 use rustc_middle::mir::visit::Visitor as MirVisitor;
 use rustc_middle::mir::{self, Local, Location};
+use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::adjustment::{CustomCoerceUnsized, PointerCast};
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::query::TyCtxtAt;
 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
 use rustc_middle::ty::{
     self, GenericParamDefKind, Instance, InstanceDef, Ty, TyCtxt, TypeFoldable, TypeVisitableExt,
@@ -402,7 +402,7 @@ fn collect_roots(tcx: TyCtxt<'_>, mode: MonoItemCollectionMode) -> Vec<MonoItem<
 }
 
 /// Collect all monomorphized items reachable from `starting_point`, and emit a note diagnostic if a
-/// post-monorphization error is encountered during a collection step.
+/// post-monomorphization error is encountered during a collection step.
 #[instrument(skip(tcx, visited, recursion_depths, recursion_limit, inlining_map), level = "debug")]
 fn collect_items_rec<'tcx>(
     tcx: TyCtxt<'tcx>,
@@ -677,7 +677,7 @@ impl<'a, 'tcx> MirNeighborCollector<'a, 'tcx> {
         self.instance.subst_mir_and_normalize_erasing_regions(
             self.tcx,
             ty::ParamEnv::reveal_all(),
-            value,
+            ty::EarlyBinder(value),
         )
     }
 }
@@ -843,7 +843,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                 }
             }
             mir::TerminatorKind::Assert { ref msg, .. } => {
-                let lang_item = match msg {
+                let lang_item = match &**msg {
                     mir::AssertKind::BoundsCheck { .. } => LangItem::PanicBoundsCheck,
                     _ => LangItem::Panic,
                 };
@@ -1230,7 +1230,7 @@ impl<'v> RootCollector<'_, 'v> {
             DefKind::GlobalAsm => {
                 debug!(
                     "RootCollector: ItemKind::GlobalAsm({})",
-                    self.tcx.def_path_str(id.owner_id.to_def_id())
+                    self.tcx.def_path_str(id.owner_id)
                 );
                 self.output.push(dummy_spanned(MonoItem::GlobalAsm(id)));
             }
diff --git a/compiler/rustc_monomorphize/src/lib.rs b/compiler/rustc_monomorphize/src/lib.rs
index 5000fb719..ecc50c3f6 100644
--- a/compiler/rustc_monomorphize/src/lib.rs
+++ b/compiler/rustc_monomorphize/src/lib.rs
@@ -10,11 +10,11 @@ extern crate tracing;
 extern crate rustc_middle;
 
 use rustc_errors::{DiagnosticMessage, SubdiagnosticMessage};
+use rustc_fluent_macro::fluent_messages;
 use rustc_hir::lang_items::LangItem;
-use rustc_macros::fluent_messages;
+use rustc_middle::query::{Providers, TyCtxtAt};
 use rustc_middle::traits;
 use rustc_middle::ty::adjustment::CustomCoerceUnsized;
-use rustc_middle::ty::query::{Providers, TyCtxtAt};
 use rustc_middle::ty::{self, Ty};
 
 mod collector;
@@ -30,8 +30,12 @@ fn custom_coerce_unsize_info<'tcx>(
     source_ty: Ty<'tcx>,
     target_ty: Ty<'tcx>,
 ) -> CustomCoerceUnsized {
-    let trait_ref =
-        ty::Binder::dummy(tcx.mk_trait_ref(LangItem::CoerceUnsized, [source_ty, target_ty]));
+    let trait_ref = ty::Binder::dummy(ty::TraitRef::from_lang_item(
+        tcx.tcx,
+        LangItem::CoerceUnsized,
+        tcx.span,
+        [source_ty, target_ty],
+    ));
 
     match tcx.codegen_select_candidate((ty::ParamEnv::reveal_all(), trait_ref)) {
         Ok(traits::ImplSource::UserDefined(traits::ImplSourceUserDefinedData {
diff --git a/compiler/rustc_monomorphize/src/partitioning/default.rs b/compiler/rustc_monomorphize/src/partitioning/default.rs
index 482b78d42..603b3ddc1 100644
--- a/compiler/rustc_monomorphize/src/partitioning/default.rs
+++ b/compiler/rustc_monomorphize/src/partitioning/default.rs
@@ -1,3 +1,4 @@
+use std::cmp;
 use std::collections::hash_map::Entry;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -14,19 +15,19 @@ use rustc_span::symbol::Symbol;
 
 use super::PartitioningCx;
 use crate::collector::InliningMap;
-use crate::partitioning::merging;
-use crate::partitioning::{
-    MonoItemPlacement, Partitioner, PostInliningPartitioning, PreInliningPartitioning,
-};
+use crate::partitioning::{MonoItemPlacement, Partition, PlacedRootMonoItems};
 
 pub struct DefaultPartitioning;
 
-impl<'tcx> Partitioner<'tcx> for DefaultPartitioning {
-    fn place_root_mono_items(
+impl<'tcx> Partition<'tcx> for DefaultPartitioning {
+    fn place_root_mono_items<I>(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        mono_items: &mut dyn Iterator<Item = MonoItem<'tcx>>,
-    ) -> PreInliningPartitioning<'tcx> {
+        mono_items: &mut I,
+    ) -> PlacedRootMonoItems<'tcx>
+    where
+        I: Iterator<Item = MonoItem<'tcx>>,
+    {
         let mut roots = FxHashSet::default();
         let mut codegen_units = FxHashMap::default();
         let is_incremental_build = cx.tcx.sess.opts.incremental.is_some();
@@ -88,38 +89,120 @@ impl<'tcx> Partitioner<'tcx> for DefaultPartitioning {
             codegen_units.insert(codegen_unit_name, CodegenUnit::new(codegen_unit_name));
         }
 
-        PreInliningPartitioning {
-            codegen_units: codegen_units.into_values().map(|codegen_unit| codegen_unit).collect(),
-            roots,
-            internalization_candidates,
-        }
+        let codegen_units = codegen_units.into_values().collect();
+        PlacedRootMonoItems { codegen_units, roots, internalization_candidates }
     }
 
     fn merge_codegen_units(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        initial_partitioning: &mut PreInliningPartitioning<'tcx>,
+        codegen_units: &mut Vec<CodegenUnit<'tcx>>,
     ) {
-        merging::merge_codegen_units(cx, initial_partitioning);
+        assert!(cx.target_cgu_count >= 1);
+
+        // Note that at this point in time the `codegen_units` here may not be
+        // in a deterministic order (but we know they're deterministically the
+        // same set). We want this merging to produce a deterministic ordering
+        // of codegen units from the input.
+        //
+        // Due to basically how we've implemented the merging below (merge the
+        // two 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(|a, b| a.name().as_str().cmp(b.name().as_str()));
+
+        // This map keeps track of what got merged into what.
+        let mut cgu_contents: FxHashMap<Symbol, Vec<Symbol>> =
+            codegen_units.iter().map(|cgu| (cgu.name(), vec![cgu.name()])).collect();
+
+        // Merge the two smallest codegen units until the target size is
+        // reached.
+        while codegen_units.len() > cx.target_cgu_count {
+            // Sort small cgus to the back
+            codegen_units.sort_by_cached_key(|cgu| cmp::Reverse(cgu.size_estimate()));
+            let mut smallest = codegen_units.pop().unwrap();
+            let second_smallest = codegen_units.last_mut().unwrap();
+
+            // Move the mono-items from `smallest` to `second_smallest`
+            second_smallest.modify_size_estimate(smallest.size_estimate());
+            for (k, v) in smallest.items_mut().drain() {
+                second_smallest.items_mut().insert(k, v);
+            }
+
+            // Record that `second_smallest` now contains all the stuff that was
+            // in `smallest` before.
+            let mut consumed_cgu_names = cgu_contents.remove(&smallest.name()).unwrap();
+            cgu_contents.get_mut(&second_smallest.name()).unwrap().append(&mut consumed_cgu_names);
+
+            debug!(
+                "CodegenUnit {} merged into CodegenUnit {}",
+                smallest.name(),
+                second_smallest.name()
+            );
+        }
+
+        let cgu_name_builder = &mut CodegenUnitNameBuilder::new(cx.tcx);
+
+        if cx.tcx.sess.opts.incremental.is_some() {
+            // If we are doing incremental compilation, we want CGU names to
+            // reflect the path of the source level module they correspond to.
+            // For CGUs that contain the code of multiple modules because of the
+            // merging done above, we use a concatenation of the names of all
+            // contained CGUs.
+            let new_cgu_names: FxHashMap<Symbol, String> = cgu_contents
+                .into_iter()
+                // This `filter` makes sure we only update the name of CGUs that
+                // were actually modified by merging.
+                .filter(|(_, cgu_contents)| cgu_contents.len() > 1)
+                .map(|(current_cgu_name, cgu_contents)| {
+                    let mut cgu_contents: Vec<&str> =
+                        cgu_contents.iter().map(|s| s.as_str()).collect();
+
+                    // Sort the names, so things are deterministic and easy to
+                    // predict. We are sorting primitive `&str`s here so we can
+                    // use unstable sort.
+                    cgu_contents.sort_unstable();
+
+                    (current_cgu_name, cgu_contents.join("--"))
+                })
+                .collect();
+
+            for cgu in codegen_units.iter_mut() {
+                if let Some(new_cgu_name) = new_cgu_names.get(&cgu.name()) {
+                    if cx.tcx.sess.opts.unstable_opts.human_readable_cgu_names {
+                        cgu.set_name(Symbol::intern(&new_cgu_name));
+                    } else {
+                        // If we don't require CGU names to be human-readable,
+                        // we use a fixed length hash of the composite CGU name
+                        // instead.
+                        let new_cgu_name = CodegenUnit::mangle_name(&new_cgu_name);
+                        cgu.set_name(Symbol::intern(&new_cgu_name));
+                    }
+                }
+            }
+        } else {
+            // If we are compiling non-incrementally we just generate simple CGU
+            // names containing an index.
+            for (index, cgu) in codegen_units.iter_mut().enumerate() {
+                let numbered_codegen_unit_name =
+                    cgu_name_builder.build_cgu_name_no_mangle(LOCAL_CRATE, &["cgu"], Some(index));
+                cgu.set_name(numbered_codegen_unit_name);
+            }
+        }
     }
 
     fn place_inlined_mono_items(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        initial_partitioning: PreInliningPartitioning<'tcx>,
-    ) -> PostInliningPartitioning<'tcx> {
-        let mut new_partitioning = Vec::new();
+        codegen_units: &mut [CodegenUnit<'tcx>],
+        roots: FxHashSet<MonoItem<'tcx>>,
+    ) -> FxHashMap<MonoItem<'tcx>, MonoItemPlacement> {
         let mut mono_item_placements = FxHashMap::default();
 
-        let PreInliningPartitioning {
-            codegen_units: initial_cgus,
-            roots,
-            internalization_candidates,
-        } = initial_partitioning;
-
-        let single_codegen_unit = initial_cgus.len() == 1;
+        let single_codegen_unit = codegen_units.len() == 1;
 
-        for old_codegen_unit in initial_cgus {
+        for old_codegen_unit in codegen_units.iter_mut() {
             // Collect all items that need to be available in this codegen unit.
             let mut reachable = FxHashSet::default();
             for root in old_codegen_unit.items().keys() {
@@ -171,14 +254,10 @@ impl<'tcx> Partitioner<'tcx> for DefaultPartitioning {
                 }
             }
 
-            new_partitioning.push(new_codegen_unit);
+            *old_codegen_unit = new_codegen_unit;
         }
 
-        return PostInliningPartitioning {
-            codegen_units: new_partitioning,
-            mono_item_placements,
-            internalization_candidates,
-        };
+        return mono_item_placements;
 
         fn follow_inlining<'tcx>(
             mono_item: MonoItem<'tcx>,
@@ -198,14 +277,16 @@ impl<'tcx> Partitioner<'tcx> for DefaultPartitioning {
     fn internalize_symbols(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        partitioning: &mut PostInliningPartitioning<'tcx>,
+        codegen_units: &mut [CodegenUnit<'tcx>],
+        mono_item_placements: FxHashMap<MonoItem<'tcx>, MonoItemPlacement>,
+        internalization_candidates: FxHashSet<MonoItem<'tcx>>,
     ) {
-        if partitioning.codegen_units.len() == 1 {
+        if codegen_units.len() == 1 {
             // Fast path for when there is only one codegen unit. In this case we
             // can internalize all candidates, since there is nowhere else they
             // could be accessed from.
-            for cgu in &mut partitioning.codegen_units {
-                for candidate in &partitioning.internalization_candidates {
+            for cgu in codegen_units {
+                for candidate in &internalization_candidates {
                     cgu.items_mut().insert(*candidate, (Linkage::Internal, Visibility::Default));
                 }
             }
@@ -222,15 +303,13 @@ impl<'tcx> Partitioner<'tcx> for DefaultPartitioning {
             }
         });
 
-        let mono_item_placements = &partitioning.mono_item_placements;
-
         // For each internalization candidates in each codegen unit, check if it is
         // accessed from outside its defining codegen unit.
-        for cgu in &mut partitioning.codegen_units {
+        for cgu in codegen_units {
             let home_cgu = MonoItemPlacement::SingleCgu { cgu_name: cgu.name() };
 
             for (accessee, linkage_and_visibility) in cgu.items_mut() {
-                if !partitioning.internalization_candidates.contains(accessee) {
+                if !internalization_candidates.contains(accessee) {
                     // This item is no candidate for internalizing, so skip it.
                     continue;
                 }
@@ -267,7 +346,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
     match mono_item {
         MonoItem::Fn(instance) => {
             let def_id = match instance.def {
-                ty::InstanceDef::Item(def) => def.did,
+                ty::InstanceDef::Item(def) => def,
                 ty::InstanceDef::VTableShim(..)
                 | ty::InstanceDef::ReifyShim(..)
                 | ty::InstanceDef::FnPtrShim(..)
@@ -302,12 +381,12 @@ fn characteristic_def_id_of_mono_item<'tcx>(
 
                 // When polymorphization is enabled, methods which do not depend on their generic
                 // parameters, but the self-type of their impl block do will fail to normalize.
-                if !tcx.sess.opts.unstable_opts.polymorphize || !instance.needs_subst() {
+                if !tcx.sess.opts.unstable_opts.polymorphize || !instance.has_param() {
                     // This is a method within an impl, find out what the self-type is:
                     let impl_self_ty = tcx.subst_and_normalize_erasing_regions(
                         instance.substs,
                         ty::ParamEnv::reveal_all(),
-                        tcx.type_of(impl_def_id).skip_binder(),
+                        tcx.type_of(impl_def_id),
                     );
                     if let Some(def_id) = characteristic_def_id_of_type(impl_self_ty) {
                         return Some(def_id);
@@ -421,10 +500,9 @@ fn mono_item_visibility<'tcx>(
     };
 
     let def_id = match instance.def {
-        InstanceDef::Item(def) => def.did,
-        InstanceDef::DropGlue(def_id, Some(_)) => def_id,
+        InstanceDef::Item(def_id) | InstanceDef::DropGlue(def_id, Some(_)) => def_id,
 
-        // We match the visiblity of statics here
+        // We match the visibility of statics here
         InstanceDef::ThreadLocalShim(def_id) => {
             return static_visibility(tcx, can_be_internalized, def_id);
         }
diff --git a/compiler/rustc_monomorphize/src/partitioning/merging.rs b/compiler/rustc_monomorphize/src/partitioning/merging.rs
deleted file mode 100644
index 5c524a184..000000000
--- a/compiler/rustc_monomorphize/src/partitioning/merging.rs
+++ /dev/null
@@ -1,111 +0,0 @@
-use std::cmp;
-
-use rustc_data_structures::fx::FxHashMap;
-use rustc_hir::def_id::LOCAL_CRATE;
-use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder};
-use rustc_span::symbol::Symbol;
-
-use super::PartitioningCx;
-use crate::partitioning::PreInliningPartitioning;
-
-pub fn merge_codegen_units<'tcx>(
-    cx: &PartitioningCx<'_, 'tcx>,
-    initial_partitioning: &mut PreInliningPartitioning<'tcx>,
-) {
-    assert!(cx.target_cgu_count >= 1);
-    let codegen_units = &mut initial_partitioning.codegen_units;
-
-    // Note that at this point in time the `codegen_units` here may not be in a
-    // deterministic order (but we know they're deterministically the same set).
-    // We want this merging to produce a deterministic ordering of codegen units
-    // from the input.
-    //
-    // Due to basically how we've implemented the merging below (merge the two
-    // 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(|a, b| a.name().as_str().cmp(b.name().as_str()));
-
-    // This map keeps track of what got merged into what.
-    let mut cgu_contents: FxHashMap<Symbol, Vec<Symbol>> =
-        codegen_units.iter().map(|cgu| (cgu.name(), vec![cgu.name()])).collect();
-
-    // Merge the two smallest codegen units until the target size is reached.
-    while codegen_units.len() > cx.target_cgu_count {
-        // Sort small cgus to the back
-        codegen_units.sort_by_cached_key(|cgu| cmp::Reverse(cgu.size_estimate()));
-        let mut smallest = codegen_units.pop().unwrap();
-        let second_smallest = codegen_units.last_mut().unwrap();
-
-        // Move the mono-items from `smallest` to `second_smallest`
-        second_smallest.modify_size_estimate(smallest.size_estimate());
-        for (k, v) in smallest.items_mut().drain() {
-            second_smallest.items_mut().insert(k, v);
-        }
-
-        // Record that `second_smallest` now contains all the stuff that was in
-        // `smallest` before.
-        let mut consumed_cgu_names = cgu_contents.remove(&smallest.name()).unwrap();
-        cgu_contents.get_mut(&second_smallest.name()).unwrap().append(&mut consumed_cgu_names);
-
-        debug!(
-            "CodegenUnit {} merged into CodegenUnit {}",
-            smallest.name(),
-            second_smallest.name()
-        );
-    }
-
-    let cgu_name_builder = &mut CodegenUnitNameBuilder::new(cx.tcx);
-
-    if cx.tcx.sess.opts.incremental.is_some() {
-        // If we are doing incremental compilation, we want CGU names to
-        // reflect the path of the source level module they correspond to.
-        // For CGUs that contain the code of multiple modules because of the
-        // merging done above, we use a concatenation of the names of
-        // all contained CGUs.
-        let new_cgu_names: FxHashMap<Symbol, String> = cgu_contents
-            .into_iter()
-            // This `filter` makes sure we only update the name of CGUs that
-            // were actually modified by merging.
-            .filter(|(_, cgu_contents)| cgu_contents.len() > 1)
-            .map(|(current_cgu_name, cgu_contents)| {
-                let mut cgu_contents: Vec<&str> = cgu_contents.iter().map(|s| s.as_str()).collect();
-
-                // Sort the names, so things are deterministic and easy to
-                // predict.
-
-                // We are sorting primitive &strs here so we can use unstable sort
-                cgu_contents.sort_unstable();
-
-                (current_cgu_name, cgu_contents.join("--"))
-            })
-            .collect();
-
-        for cgu in codegen_units.iter_mut() {
-            if let Some(new_cgu_name) = new_cgu_names.get(&cgu.name()) {
-                if cx.tcx.sess.opts.unstable_opts.human_readable_cgu_names {
-                    cgu.set_name(Symbol::intern(&new_cgu_name));
-                } else {
-                    // If we don't require CGU names to be human-readable, we
-                    // use a fixed length hash of the composite CGU name
-                    // instead.
-                    let new_cgu_name = CodegenUnit::mangle_name(&new_cgu_name);
-                    cgu.set_name(Symbol::intern(&new_cgu_name));
-                }
-            }
-        }
-    } else {
-        // If we are compiling non-incrementally we just generate simple CGU
-        // names containing an index.
-        for (index, cgu) in codegen_units.iter_mut().enumerate() {
-            cgu.set_name(numbered_codegen_unit_name(cgu_name_builder, index));
-        }
-    }
-}
-
-fn numbered_codegen_unit_name(
-    name_builder: &mut CodegenUnitNameBuilder<'_>,
-    index: usize,
-) -> Symbol {
-    name_builder.build_cgu_name_no_mangle(LOCAL_CRATE, &["cgu"], Some(index))
-}
diff --git a/compiler/rustc_monomorphize/src/partitioning/mod.rs b/compiler/rustc_monomorphize/src/partitioning/mod.rs
index 18aa0742c..d0b23ca9e 100644
--- a/compiler/rustc_monomorphize/src/partitioning/mod.rs
+++ b/compiler/rustc_monomorphize/src/partitioning/mod.rs
@@ -93,7 +93,6 @@
 //! inlining, even when they are not marked `#[inline]`.
 
 mod default;
-mod merging;
 
 use std::cmp;
 use std::fs::{self, File};
@@ -106,8 +105,8 @@ use rustc_hir::def_id::{DefIdSet, LOCAL_CRATE};
 use rustc_middle::mir;
 use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::mir::mono::{CodegenUnit, Linkage};
+use rustc_middle::query::Providers;
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{DumpMonoStatsFormat, SwitchWithOptPath};
 use rustc_span::symbol::Symbol;
@@ -118,58 +117,135 @@ use crate::errors::{
     CouldntDumpMonoStats, SymbolAlreadyDefined, UnknownCguCollectionMode, UnknownPartitionStrategy,
 };
 
-pub struct PartitioningCx<'a, 'tcx> {
+enum Partitioner {
+    Default(default::DefaultPartitioning),
+    // Other partitioning strategies can go here.
+    Unknown,
+}
+
+impl<'tcx> Partition<'tcx> for Partitioner {
+    fn place_root_mono_items<I>(
+        &mut self,
+        cx: &PartitioningCx<'_, 'tcx>,
+        mono_items: &mut I,
+    ) -> PlacedRootMonoItems<'tcx>
+    where
+        I: Iterator<Item = MonoItem<'tcx>>,
+    {
+        match self {
+            Partitioner::Default(partitioner) => partitioner.place_root_mono_items(cx, mono_items),
+            Partitioner::Unknown => cx.tcx.sess.emit_fatal(UnknownPartitionStrategy),
+        }
+    }
+
+    fn merge_codegen_units(
+        &mut self,
+        cx: &PartitioningCx<'_, 'tcx>,
+        codegen_units: &mut Vec<CodegenUnit<'tcx>>,
+    ) {
+        match self {
+            Partitioner::Default(partitioner) => partitioner.merge_codegen_units(cx, codegen_units),
+            Partitioner::Unknown => cx.tcx.sess.emit_fatal(UnknownPartitionStrategy),
+        }
+    }
+
+    fn place_inlined_mono_items(
+        &mut self,
+        cx: &PartitioningCx<'_, 'tcx>,
+        codegen_units: &mut [CodegenUnit<'tcx>],
+        roots: FxHashSet<MonoItem<'tcx>>,
+    ) -> FxHashMap<MonoItem<'tcx>, MonoItemPlacement> {
+        match self {
+            Partitioner::Default(partitioner) => {
+                partitioner.place_inlined_mono_items(cx, codegen_units, roots)
+            }
+            Partitioner::Unknown => cx.tcx.sess.emit_fatal(UnknownPartitionStrategy),
+        }
+    }
+
+    fn internalize_symbols(
+        &mut self,
+        cx: &PartitioningCx<'_, 'tcx>,
+        codegen_units: &mut [CodegenUnit<'tcx>],
+        mono_item_placements: FxHashMap<MonoItem<'tcx>, MonoItemPlacement>,
+        internalization_candidates: FxHashSet<MonoItem<'tcx>>,
+    ) {
+        match self {
+            Partitioner::Default(partitioner) => partitioner.internalize_symbols(
+                cx,
+                codegen_units,
+                mono_item_placements,
+                internalization_candidates,
+            ),
+            Partitioner::Unknown => cx.tcx.sess.emit_fatal(UnknownPartitionStrategy),
+        }
+    }
+}
+
+struct PartitioningCx<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     target_cgu_count: usize,
     inlining_map: &'a InliningMap<'tcx>,
 }
 
-trait Partitioner<'tcx> {
-    fn place_root_mono_items(
+pub struct PlacedRootMonoItems<'tcx> {
+    codegen_units: Vec<CodegenUnit<'tcx>>,
+    roots: FxHashSet<MonoItem<'tcx>>,
+    internalization_candidates: FxHashSet<MonoItem<'tcx>>,
+}
+
+trait Partition<'tcx> {
+    fn place_root_mono_items<I>(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        mono_items: &mut dyn Iterator<Item = MonoItem<'tcx>>,
-    ) -> PreInliningPartitioning<'tcx>;
+        mono_items: &mut I,
+    ) -> PlacedRootMonoItems<'tcx>
+    where
+        I: Iterator<Item = MonoItem<'tcx>>;
 
     fn merge_codegen_units(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        initial_partitioning: &mut PreInliningPartitioning<'tcx>,
+        codegen_units: &mut Vec<CodegenUnit<'tcx>>,
     );
 
     fn place_inlined_mono_items(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        initial_partitioning: PreInliningPartitioning<'tcx>,
-    ) -> PostInliningPartitioning<'tcx>;
+        codegen_units: &mut [CodegenUnit<'tcx>],
+        roots: FxHashSet<MonoItem<'tcx>>,
+    ) -> FxHashMap<MonoItem<'tcx>, MonoItemPlacement>;
 
     fn internalize_symbols(
         &mut self,
         cx: &PartitioningCx<'_, 'tcx>,
-        partitioning: &mut PostInliningPartitioning<'tcx>,
+        codegen_units: &mut [CodegenUnit<'tcx>],
+        mono_item_placements: FxHashMap<MonoItem<'tcx>, MonoItemPlacement>,
+        internalization_candidates: FxHashSet<MonoItem<'tcx>>,
     );
 }
 
-fn get_partitioner<'tcx>(tcx: TyCtxt<'tcx>) -> Box<dyn Partitioner<'tcx>> {
+fn get_partitioner(tcx: TyCtxt<'_>) -> Partitioner {
     let strategy = match &tcx.sess.opts.unstable_opts.cgu_partitioning_strategy {
         None => "default",
         Some(s) => &s[..],
     };
 
     match strategy {
-        "default" => Box::new(default::DefaultPartitioning),
-        _ => {
-            tcx.sess.emit_fatal(UnknownPartitionStrategy);
-        }
+        "default" => Partitioner::Default(default::DefaultPartitioning),
+        _ => Partitioner::Unknown,
     }
 }
 
-pub fn partition<'tcx>(
+fn partition<'tcx, I>(
     tcx: TyCtxt<'tcx>,
-    mono_items: &mut dyn Iterator<Item = MonoItem<'tcx>>,
+    mono_items: &mut I,
     max_cgu_count: usize,
     inlining_map: &InliningMap<'tcx>,
-) -> Vec<CodegenUnit<'tcx>> {
+) -> Vec<CodegenUnit<'tcx>>
+where
+    I: Iterator<Item = MonoItem<'tcx>>,
+{
     let _prof_timer = tcx.prof.generic_activity("cgu_partitioning");
 
     let mut partitioner = get_partitioner(tcx);
@@ -177,40 +253,51 @@ pub fn partition<'tcx>(
     // In the first step, we place all regular monomorphizations into their
     // respective 'home' codegen unit. Regular monomorphizations are all
     // functions and statics defined in the local crate.
-    let mut initial_partitioning = {
+    let PlacedRootMonoItems { mut codegen_units, roots, internalization_candidates } = {
         let _prof_timer = tcx.prof.generic_activity("cgu_partitioning_place_roots");
         partitioner.place_root_mono_items(cx, mono_items)
     };
 
-    initial_partitioning.codegen_units.iter_mut().for_each(|cgu| cgu.create_size_estimate(tcx));
+    for cgu in &mut codegen_units {
+        cgu.create_size_estimate(tcx);
+    }
 
-    debug_dump(tcx, "INITIAL PARTITIONING:", initial_partitioning.codegen_units.iter());
+    debug_dump(tcx, "INITIAL PARTITIONING", &codegen_units);
 
     // Merge until we have at most `max_cgu_count` codegen units.
+    // `merge_codegen_units` is responsible for updating the CGU size
+    // estimates.
     {
         let _prof_timer = tcx.prof.generic_activity("cgu_partitioning_merge_cgus");
-        partitioner.merge_codegen_units(cx, &mut initial_partitioning);
-        debug_dump(tcx, "POST MERGING:", initial_partitioning.codegen_units.iter());
+        partitioner.merge_codegen_units(cx, &mut codegen_units);
+        debug_dump(tcx, "POST MERGING", &codegen_units);
     }
 
     // In the next step, we use the inlining map to determine which additional
     // monomorphizations have to go into each codegen unit. These additional
     // monomorphizations can be drop-glue, functions from external crates, and
     // local functions the definition of which is marked with `#[inline]`.
-    let mut post_inlining = {
+    let mono_item_placements = {
         let _prof_timer = tcx.prof.generic_activity("cgu_partitioning_place_inline_items");
-        partitioner.place_inlined_mono_items(cx, initial_partitioning)
+        partitioner.place_inlined_mono_items(cx, &mut codegen_units, roots)
     };
 
-    post_inlining.codegen_units.iter_mut().for_each(|cgu| cgu.create_size_estimate(tcx));
+    for cgu in &mut codegen_units {
+        cgu.create_size_estimate(tcx);
+    }
 
-    debug_dump(tcx, "POST INLINING:", post_inlining.codegen_units.iter());
+    debug_dump(tcx, "POST INLINING", &codegen_units);
 
     // Next we try to make as many symbols "internal" as possible, so LLVM has
     // more freedom to optimize.
     if !tcx.sess.link_dead_code() {
         let _prof_timer = tcx.prof.generic_activity("cgu_partitioning_internalize_symbols");
-        partitioner.internalize_symbols(cx, &mut post_inlining);
+        partitioner.internalize_symbols(
+            cx,
+            &mut codegen_units,
+            mono_item_placements,
+            internalization_candidates,
+        );
     }
 
     let instrument_dead_code =
@@ -218,7 +305,7 @@ pub fn partition<'tcx>(
 
     if instrument_dead_code {
         assert!(
-            post_inlining.codegen_units.len() > 0,
+            codegen_units.len() > 0,
             "There must be at least one CGU that code coverage data can be generated in."
         );
 
@@ -229,7 +316,7 @@ pub fn partition<'tcx>(
         // the object file (CGU) containing the dead function stubs is included
         // in the final binary. This will probably require forcing these
         // function symbols to be included via `-u` or `/include` linker args.
-        let mut cgus: Vec<_> = post_inlining.codegen_units.iter_mut().collect();
+        let mut cgus: Vec<_> = codegen_units.iter_mut().collect();
         cgus.sort_by_key(|cgu| cgu.size_estimate());
 
         let dead_code_cgu =
@@ -240,27 +327,17 @@ pub fn partition<'tcx>(
             } else {
                 // If there are no CGUs that have externally linked items,
                 // then we just pick the first CGU as a fallback.
-                &mut post_inlining.codegen_units[0]
+                &mut codegen_units[0]
             };
         dead_code_cgu.make_code_coverage_dead_code_cgu();
     }
 
     // Finally, sort by codegen unit name, so that we get deterministic results.
-    let PostInliningPartitioning {
-        codegen_units: mut result,
-        mono_item_placements: _,
-        internalization_candidates: _,
-    } = post_inlining;
+    codegen_units.sort_by(|a, b| a.name().as_str().cmp(b.name().as_str()));
 
-    result.sort_by(|a, b| a.name().as_str().cmp(b.name().as_str()));
+    debug_dump(tcx, "FINAL", &codegen_units);
 
-    result
-}
-
-pub struct PreInliningPartitioning<'tcx> {
-    codegen_units: Vec<CodegenUnit<'tcx>>,
-    roots: FxHashSet<MonoItem<'tcx>>,
-    internalization_candidates: FxHashSet<MonoItem<'tcx>>,
+    codegen_units
 }
 
 /// For symbol internalization, we need to know whether a symbol/mono-item is
@@ -272,39 +349,37 @@ enum MonoItemPlacement {
     MultipleCgus,
 }
 
-struct PostInliningPartitioning<'tcx> {
-    codegen_units: Vec<CodegenUnit<'tcx>>,
-    mono_item_placements: FxHashMap<MonoItem<'tcx>, MonoItemPlacement>,
-    internalization_candidates: FxHashSet<MonoItem<'tcx>>,
-}
-
-fn debug_dump<'a, 'tcx, I>(tcx: TyCtxt<'tcx>, label: &str, cgus: I)
-where
-    I: Iterator<Item = &'a CodegenUnit<'tcx>>,
-    'tcx: 'a,
-{
+fn debug_dump<'a, 'tcx: 'a>(tcx: TyCtxt<'tcx>, label: &str, cgus: &[CodegenUnit<'tcx>]) {
     let dump = move || {
         use std::fmt::Write;
 
+        let num_cgus = cgus.len();
+        let max = cgus.iter().map(|cgu| cgu.size_estimate()).max().unwrap();
+        let min = cgus.iter().map(|cgu| cgu.size_estimate()).min().unwrap();
+        let ratio = max as f64 / min as f64;
+
         let s = &mut String::new();
-        let _ = writeln!(s, "{label}");
+        let _ = writeln!(
+            s,
+            "{label} ({num_cgus} CodegenUnits, max={max}, min={min}, max/min={ratio:.1}):"
+        );
         for cgu in cgus {
             let _ =
-                writeln!(s, "CodegenUnit {} estimated size {} :", cgu.name(), cgu.size_estimate());
+                writeln!(s, "CodegenUnit {} estimated size {}:", cgu.name(), cgu.size_estimate());
 
             for (mono_item, linkage) in cgu.items() {
                 let symbol_name = mono_item.symbol_name(tcx).name;
                 let symbol_hash_start = symbol_name.rfind('h');
                 let symbol_hash = symbol_hash_start.map_or("<no hash>", |i| &symbol_name[i..]);
 
-                let _ = writeln!(
+                let _ = with_no_trimmed_paths!(writeln!(
                     s,
                     " - {} [{:?}] [{}] estimated size {}",
                     mono_item,
                     linkage,
                     symbol_hash,
                     mono_item.size_estimate(tcx)
-                );
+                ));
             }
 
             let _ = writeln!(s);
@@ -380,7 +455,7 @@ fn collect_and_partition_mono_items(tcx: TyCtxt<'_>, (): ()) -> (&DefIdSet, &[Co
             || {
                 let mut codegen_units = partition(
                     tcx,
-                    &mut items.iter().cloned(),
+                    &mut items.iter().copied(),
                     tcx.sess.codegen_units(),
                     &inlining_map,
                 );
diff --git a/compiler/rustc_monomorphize/src/polymorphize.rs b/compiler/rustc_monomorphize/src/polymorphize.rs
index 63263a642..88a3e0285 100644
--- a/compiler/rustc_monomorphize/src/polymorphize.rs
+++ b/compiler/rustc_monomorphize/src/polymorphize.rs
@@ -11,9 +11,9 @@ use rustc_middle::mir::{
     visit::{TyContext, Visitor},
     Constant, ConstantKind, Local, LocalDecl, Location,
 };
+use rustc_middle::query::Providers;
 use rustc_middle::ty::{
     self,
-    query::Providers,
     subst::SubstsRef,
     visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor},
     Const, Ty, TyCtxt, UnusedGenericParams,
@@ -232,7 +232,7 @@ impl<'a, 'tcx> MarkUsedGenericParams<'a, 'tcx> {
     /// a closure, generator or constant).
     #[instrument(level = "debug", skip(self, def_id, substs))]
     fn visit_child_body(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) {
-        let instance = ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id));
+        let instance = ty::InstanceDef::Item(def_id);
         let unused = self.tcx.unused_generic_params(instance);
         debug!(?self.unused_parameters, ?unused);
         for (i, arg) in substs.iter().enumerate() {
@@ -272,10 +272,10 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkUsedGenericParams<'a, 'tcx> {
                 // Avoid considering `T` unused when constants are of the form:
                 //   `<Self as Foo<T>>::foo::promoted[p]`
                 if let Some(p) = promoted {
-                    if self.def_id == def.did && !self.tcx.generics_of(def.did).has_self {
+                    if self.def_id == def && !self.tcx.generics_of(def).has_self {
                         // If there is a promoted, don't look at the substs - since it will always contain
                         // the generic parameters, instead, traverse the promoted MIR.
-                        let promoted = self.tcx.promoted_mir(def.did);
+                        let promoted = self.tcx.promoted_mir(def);
                         self.visit_body(&promoted[p]);
                     }
                 }
@@ -305,9 +305,9 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for MarkUsedGenericParams<'a, 'tcx> {
                 ControlFlow::Continue(())
             }
             ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs })
-                if matches!(self.tcx.def_kind(def.did), DefKind::AnonConst) =>
+                if matches!(self.tcx.def_kind(def), DefKind::AnonConst) =>
             {
-                self.visit_child_body(def.did, substs);
+                self.visit_child_body(def, substs);
                 ControlFlow::Continue(())
             }
             _ => c.super_visit_with(self),
diff --git a/compiler/rustc_monomorphize/src/util.rs b/compiler/rustc_monomorphize/src/util.rs
index 33e1f6ce3..d12bfc6f6 100644
--- a/compiler/rustc_monomorphize/src/util.rs
+++ b/compiler/rustc_monomorphize/src/util.rs
@@ -29,12 +29,12 @@ pub(crate) fn dump_closure_profile<'tcx>(tcx: TyCtxt<'tcx>, closure_instance: In
         let before_feature_tys = tcx.subst_and_normalize_erasing_regions(
             closure_instance.substs,
             param_env,
-            before_feature_tys,
+            ty::EarlyBinder(before_feature_tys),
         );
         let after_feature_tys = tcx.subst_and_normalize_erasing_regions(
             closure_instance.substs,
             param_env,
-            after_feature_tys,
+            ty::EarlyBinder(after_feature_tys),
         );
 
         let new_size = tcx