diff --git a/RELEASES.md b/RELEASES.md
index 2c91ddf782674..5e4827be4ecfd 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -143,6 +143,8 @@ Compatibility Notes
 - [Turn `proc_macro_back_compat` lint into a hard error.](https://github.com/rust-lang/rust/pull/125596/)
 - [Detect unused structs even when implementing private traits](https://github.com/rust-lang/rust/pull/122382/)
 - [`std::sync::ReentrantLockGuard<T>` is no longer `Sync` if `T: !Sync`](https://github.com/rust-lang/rust/pull/125527) which means [`std::io::StdoutLock` and `std::io::StderrLock` are no longer Sync](https://github.com/rust-lang/rust/issues/127340)
+- [Type inference will fail in some cases due to new implementations of `FromIterator for Box<str>`.](https://github.com/rust-lang/rust/pull/99969/)
+  Notably, this breaks versions of the `time` crate before 0.3.35, due to no longer inferring the implementation for `Box<[_]>`.
 
 <a id="1.80-Internal-Changes"></a>
 
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 30f90bada9adc..554a6d26ad901 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -629,6 +629,9 @@ pub fn file_metadata<'ll>(cx: &CodegenCx<'ll, '_>, source_file: &SourceFile) ->
         };
         let hash_value = hex_encode(source_file.src_hash.hash_bytes());
 
+        let source =
+            cx.sess().opts.unstable_opts.embed_source.then_some(()).and(source_file.src.as_ref());
+
         unsafe {
             llvm::LLVMRustDIBuilderCreateFile(
                 DIB(cx),
@@ -639,6 +642,8 @@ pub fn file_metadata<'ll>(cx: &CodegenCx<'ll, '_>, source_file: &SourceFile) ->
                 hash_kind,
                 hash_value.as_ptr().cast(),
                 hash_value.len(),
+                source.map_or(ptr::null(), |x| x.as_ptr().cast()),
+                source.map_or(0, |x| x.len()),
             )
         }
     }
@@ -659,6 +664,8 @@ pub fn unknown_file_metadata<'ll>(cx: &CodegenCx<'ll, '_>) -> &'ll DIFile {
             llvm::ChecksumKind::None,
             hash_value.as_ptr().cast(),
             hash_value.len(),
+            ptr::null(),
+            0,
         )
     })
 }
@@ -943,6 +950,8 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
             llvm::ChecksumKind::None,
             ptr::null(),
             0,
+            ptr::null(),
+            0,
         );
 
         let unit_metadata = llvm::LLVMRustDIBuilderCreateCompileUnit(
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index faabbcb020d5f..7a495174ff1aa 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -1860,6 +1860,8 @@ extern "C" {
         CSKind: ChecksumKind,
         Checksum: *const c_char,
         ChecksumLen: size_t,
+        Source: *const c_char,
+        SourceLen: size_t,
     ) -> &'a DIFile;
 
     pub fn LLVMRustDIBuilderCreateSubroutineType<'a>(
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 16eeb57b2b967..14c5f8d9f16da 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -529,7 +529,7 @@ fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDe
 
         match tcx.named_bound_var(hir_id) {
             Some(ResolvedArg::EarlyBound(def_id)) => {
-                expected_captures.insert(def_id);
+                expected_captures.insert(def_id.to_def_id());
 
                 // Make sure we allow capturing these lifetimes through `Self` and
                 // `T::Assoc` projection syntax, too. These will occur when we only
@@ -538,7 +538,7 @@ fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDe
                 // feature -- see <https://github.com/rust-lang/rust/pull/115659>.
                 if let DefKind::LifetimeParam = tcx.def_kind(def_id)
                     && let Some(def_id) = tcx
-                        .map_opaque_lifetime_to_parent_lifetime(def_id.expect_local())
+                        .map_opaque_lifetime_to_parent_lifetime(def_id)
                         .opt_param_def_id(tcx, tcx.parent(opaque_def_id.to_def_id()))
                 {
                     shadowed_captures.insert(def_id);
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
index 80daaa60324a3..d2b7ede65234f 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
@@ -7,7 +7,8 @@ use rustc_lint_defs::builtin::{REFINING_IMPL_TRAIT_INTERNAL, REFINING_IMPL_TRAIT
 use rustc_middle::span_bug;
 use rustc_middle::traits::{ObligationCause, Reveal};
 use rustc_middle::ty::{
-    self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperVisitable, TypeVisitable, TypeVisitor,
+    self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt, TypeVisitor,
 };
 use rustc_span::Span;
 use rustc_trait_selection::regions::InferCtxtRegionExt;
@@ -177,6 +178,10 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
         return;
     };
 
+    if trait_bounds.references_error() || impl_bounds.references_error() {
+        return;
+    }
+
     // For quicker lookup, use an `IndexSet` (we don't use one earlier because
     // it's not foldable..).
     // Also, We have to anonymize binders in these types because they may contain
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index ae0c70d232685..0cf9e128bceef 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -13,7 +13,6 @@ use rustc_ast::visit::walk_list;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{GenericArg, GenericParam, GenericParamKind, HirId, HirIdMap, LifetimeName, Node};
 use rustc_macros::extension;
@@ -22,7 +21,7 @@ use rustc_middle::middle::resolve_bound_vars::*;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_middle::{bug, span_bug};
-use rustc_span::def_id::DefId;
+use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 
@@ -32,7 +31,7 @@ use crate::errors;
 impl ResolvedArg {
     fn early(param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg) {
         debug!("ResolvedArg::early: def_id={:?}", param.def_id);
-        (param.def_id, ResolvedArg::EarlyBound(param.def_id.to_def_id()))
+        (param.def_id, ResolvedArg::EarlyBound(param.def_id))
     }
 
     fn late(idx: u32, param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg) {
@@ -41,10 +40,10 @@ impl ResolvedArg {
             "ResolvedArg::late: idx={:?}, param={:?} depth={:?} def_id={:?}",
             idx, param, depth, param.def_id,
         );
-        (param.def_id, ResolvedArg::LateBound(depth, idx, param.def_id.to_def_id()))
+        (param.def_id, ResolvedArg::LateBound(depth, idx, param.def_id))
     }
 
-    fn id(&self) -> Option<DefId> {
+    fn id(&self) -> Option<LocalDefId> {
         match *self {
             ResolvedArg::StaticLifetime | ResolvedArg::Error(_) => None,
 
@@ -288,13 +287,14 @@ fn late_arg_as_bound_arg<'tcx>(
 ) -> ty::BoundVariableKind {
     match arg {
         ResolvedArg::LateBound(_, _, def_id) => {
-            let name = tcx.hir().name(tcx.local_def_id_to_hir_id(def_id.expect_local()));
+            let def_id = def_id.to_def_id();
+            let name = tcx.item_name(def_id);
             match param.kind {
                 GenericParamKind::Lifetime { .. } => {
-                    ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name))
+                    ty::BoundVariableKind::Region(ty::BrNamed(def_id, name))
                 }
                 GenericParamKind::Type { .. } => {
-                    ty::BoundVariableKind::Ty(ty::BoundTyKind::Param(*def_id, name))
+                    ty::BoundVariableKind::Ty(ty::BoundTyKind::Param(def_id, name))
                 }
                 GenericParamKind::Const { .. } => ty::BoundVariableKind::Const,
             }
@@ -717,7 +717,6 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     // In the future, this should be fixed and this error should be removed.
                     let def = self.map.defs.get(&lifetime.hir_id).copied();
                     let Some(ResolvedArg::LateBound(_, _, lifetime_def_id)) = def else { continue };
-                    let Some(lifetime_def_id) = lifetime_def_id.as_local() else { continue };
                     let lifetime_hir_id = self.tcx.local_def_id_to_hir_id(lifetime_def_id);
 
                     let bad_place = match self.tcx.hir_node(self.tcx.parent_hir_id(lifetime_hir_id))
@@ -1150,7 +1149,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                             .param_def_id_to_index(self.tcx, region_def_id.to_def_id())
                             .is_some()
                     {
-                        break Some(ResolvedArg::EarlyBound(region_def_id.to_def_id()));
+                        break Some(ResolvedArg::EarlyBound(region_def_id));
                     }
                     break None;
                 }
@@ -1259,7 +1258,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                     kind => span_bug!(
                         use_span,
                         "did not expect to resolve lifetime to {}",
-                        kind.descr(param_def_id)
+                        kind.descr(param_def_id.to_def_id())
                     ),
                 };
                 def = ResolvedArg::Error(guar);
@@ -1277,10 +1276,10 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                         kind: hir::ImplItemKind::Fn(..),
                         ..
                     }) => {
-                        def = ResolvedArg::Free(owner_id.to_def_id(), def.id().unwrap());
+                        def = ResolvedArg::Free(owner_id.def_id, def.id().unwrap());
                     }
                     Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(closure), .. }) => {
-                        def = ResolvedArg::Free(closure.def_id.to_def_id(), def.id().unwrap());
+                        def = ResolvedArg::Free(closure.def_id, def.id().unwrap());
                     }
                     _ => {}
                 }
@@ -1351,7 +1350,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                             .param_def_id_to_index(self.tcx, param_def_id.to_def_id())
                             .is_some()
                     {
-                        break Some(ResolvedArg::EarlyBound(param_def_id.to_def_id()));
+                        break Some(ResolvedArg::EarlyBound(param_def_id));
                     }
                     break None;
                 }
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 2fb1bcf2dbfff..5c8ecf254a54e 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -296,25 +296,29 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             Some(rbv::ResolvedArg::StaticLifetime) => tcx.lifetimes.re_static,
 
             Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => {
-                let name = lifetime_name(def_id.expect_local());
+                let name = lifetime_name(def_id);
                 let br = ty::BoundRegion {
                     var: ty::BoundVar::from_u32(index),
-                    kind: ty::BrNamed(def_id, name),
+                    kind: ty::BrNamed(def_id.to_def_id(), name),
                 };
                 ty::Region::new_bound(tcx, debruijn, br)
             }
 
             Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
-                let name = tcx.hir().ty_param_name(def_id.expect_local());
-                let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
+                let name = tcx.hir().ty_param_name(def_id);
+                let item_def_id = tcx.hir().ty_param_owner(def_id);
                 let generics = tcx.generics_of(item_def_id);
-                let index = generics.param_def_id_to_index[&def_id];
+                let index = generics.param_def_id_to_index[&def_id.to_def_id()];
                 ty::Region::new_early_param(tcx, ty::EarlyParamRegion { index, name })
             }
 
             Some(rbv::ResolvedArg::Free(scope, id)) => {
-                let name = lifetime_name(id.expect_local());
-                ty::Region::new_late_param(tcx, scope, ty::BrNamed(id, name))
+                let name = lifetime_name(id);
+                ty::Region::new_late_param(
+                    tcx,
+                    scope.to_def_id(),
+                    ty::BrNamed(id.to_def_id(), name),
+                )
 
                 // (*) -- not late-bound, won't change
             }
@@ -1953,15 +1957,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let tcx = self.tcx();
         match tcx.named_bound_var(hir_id) {
             Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => {
-                let name = tcx.item_name(def_id);
+                let name = tcx.item_name(def_id.to_def_id());
                 let br = ty::BoundTy {
                     var: ty::BoundVar::from_u32(index),
-                    kind: ty::BoundTyKind::Param(def_id, name),
+                    kind: ty::BoundTyKind::Param(def_id.to_def_id(), name),
                 };
                 Ty::new_bound(tcx, debruijn, br)
             }
             Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
-                let def_id = def_id.expect_local();
                 let item_def_id = tcx.hir().ty_param_owner(def_id);
                 let generics = tcx.generics_of(item_def_id);
                 let index = generics.param_def_id_to_index[&def_id.to_def_id()];
@@ -1982,10 +1985,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
                 // Find the name and index of the const parameter by indexing the generics of
                 // the parent item and construct a `ParamConst`.
-                let item_def_id = tcx.parent(def_id);
+                let item_def_id = tcx.local_parent(def_id);
                 let generics = tcx.generics_of(item_def_id);
-                let index = generics.param_def_id_to_index[&def_id];
-                let name = tcx.item_name(def_id);
+                let index = generics.param_def_id_to_index[&def_id.to_def_id()];
+                let name = tcx.item_name(def_id.to_def_id());
                 ty::Const::new_param(tcx, ty::ParamConst::new(index, name))
             }
             Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 34f2dca7c42ff..486136a2bcc10 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -774,6 +774,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(direct_access_external_data, Some(true));
     tracked!(dual_proc_macros, true);
     tracked!(dwarf_version, Some(5));
+    tracked!(embed_source, true);
     tracked!(emit_thin_lto, false);
     tracked!(export_executable_symbols, true);
     tracked!(fewer_names, Some(true));
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 85132dd4f98f0..d8482567bbe5b 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1925,8 +1925,8 @@ impl ExplicitOutlivesRequirements {
     fn lifetimes_outliving_lifetime<'tcx>(
         tcx: TyCtxt<'tcx>,
         inferred_outlives: impl Iterator<Item = &'tcx (ty::Clause<'tcx>, Span)>,
-        item: DefId,
-        lifetime: DefId,
+        item: LocalDefId,
+        lifetime: LocalDefId,
     ) -> Vec<ty::Region<'tcx>> {
         let item_generics = tcx.generics_of(item);
 
@@ -1934,7 +1934,7 @@ impl ExplicitOutlivesRequirements {
             .filter_map(|(clause, _)| match clause.kind().skip_binder() {
                 ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
                     ty::ReEarlyParam(ebr)
-                        if item_generics.region_param(ebr, tcx).def_id == lifetime =>
+                        if item_generics.region_param(ebr, tcx).def_id == lifetime.to_def_id() =>
                     {
                         Some(b)
                     }
@@ -1982,7 +1982,7 @@ impl ExplicitOutlivesRequirements {
                 let is_inferred = match tcx.named_bound_var(lifetime.hir_id) {
                     Some(ResolvedArg::EarlyBound(def_id)) => inferred_outlives
                         .iter()
-                        .any(|r| matches!(**r, ty::ReEarlyParam(ebr) if { item_generics.region_param(ebr, tcx).def_id == def_id })),
+                        .any(|r| matches!(**r, ty::ReEarlyParam(ebr) if { item_generics.region_param(ebr, tcx).def_id == def_id.to_def_id() })),
                     _ => false,
                 };
 
@@ -2097,7 +2097,7 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                                         inferred_outlives
                                             .iter()
                                             .filter(|(_, span)| !predicate.span.contains(*span)),
-                                        item.owner_id.to_def_id(),
+                                        item.owner_id.def_id,
                                         region_def_id,
                                     ),
                                     &predicate.bounds,
diff --git a/compiler/rustc_lint/src/drop_forget_useless.rs b/compiler/rustc_lint/src/drop_forget_useless.rs
index 2060858cc8af0..a9de258e005c9 100644
--- a/compiler/rustc_lint/src/drop_forget_useless.rs
+++ b/compiler/rustc_lint/src/drop_forget_useless.rs
@@ -151,10 +151,11 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetUseless {
                     && let Node::Stmt(stmt) = node
                     && let StmtKind::Semi(e) = stmt.kind
                     && e.hir_id == expr.hir_id
+                    && let Some(arg_span) = arg.span.find_ancestor_inside(expr.span)
                 {
                     UseLetUnderscoreIgnoreSuggestion::Suggestion {
-                        start_span: expr.span.shrink_to_lo().until(arg.span),
-                        end_span: arg.span.shrink_to_hi().until(expr.span.shrink_to_hi()),
+                        start_span: expr.span.shrink_to_lo().until(arg_span),
+                        end_span: arg_span.shrink_to_hi().until(expr.span.shrink_to_hi()),
                     }
                 } else {
                     UseLetUnderscoreIgnoreSuggestion::Note
diff --git a/compiler/rustc_lint/src/impl_trait_overcaptures.rs b/compiler/rustc_lint/src/impl_trait_overcaptures.rs
index 990fb2d16f9dd..2e0da69e92070 100644
--- a/compiler/rustc_lint/src/impl_trait_overcaptures.rs
+++ b/compiler/rustc_lint/src/impl_trait_overcaptures.rs
@@ -300,16 +300,17 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for VisitOpaqueTypes<'tcx> {
                         Some(
                             ResolvedArg::EarlyBound(def_id) | ResolvedArg::LateBound(_, _, def_id),
                         ) => {
-                            if self.tcx.def_kind(self.tcx.parent(def_id)) == DefKind::OpaqueTy {
+                            if self.tcx.def_kind(self.tcx.local_parent(def_id)) == DefKind::OpaqueTy
+                            {
                                 let def_id = self
                                     .tcx
-                                    .map_opaque_lifetime_to_parent_lifetime(def_id.expect_local())
+                                    .map_opaque_lifetime_to_parent_lifetime(def_id)
                                     .opt_param_def_id(self.tcx, self.parent_def_id.to_def_id())
                                     .expect("variable should have been duplicated from parent");
 
                                 explicitly_captured.insert(def_id);
                             } else {
-                                explicitly_captured.insert(def_id);
+                                explicitly_captured.insert(def_id.to_def_id());
                             }
                         }
                         _ => {
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 79a68b2ff0e67..ed12318c88dae 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -913,14 +913,19 @@ extern "C" LLVMMetadataRef
 LLVMRustDIBuilderCreateFile(LLVMRustDIBuilderRef Builder, const char *Filename,
                             size_t FilenameLen, const char *Directory,
                             size_t DirectoryLen, LLVMRustChecksumKind CSKind,
-                            const char *Checksum, size_t ChecksumLen) {
+                            const char *Checksum, size_t ChecksumLen,
+                            const char *Source, size_t SourceLen) {
 
   std::optional<DIFile::ChecksumKind> llvmCSKind = fromRust(CSKind);
   std::optional<DIFile::ChecksumInfo<StringRef>> CSInfo{};
   if (llvmCSKind)
     CSInfo.emplace(*llvmCSKind, StringRef{Checksum, ChecksumLen});
+  std::optional<StringRef> oSource{};
+  if (Source)
+    oSource = StringRef(Source, SourceLen);
   return wrap(Builder->createFile(StringRef(Filename, FilenameLen),
-                                  StringRef(Directory, DirectoryLen), CSInfo));
+                                  StringRef(Directory, DirectoryLen), CSInfo,
+                                  oSource));
 }
 
 extern "C" LLVMMetadataRef
diff --git a/compiler/rustc_middle/src/middle/resolve_bound_vars.rs b/compiler/rustc_middle/src/middle/resolve_bound_vars.rs
index a4f6d7afe4d11..32e2f3b4b1685 100644
--- a/compiler/rustc_middle/src/middle/resolve_bound_vars.rs
+++ b/compiler/rustc_middle/src/middle/resolve_bound_vars.rs
@@ -2,7 +2,7 @@
 
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorGuaranteed;
-use rustc_hir::def_id::DefId;
+use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::{ItemLocalId, OwnerId};
 use rustc_macros::{Decodable, Encodable, HashStable, TyDecodable, TyEncodable};
 
@@ -11,9 +11,9 @@ use crate::ty;
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
 pub enum ResolvedArg {
     StaticLifetime,
-    EarlyBound(/* decl */ DefId),
-    LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* decl */ DefId),
-    Free(DefId, /* lifetime decl */ DefId),
+    EarlyBound(/* decl */ LocalDefId),
+    LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* decl */ LocalDefId),
+    Free(LocalDefId, /* lifetime decl */ LocalDefId),
     Error(ErrorGuaranteed),
 }
 
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 9b39b84970420..cad3515f06809 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -3035,13 +3035,13 @@ impl<'tcx> TyCtxt<'tcx> {
 
             match self.named_bound_var(lifetime.hir_id) {
                 Some(resolve_bound_vars::ResolvedArg::EarlyBound(ebv)) => {
-                    let new_parent = self.parent(ebv);
+                    let new_parent = self.local_parent(ebv);
 
                     // If we map to another opaque, then it should be a parent
                     // of the opaque we mapped from. Continue mapping.
                     if matches!(self.def_kind(new_parent), DefKind::OpaqueTy) {
-                        debug_assert_eq!(self.parent(parent.to_def_id()), new_parent);
-                        opaque_lifetime_param_def_id = ebv.expect_local();
+                        debug_assert_eq!(self.local_parent(parent), new_parent);
+                        opaque_lifetime_param_def_id = ebv;
                         continue;
                     }
 
@@ -3050,20 +3050,20 @@ impl<'tcx> TyCtxt<'tcx> {
                         self,
                         ty::EarlyParamRegion {
                             index: generics
-                                .param_def_id_to_index(self, ebv)
+                                .param_def_id_to_index(self, ebv.to_def_id())
                                 .expect("early-bound var should be present in fn generics"),
-                            name: self.hir().name(self.local_def_id_to_hir_id(ebv.expect_local())),
+                            name: self.item_name(ebv.to_def_id()),
                         },
                     );
                 }
                 Some(resolve_bound_vars::ResolvedArg::LateBound(_, _, lbv)) => {
-                    let new_parent = self.parent(lbv);
+                    let new_parent = self.local_parent(lbv);
                     return ty::Region::new_late_param(
                         self,
-                        new_parent,
+                        new_parent.to_def_id(),
                         ty::BoundRegionKind::BrNamed(
-                            lbv,
-                            self.hir().name(self.local_def_id_to_hir_id(lbv.expect_local())),
+                            lbv.to_def_id(),
+                            self.item_name(lbv.to_def_id()),
                         ),
                     );
                 }
diff --git a/compiler/rustc_session/messages.ftl b/compiler/rustc_session/messages.ftl
index b84280a3ccf3f..01c371ee49884 100644
--- a/compiler/rustc_session/messages.ftl
+++ b/compiler/rustc_session/messages.ftl
@@ -14,6 +14,10 @@ session_crate_name_empty = crate name must not be empty
 
 session_crate_name_invalid = crate names cannot start with a `-`, but `{$s}` has a leading hyphen
 
+session_embed_source_insufficient_dwarf_version = `-Zembed-source=y` requires at least `-Z dwarf-version=5` but DWARF version is {$dwarf_version}
+
+session_embed_source_requires_debug_info = `-Zembed-source=y` requires debug information to be enabled
+
 session_expr_parentheses_needed = parentheses are required to parse this as an expression
 
 session_failed_to_create_profiler = failed to create profiler: {$err}
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 5cc54a5855bbe..15bbd4ff7bf4b 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -165,6 +165,16 @@ pub(crate) struct UnsupportedDwarfVersion {
     pub(crate) dwarf_version: u32,
 }
 
+#[derive(Diagnostic)]
+#[diag(session_embed_source_insufficient_dwarf_version)]
+pub(crate) struct EmbedSourceInsufficientDwarfVersion {
+    pub(crate) dwarf_version: u32,
+}
+
+#[derive(Diagnostic)]
+#[diag(session_embed_source_requires_debug_info)]
+pub(crate) struct EmbedSourceRequiresDebugInfo;
+
 #[derive(Diagnostic)]
 #[diag(session_target_stack_protector_not_supported)]
 pub(crate) struct StackProtectorNotSupportedForTarget<'a> {
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index df72e2430fd50..23231fbffbfdb 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1701,6 +1701,8 @@ options! {
         them only if an error has not been emitted"),
     ehcont_guard: bool = (false, parse_bool, [TRACKED],
         "generate Windows EHCont Guard tables"),
+    embed_source: bool = (false, parse_bool, [TRACKED],
+        "embed source text in DWARF debug sections (default: no)"),
     emit_stack_sizes: bool = (false, parse_bool, [UNTRACKED],
         "emit a section containing stack size metadata (default: no)"),
     emit_thin_lto: bool = (true, parse_bool, [TRACKED],
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 693867c3853da..68efd0faea5c1 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -37,8 +37,9 @@ use rustc_target::spec::{
 use crate::code_stats::CodeStats;
 pub use crate::code_stats::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
 use crate::config::{
-    self, CoverageLevel, CrateType, ErrorOutputType, FunctionReturn, Input, InstrumentCoverage,
-    OptLevel, OutFileName, OutputType, RemapPathScopeComponents, SwitchWithOptPath,
+    self, CoverageLevel, CrateType, DebugInfo, ErrorOutputType, FunctionReturn, Input,
+    InstrumentCoverage, OptLevel, OutFileName, OutputType, RemapPathScopeComponents,
+    SwitchWithOptPath,
 };
 use crate::parse::{add_feature_diagnostics, ParseSess};
 use crate::search_paths::{PathKind, SearchPath};
@@ -1306,6 +1307,19 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
             .emit_err(errors::SplitDebugInfoUnstablePlatform { debuginfo: sess.split_debuginfo() });
     }
 
+    if sess.opts.unstable_opts.embed_source {
+        let dwarf_version =
+            sess.opts.unstable_opts.dwarf_version.unwrap_or(sess.target.default_dwarf_version);
+
+        if dwarf_version < 5 {
+            sess.dcx().emit_warn(errors::EmbedSourceInsufficientDwarfVersion { dwarf_version });
+        }
+
+        if sess.opts.debuginfo == DebugInfo::None {
+            sess.dcx().emit_warn(errors::EmbedSourceRequiresDebugInfo);
+        }
+    }
+
     if sess.opts.unstable_opts.instrument_xray.is_some() && !sess.target.options.supports_xray {
         sess.dcx().emit_err(errors::InstrumentationNotSupported { us: "XRay".to_string() });
     }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs
index 3f35391be1355..cd61747917a88 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs
@@ -101,7 +101,7 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
                     // region at the right depth with the same index
                     (Some(rbv::ResolvedArg::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
                         debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
-                        if id == def_id {
+                        if id.to_def_id() == def_id {
                             return ControlFlow::Break(arg);
                         }
                     }
@@ -118,7 +118,7 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
                             debruijn_index
                         );
                         debug!("LateBound id={:?} def_id={:?}", id, def_id);
-                        if debruijn_index == self.current_index && id == def_id {
+                        if debruijn_index == self.current_index && id.to_def_id() == def_id {
                             return ControlFlow::Break(arg);
                         }
                     }
@@ -192,7 +192,7 @@ impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
             // the lifetime of the TyPath!
             (Some(rbv::ResolvedArg::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
                 debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
-                if id == def_id {
+                if id.to_def_id() == def_id {
                     return ControlFlow::Break(());
                 }
             }
@@ -201,7 +201,7 @@ impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
                 debug!("FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", debruijn_index,);
                 debug!("id={:?}", id);
                 debug!("def_id={:?}", def_id);
-                if debruijn_index == self.current_index && id == def_id {
+                if debruijn_index == self.current_index && id.to_def_id() == def_id {
                     return ControlFlow::Break(());
                 }
             }
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index ce23b7735f8bd..bdfee55d8d183 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -1885,6 +1885,22 @@ impl Config {
                     warn("link-shared");
                 }
 
+                // FIXME(#129153): instead of all the ad-hoc `download-ci-llvm` checks that follow,
+                // use the `builder-config` present in tarballs since #128822 to compare the local
+                // config to the ones used to build the LLVM artifacts on CI, and only notify users
+                // if they've chosen a different value.
+
+                if libzstd.is_some() {
+                    println!(
+                        "WARNING: when using `download-ci-llvm`, the local `llvm.libzstd` option, \
+                        like almost all `llvm.*` options, will be ignored and set by the LLVM CI \
+                        artifacts builder config."
+                    );
+                    println!(
+                        "HELP: To use `llvm.libzstd` for LLVM/LLD builds, set `download-ci-llvm` option to false."
+                    );
+                }
+
                 // None of the LLVM options, except assertions, are supported
                 // when using downloaded LLVM. We could just ignore these but
                 // that's potentially confusing, so force them to not be
@@ -1894,7 +1910,6 @@ impl Config {
                 check_ci_llvm!(optimize_toml);
                 check_ci_llvm!(thin_lto);
                 check_ci_llvm!(release_debuginfo);
-                check_ci_llvm!(libzstd);
                 check_ci_llvm!(targets);
                 check_ci_llvm!(experimental_targets);
                 check_ci_llvm!(clang_cl);
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
index 61e9694f1e2ae..e857f38e68a85 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
@@ -62,9 +62,9 @@ COPY host-x86_64/dist-x86_64-linux/build-clang.sh /tmp/
 RUN ./build-clang.sh
 ENV CC=clang CXX=clang++
 
-# rustc's LLVM needs zstd.
-COPY scripts/zstd.sh /tmp/
-RUN ./zstd.sh
+# Build zstd to enable `llvm.libzstd`.
+COPY host-x86_64/dist-x86_64-linux/build-zstd.sh /tmp/
+RUN ./build-zstd.sh
 
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
diff --git a/src/ci/docker/scripts/zstd.sh b/src/ci/docker/host-x86_64/dist-x86_64-linux/build-zstd.sh
similarity index 100%
rename from src/ci/docker/scripts/zstd.sh
rename to src/ci/docker/host-x86_64/dist-x86_64-linux/build-zstd.sh
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu/Dockerfile
index 19683317126ab..83c2aa8cfb3b7 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu/Dockerfile
@@ -28,5 +28,6 @@ ENV RUST_CONFIGURE_ARGS \
  --build=x86_64-unknown-linux-gnu \
  --enable-sanitizers \
  --enable-profiler \
- --enable-compiler-docs
+ --enable-compiler-docs \
+ --set llvm.libzstd=true
 ENV SCRIPT python3 ../x.py --stage 2 test
diff --git a/src/doc/rustc/src/SUMMARY.md b/src/doc/rustc/src/SUMMARY.md
index cb0b2e63452de..4e34e2667cfc0 100644
--- a/src/doc/rustc/src/SUMMARY.md
+++ b/src/doc/rustc/src/SUMMARY.md
@@ -81,6 +81,7 @@
     - [wasm32-wasip1](platform-support/wasm32-wasip1.md)
     - [wasm32-wasip1-threads](platform-support/wasm32-wasip1-threads.md)
     - [wasm32-wasip2](platform-support/wasm32-wasip2.md)
+    - [wasm32-unknown-unknown](platform-support/wasm32-unknown-unknown.md)
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
     - [\*-win7-windows-msvc](platform-support/win7-windows-msvc.md)
     - [x86_64-fortanix-unknown-sgx](platform-support/x86_64-fortanix-unknown-sgx.md)
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index 667758a120305..dd478e9df379e 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -192,7 +192,7 @@ target | std | notes
 [`thumbv8m.main-none-eabi`](platform-support/thumbv8m.main-none-eabi.md) | * | Bare Armv8-M Mainline
 [`thumbv8m.main-none-eabihf`](platform-support/thumbv8m.main-none-eabi.md) | * | Bare Armv8-M Mainline, hardfloat
 `wasm32-unknown-emscripten` | ✓ | WebAssembly via Emscripten
-`wasm32-unknown-unknown` | ✓ | WebAssembly
+[`wasm32-unknown-unknown`](platform-support/wasm32-unknown-unknown.md) | ✓ | WebAssembly
 `wasm32-wasi` | ✓ | WebAssembly with WASI (undergoing a [rename to `wasm32-wasip1`][wasi-rename])
 [`wasm32-wasip1`](platform-support/wasm32-wasip1.md) | ✓ | WebAssembly with WASI
 [`wasm32-wasip1-threads`](platform-support/wasm32-wasip1-threads.md) | ✓ | WebAssembly with WASI Preview 1 and threads
diff --git a/src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md b/src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md
new file mode 100644
index 0000000000000..ee37e5e90cfb4
--- /dev/null
+++ b/src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md
@@ -0,0 +1,198 @@
+# `wasm32-unknown-unknown`
+
+**Tier: 2**
+
+The `wasm32-unknown-unknown` target is a WebAssembly compilation target which
+does not import any functions from the host for the standard library. This is
+the "minimal" WebAssembly in the sense of making the fewest assumptions about
+the host environment. This target is often used when compiling to the web or
+JavaScript environments as there is no standard for what functions can be
+imported on the web. This target can also be useful for creating minimal or
+bare-bones WebAssembly binaries.
+
+The `wasm32-unknown-unknown` target has support for the Rust standard library
+but many parts of the standard library do not work and return errors. For
+example `println!` does nothing, `std::fs` always return errors, and
+`std::thread::spawn` will panic. There is no means by which this can be
+overridden. For a WebAssembly target that more fully supports the standard
+library see the [`wasm32-wasip1`](./wasm32-wasip1.md) or
+[`wasm32-wasip2`](./wasm32-wasip2.md) targets.
+
+The `wasm32-unknown-unknown` target has full support for the `core` and `alloc`
+crates. It additionally supports the `HashMap` type in the `std` crate, although
+hash maps are not randomized like they are on other platforms.
+
+One existing user of this target (please feel free to edit and expand this list
+too) is the [`wasm-bindgen` project](https://github.com/rustwasm/wasm-bindgen)
+which facilitates Rust code interoperating with JavaScript code. Note, though,
+that not all uses of `wasm32-unknown-unknown` are using JavaScript and the web.
+
+## Target maintainers
+
+When this target was added to the compiler platform-specific documentation here
+was not maintained at that time. This means that the list below is not
+exhaustive and there are more interested parties in this target. That being
+said since when this document was last updated those interested in maintaining
+this target are:
+
+- Alex Crichton, https://github.com/alexcrichton
+
+## Requirements
+
+This target is cross-compiled. The target includes support for `std` itself,
+but as mentioned above many pieces of functionality that require an operating
+system do not work and will return errors.
+
+This target currently has no equivalent in C/C++. There is no C/C++ toolchain
+for this target. While interop is theoretically possible it's recommended to
+instead use one of:
+
+* `wasm32-unknown-emscripten` - for web-based use cases the Emscripten
+  toolchain is typically chosen for running C/C++.
+* [`wasm32-wasip1`](./wasm32-wasip1.md) - the wasi-sdk toolchain is used to
+  compile C/C++ on this target and can interop with Rust code. WASI works on
+  the web so far as there's no blocker, but an implementation of WASI APIs
+  must be either chosen or reimplemented.
+
+This target has no build requirements beyond what's in-tree in the Rust
+repository. Linking binaries requires LLD to be enabled for the `wasm-ld`
+driver. This target uses the `dlmalloc` crate as the default global allocator.
+
+## Building the target
+
+Building this target can be done by:
+
+* Configure the `wasm32-unknown-unknown` target to get built.
+* Configure LLD to be built.
+* Ensure the `WebAssembly` target backend is not disabled in LLVM.
+
+These are all controlled through `config.toml` options. It should be possible
+to build this target on any platform.
+
+## Building Rust programs
+
+Rust programs can be compiled by adding this target via rustup:
+
+```sh
+$ rustup target add wasm32-unknown-unknown
+```
+
+and then compiling with the target:
+
+```sh
+$ rustc foo.rs --target wasm32-unknown-unknown
+$ file foo.wasm
+```
+
+## Cross-compilation
+
+This target can be cross-compiled from any host.
+
+## Testing
+
+This target is not tested in CI for the rust-lang/rust repository. Many tests
+must be disabled to run on this target and failures are non-obvious because
+`println!` doesn't work in the standard library. It's recommended to test the
+`wasm32-wasip1` target instead for WebAssembly compatibility.
+
+## Conditionally compiling code
+
+It's recommended to conditionally compile code for this target with:
+
+```text
+#[cfg(all(target_family = "wasm", target_os = "unknown"))]
+```
+
+Note that there is no way to tell via `#[cfg]` whether code will be running on
+the web or not.
+
+## Enabled WebAssembly features
+
+WebAssembly is an evolving standard which adds new features such as new
+instructions over time. This target's default set of supported WebAssembly
+features will additionally change over time. The `wasm32-unknown-unknown` target
+inherits the default settings of LLVM which typically matches the default
+settings of Emscripten as well.
+
+Changes to WebAssembly go through a [proposals process][proposals] but reaching
+the final stage (stage 5) does not automatically mean that the feature will be
+enabled in LLVM and Rust by default. At this time the general guidance is that
+features must be present in most engines for a "good chunk of time" before
+they're enabled in LLVM by default. There is currently no exact number of
+months or engines that are required to enable features by default.
+
+[proposals]: https://github.com/WebAssembly/proposals
+
+As of the time of this writing the proposals that are enabled by default (the
+`generic` CPU in LLVM terminology) are:
+
+* `multivalue`
+* `mutable-globals`
+* `reference-types`
+* `sign-ext`
+
+If you're compiling WebAssembly code for an engine that does not support a
+feature in LLVM's default feature set then the feature must be disabled at
+compile time. Note, though, that enabled features may be used in the standard
+library or precompiled libraries shipped via rustup. This means that not only
+does your own code need to be compiled with the correct set of flags but the
+Rust standard library additionally must be recompiled.
+
+Compiling all code for the initial release of WebAssembly looks like:
+
+```sh
+$ export RUSTFLAGS=-Ctarget-cpu=mvp
+$ cargo +nightly build -Zbuild-std=panic_abort,std --target wasm32-unknown-unknown
+```
+
+Here the `mvp` "cpu" is a placeholder in LLVM for disabling all supported
+features by default. Cargo's `-Zbuild-std` feature, a Nightly Rust feature, is
+then used to recompile the standard library in addition to your own code. This
+will produce a binary that uses only the original WebAssembly features by
+default and no proposals since its inception.
+
+To enable individual features it can be done with `-Ctarget-feature=+foo`.
+Available features for Rust code itself are documented in the [reference] and
+can also be found through:
+
+```sh
+$ rustc -Ctarget-feature=help --target wasm32-unknown-unknown
+```
+
+You'll need to consult your WebAssembly engine's documentation to learn more
+about the supported WebAssembly features the engine has.
+
+[reference]: https://doc.rust-lang.org/reference/attributes/codegen.html#wasm32-or-wasm64
+
+Note that it is still possible for Rust crates and libraries to enable
+WebAssembly features on a per-function level. This means that the build
+command above may not be sufficient to disable all WebAssembly features. If the
+final binary still has SIMD instructions, for example, the function in question
+will need to be found and the crate in question will likely contain something
+like:
+
+```rust,ignore (not-always-compiled-to-wasm)
+#[target_feature(enable = "simd128")]
+fn foo() {
+    // ...
+}
+```
+
+In this situation there is no compiler flag to disable emission of SIMD
+instructions and the crate must instead be modified to not include this function
+at compile time either by default or through a Cargo feature. For crate authors
+it's recommended to avoid `#[target_feature(enable = "...")]` except where
+necessary and instead use:
+
+```rust,ignore (not-always-compiled-to-wasm)
+#[cfg(target_feature = "simd128")]
+fn foo() {
+    // ...
+}
+```
+
+That is to say instead of enabling target features it's recommended to
+conditionally compile code instead. This is notably different to the way native
+platforms such as x86\_64 work, and this is due to the fact that WebAssembly
+binaries must only contain code the engine understands. Native binaries work so
+long as the CPU doesn't execute unknown code dynamically at runtime.
diff --git a/src/doc/rustc/src/platform-support/wasm32-wasip1-threads.md b/src/doc/rustc/src/platform-support/wasm32-wasip1-threads.md
index c3eda26ca8ef9..994c0f4bbb3e9 100644
--- a/src/doc/rustc/src/platform-support/wasm32-wasip1-threads.md
+++ b/src/doc/rustc/src/platform-support/wasm32-wasip1-threads.md
@@ -162,3 +162,17 @@ It's recommended to conditionally compile code for this target with:
 Prior to Rust 1.80 the `target_env = "p1"` key was not set. Currently the
 `target_feature = "atomics"` is Nightly-only. Note that the precise `#[cfg]`
 necessary to detect this target may change as the target becomes more stable.
+
+## Enabled WebAssembly features
+
+The default set of WebAssembly features enabled for compilation includes two
+more features in addition to that which
+[`wasm32-unknown-unknown`](./wasm32-unknown-unknown.md) enables:
+
+* `bulk-memory`
+* `atomics`
+
+For more information about features see the documentation for
+[`wasm32-unknown-unknown`](./wasm32-unknown-unknown.md), but note that the
+`mvp` CPU in LLVM does not support this target as it's required that
+`bulk-memory`, `atomics`, and `mutable-globals` are all enabled.
diff --git a/src/doc/rustc/src/platform-support/wasm32-wasip1.md b/src/doc/rustc/src/platform-support/wasm32-wasip1.md
index fb70bbdc2b403..0e4def6768dc4 100644
--- a/src/doc/rustc/src/platform-support/wasm32-wasip1.md
+++ b/src/doc/rustc/src/platform-support/wasm32-wasip1.md
@@ -132,3 +132,9 @@ It's recommended to conditionally compile code for this target with:
 
 Note that the `target_env = "p1"` condition first appeared in Rust 1.80. Prior
 to Rust 1.80 the `target_env` condition was not set.
+
+## Enabled WebAssembly features
+
+The default set of WebAssembly features enabled for compilation is currently the
+same as [`wasm32-unknown-unknown`](./wasm32-unknown-unknown.md). See the
+documentation there for more information.
diff --git a/src/doc/rustc/src/platform-support/wasm32-wasip2.md b/src/doc/rustc/src/platform-support/wasm32-wasip2.md
index 1e53fbc178e2e..bb2348b201e39 100644
--- a/src/doc/rustc/src/platform-support/wasm32-wasip2.md
+++ b/src/doc/rustc/src/platform-support/wasm32-wasip2.md
@@ -61,3 +61,9 @@ It's recommended to conditionally compile code for this target with:
 ```text
 #[cfg(all(target_os = "wasi", target_env = "p2"))]
 ```
+
+## Enabled WebAssembly features
+
+The default set of WebAssembly features enabled for compilation is currently the
+same as [`wasm32-unknown-unknown`](./wasm32-unknown-unknown.md). See the
+documentation there for more information.
diff --git a/src/doc/unstable-book/src/compiler-flags/embed-source.md b/src/doc/unstable-book/src/compiler-flags/embed-source.md
new file mode 100644
index 0000000000000..01a11e3779712
--- /dev/null
+++ b/src/doc/unstable-book/src/compiler-flags/embed-source.md
@@ -0,0 +1,12 @@
+# `embed-source`
+
+This flag controls whether the compiler embeds the program source code text into
+the object debug information section. It takes one of the following values:
+
+* `y`, `yes`, `on` or `true`: put source code in debug info.
+* `n`, `no`, `off`, `false` or no value: omit source code from debug info (the default).
+
+This flag is ignored in configurations that don't emit DWARF debug information
+and is ignored on non-LLVM backends. `-Z embed-source` requires DWARFv5. Use
+`-Z dwarf-version=5` to control the compiler's DWARF target version and `-g` to
+enable debug info generation.
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index db81b4c4282a1..5260e363dd68c 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -272,7 +272,7 @@ fn clean_lifetime<'tcx>(lifetime: &hir::Lifetime, cx: &mut DocContext<'tcx>) ->
         | rbv::ResolvedArg::LateBound(_, _, did)
         | rbv::ResolvedArg::Free(_, did),
     ) = cx.tcx.named_bound_var(lifetime.hir_id)
-        && let Some(lt) = cx.args.get(&did).and_then(|arg| arg.as_lt())
+        && let Some(lt) = cx.args.get(&did.to_def_id()).and_then(|arg| arg.as_lt())
     {
         return lt.clone();
     }
diff --git a/src/tools/compiletest/src/command-list.rs b/src/tools/compiletest/src/command-list.rs
index 7f8080235c870..a559d6f81a240 100644
--- a/src/tools/compiletest/src/command-list.rs
+++ b/src/tools/compiletest/src/command-list.rs
@@ -141,6 +141,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "needs-force-clang-based-tests",
     "needs-git-hash",
     "needs-llvm-components",
+    "needs-llvm-zstd",
     "needs-profiler-support",
     "needs-relocation-model-pic",
     "needs-run-enabled",
diff --git a/src/tools/compiletest/src/header.rs b/src/tools/compiletest/src/header.rs
index 1fc24301c85e6..277a88584ba60 100644
--- a/src/tools/compiletest/src/header.rs
+++ b/src/tools/compiletest/src/header.rs
@@ -1203,6 +1203,107 @@ pub fn extract_llvm_version_from_binary(binary_path: &str) -> Option<u32> {
     None
 }
 
+/// For tests using the `needs-llvm-zstd` directive:
+/// - for local LLVM builds, try to find the static zstd library in the llvm-config system libs.
+/// - for `download-ci-llvm`, see if `lld` was built with zstd support.
+pub fn llvm_has_libzstd(config: &Config) -> bool {
+    // Strategy 1: works for local builds but not with `download-ci-llvm`.
+    //
+    // We check whether `llvm-config` returns the zstd library. Bootstrap's `llvm.libzstd` will only
+    // ask to statically link it when building LLVM, so we only check if the list of system libs
+    // contains a path to that static lib, and that it exists.
+    //
+    // See compiler/rustc_llvm/build.rs for more details and similar expectations.
+    fn is_zstd_in_config(llvm_bin_dir: &Path) -> Option<()> {
+        let llvm_config_path = llvm_bin_dir.join("llvm-config");
+        let output = Command::new(llvm_config_path).arg("--system-libs").output().ok()?;
+        assert!(output.status.success(), "running llvm-config --system-libs failed");
+
+        let libs = String::from_utf8(output.stdout).ok()?;
+        for lib in libs.split_whitespace() {
+            if lib.ends_with("libzstd.a") && Path::new(lib).exists() {
+                return Some(());
+            }
+        }
+
+        None
+    }
+
+    // Strategy 2: `download-ci-llvm`'s `llvm-config --system-libs` will not return any libs to
+    // use.
+    //
+    // The CI artifacts also don't contain the bootstrap config used to build them: otherwise we
+    // could have looked at the `llvm.libzstd` config.
+    //
+    // We infer whether `LLVM_ENABLE_ZSTD` was used to build LLVM as a byproduct of testing whether
+    // `lld` supports it. If not, an error will be emitted: "LLVM was not built with
+    // LLVM_ENABLE_ZSTD or did not find zstd at build time".
+    #[cfg(unix)]
+    fn is_lld_built_with_zstd(llvm_bin_dir: &Path) -> Option<()> {
+        let lld_path = llvm_bin_dir.join("lld");
+        if lld_path.exists() {
+            // We can't call `lld` as-is, it expects to be invoked by a compiler driver using a
+            // different name. Prepare a temporary symlink to do that.
+            let lld_symlink_path = llvm_bin_dir.join("ld.lld");
+            if !lld_symlink_path.exists() {
+                std::os::unix::fs::symlink(lld_path, &lld_symlink_path).ok()?;
+            }
+
+            // Run `lld` with a zstd flag. We expect this command to always error here, we don't
+            // want to link actual files and don't pass any.
+            let output = Command::new(&lld_symlink_path)
+                .arg("--compress-debug-sections=zstd")
+                .output()
+                .ok()?;
+            assert!(!output.status.success());
+
+            // Look for a specific error caused by LLVM not being built with zstd support. We could
+            // also look for the "no input files" message, indicating the zstd flag was accepted.
+            let stderr = String::from_utf8(output.stderr).ok()?;
+            let zstd_available = !stderr.contains("LLVM was not built with LLVM_ENABLE_ZSTD");
+
+            // We don't particularly need to clean the link up (so the previous commands could fail
+            // in theory but won't in practice), but we can try.
+            std::fs::remove_file(lld_symlink_path).ok()?;
+
+            if zstd_available {
+                return Some(());
+            }
+        }
+
+        None
+    }
+
+    #[cfg(not(unix))]
+    fn is_lld_built_with_zstd(llvm_bin_dir: &Path) -> Option<()> {
+        None
+    }
+
+    if let Some(llvm_bin_dir) = &config.llvm_bin_dir {
+        // Strategy 1: for local LLVM builds.
+        if is_zstd_in_config(llvm_bin_dir).is_some() {
+            return true;
+        }
+
+        // Strategy 2: for LLVM artifacts built on CI via `download-ci-llvm`.
+        //
+        // It doesn't work for cases where the artifacts don't contain the linker, but it's
+        // best-effort: CI has `llvm.libzstd` and `lld` enabled on the x64 linux artifacts, so it
+        // will at least work there.
+        //
+        // If this can be improved and expanded to less common cases in the future, it should.
+        if config.target == "x86_64-unknown-linux-gnu"
+            && config.host == config.target
+            && is_lld_built_with_zstd(llvm_bin_dir).is_some()
+        {
+            return true;
+        }
+    }
+
+    // Otherwise, all hope is lost.
+    false
+}
+
 /// Takes a directive of the form "<version1> [- <version2>]",
 /// returns the numeric representation of <version1> and <version2> as
 /// tuple: (<version1> as u32, <version2> as u32)
diff --git a/src/tools/compiletest/src/header/needs.rs b/src/tools/compiletest/src/header/needs.rs
index 8f935d5b74441..72b1b9c6d480a 100644
--- a/src/tools/compiletest/src/header/needs.rs
+++ b/src/tools/compiletest/src/header/needs.rs
@@ -1,5 +1,5 @@
 use crate::common::{Config, Sanitizer};
-use crate::header::IgnoreDecision;
+use crate::header::{llvm_has_libzstd, IgnoreDecision};
 
 pub(super) fn handle_needs(
     cache: &CachedNeedsConditions,
@@ -144,6 +144,11 @@ pub(super) fn handle_needs(
             condition: cache.symlinks,
             ignore_reason: "ignored if symlinks are unavailable",
         },
+        Need {
+            name: "needs-llvm-zstd",
+            condition: cache.llvm_zstd,
+            ignore_reason: "ignored if LLVM wasn't build with zstd for ELF section compression",
+        },
     ];
 
     let (name, comment) = match ln.split_once([':', ' ']) {
@@ -169,7 +174,7 @@ pub(super) fn handle_needs(
             } else {
                 return IgnoreDecision::Ignore {
                     reason: if let Some(comment) = comment {
-                        format!("{} ({comment})", need.ignore_reason)
+                        format!("{} ({})", need.ignore_reason, comment.trim())
                     } else {
                         need.ignore_reason.into()
                     },
@@ -210,6 +215,8 @@ pub(super) struct CachedNeedsConditions {
     rust_lld: bool,
     dlltool: bool,
     symlinks: bool,
+    /// Whether LLVM built with zstd, for the `needs-llvm-zstd` directive.
+    llvm_zstd: bool,
 }
 
 impl CachedNeedsConditions {
@@ -253,6 +260,7 @@ impl CachedNeedsConditions {
                 .join(if config.host.contains("windows") { "rust-lld.exe" } else { "rust-lld" })
                 .exists(),
 
+            llvm_zstd: llvm_has_libzstd(&config),
             dlltool: find_dlltool(&config),
             symlinks: has_symlinks(),
         }
diff --git a/src/tools/miri/Cargo.toml b/src/tools/miri/Cargo.toml
index e12f3f9012f0d..4b7f3483ff7db 100644
--- a/src/tools/miri/Cargo.toml
+++ b/src/tools/miri/Cargo.toml
@@ -20,7 +20,7 @@ doctest = false # and no doc tests
 [dependencies]
 getrandom = { version = "0.2", features = ["std"] }
 rand = "0.8"
-smallvec = "1.7"
+smallvec = { version = "1.7", features = ["drain_filter"] }
 aes = { version = "0.8.3", features = ["hazmat"] }
 measureme = "11"
 ctrlc = "3.2.5"
diff --git a/src/tools/miri/rust-version b/src/tools/miri/rust-version
index c3f4f4b5d8220..1eca86baeaa21 100644
--- a/src/tools/miri/rust-version
+++ b/src/tools/miri/rust-version
@@ -1 +1 @@
-f24a6ba06f4190d8ec4f22d1baa800e64b1900cb
+fdf61d499c8a8421ecf98e7924bb87caf43a9938
diff --git a/src/tools/miri/src/borrow_tracker/tree_borrows/tree.rs b/src/tools/miri/src/borrow_tracker/tree_borrows/tree.rs
index 90bd11032185c..56643c6cbe811 100644
--- a/src/tools/miri/src/borrow_tracker/tree_borrows/tree.rs
+++ b/src/tools/miri/src/borrow_tracker/tree_borrows/tree.rs
@@ -10,7 +10,7 @@
 //!   and the relative position of the access;
 //! - idempotency properties asserted in `perms.rs` (for optimizations)
 
-use std::fmt;
+use std::{fmt, mem};
 
 use smallvec::SmallVec;
 
@@ -699,8 +699,7 @@ impl<'tcx> Tree {
 /// Integration with the BorTag garbage collector
 impl Tree {
     pub fn remove_unreachable_tags(&mut self, live_tags: &FxHashSet<BorTag>) {
-        let root_is_needed = self.keep_only_needed(self.root, live_tags); // root can't be removed
-        assert!(root_is_needed);
+        self.remove_useless_children(self.root, live_tags);
         // Right after the GC runs is a good moment to check if we can
         // merge some adjacent ranges that were made equal by the removal of some
         // tags (this does not necessarily mean that they have identical internal representations,
@@ -708,9 +707,16 @@ impl Tree {
         self.rperms.merge_adjacent_thorough();
     }
 
+    /// Checks if a node is useless and should be GC'ed.
+    /// A node is useless if it has no children and also the tag is no longer live.
+    fn is_useless(&self, idx: UniIndex, live: &FxHashSet<BorTag>) -> bool {
+        let node = self.nodes.get(idx).unwrap();
+        node.children.is_empty() && !live.contains(&node.tag)
+    }
+
     /// Traverses the entire tree looking for useless tags.
-    /// Returns true iff the tag it was called on is still live or has live children,
-    /// and removes from the tree all tags that have no live children.
+    /// Removes from the tree all useless child nodes of root.
+    /// It will not delete the root itself.
     ///
     /// NOTE: This leaves in the middle of the tree tags that are unreachable but have
     /// reachable children. There is a potential for compacting the tree by reassigning
@@ -721,42 +727,60 @@ impl Tree {
     /// `child: Reserved`. This tree can exist. If we blindly delete `parent` and reassign
     /// `child` to be a direct child of `root` then Writes to `child` are now permitted
     /// whereas they were not when `parent` was still there.
-    fn keep_only_needed(&mut self, idx: UniIndex, live: &FxHashSet<BorTag>) -> bool {
-        let node = self.nodes.get(idx).unwrap();
-        // FIXME: this function does a lot of cloning, a 2-pass approach is possibly
-        // more efficient. It could consist of
-        // 1. traverse the Tree, collect all useless tags in a Vec
-        // 2. traverse the Vec, remove all tags previously selected
-        // Bench it.
-        let children: SmallVec<_> = node
-            .children
-            .clone()
-            .into_iter()
-            .filter(|child| self.keep_only_needed(*child, live))
-            .collect();
-        let no_children = children.is_empty();
-        let node = self.nodes.get_mut(idx).unwrap();
-        node.children = children;
-        if !live.contains(&node.tag) && no_children {
-            // All of the children and this node are unreachable, delete this tag
-            // from the tree (the children have already been deleted by recursive
-            // calls).
-            // Due to the API of UniMap we must absolutely call
-            // `UniValMap::remove` for the key of this tag on *all* maps that used it
-            // (which are `self.nodes` and every range of `self.rperms`)
-            // before we can safely apply `UniValMap::forget` to truly remove
-            // the tag from the mapping.
-            let tag = node.tag;
-            self.nodes.remove(idx);
-            for (_perms_range, perms) in self.rperms.iter_mut_all() {
-                perms.remove(idx);
+    fn remove_useless_children(&mut self, root: UniIndex, live: &FxHashSet<BorTag>) {
+        // To avoid stack overflows, we roll our own stack.
+        // Each element in the stack consists of the current tag, and the number of the
+        // next child to be processed.
+
+        // The other functions are written using the `TreeVisitorStack`, but that does not work here
+        // since we need to 1) do a post-traversal and 2) remove nodes from the tree.
+        // Since we do a post-traversal (by deleting nodes only after handling all children),
+        // we also need to be a bit smarter than "pop node, push all children."
+        let mut stack = vec![(root, 0)];
+        while let Some((tag, nth_child)) = stack.last_mut() {
+            let node = self.nodes.get(*tag).unwrap();
+            if *nth_child < node.children.len() {
+                // Visit the child by pushing it to the stack.
+                // Also increase `nth_child` so that when we come back to the `tag` node, we
+                // look at the next child.
+                let next_child = node.children[*nth_child];
+                *nth_child += 1;
+                stack.push((next_child, 0));
+                continue;
+            } else {
+                // We have processed all children of `node`, so now it is time to process `node` itself.
+                // First, get the current children of `node`. To appease the borrow checker,
+                // we have to temporarily move the list out of the node, and then put the
+                // list of remaining children back in.
+                let mut children_of_node =
+                    mem::take(&mut self.nodes.get_mut(*tag).unwrap().children);
+                // Remove all useless children, and save them for later.
+                // The closure needs `&self` and the loop below needs `&mut self`, so we need to `collect`
+                // in to a temporary list.
+                let to_remove: Vec<_> =
+                    children_of_node.drain_filter(|x| self.is_useless(*x, live)).collect();
+                // Put back the now-filtered vector.
+                self.nodes.get_mut(*tag).unwrap().children = children_of_node;
+                // Now, all that is left is unregistering the children saved in `to_remove`.
+                for idx in to_remove {
+                    // Note: In the rest of this comment, "this node" refers to `idx`.
+                    // This node has no more children (if there were any, they have already been removed).
+                    // It is also unreachable as determined by the GC, so we can remove it everywhere.
+                    // Due to the API of UniMap we must make sure to call
+                    // `UniValMap::remove` for the key of this node on *all* maps that used it
+                    // (which are `self.nodes` and every range of `self.rperms`)
+                    // before we can safely apply `UniKeyMap::remove` to truly remove
+                    // this tag from the `tag_mapping`.
+                    let node = self.nodes.remove(idx).unwrap();
+                    for (_perms_range, perms) in self.rperms.iter_mut_all() {
+                        perms.remove(idx);
+                    }
+                    self.tag_mapping.remove(&node.tag);
+                }
+                // We are done, the parent can continue.
+                stack.pop();
+                continue;
             }
-            self.tag_mapping.remove(&tag);
-            // The tag has been deleted, inform the caller
-            false
-        } else {
-            // The tag is still live or has live children, it must be kept
-            true
         }
     }
 }
diff --git a/src/tools/miri/src/borrow_tracker/tree_borrows/unimap.rs b/src/tools/miri/src/borrow_tracker/tree_borrows/unimap.rs
index f45b2d9e00a6a..92bae6203b3c0 100644
--- a/src/tools/miri/src/borrow_tracker/tree_borrows/unimap.rs
+++ b/src/tools/miri/src/borrow_tracker/tree_borrows/unimap.rs
@@ -12,7 +12,7 @@
 
 #![allow(dead_code)]
 
-use std::hash::Hash;
+use std::{hash::Hash, mem};
 
 use rustc_data_structures::fx::FxHashMap;
 
@@ -187,13 +187,16 @@ impl<V> UniValMap<V> {
         self.data.get_mut(idx.idx as usize).and_then(Option::as_mut)
     }
 
-    /// Delete any value associated with this index. Ok even if the index
-    /// has no associated value.
-    pub fn remove(&mut self, idx: UniIndex) {
+    /// Delete any value associated with this index.
+    /// Returns None if the value was not present, otherwise
+    /// returns the previously stored value.
+    pub fn remove(&mut self, idx: UniIndex) -> Option<V> {
         if idx.idx as usize >= self.data.len() {
-            return;
+            return None;
         }
-        self.data[idx.idx as usize] = None;
+        let mut res = None;
+        mem::swap(&mut res, &mut self.data[idx.idx as usize]);
+        res
     }
 }
 
diff --git a/src/tools/miri/src/shims/unix/fs.rs b/src/tools/miri/src/shims/unix/fs.rs
index 80f4b89bf34d3..e00758bb98de6 100644
--- a/src/tools/miri/src/shims/unix/fs.rs
+++ b/src/tools/miri/src/shims/unix/fs.rs
@@ -1204,14 +1204,14 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         )?;
                     }
                     "freebsd" => {
-                        this.write_int(ino, &this.project_field_named(&entry_place, "d_fileno")?)?;
-                        // `d_off` only exists on FreeBSD 12+, but we support v11 as well.
-                        // `libc` uses a build script to determine which version of the API to use,
-                        // and cross-builds always end up using v11.
-                        // To support both v11 and v12+, we dynamically check whether the field exists.
-                        if this.projectable_has_field(&entry_place, "d_off") {
-                            this.write_int(0, &this.project_field_named(&entry_place, "d_off")?)?;
-                        }
+                        #[rustfmt::skip]
+                        this.write_int_fields_named(
+                            &[
+                                ("d_fileno", ino.into()),
+                                ("d_off", 0),
+                            ],
+                            &entry_place,
+                        )?;
                     }
                     _ => unreachable!(),
                 }
diff --git a/src/tools/miri/src/shims/x86/mod.rs b/src/tools/miri/src/shims/x86/mod.rs
index c1117e4d811f7..305e59fa0cd60 100644
--- a/src/tools/miri/src/shims/x86/mod.rs
+++ b/src/tools/miri/src/shims/x86/mod.rs
@@ -15,6 +15,7 @@ mod aesni;
 mod avx;
 mod avx2;
 mod bmi;
+mod sha;
 mod sse;
 mod sse2;
 mod sse3;
@@ -105,6 +106,11 @@ pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     this, link_name, abi, args, dest,
                 );
             }
+            name if name.starts_with("sha") => {
+                return sha::EvalContextExt::emulate_x86_sha_intrinsic(
+                    this, link_name, abi, args, dest,
+                );
+            }
             name if name.starts_with("sse.") => {
                 return sse::EvalContextExt::emulate_x86_sse_intrinsic(
                     this, link_name, abi, args, dest,
diff --git a/src/tools/miri/src/shims/x86/sha.rs b/src/tools/miri/src/shims/x86/sha.rs
new file mode 100644
index 0000000000000..e9cc28be34cff
--- /dev/null
+++ b/src/tools/miri/src/shims/x86/sha.rs
@@ -0,0 +1,221 @@
+//! Implements sha256 SIMD instructions of x86 targets
+//!
+//! The functions that actually compute SHA256 were copied from [RustCrypto's sha256 module].
+//!
+//! [RustCrypto's sha256 module]: https://github.com/RustCrypto/hashes/blob/6be8466247e936c415d8aafb848697f39894a386/sha2/src/sha256/soft.rs
+
+use rustc_span::Symbol;
+use rustc_target::spec::abi::Abi;
+
+use crate::*;
+
+impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
+pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
+    fn emulate_x86_sha_intrinsic(
+        &mut self,
+        link_name: Symbol,
+        abi: Abi,
+        args: &[OpTy<'tcx>],
+        dest: &MPlaceTy<'tcx>,
+    ) -> InterpResult<'tcx, EmulateItemResult> {
+        let this = self.eval_context_mut();
+        this.expect_target_feature_for_intrinsic(link_name, "sha")?;
+        // Prefix should have already been checked.
+        let unprefixed_name = link_name.as_str().strip_prefix("llvm.x86.sha").unwrap();
+
+        fn read<'c>(this: &mut MiriInterpCx<'c>, reg: &MPlaceTy<'c>) -> InterpResult<'c, [u32; 4]> {
+            let mut res = [0; 4];
+            // We reverse the order because x86 is little endian but the copied implementation uses
+            // big endian.
+            for (i, dst) in res.iter_mut().rev().enumerate() {
+                let projected = &this.project_index(reg, i.try_into().unwrap())?;
+                *dst = this.read_scalar(projected)?.to_u32()?
+            }
+            Ok(res)
+        }
+
+        fn write<'c>(
+            this: &mut MiriInterpCx<'c>,
+            dest: &MPlaceTy<'c>,
+            val: [u32; 4],
+        ) -> InterpResult<'c, ()> {
+            // We reverse the order because x86 is little endian but the copied implementation uses
+            // big endian.
+            for (i, part) in val.into_iter().rev().enumerate() {
+                let projected = &this.project_index(dest, i.try_into().unwrap())?;
+                this.write_scalar(Scalar::from_u32(part), projected)?;
+            }
+            Ok(())
+        }
+
+        match unprefixed_name {
+            // Used to implement the _mm_sha256rnds2_epu32 function.
+            "256rnds2" => {
+                let [a, b, k] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+
+                let (a_reg, a_len) = this.operand_to_simd(a)?;
+                let (b_reg, b_len) = this.operand_to_simd(b)?;
+                let (k_reg, k_len) = this.operand_to_simd(k)?;
+                let (dest, dest_len) = this.mplace_to_simd(dest)?;
+
+                assert_eq!(a_len, 4);
+                assert_eq!(b_len, 4);
+                assert_eq!(k_len, 4);
+                assert_eq!(dest_len, 4);
+
+                let a = read(this, &a_reg)?;
+                let b = read(this, &b_reg)?;
+                let k = read(this, &k_reg)?;
+
+                let result = sha256_digest_round_x2(a, b, k);
+                write(this, &dest, result)?;
+            }
+            // Used to implement the _mm_sha256msg1_epu32 function.
+            "256msg1" => {
+                let [a, b] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+
+                let (a_reg, a_len) = this.operand_to_simd(a)?;
+                let (b_reg, b_len) = this.operand_to_simd(b)?;
+                let (dest, dest_len) = this.mplace_to_simd(dest)?;
+
+                assert_eq!(a_len, 4);
+                assert_eq!(b_len, 4);
+                assert_eq!(dest_len, 4);
+
+                let a = read(this, &a_reg)?;
+                let b = read(this, &b_reg)?;
+
+                let result = sha256msg1(a, b);
+                write(this, &dest, result)?;
+            }
+            // Used to implement the _mm_sha256msg2_epu32 function.
+            "256msg2" => {
+                let [a, b] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+
+                let (a_reg, a_len) = this.operand_to_simd(a)?;
+                let (b_reg, b_len) = this.operand_to_simd(b)?;
+                let (dest, dest_len) = this.mplace_to_simd(dest)?;
+
+                assert_eq!(a_len, 4);
+                assert_eq!(b_len, 4);
+                assert_eq!(dest_len, 4);
+
+                let a = read(this, &a_reg)?;
+                let b = read(this, &b_reg)?;
+
+                let result = sha256msg2(a, b);
+                write(this, &dest, result)?;
+            }
+            _ => return Ok(EmulateItemResult::NotSupported),
+        }
+        Ok(EmulateItemResult::NeedsReturn)
+    }
+}
+
+#[inline(always)]
+fn shr(v: [u32; 4], o: u32) -> [u32; 4] {
+    [v[0] >> o, v[1] >> o, v[2] >> o, v[3] >> o]
+}
+
+#[inline(always)]
+fn shl(v: [u32; 4], o: u32) -> [u32; 4] {
+    [v[0] << o, v[1] << o, v[2] << o, v[3] << o]
+}
+
+#[inline(always)]
+fn or(a: [u32; 4], b: [u32; 4]) -> [u32; 4] {
+    [a[0] | b[0], a[1] | b[1], a[2] | b[2], a[3] | b[3]]
+}
+
+#[inline(always)]
+fn xor(a: [u32; 4], b: [u32; 4]) -> [u32; 4] {
+    [a[0] ^ b[0], a[1] ^ b[1], a[2] ^ b[2], a[3] ^ b[3]]
+}
+
+#[inline(always)]
+fn add(a: [u32; 4], b: [u32; 4]) -> [u32; 4] {
+    [
+        a[0].wrapping_add(b[0]),
+        a[1].wrapping_add(b[1]),
+        a[2].wrapping_add(b[2]),
+        a[3].wrapping_add(b[3]),
+    ]
+}
+
+fn sha256load(v2: [u32; 4], v3: [u32; 4]) -> [u32; 4] {
+    [v3[3], v2[0], v2[1], v2[2]]
+}
+
+fn sha256_digest_round_x2(cdgh: [u32; 4], abef: [u32; 4], wk: [u32; 4]) -> [u32; 4] {
+    macro_rules! big_sigma0 {
+        ($a:expr) => {
+            ($a.rotate_right(2) ^ $a.rotate_right(13) ^ $a.rotate_right(22))
+        };
+    }
+    macro_rules! big_sigma1 {
+        ($a:expr) => {
+            ($a.rotate_right(6) ^ $a.rotate_right(11) ^ $a.rotate_right(25))
+        };
+    }
+    macro_rules! bool3ary_202 {
+        ($a:expr, $b:expr, $c:expr) => {
+            $c ^ ($a & ($b ^ $c))
+        };
+    } // Choose, MD5F, SHA1C
+    macro_rules! bool3ary_232 {
+        ($a:expr, $b:expr, $c:expr) => {
+            ($a & $b) ^ ($a & $c) ^ ($b & $c)
+        };
+    } // Majority, SHA1M
+
+    let [_, _, wk1, wk0] = wk;
+    let [a0, b0, e0, f0] = abef;
+    let [c0, d0, g0, h0] = cdgh;
+
+    // a round
+    let x0 =
+        big_sigma1!(e0).wrapping_add(bool3ary_202!(e0, f0, g0)).wrapping_add(wk0).wrapping_add(h0);
+    let y0 = big_sigma0!(a0).wrapping_add(bool3ary_232!(a0, b0, c0));
+    let (a1, b1, c1, d1, e1, f1, g1, h1) =
+        (x0.wrapping_add(y0), a0, b0, c0, x0.wrapping_add(d0), e0, f0, g0);
+
+    // a round
+    let x1 =
+        big_sigma1!(e1).wrapping_add(bool3ary_202!(e1, f1, g1)).wrapping_add(wk1).wrapping_add(h1);
+    let y1 = big_sigma0!(a1).wrapping_add(bool3ary_232!(a1, b1, c1));
+    let (a2, b2, _, _, e2, f2, _, _) =
+        (x1.wrapping_add(y1), a1, b1, c1, x1.wrapping_add(d1), e1, f1, g1);
+
+    [a2, b2, e2, f2]
+}
+
+fn sha256msg1(v0: [u32; 4], v1: [u32; 4]) -> [u32; 4] {
+    // sigma 0 on vectors
+    #[inline]
+    fn sigma0x4(x: [u32; 4]) -> [u32; 4] {
+        let t1 = or(shr(x, 7), shl(x, 25));
+        let t2 = or(shr(x, 18), shl(x, 14));
+        let t3 = shr(x, 3);
+        xor(xor(t1, t2), t3)
+    }
+
+    add(v0, sigma0x4(sha256load(v0, v1)))
+}
+
+fn sha256msg2(v4: [u32; 4], v3: [u32; 4]) -> [u32; 4] {
+    macro_rules! sigma1 {
+        ($a:expr) => {
+            $a.rotate_right(17) ^ $a.rotate_right(19) ^ ($a >> 10)
+        };
+    }
+
+    let [x3, x2, x1, x0] = v4;
+    let [w15, w14, _, _] = v3;
+
+    let w16 = x0.wrapping_add(sigma1!(w14));
+    let w17 = x1.wrapping_add(sigma1!(w15));
+    let w18 = x2.wrapping_add(sigma1!(w16));
+    let w19 = x3.wrapping_add(sigma1!(w17));
+
+    [w19, w18, w17, w16]
+}
diff --git a/src/tools/miri/test_dependencies/Cargo.lock b/src/tools/miri/test_dependencies/Cargo.lock
index e94bef529521e..bbead8782233c 100644
--- a/src/tools/miri/test_dependencies/Cargo.lock
+++ b/src/tools/miri/test_dependencies/Cargo.lock
@@ -119,9 +119,9 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.155"
+version = "0.2.158"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "97b3888a4aecf77e811145cadf6eef5901f4782c53886191b2f693f24761847c"
+checksum = "d8adc4bb1803a324070e64a98ae98f38934d91957a99cfb3a43dcbc01bc56439"
 
 [[package]]
 name = "linux-raw-sys"
diff --git a/src/tools/miri/tests/fail/alloc/global_system_mixup.rs b/src/tools/miri/tests/fail/alloc/global_system_mixup.rs
index 19c62913b4c66..804aa13660b99 100644
--- a/src/tools/miri/tests/fail/alloc/global_system_mixup.rs
+++ b/src/tools/miri/tests/fail/alloc/global_system_mixup.rs
@@ -13,7 +13,5 @@ use std::alloc::{Allocator, Global, Layout, System};
 fn main() {
     let l = Layout::from_size_align(1, 1).unwrap();
     let ptr = Global.allocate(l).unwrap().as_non_null_ptr();
-    unsafe {
-        System.deallocate(ptr, l);
-    }
+    unsafe { System.deallocate(ptr, l) };
 }
diff --git a/src/tools/miri/tests/fail/alloc/global_system_mixup.stderr b/src/tools/miri/tests/fail/alloc/global_system_mixup.stderr
index 7006b96ee1e61..7790956414961 100644
--- a/src/tools/miri/tests/fail/alloc/global_system_mixup.stderr
+++ b/src/tools/miri/tests/fail/alloc/global_system_mixup.stderr
@@ -12,7 +12,7 @@ LL |         FREE();
 note: inside `main`
   --> $DIR/global_system_mixup.rs:LL:CC
    |
-LL |         System.deallocate(ptr, l);
+LL |     unsafe { System.deallocate(ptr, l) };
    | ^
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.rs b/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.rs
new file mode 100644
index 0000000000000..aed5cb1125817
--- /dev/null
+++ b/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.rs
@@ -0,0 +1,19 @@
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+//@[tree]error-in-other-file: /deallocation .* is forbidden/
+use std::alloc::{alloc, dealloc, Layout};
+
+// `x` is strongly protected but covers zero bytes.
+// Let's see if deallocating the allocation x points to is UB:
+// in TB, it is UB, but in SB it is not.
+fn test(_x: &mut (), ptr: *mut u8, l: Layout) {
+    unsafe { dealloc(ptr, l) };
+}
+
+fn main() {
+    let l = Layout::from_size_align(1, 1).unwrap();
+    let ptr = unsafe { alloc(l) };
+    unsafe { test(&mut *ptr.cast::<()>(), ptr, l) };
+    // In SB the test would pass if it weren't for this line.
+    unsafe { std::hint::unreachable_unchecked() }; //~[stack] ERROR: unreachable
+}
diff --git a/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.stack.stderr b/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.stack.stderr
new file mode 100644
index 0000000000000..672682ff29401
--- /dev/null
+++ b/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.stack.stderr
@@ -0,0 +1,15 @@
+error: Undefined Behavior: entering unreachable code
+  --> $DIR/zero-sized-protected.rs:LL:CC
+   |
+LL |     unsafe { std::hint::unreachable_unchecked() };
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ entering unreachable code
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `main` at $DIR/zero-sized-protected.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.tree.stderr b/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.tree.stderr
new file mode 100644
index 0000000000000..ef981038e5540
--- /dev/null
+++ b/src/tools/miri/tests/fail/both_borrows/zero-sized-protected.tree.stderr
@@ -0,0 +1,36 @@
+error: Undefined Behavior: deallocation through <TAG> (root of the allocation) at ALLOC[0x0] is forbidden
+  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+   |
+LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deallocation through <TAG> (root of the allocation) at ALLOC[0x0] is forbidden
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: the allocation of the accessed tag <TAG> (root of the allocation) also contains the strongly protected tag <TAG>
+   = help: the strongly protected tag <TAG> disallows deallocations
+help: the accessed tag <TAG> was created here
+  --> $DIR/zero-sized-protected.rs:LL:CC
+   |
+LL |     let ptr = unsafe { alloc(l) };
+   |                        ^^^^^^^^
+help: the strongly protected tag <TAG> was created here, in the initial state Reserved
+  --> $DIR/zero-sized-protected.rs:LL:CC
+   |
+LL | fn test(_x: &mut (), ptr: *mut u8, l: Layout) {
+   |         ^^
+   = note: BACKTRACE (of the first span):
+   = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
+note: inside `test`
+  --> $DIR/zero-sized-protected.rs:LL:CC
+   |
+LL |     unsafe { dealloc(ptr, l) };
+   |              ^^^^^^^^^^^^^^^
+note: inside `main`
+  --> $DIR/zero-sized-protected.rs:LL:CC
+   |
+LL |     unsafe { test(&mut *ptr.cast::<()>(), ptr, l) };
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/pass-dep/libc/libc-epoll.rs b/src/tools/miri/tests/pass-dep/libc/libc-epoll.rs
index e28cafd3c285b..052ce73de237f 100644
--- a/src/tools/miri/tests/pass-dep/libc/libc-epoll.rs
+++ b/src/tools/miri/tests/pass-dep/libc/libc-epoll.rs
@@ -1,8 +1,7 @@
 //@only-target-linux
 
-#![feature(exposed_provenance)] // Needed for fn test_pointer()
+#![feature(strict_provenance)]
 use std::convert::TryInto;
-use std::mem::MaybeUninit;
 
 fn main() {
     test_epoll_socketpair();
@@ -17,7 +16,6 @@ fn main() {
     test_no_notification_for_unregister_flag();
     test_epoll_ctl_mod();
     test_epoll_ctl_del();
-    test_pointer();
     test_two_same_fd_in_same_epoll_instance();
     test_epoll_wait_maxevent_zero();
     test_socketpair_epollerr();
@@ -261,24 +259,6 @@ fn test_epoll_eventfd() {
     check_epoll_wait::<8>(epfd, &[(expected_event, expected_value)]);
 }
 
-fn test_pointer() {
-    // Create an epoll instance.
-    let epfd = unsafe { libc::epoll_create1(0) };
-    assert_ne!(epfd, -1);
-
-    // Create a socketpair instance.
-    let mut fds = [-1, -1];
-    let res = unsafe { libc::socketpair(libc::AF_UNIX, libc::SOCK_STREAM, 0, fds.as_mut_ptr()) };
-    assert_eq!(res, 0);
-
-    // Register fd[1] with EPOLLIN|EPOLLOUT|EPOLLET
-    let data = MaybeUninit::<u64>::uninit().as_ptr();
-    let mut ev =
-        libc::epoll_event { events: EPOLL_IN_OUT_ET, u64: data.expose_provenance() as u64 };
-    let res = unsafe { libc::epoll_ctl(epfd, libc::EPOLL_CTL_ADD, fds[1], &mut ev) };
-    assert_eq!(res, 0);
-}
-
 // When read/write happened on one side of the socketpair, only the other side will be notified.
 fn test_epoll_socketpair_both_sides() {
     // Create an epoll instance.
@@ -543,9 +523,9 @@ fn test_epoll_wait_maxevent_zero() {
     // Create an epoll instance.
     let epfd = unsafe { libc::epoll_create1(0) };
     assert_ne!(epfd, -1);
-    // It is ok to use uninitialised pointer here because it will error out before the
-    // pointer actually get accessed.
-    let array_ptr = MaybeUninit::<libc::epoll_event>::uninit().as_mut_ptr();
+    // It is ok to use a dangling pointer here because it will error out before the
+    // pointer actually gets accessed.
+    let array_ptr = std::ptr::without_provenance_mut::<libc::epoll_event>(0x100);
     let res = unsafe { libc::epoll_wait(epfd, array_ptr, 0, 0) };
     let e = std::io::Error::last_os_error();
     assert_eq!(e.raw_os_error(), Some(libc::EINVAL));
diff --git a/src/tools/miri/tests/pass/shims/x86/intrinsics-sha.rs b/src/tools/miri/tests/pass/shims/x86/intrinsics-sha.rs
new file mode 100644
index 0000000000000..e65fdc3fbed68
--- /dev/null
+++ b/src/tools/miri/tests/pass/shims/x86/intrinsics-sha.rs
@@ -0,0 +1,270 @@
+// Ignore everything except x86 and x86_64
+// Any new targets that are added to CI should be ignored here.
+// (We cannot use `cfg`-based tricks here since the `target-feature` flags below only work on x86.)
+//@ignore-target-aarch64
+//@ignore-target-arm
+//@ignore-target-avr
+//@ignore-target-s390x
+//@ignore-target-thumbv7em
+//@ignore-target-wasm32
+//@compile-flags: -C target-feature=+sha,+sse2,+ssse3,+sse4.1
+
+#[cfg(target_arch = "x86")]
+use std::arch::x86::*;
+#[cfg(target_arch = "x86_64")]
+use std::arch::x86_64::*;
+
+macro_rules! rounds4 {
+    ($abef:ident, $cdgh:ident, $rest:expr, $i:expr) => {{
+        let k = K32X4[$i];
+        let kv = _mm_set_epi32(k[0] as i32, k[1] as i32, k[2] as i32, k[3] as i32);
+        let t1 = _mm_add_epi32($rest, kv);
+        $cdgh = _mm_sha256rnds2_epu32($cdgh, $abef, t1);
+        let t2 = _mm_shuffle_epi32(t1, 0x0E);
+        $abef = _mm_sha256rnds2_epu32($abef, $cdgh, t2);
+    }};
+}
+
+macro_rules! schedule_rounds4 {
+    (
+        $abef:ident, $cdgh:ident,
+        $w0:expr, $w1:expr, $w2:expr, $w3:expr, $w4:expr,
+        $i: expr
+    ) => {{
+        $w4 = schedule($w0, $w1, $w2, $w3);
+        rounds4!($abef, $cdgh, $w4, $i);
+    }};
+}
+
+fn main() {
+    assert!(is_x86_feature_detected!("sha"));
+    assert!(is_x86_feature_detected!("sse2"));
+    assert!(is_x86_feature_detected!("ssse3"));
+    assert!(is_x86_feature_detected!("sse4.1"));
+
+    unsafe {
+        test_sha256rnds2();
+        test_sha256msg1();
+        test_sha256msg2();
+        test_sha256();
+    }
+}
+
+#[target_feature(enable = "sha,sse2,ssse3,sse4.1")]
+unsafe fn test_sha256rnds2() {
+    let test_vectors = [
+        (
+            [0x3c6ef372, 0xa54ff53a, 0x1f83d9ab, 0x5be0cd19],
+            [0x6a09e667, 0xbb67ae85, 0x510e527f, 0x9b05688c],
+            [0x592340c6, 0x17386142, 0x91a0b7b1, 0x94ffa30c],
+            [0xeef39c6c, 0x4e7dfbc1, 0x467a98f3, 0xeb3d5616],
+        ),
+        (
+            [0x6a09e667, 0xbb67ae85, 0x510e527f, 0x9b05688c],
+            [0xeef39c6c, 0x4e7dfbc1, 0x467a98f3, 0xeb3d5616],
+            [0x91a0b7b1, 0x94ffa30c, 0x592340c6, 0x17386142],
+            [0x7e7f3c9d, 0x78db9a20, 0xd82fe6ed, 0xaf1f2704],
+        ),
+        (
+            [0xeef39c6c, 0x4e7dfbc1, 0x467a98f3, 0xeb3d5616],
+            [0x7e7f3c9d, 0x78db9a20, 0xd82fe6ed, 0xaf1f2704],
+            [0x1a89c3f6, 0xf3b6e817, 0x7a5a8511, 0x8bcc35cf],
+            [0xc9292f7e, 0x49137bd9, 0x7e5f9e08, 0xd10f9247],
+        ),
+    ];
+    for (cdgh, abef, wk, expected) in test_vectors {
+        let output_reg = _mm_sha256rnds2_epu32(set_arr(cdgh), set_arr(abef), set_arr(wk));
+        let mut output = [0u32; 4];
+        _mm_storeu_si128(output.as_mut_ptr().cast(), output_reg);
+        // The values are stored as little endian, so we need to reverse them
+        output.reverse();
+        assert_eq!(output, expected);
+    }
+}
+
+#[target_feature(enable = "sha,sse2,ssse3,sse4.1")]
+unsafe fn test_sha256msg1() {
+    let test_vectors = [
+        (
+            [0x6f6d6521, 0x61776573, 0x20697320, 0x52757374],
+            [0x6f6d6521, 0x61776573, 0x20697320, 0x52757374],
+            [0x2da4b536, 0x77f29328, 0x541a4d59, 0x6afb680c],
+        ),
+        (
+            [0x6f6d6521, 0x61776573, 0x20697320, 0x52757374],
+            [0x6f6d6521, 0x61776573, 0x20697320, 0x52757374],
+            [0x2da4b536, 0x77f29328, 0x541a4d59, 0x6afb680c],
+        ),
+        (
+            [0x6f6d6521, 0x61776573, 0x20697320, 0x52757374],
+            [0x6f6d6521, 0x61776573, 0x20697320, 0x52757374],
+            [0x2da4b536, 0x77f29328, 0x541a4d59, 0x6afb680c],
+        ),
+    ];
+    for (v0, v1, expected) in test_vectors {
+        let output_reg = _mm_sha256msg1_epu32(set_arr(v0), set_arr(v1));
+        let mut output = [0u32; 4];
+        _mm_storeu_si128(output.as_mut_ptr().cast(), output_reg);
+        // The values are stored as little endian, so we need to reverse them
+        output.reverse();
+        assert_eq!(output, expected);
+    }
+}
+
+#[target_feature(enable = "sha,sse2,ssse3,sse4.1")]
+unsafe fn test_sha256msg2() {
+    let test_vectors = [
+        (
+            [0x801a28aa, 0xe75ff849, 0xb591b2cc, 0x8b64db2c],
+            [0x6f6d6521, 0x61776573, 0x20697320, 0x52757374],
+            [0xe7c46c4e, 0x8ce92ccc, 0xd3c0f3ce, 0xe9745c78],
+        ),
+        (
+            [0x171911ae, 0xe75ff849, 0xb591b2cc, 0x8b64db2c],
+            [0xe7c46c4e, 0x8ce92ccc, 0xd3c0f3ce, 0xe9745c78],
+            [0xc17c6ea3, 0xc4d10083, 0x712910cd, 0x3f41c8ce],
+        ),
+        (
+            [0x6ce67e04, 0x5fb6ff76, 0xe1037a25, 0x3ebc5bda],
+            [0xc17c6ea3, 0xc4d10083, 0x712910cd, 0x3f41c8ce],
+            [0xf5ab4eff, 0x83d732a5, 0x9bb941af, 0xdf1d0a8c],
+        ),
+    ];
+    for (v4, v3, expected) in test_vectors {
+        let output_reg = _mm_sha256msg2_epu32(set_arr(v4), set_arr(v3));
+        let mut output = [0u32; 4];
+        _mm_storeu_si128(output.as_mut_ptr().cast(), output_reg);
+        // The values are stored as little endian, so we need to reverse them
+        output.reverse();
+        assert_eq!(output, expected);
+    }
+}
+
+#[target_feature(enable = "sha,sse2,ssse3,sse4.1")]
+unsafe fn set_arr(x: [u32; 4]) -> __m128i {
+    _mm_set_epi32(x[0] as i32, x[1] as i32, x[2] as i32, x[3] as i32)
+}
+
+#[target_feature(enable = "sha,sse2,ssse3,sse4.1")]
+unsafe fn test_sha256() {
+    use std::fmt::Write;
+
+    /// The initial state of the hash engine.
+    const INITIAL_STATE: [u32; 8] = [
+        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab,
+        0x5be0cd19,
+    ];
+
+    // We don't want to bother with hash finalization algorithm so we just feed constant data.
+    // This is the content that's being hashed - you can feed it to sha256sum and it'll output
+    // the same hash (beware of newlines though).
+    let first_block = *b"Rust is awesome!Rust is awesome!Rust is awesome!Rust is awesome!";
+    // sha256 is fianlized by appending 0x80, then zeros and finally the data lenght at the
+    // end.
+    let mut final_block = [0; 64];
+    final_block[0] = 0x80;
+    final_block[(64 - 8)..].copy_from_slice(&(8u64 * 64).to_be_bytes());
+
+    let mut state = INITIAL_STATE;
+    digest_blocks(&mut state, &[first_block, final_block]);
+
+    // We compare strings because it's easier to check the hex and the output of panic.
+    let mut hash = String::new();
+    for chunk in &state {
+        write!(hash, "{:08x}", chunk).expect("writing to String doesn't fail");
+    }
+    assert_eq!(hash, "1b2293d21b17a0cb0c18737307c37333dea775eded18cefed45e50389f9f8184");
+}
+
+// Almost full SHA256 implementation copied from RustCrypto's sha2 crate
+// https://github.com/RustCrypto/hashes/blob/6be8466247e936c415d8aafb848697f39894a386/sha2/src/sha256/x86.rs
+
+#[target_feature(enable = "sha,sse2,ssse3,sse4.1")]
+unsafe fn schedule(v0: __m128i, v1: __m128i, v2: __m128i, v3: __m128i) -> __m128i {
+    let t1 = _mm_sha256msg1_epu32(v0, v1);
+    let t2 = _mm_alignr_epi8(v3, v2, 4);
+    let t3 = _mm_add_epi32(t1, t2);
+    _mm_sha256msg2_epu32(t3, v3)
+}
+
+// we use unaligned loads with `__m128i` pointers
+#[allow(clippy::cast_ptr_alignment)]
+#[target_feature(enable = "sha,sse2,ssse3,sse4.1")]
+unsafe fn digest_blocks(state: &mut [u32; 8], blocks: &[[u8; 64]]) {
+    #[allow(non_snake_case)]
+    let MASK: __m128i =
+        _mm_set_epi64x(0x0C0D_0E0F_0809_0A0Bu64 as i64, 0x0405_0607_0001_0203u64 as i64);
+
+    let state_ptr: *const __m128i = state.as_ptr().cast();
+    let dcba = _mm_loadu_si128(state_ptr.add(0));
+    let efgh = _mm_loadu_si128(state_ptr.add(1));
+
+    let cdab = _mm_shuffle_epi32(dcba, 0xB1);
+    let efgh = _mm_shuffle_epi32(efgh, 0x1B);
+    let mut abef = _mm_alignr_epi8(cdab, efgh, 8);
+    let mut cdgh = _mm_blend_epi16(efgh, cdab, 0xF0);
+
+    for block in blocks {
+        let abef_save = abef;
+        let cdgh_save = cdgh;
+
+        let block_ptr: *const __m128i = block.as_ptr().cast();
+        let mut w0 = _mm_shuffle_epi8(_mm_loadu_si128(block_ptr.add(0)), MASK);
+        let mut w1 = _mm_shuffle_epi8(_mm_loadu_si128(block_ptr.add(1)), MASK);
+        let mut w2 = _mm_shuffle_epi8(_mm_loadu_si128(block_ptr.add(2)), MASK);
+        let mut w3 = _mm_shuffle_epi8(_mm_loadu_si128(block_ptr.add(3)), MASK);
+        let mut w4;
+
+        rounds4!(abef, cdgh, w0, 0);
+        rounds4!(abef, cdgh, w1, 1);
+        rounds4!(abef, cdgh, w2, 2);
+        rounds4!(abef, cdgh, w3, 3);
+        schedule_rounds4!(abef, cdgh, w0, w1, w2, w3, w4, 4);
+        schedule_rounds4!(abef, cdgh, w1, w2, w3, w4, w0, 5);
+        schedule_rounds4!(abef, cdgh, w2, w3, w4, w0, w1, 6);
+        schedule_rounds4!(abef, cdgh, w3, w4, w0, w1, w2, 7);
+        schedule_rounds4!(abef, cdgh, w4, w0, w1, w2, w3, 8);
+        schedule_rounds4!(abef, cdgh, w0, w1, w2, w3, w4, 9);
+        schedule_rounds4!(abef, cdgh, w1, w2, w3, w4, w0, 10);
+        schedule_rounds4!(abef, cdgh, w2, w3, w4, w0, w1, 11);
+        schedule_rounds4!(abef, cdgh, w3, w4, w0, w1, w2, 12);
+        schedule_rounds4!(abef, cdgh, w4, w0, w1, w2, w3, 13);
+        schedule_rounds4!(abef, cdgh, w0, w1, w2, w3, w4, 14);
+        schedule_rounds4!(abef, cdgh, w1, w2, w3, w4, w0, 15);
+
+        abef = _mm_add_epi32(abef, abef_save);
+        cdgh = _mm_add_epi32(cdgh, cdgh_save);
+    }
+
+    let feba = _mm_shuffle_epi32(abef, 0x1B);
+    let dchg = _mm_shuffle_epi32(cdgh, 0xB1);
+    let dcba = _mm_blend_epi16(feba, dchg, 0xF0);
+    let hgef = _mm_alignr_epi8(dchg, feba, 8);
+
+    let state_ptr_mut: *mut __m128i = state.as_mut_ptr().cast();
+    _mm_storeu_si128(state_ptr_mut.add(0), dcba);
+    _mm_storeu_si128(state_ptr_mut.add(1), hgef);
+}
+
+/// Swapped round constants for SHA-256 family of digests
+pub static K32X4: [[u32; 4]; 16] = {
+    let mut res = [[0u32; 4]; 16];
+    let mut i = 0;
+    while i < 16 {
+        res[i] = [K32[4 * i + 3], K32[4 * i + 2], K32[4 * i + 1], K32[4 * i]];
+        i += 1;
+    }
+    res
+};
+
+/// Round constants for SHA-256 family of digests
+pub static K32: [u32; 64] = [
+    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
+];
diff --git a/tests/run-make/rust-lld-compress-debug-sections/main.rs b/tests/run-make/compressed-debuginfo-zstd/main.rs
similarity index 100%
rename from tests/run-make/rust-lld-compress-debug-sections/main.rs
rename to tests/run-make/compressed-debuginfo-zstd/main.rs
diff --git a/tests/run-make/compressed-debuginfo-zstd/rmake.rs b/tests/run-make/compressed-debuginfo-zstd/rmake.rs
new file mode 100644
index 0000000000000..8356373e949aa
--- /dev/null
+++ b/tests/run-make/compressed-debuginfo-zstd/rmake.rs
@@ -0,0 +1,42 @@
+// Checks debuginfo compression both for the always-enabled zlib, and when the optional zstd is
+// enabled:
+// - via rustc's `debuginfo-compression`,
+// - and via rust-lld's `compress-debug-sections`
+
+//@ needs-llvm-zstd: we want LLVM/LLD to be built with zstd support
+//@ needs-rust-lld: the system linker will most likely not support zstd
+//@ only-linux
+//@ ignore-cross-compile
+
+use run_make_support::{llvm_readobj, run_in_tmpdir, Rustc};
+
+fn check_compression(compression: &str, to_find: &str) {
+    // check compressed debug sections via rustc flag
+    prepare_and_check(to_find, |rustc| {
+        rustc.arg(&format!("-Zdebuginfo-compression={compression}"))
+    });
+
+    // check compressed debug sections via rust-lld flag
+    prepare_and_check(to_find, |rustc| {
+        rustc.link_arg(&format!("-Wl,--compress-debug-sections={compression}"))
+    });
+}
+
+fn prepare_and_check<F: FnOnce(&mut Rustc) -> &mut Rustc>(to_find: &str, prepare_rustc: F) {
+    run_in_tmpdir(|| {
+        let mut rustc = Rustc::new();
+        rustc
+            .arg("-Zlinker-features=+lld")
+            .arg("-Clink-self-contained=+linker")
+            .arg("-Zunstable-options")
+            .arg("-Cdebuginfo=full")
+            .input("main.rs");
+        prepare_rustc(&mut rustc).run();
+        llvm_readobj().arg("-t").arg("main").run().assert_stdout_contains(to_find);
+    });
+}
+
+fn main() {
+    check_compression("zlib", "ZLIB");
+    check_compression("zstd", "ZSTD");
+}
diff --git a/tests/run-make/compressed-debuginfo/rmake.rs b/tests/run-make/compressed-debuginfo/rmake.rs
index 5ba1a1852d51b..362b2e2e1e449 100644
--- a/tests/run-make/compressed-debuginfo/rmake.rs
+++ b/tests/run-make/compressed-debuginfo/rmake.rs
@@ -1,11 +1,9 @@
-// Checks the `debuginfo-compression` option.
+// Checks the always enabled `debuginfo-compression` option: zlib.
 
 //@ only-linux
 //@ ignore-cross-compile
 
-// FIXME: This test isn't comprehensive and isn't covering all possible combinations.
-
-use run_make_support::{assert_contains, llvm_readobj, run_in_tmpdir, rustc};
+use run_make_support::{llvm_readobj, run_in_tmpdir, rustc};
 
 fn check_compression(compression: &str, to_find: &str) {
     run_in_tmpdir(|| {
@@ -17,19 +15,10 @@ fn check_compression(compression: &str, to_find: &str) {
             .arg(&format!("-Zdebuginfo-compression={compression}"))
             .input("foo.rs")
             .run();
-        let stderr = out.stderr_utf8();
-        if stderr.is_empty() {
-            llvm_readobj().arg("-t").arg("foo.o").run().assert_stdout_contains(to_find);
-        } else {
-            assert_contains(
-                stderr,
-                format!("unknown debuginfo compression algorithm {compression}"),
-            );
-        }
+        llvm_readobj().arg("-t").arg("foo.o").run().assert_stdout_contains(to_find);
     });
 }
 
 fn main() {
     check_compression("zlib", "ZLIB");
-    check_compression("zstd", "ZSTD");
 }
diff --git a/tests/run-make/embed-source-dwarf/main.rs b/tests/run-make/embed-source-dwarf/main.rs
new file mode 100644
index 0000000000000..c80af84f41415
--- /dev/null
+++ b/tests/run-make/embed-source-dwarf/main.rs
@@ -0,0 +1,2 @@
+// hello
+fn main() {}
diff --git a/tests/run-make/embed-source-dwarf/rmake.rs b/tests/run-make/embed-source-dwarf/rmake.rs
new file mode 100644
index 0000000000000..06d550121b0de
--- /dev/null
+++ b/tests/run-make/embed-source-dwarf/rmake.rs
@@ -0,0 +1,70 @@
+//@ ignore-windows
+//@ ignore-apple
+
+// LLVM 17's embed-source implementation requires that source code is attached
+// for all files in the output DWARF debug info. This restriction was lifted in
+// LLVM 18 (87e22bdd2bd6d77d782f9d64b3e3ae5bdcd5080d).
+//@ min-llvm-version: 18
+
+// This test should be replaced with one in tests/debuginfo once we can easily
+// tell via GDB or LLDB if debuginfo contains source code. Cheap tricks in LLDB
+// like setting an invalid source map path don't appear to work, maybe this'll
+// become easier once GDB supports DWARFv6?
+
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::rc::Rc;
+
+use gimli::{AttributeValue, EndianRcSlice, Reader, RunTimeEndian};
+use object::{Object, ObjectSection};
+use run_make_support::{gimli, object, rfs, rustc};
+
+fn main() {
+    let output = PathBuf::from("embed-source-main");
+    rustc()
+        .input("main.rs")
+        .output(&output)
+        .arg("-g")
+        .arg("-Zembed-source=yes")
+        .arg("-Zdwarf-version=5")
+        .run();
+    let output = rfs::read(output);
+    let obj = object::File::parse(output.as_slice()).unwrap();
+    let endian = if obj.is_little_endian() { RunTimeEndian::Little } else { RunTimeEndian::Big };
+    let dwarf = gimli::Dwarf::load(|section| -> Result<_, ()> {
+        let data = obj.section_by_name(section.name()).map(|s| s.uncompressed_data().unwrap());
+        Ok(EndianRcSlice::new(Rc::from(data.unwrap_or_default().as_ref()), endian))
+    })
+    .unwrap();
+
+    let mut sources = HashMap::new();
+
+    let mut iter = dwarf.units();
+    while let Some(header) = iter.next().unwrap() {
+        let unit = dwarf.unit(header).unwrap();
+        let unit = unit.unit_ref(&dwarf);
+
+        if let Some(program) = &unit.line_program {
+            let header = program.header();
+            for file in header.file_names() {
+                if let Some(source) = file.source() {
+                    let path = unit
+                        .attr_string(file.path_name())
+                        .unwrap()
+                        .to_string_lossy()
+                        .unwrap()
+                        .to_string();
+                    let source =
+                        unit.attr_string(source).unwrap().to_string_lossy().unwrap().to_string();
+                    if !source.is_empty() {
+                        sources.insert(path, source);
+                    }
+                }
+            }
+        }
+    }
+
+    dbg!(&sources);
+    assert_eq!(sources.len(), 1);
+    assert_eq!(sources.get("main.rs").unwrap(), "// hello\nfn main() {}\n");
+}
diff --git a/tests/run-make/rust-lld-compress-debug-sections/rmake.rs b/tests/run-make/rust-lld-compress-debug-sections/rmake.rs
deleted file mode 100644
index ea4997fab8099..0000000000000
--- a/tests/run-make/rust-lld-compress-debug-sections/rmake.rs
+++ /dev/null
@@ -1,39 +0,0 @@
-// Checks the `compress-debug-sections` option on rust-lld.
-
-//@ needs-rust-lld
-//@ only-linux
-//@ ignore-cross-compile
-
-// FIXME: This test isn't comprehensive and isn't covering all possible combinations.
-
-use run_make_support::{assert_contains, llvm_readobj, run_in_tmpdir, rustc};
-
-fn check_compression(compression: &str, to_find: &str) {
-    run_in_tmpdir(|| {
-        let out = rustc()
-            .arg("-Zlinker-features=+lld")
-            .arg("-Clink-self-contained=+linker")
-            .arg("-Zunstable-options")
-            .arg("-Cdebuginfo=full")
-            .link_arg(&format!("-Wl,--compress-debug-sections={compression}"))
-            .input("main.rs")
-            .run_unchecked();
-        let stderr = out.stderr_utf8();
-        if stderr.is_empty() {
-            llvm_readobj().arg("-t").arg("main").run().assert_stdout_contains(to_find);
-        } else {
-            assert_contains(
-                stderr,
-                format!(
-                    "LLVM was not built with LLVM_ENABLE_{to_find} \
-                     or did not find {compression} at build time"
-                ),
-            );
-        }
-    });
-}
-
-fn main() {
-    check_compression("zlib", "ZLIB");
-    check_compression("zstd", "ZSTD");
-}
diff --git a/tests/ui/impl-trait/in-trait/refine-err.rs b/tests/ui/impl-trait/in-trait/refine-err.rs
new file mode 100644
index 0000000000000..7518cee97c444
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/refine-err.rs
@@ -0,0 +1,14 @@
+#![deny(refining_impl_trait)]
+
+trait FromRow {
+    fn prepare(self) -> impl Fn() -> T;
+    //~^ ERROR cannot find type `T` in this scope
+}
+
+impl<T> FromRow for T {
+    fn prepare(self) -> impl Fn() -> T {
+        || todo!()
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/in-trait/refine-err.stderr b/tests/ui/impl-trait/in-trait/refine-err.stderr
new file mode 100644
index 0000000000000..6b4ef74d50afc
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/refine-err.stderr
@@ -0,0 +1,9 @@
+error[E0412]: cannot find type `T` in this scope
+  --> $DIR/refine-err.rs:4:38
+   |
+LL |     fn prepare(self) -> impl Fn() -> T;
+   |                                      ^ not found in this scope
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0412`.
diff --git a/tests/ui/impl-trait/in-trait/span-bug-issue-121457.rs b/tests/ui/impl-trait/in-trait/span-bug-issue-121457.rs
index 7a51037324f28..ab21dae7dc50d 100644
--- a/tests/ui/impl-trait/in-trait/span-bug-issue-121457.rs
+++ b/tests/ui/impl-trait/in-trait/span-bug-issue-121457.rs
@@ -14,7 +14,6 @@ impl<'a, I: 'a + Iterable> Iterable for &'a I {
     //~^ ERROR binding for associated type `Item` references lifetime `'missing`
     //~| ERROR binding for associated type `Item` references lifetime `'missing`
     //~| ERROR `()` is not an iterator
-    //~| WARNING impl trait in impl method signature does not match trait method signature
 }
 
 fn main() {}
diff --git a/tests/ui/impl-trait/in-trait/span-bug-issue-121457.stderr b/tests/ui/impl-trait/in-trait/span-bug-issue-121457.stderr
index 67c4df0f3a9eb..d8a2eef94a180 100644
--- a/tests/ui/impl-trait/in-trait/span-bug-issue-121457.stderr
+++ b/tests/ui/impl-trait/in-trait/span-bug-issue-121457.stderr
@@ -32,24 +32,7 @@ LL |     fn iter(&self) -> impl for<'missing> Iterator<Item = Self::Item<'missin
    |
    = help: the trait `Iterator` is not implemented for `()`
 
-warning: impl trait in impl method signature does not match trait method signature
-  --> $DIR/span-bug-issue-121457.rs:13:51
-   |
-LL |     fn iter(&self) -> impl Iterator;
-   |                       ------------- return type from trait method defined here
-...
-LL |     fn iter(&self) -> impl for<'missing> Iterator<Item = Self::Item<'missing>> {}
-   |                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^ this bound is stronger than that defined on the trait
-   |
-   = note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
-   = note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
-   = note: `#[warn(refining_impl_trait_reachable)]` on by default
-help: replace the return type so that it matches the trait
-   |
-LL |     fn iter(&self) -> impl Iterator {}
-   |                       ~~~~~~~~~~~~~
-
-error: aborting due to 4 previous errors; 1 warning emitted
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0195, E0277, E0582.
 For more information about an error, try `rustc --explain E0195`.
diff --git a/tests/ui/lint/dropping_copy_types-macros.fixed b/tests/ui/lint/dropping_copy_types-macros.fixed
new file mode 100644
index 0000000000000..a8ceedadc8063
--- /dev/null
+++ b/tests/ui/lint/dropping_copy_types-macros.fixed
@@ -0,0 +1,12 @@
+//@ check-fail
+//@ run-rustfix
+
+#![deny(dropping_copy_types)]
+
+use std::fmt::Write;
+
+fn main() {
+    let mut msg = String::new();
+    let _ = writeln!(&mut msg, "test");
+    //~^ ERROR calls to `std::mem::drop`
+}
diff --git a/tests/ui/lint/dropping_copy_types-macros.rs b/tests/ui/lint/dropping_copy_types-macros.rs
new file mode 100644
index 0000000000000..b249b0c868f37
--- /dev/null
+++ b/tests/ui/lint/dropping_copy_types-macros.rs
@@ -0,0 +1,12 @@
+//@ check-fail
+//@ run-rustfix
+
+#![deny(dropping_copy_types)]
+
+use std::fmt::Write;
+
+fn main() {
+    let mut msg = String::new();
+    drop(writeln!(&mut msg, "test"));
+    //~^ ERROR calls to `std::mem::drop`
+}
diff --git a/tests/ui/lint/dropping_copy_types-macros.stderr b/tests/ui/lint/dropping_copy_types-macros.stderr
new file mode 100644
index 0000000000000..117e9f4fe099c
--- /dev/null
+++ b/tests/ui/lint/dropping_copy_types-macros.stderr
@@ -0,0 +1,21 @@
+error: calls to `std::mem::drop` with a value that implements `Copy` does nothing
+  --> $DIR/dropping_copy_types-macros.rs:10:5
+   |
+LL |     drop(writeln!(&mut msg, "test"));
+   |     ^^^^^--------------------------^
+   |          |
+   |          argument has type `Result<(), std::fmt::Error>`
+   |
+note: the lint level is defined here
+  --> $DIR/dropping_copy_types-macros.rs:4:9
+   |
+LL | #![deny(dropping_copy_types)]
+   |         ^^^^^^^^^^^^^^^^^^^
+help: use `let _ = ...` to ignore the expression or result
+   |
+LL -     drop(writeln!(&mut msg, "test"));
+LL +     let _ = writeln!(&mut msg, "test");
+   |
+
+error: aborting due to 1 previous error
+