diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 8b740b7774089..2267f09ec1f11 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -322,10 +322,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
             },
             ItemKind::ForeignMod(ref fm) => {
                 if fm.abi.is_none() {
-                    self.maybe_lint_missing_abi(span, id, abi::Abi::C);
+                    self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
                 }
                 hir::ItemKind::ForeignMod {
-                    abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
+                    abi: fm.abi.map_or(abi::Abi::C { unwind: false }, |abi| self.lower_abi(abi)),
                     items: self
                         .arena
                         .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
@@ -1322,8 +1322,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         match ext {
             Extern::None => abi::Abi::Rust,
             Extern::Implicit => {
-                self.maybe_lint_missing_abi(span, id, abi::Abi::C);
-                abi::Abi::C
+                self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
+                abi::Abi::C { unwind: false }
             }
             Extern::Explicit(abi) => self.lower_abi(abi),
         }
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 474ec2b589b71..acfbec6fa21b5 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -164,6 +164,38 @@ impl<'a> PostExpansionVisitor<'a> {
                     "C-cmse-nonsecure-call ABI is experimental and subject to change"
                 );
             }
+            "C-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "C-unwind ABI is experimental and subject to change"
+                );
+            }
+            "stdcall-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "stdcall-unwind ABI is experimental and subject to change"
+                );
+            }
+            "system-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "system-unwind ABI is experimental and subject to change"
+                );
+            }
+            "thiscall-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "thiscall-unwind ABI is experimental and subject to change"
+                );
+            }
             abi => self
                 .sess
                 .parse_sess
diff --git a/compiler/rustc_builtin_macros/src/source_util.rs b/compiler/rustc_builtin_macros/src/source_util.rs
index 28efd483c8670..4aafcb2fb6dfe 100644
--- a/compiler/rustc_builtin_macros/src/source_util.rs
+++ b/compiler/rustc_builtin_macros/src/source_util.rs
@@ -4,7 +4,7 @@ use rustc_ast::token;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast_pretty::pprust;
 use rustc_expand::base::{self, *};
-use rustc_expand::module::DirectoryOwnership;
+use rustc_expand::module::DirOwnership;
 use rustc_parse::parser::{ForceCollect, Parser};
 use rustc_parse::{self, new_parser_from_file};
 use rustc_session::lint::builtin::INCOMPLETE_INCLUDE;
@@ -101,7 +101,7 @@ pub fn expand_include<'cx>(
         None => return DummyResult::any(sp),
     };
     // The file will be added to the code map by the parser
-    let mut file = match cx.resolve_path(file, sp) {
+    let file = match cx.resolve_path(file, sp) {
         Ok(f) => f,
         Err(mut err) => {
             err.emit();
@@ -114,10 +114,9 @@ pub fn expand_include<'cx>(
     // then the path of `bar.rs` should be relative to the directory of `file`.
     // See https://github.com/rust-lang/rust/pull/69838/files#r395217057 for a discussion.
     // `MacroExpander::fully_expand_fragment` later restores, so "stack discipline" is maintained.
-    file.pop();
-    cx.current_expansion.directory_ownership = DirectoryOwnership::Owned { relative: None };
-    let mod_path = cx.current_expansion.module.mod_path.clone();
-    cx.current_expansion.module = Rc::new(ModuleData { mod_path, directory: file });
+    let dir_path = file.parent().unwrap_or(&file).to_owned();
+    cx.current_expansion.module = Rc::new(cx.current_expansion.module.with_dir_path(dir_path));
+    cx.current_expansion.dir_ownership = DirOwnership::Owned { relative: None };
 
     struct ExpandResult<'a> {
         p: Parser<'a>,
diff --git a/compiler/rustc_codegen_cranelift/src/abi/mod.rs b/compiler/rustc_codegen_cranelift/src/abi/mod.rs
index b2647e6c8d384..83bb1d0172fbb 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/mod.rs
@@ -542,7 +542,7 @@ pub(crate) fn codegen_terminator_call<'tcx>(
 
     // FIXME find a cleaner way to support varargs
     if fn_sig.c_variadic {
-        if fn_sig.abi != Abi::C {
+        if !matches!(fn_sig.abi, Abi::C { .. }) {
             fx.tcx.sess.span_fatal(
                 span,
                 &format!("Variadic call for non-C abi {:?}", fn_sig.abi),
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 929cc56294d3d..5bd06e8e7d115 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -1,11 +1,11 @@
 use crate::expand::{self, AstFragment, Invocation};
-use crate::module::DirectoryOwnership;
+use crate::module::DirOwnership;
 
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Nonterminal};
 use rustc_ast::tokenstream::{CanSynthesizeMissingTokens, LazyTokenStream, TokenStream};
 use rustc_ast::visit::{AssocCtxt, Visitor};
-use rustc_ast::{self as ast, AstLike, Attribute, NodeId, PatKind};
+use rustc_ast::{self as ast, AstLike, Attribute, Item, NodeId, PatKind};
 use rustc_attr::{self as attr, Deprecation, Stability};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{self, Lrc};
@@ -900,10 +900,26 @@ pub trait ResolverExpand {
     fn cfg_accessible(&mut self, expn_id: ExpnId, path: &ast::Path) -> Result<bool, Indeterminate>;
 }
 
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct ModuleData {
+    /// Path to the module starting from the crate name, like `my_crate::foo::bar`.
     pub mod_path: Vec<Ident>,
-    pub directory: PathBuf,
+    /// Stack of paths to files loaded by out-of-line module items,
+    /// used to detect and report recursive module inclusions.
+    pub file_path_stack: Vec<PathBuf>,
+    /// Directory to search child module files in,
+    /// often (but not necessarily) the parent of the top file path on the `file_path_stack`.
+    pub dir_path: PathBuf,
+}
+
+impl ModuleData {
+    pub fn with_dir_path(&self, dir_path: PathBuf) -> ModuleData {
+        ModuleData {
+            mod_path: self.mod_path.clone(),
+            file_path_stack: self.file_path_stack.clone(),
+            dir_path,
+        }
+    }
 }
 
 #[derive(Clone)]
@@ -911,10 +927,13 @@ pub struct ExpansionData {
     pub id: ExpnId,
     pub depth: usize,
     pub module: Rc<ModuleData>,
-    pub directory_ownership: DirectoryOwnership,
+    pub dir_ownership: DirOwnership,
     pub prior_type_ascription: Option<(Span, bool)>,
 }
 
+type OnExternModLoaded<'a> =
+    Option<&'a dyn Fn(Ident, Vec<Attribute>, Vec<P<Item>>, Span) -> (Vec<Attribute>, Vec<P<Item>>)>;
+
 /// One of these is made during expansion and incrementally updated as we go;
 /// when a macro expansion occurs, the resulting nodes have the `backtrace()
 /// -> expn_data` of their expansion context stored into their span.
@@ -932,7 +951,7 @@ pub struct ExtCtxt<'a> {
     /// Called directly after having parsed an external `mod foo;` in expansion.
     ///
     /// `Ident` is the module name.
-    pub(super) extern_mod_loaded: Option<&'a dyn Fn(&ast::Crate, Ident)>,
+    pub(super) extern_mod_loaded: OnExternModLoaded<'a>,
 }
 
 impl<'a> ExtCtxt<'a> {
@@ -940,7 +959,7 @@ impl<'a> ExtCtxt<'a> {
         sess: &'a Session,
         ecfg: expand::ExpansionConfig<'a>,
         resolver: &'a mut dyn ResolverExpand,
-        extern_mod_loaded: Option<&'a dyn Fn(&ast::Crate, Ident)>,
+        extern_mod_loaded: OnExternModLoaded<'a>,
     ) -> ExtCtxt<'a> {
         ExtCtxt {
             sess,
@@ -952,8 +971,8 @@ impl<'a> ExtCtxt<'a> {
             current_expansion: ExpansionData {
                 id: ExpnId::root(),
                 depth: 0,
-                module: Rc::new(ModuleData { mod_path: Vec::new(), directory: PathBuf::new() }),
-                directory_ownership: DirectoryOwnership::Owned { relative: None },
+                module: Default::default(),
+                dir_ownership: DirOwnership::Owned { relative: None },
                 prior_type_ascription: None,
             },
             force_mode: false,
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index b474cad1242e8..dd2eaa0f3d53c 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -3,7 +3,7 @@ use crate::config::StripUnconfigured;
 use crate::configure;
 use crate::hygiene::SyntaxContext;
 use crate::mbe::macro_rules::annotate_err_with_kind;
-use crate::module::{parse_external_mod, push_directory, Directory, DirectoryOwnership};
+use crate::module::{mod_dir_path, parse_external_mod, DirOwnership, ParsedExternalMod};
 use crate::placeholders::{placeholder, PlaceholderExpander};
 
 use rustc_ast as ast;
@@ -355,16 +355,17 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
     // FIXME: Avoid visiting the crate as a `Mod` item,
     // make crate a first class expansion target instead.
     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
-        let mut module = ModuleData {
-            mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
-            directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
-                FileName::Real(name) => name.into_local_path(),
-                other => PathBuf::from(other.to_string()),
-            },
+        let file_path = match self.cx.source_map().span_to_unmapped_path(krate.span) {
+            FileName::Real(name) => name.into_local_path(),
+            other => PathBuf::from(other.to_string()),
         };
-        module.directory.pop();
-        self.cx.root_path = module.directory.clone();
-        self.cx.current_expansion.module = Rc::new(module);
+        let dir_path = file_path.parent().unwrap_or(&file_path).to_owned();
+        self.cx.root_path = dir_path.clone();
+        self.cx.current_expansion.module = Rc::new(ModuleData {
+            mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
+            file_path_stack: vec![file_path],
+            dir_path,
+        });
 
         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
             attrs: krate.attrs,
@@ -1245,10 +1246,12 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
     }
 
     fn visit_block(&mut self, block: &mut P<Block>) {
-        let old_directory_ownership = self.cx.current_expansion.directory_ownership;
-        self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
+        let orig_dir_ownership = mem::replace(
+            &mut self.cx.current_expansion.dir_ownership,
+            DirOwnership::UnownedViaBlock,
+        );
         noop_visit_block(block, self);
-        self.cx.current_expansion.directory_ownership = old_directory_ownership;
+        self.cx.current_expansion.dir_ownership = orig_dir_ownership;
     }
 
     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
@@ -1276,63 +1279,76 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
                 })
             }
             ast::ItemKind::Mod(_, ref mut mod_kind) if ident != Ident::invalid() => {
-                let sess = &self.cx.sess.parse_sess;
-                let orig_ownership = self.cx.current_expansion.directory_ownership;
-                let mut module = (*self.cx.current_expansion.module).clone();
-
-                let pushed = &mut false; // Record `parse_external_mod` pushing so we can pop.
-                let dir = Directory { ownership: orig_ownership, path: module.directory };
-                let Directory { ownership, path } = match mod_kind {
-                    ModKind::Loaded(_, Inline::Yes, _) => {
+                let (file_path, dir_path, dir_ownership) = match mod_kind {
+                    ModKind::Loaded(_, inline, _) => {
                         // Inline `mod foo { ... }`, but we still need to push directories.
+                        assert!(
+                            *inline == Inline::Yes,
+                            "`mod` item is loaded from a file for the second time"
+                        );
+                        let (dir_path, dir_ownership) = mod_dir_path(
+                            &self.cx.sess,
+                            ident,
+                            &attrs,
+                            &self.cx.current_expansion.module,
+                            self.cx.current_expansion.dir_ownership,
+                        );
                         item.attrs = attrs;
-                        push_directory(&self.cx.sess, ident, &item.attrs, dir)
-                    }
-                    ModKind::Loaded(_, Inline::No, _) => {
-                        panic!("`mod` item is loaded from a file for the second time")
+                        (None, dir_path, dir_ownership)
                     }
                     ModKind::Unloaded => {
                         // We have an outline `mod foo;` so we need to parse the file.
-                        let (items, inner_span, dir) =
-                            parse_external_mod(&self.cx.sess, ident, span, dir, &mut attrs, pushed);
+                        let old_attrs_len = attrs.len();
+                        let ParsedExternalMod {
+                            mut items,
+                            inner_span,
+                            file_path,
+                            dir_path,
+                            dir_ownership,
+                        } = parse_external_mod(
+                            &self.cx.sess,
+                            ident,
+                            span,
+                            &self.cx.current_expansion.module,
+                            self.cx.current_expansion.dir_ownership,
+                            &mut attrs,
+                        );
 
-                        let krate =
-                            ast::Crate { attrs, items, span: inner_span, proc_macros: vec![] };
                         if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
-                            extern_mod_loaded(&krate, ident);
+                            (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
                         }
 
-                        *mod_kind = ModKind::Loaded(krate.items, Inline::No, inner_span);
-                        item.attrs = krate.attrs;
-                        // File can have inline attributes, e.g., `#![cfg(...)]` & co. => Reconfigure.
-                        item = match self.configure(item) {
-                            Some(node) => node,
-                            None => {
-                                if *pushed {
-                                    sess.included_mod_stack.borrow_mut().pop();
-                                }
-                                return Default::default();
-                            }
-                        };
-                        dir
+                        *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);
+                        item.attrs = attrs;
+                        if item.attrs.len() > old_attrs_len {
+                            // If we loaded an out-of-line module and added some inner attributes,
+                            // then we need to re-configure it.
+                            // FIXME: Attributes also need to be recollected
+                            // for resolution and expansion.
+                            item = configure!(self, item);
+                        }
+                        (Some(file_path), dir_path, dir_ownership)
                     }
                 };
 
                 // Set the module info before we flat map.
-                self.cx.current_expansion.directory_ownership = ownership;
-                module.directory = path;
+                let mut module = self.cx.current_expansion.module.with_dir_path(dir_path);
                 module.mod_path.push(ident);
+                if let Some(file_path) = file_path {
+                    module.file_path_stack.push(file_path);
+                }
+
                 let orig_module =
                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
+                let orig_dir_ownership =
+                    mem::replace(&mut self.cx.current_expansion.dir_ownership, dir_ownership);
 
                 let result = noop_flat_map_item(item, self);
 
                 // Restore the module info.
+                self.cx.current_expansion.dir_ownership = orig_dir_ownership;
                 self.cx.current_expansion.module = orig_module;
-                self.cx.current_expansion.directory_ownership = orig_ownership;
-                if *pushed {
-                    sess.included_mod_stack.borrow_mut().pop();
-                }
+
                 result
             }
             _ => {
diff --git a/compiler/rustc_expand/src/lib.rs b/compiler/rustc_expand/src/lib.rs
index c5d8ff25ea94b..1a93975533de0 100644
--- a/compiler/rustc_expand/src/lib.rs
+++ b/compiler/rustc_expand/src/lib.rs
@@ -1,5 +1,7 @@
+#![feature(bool_to_option)]
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]
+#![feature(destructuring_assignment)]
 #![feature(or_patterns)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]
diff --git a/compiler/rustc_expand/src/module.rs b/compiler/rustc_expand/src/module.rs
index 076d3b02be93f..2ec656d4895e7 100644
--- a/compiler/rustc_expand/src/module.rs
+++ b/compiler/rustc_expand/src/module.rs
@@ -1,232 +1,155 @@
+use crate::base::ModuleData;
 use rustc_ast::ptr::P;
 use rustc_ast::{token, Attribute, Item};
-use rustc_errors::{struct_span_err, PResult};
+use rustc_errors::{struct_span_err, DiagnosticBuilder};
 use rustc_parse::new_parser_from_file;
 use rustc_session::parse::ParseSess;
 use rustc_session::Session;
-use rustc_span::source_map::{FileName, Span};
 use rustc_span::symbol::{sym, Ident};
+use rustc_span::Span;
 
 use std::path::{self, Path, PathBuf};
 
-#[derive(Clone)]
-pub struct Directory {
-    pub path: PathBuf,
-    pub ownership: DirectoryOwnership,
-}
-
 #[derive(Copy, Clone)]
-pub enum DirectoryOwnership {
+pub enum DirOwnership {
     Owned {
         // None if `mod.rs`, `Some("foo")` if we're in `foo.rs`.
         relative: Option<Ident>,
     },
     UnownedViaBlock,
-    UnownedViaMod,
 }
 
-/// Information about the path to a module.
 // Public for rustfmt usage.
-pub struct ModulePath<'a> {
-    name: String,
-    path_exists: bool,
-    pub result: PResult<'a, ModulePathSuccess>,
+pub struct ModulePathSuccess {
+    pub file_path: PathBuf,
+    pub dir_ownership: DirOwnership,
 }
 
-// Public for rustfmt usage.
-pub struct ModulePathSuccess {
-    pub path: PathBuf,
-    pub ownership: DirectoryOwnership,
+crate struct ParsedExternalMod {
+    pub items: Vec<P<Item>>,
+    pub inner_span: Span,
+    pub file_path: PathBuf,
+    pub dir_path: PathBuf,
+    pub dir_ownership: DirOwnership,
+}
+
+pub enum ModError<'a> {
+    CircularInclusion(Vec<PathBuf>),
+    ModInBlock(Option<Ident>),
+    FileNotFound(Ident, PathBuf),
+    MultipleCandidates(Ident, String, String),
+    ParserError(DiagnosticBuilder<'a>),
 }
 
 crate fn parse_external_mod(
     sess: &Session,
-    id: Ident,
+    ident: Ident,
     span: Span, // The span to blame on errors.
-    Directory { mut ownership, path }: Directory,
+    module: &ModuleData,
+    mut dir_ownership: DirOwnership,
     attrs: &mut Vec<Attribute>,
-    pop_mod_stack: &mut bool,
-) -> (Vec<P<Item>>, Span, Directory) {
+) -> ParsedExternalMod {
     // We bail on the first error, but that error does not cause a fatal error... (1)
-    let result: PResult<'_, _> = try {
+    let result: Result<_, ModError<'_>> = try {
         // Extract the file path and the new ownership.
-        let mp = submod_path(sess, id, span, &attrs, ownership, &path)?;
-        ownership = mp.ownership;
+        let mp = mod_file_path(sess, ident, &attrs, &module.dir_path, dir_ownership)?;
+        dir_ownership = mp.dir_ownership;
 
         // Ensure file paths are acyclic.
-        let mut included_mod_stack = sess.parse_sess.included_mod_stack.borrow_mut();
-        error_on_circular_module(&sess.parse_sess, span, &mp.path, &included_mod_stack)?;
-        included_mod_stack.push(mp.path.clone());
-        *pop_mod_stack = true; // We have pushed, so notify caller.
-        drop(included_mod_stack);
+        if let Some(pos) = module.file_path_stack.iter().position(|p| p == &mp.file_path) {
+            Err(ModError::CircularInclusion(module.file_path_stack[pos..].to_vec()))?;
+        }
 
         // Actually parse the external file as a module.
-        let mut parser = new_parser_from_file(&sess.parse_sess, &mp.path, Some(span));
-        let (mut inner_attrs, items, inner_span) = parser.parse_mod(&token::Eof)?;
+        let mut parser = new_parser_from_file(&sess.parse_sess, &mp.file_path, Some(span));
+        let (mut inner_attrs, items, inner_span) =
+            parser.parse_mod(&token::Eof).map_err(|err| ModError::ParserError(err))?;
         attrs.append(&mut inner_attrs);
-        (items, inner_span)
+        (items, inner_span, mp.file_path)
     };
     // (1) ...instead, we return a dummy module.
-    let (items, inner_span) = result.map_err(|mut err| err.emit()).unwrap_or_default();
+    let (items, inner_span, file_path) =
+        result.map_err(|err| err.report(sess, span)).unwrap_or_default();
 
-    // Extract the directory path for submodules of  the module.
-    let path = sess.source_map().span_to_unmapped_path(inner_span);
-    let mut path = match path {
-        FileName::Real(name) => name.into_local_path(),
-        other => PathBuf::from(other.to_string()),
-    };
-    path.pop();
+    // Extract the directory path for submodules of the module.
+    let dir_path = file_path.parent().unwrap_or(&file_path).to_owned();
 
-    (items, inner_span, Directory { ownership, path })
+    ParsedExternalMod { items, inner_span, file_path, dir_path, dir_ownership }
 }
 
-fn error_on_circular_module<'a>(
-    sess: &'a ParseSess,
-    span: Span,
-    path: &Path,
-    included_mod_stack: &[PathBuf],
-) -> PResult<'a, ()> {
-    if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
-        let mut err = String::from("circular modules: ");
-        for p in &included_mod_stack[i..] {
-            err.push_str(&p.to_string_lossy());
-            err.push_str(" -> ");
-        }
-        err.push_str(&path.to_string_lossy());
-        return Err(sess.span_diagnostic.struct_span_err(span, &err[..]));
-    }
-    Ok(())
-}
-
-crate fn push_directory(
+crate fn mod_dir_path(
     sess: &Session,
-    id: Ident,
+    ident: Ident,
     attrs: &[Attribute],
-    Directory { mut ownership, mut path }: Directory,
-) -> Directory {
-    if let Some(filename) = sess.first_attr_value_str_by_name(attrs, sym::path) {
-        path.push(&*filename.as_str());
-        ownership = DirectoryOwnership::Owned { relative: None };
-    } else {
-        // We have to push on the current module name in the case of relative
-        // paths in order to ensure that any additional module paths from inline
-        // `mod x { ... }` come after the relative extension.
-        //
-        // For example, a `mod z { ... }` inside `x/y.rs` should set the current
-        // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
-        if let DirectoryOwnership::Owned { relative } = &mut ownership {
-            if let Some(ident) = relative.take() {
-                // Remove the relative offset.
-                path.push(&*ident.as_str());
-            }
+    module: &ModuleData,
+    mut dir_ownership: DirOwnership,
+) -> (PathBuf, DirOwnership) {
+    if let Some(file_path) = mod_file_path_from_attr(sess, attrs, &module.dir_path) {
+        // For inline modules file path from `#[path]` is actually the directory path
+        // for historical reasons, so we don't pop the last segment here.
+        return (file_path, DirOwnership::Owned { relative: None });
+    }
+
+    // We have to push on the current module name in the case of relative
+    // paths in order to ensure that any additional module paths from inline
+    // `mod x { ... }` come after the relative extension.
+    //
+    // For example, a `mod z { ... }` inside `x/y.rs` should set the current
+    // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
+    let mut dir_path = module.dir_path.clone();
+    if let DirOwnership::Owned { relative } = &mut dir_ownership {
+        if let Some(ident) = relative.take() {
+            // Remove the relative offset.
+            dir_path.push(&*ident.as_str());
         }
-        path.push(&*id.as_str());
     }
-    Directory { ownership, path }
+    dir_path.push(&*ident.as_str());
+
+    (dir_path, dir_ownership)
 }
 
-fn submod_path<'a>(
+fn mod_file_path<'a>(
     sess: &'a Session,
-    id: Ident,
-    span: Span,
+    ident: Ident,
     attrs: &[Attribute],
-    ownership: DirectoryOwnership,
     dir_path: &Path,
-) -> PResult<'a, ModulePathSuccess> {
-    if let Some(path) = submod_path_from_attr(sess, attrs, dir_path) {
-        let ownership = match path.file_name().and_then(|s| s.to_str()) {
-            // All `#[path]` files are treated as though they are a `mod.rs` file.
-            // This means that `mod foo;` declarations inside `#[path]`-included
-            // files are siblings,
-            //
-            // Note that this will produce weirdness when a file named `foo.rs` is
-            // `#[path]` included and contains a `mod foo;` declaration.
-            // If you encounter this, it's your own darn fault :P
-            Some(_) => DirectoryOwnership::Owned { relative: None },
-            _ => DirectoryOwnership::UnownedViaMod,
-        };
-        return Ok(ModulePathSuccess { ownership, path });
+    dir_ownership: DirOwnership,
+) -> Result<ModulePathSuccess, ModError<'a>> {
+    if let Some(file_path) = mod_file_path_from_attr(sess, attrs, dir_path) {
+        // All `#[path]` files are treated as though they are a `mod.rs` file.
+        // This means that `mod foo;` declarations inside `#[path]`-included
+        // files are siblings,
+        //
+        // Note that this will produce weirdness when a file named `foo.rs` is
+        // `#[path]` included and contains a `mod foo;` declaration.
+        // If you encounter this, it's your own darn fault :P
+        let dir_ownership = DirOwnership::Owned { relative: None };
+        return Ok(ModulePathSuccess { file_path, dir_ownership });
     }
 
-    let relative = match ownership {
-        DirectoryOwnership::Owned { relative } => relative,
-        DirectoryOwnership::UnownedViaBlock | DirectoryOwnership::UnownedViaMod => None,
+    let relative = match dir_ownership {
+        DirOwnership::Owned { relative } => relative,
+        DirOwnership::UnownedViaBlock => None,
     };
-    let ModulePath { path_exists, name, result } =
-        default_submod_path(&sess.parse_sess, id, span, relative, dir_path);
-    match ownership {
-        DirectoryOwnership::Owned { .. } => Ok(result?),
-        DirectoryOwnership::UnownedViaBlock => {
-            let _ = result.map_err(|mut err| err.cancel());
-            error_decl_mod_in_block(&sess.parse_sess, span, path_exists, &name)
-        }
-        DirectoryOwnership::UnownedViaMod => {
-            let _ = result.map_err(|mut err| err.cancel());
-            error_cannot_declare_mod_here(&sess.parse_sess, span, path_exists, &name)
-        }
+    let result = default_submod_path(&sess.parse_sess, ident, relative, dir_path);
+    match dir_ownership {
+        DirOwnership::Owned { .. } => result,
+        DirOwnership::UnownedViaBlock => Err(ModError::ModInBlock(match result {
+            Ok(_) | Err(ModError::MultipleCandidates(..)) => Some(ident),
+            _ => None,
+        })),
     }
 }
 
-fn error_decl_mod_in_block<'a, T>(
-    sess: &'a ParseSess,
-    span: Span,
-    path_exists: bool,
-    name: &str,
-) -> PResult<'a, T> {
-    let msg = "Cannot declare a non-inline module inside a block unless it has a path attribute";
-    let mut err = sess.span_diagnostic.struct_span_err(span, msg);
-    if path_exists {
-        let msg = format!("Maybe `use` the module `{}` instead of redeclaring it", name);
-        err.span_note(span, &msg);
-    }
-    Err(err)
-}
-
-fn error_cannot_declare_mod_here<'a, T>(
-    sess: &'a ParseSess,
-    span: Span,
-    path_exists: bool,
-    name: &str,
-) -> PResult<'a, T> {
-    let mut err =
-        sess.span_diagnostic.struct_span_err(span, "cannot declare a new module at this location");
-    if !span.is_dummy() {
-        if let FileName::Real(src_name) = sess.source_map().span_to_filename(span) {
-            let src_path = src_name.into_local_path();
-            if let Some(stem) = src_path.file_stem() {
-                let mut dest_path = src_path.clone();
-                dest_path.set_file_name(stem);
-                dest_path.push("mod.rs");
-                err.span_note(
-                    span,
-                    &format!(
-                        "maybe move this module `{}` to its own directory via `{}`",
-                        src_path.display(),
-                        dest_path.display()
-                    ),
-                );
-            }
-        }
-    }
-    if path_exists {
-        err.span_note(
-            span,
-            &format!("... or maybe `use` the module `{}` instead of possibly redeclaring it", name),
-        );
-    }
-    Err(err)
-}
-
 /// Derive a submodule path from the first found `#[path = "path_string"]`.
 /// The provided `dir_path` is joined with the `path_string`.
-pub(super) fn submod_path_from_attr(
+fn mod_file_path_from_attr(
     sess: &Session,
     attrs: &[Attribute],
     dir_path: &Path,
 ) -> Option<PathBuf> {
     // Extract path string from first `#[path = "path_string"]` attribute.
-    let path_string = sess.first_attr_value_str_by_name(attrs, sym::path)?;
-    let path_string = path_string.as_str();
+    let path_string = sess.first_attr_value_str_by_name(attrs, sym::path)?.as_str();
 
     // On windows, the base path might have the form
     // `\\?\foo\bar` in which case it does not tolerate
@@ -242,15 +165,14 @@ pub(super) fn submod_path_from_attr(
 // Public for rustfmt usage.
 pub fn default_submod_path<'a>(
     sess: &'a ParseSess,
-    id: Ident,
-    span: Span,
+    ident: Ident,
     relative: Option<Ident>,
     dir_path: &Path,
-) -> ModulePath<'a> {
+) -> Result<ModulePathSuccess, ModError<'a>> {
     // If we're in a foo.rs file instead of a mod.rs file,
     // we need to look for submodules in
-    // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
-    // `./<id>.rs` and `./<id>/mod.rs`.
+    // `./foo/<ident>.rs` and `./foo/<ident>/mod.rs` rather than
+    // `./<ident>.rs` and `./<ident>/mod.rs`.
     let relative_prefix_string;
     let relative_prefix = if let Some(ident) = relative {
         relative_prefix_string = format!("{}{}", ident.name, path::MAIN_SEPARATOR);
@@ -259,7 +181,7 @@ pub fn default_submod_path<'a>(
         ""
     };
 
-    let mod_name = id.name.to_string();
+    let mod_name = ident.name.to_string();
     let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
     let secondary_path_str =
         format!("{}{}{}mod.rs", relative_prefix, mod_name, path::MAIN_SEPARATOR);
@@ -268,44 +190,74 @@ pub fn default_submod_path<'a>(
     let default_exists = sess.source_map().file_exists(&default_path);
     let secondary_exists = sess.source_map().file_exists(&secondary_path);
 
-    let result = match (default_exists, secondary_exists) {
+    match (default_exists, secondary_exists) {
         (true, false) => Ok(ModulePathSuccess {
-            path: default_path,
-            ownership: DirectoryOwnership::Owned { relative: Some(id) },
+            file_path: default_path,
+            dir_ownership: DirOwnership::Owned { relative: Some(ident) },
         }),
         (false, true) => Ok(ModulePathSuccess {
-            path: secondary_path,
-            ownership: DirectoryOwnership::Owned { relative: None },
+            file_path: secondary_path,
+            dir_ownership: DirOwnership::Owned { relative: None },
         }),
-        (false, false) => {
-            let mut err = struct_span_err!(
-                sess.span_diagnostic,
-                span,
-                E0583,
-                "file not found for module `{}`",
-                mod_name,
-            );
-            err.help(&format!(
-                "to create the module `{}`, create file \"{}\"",
-                mod_name,
-                default_path.display(),
-            ));
-            Err(err)
-        }
+        (false, false) => Err(ModError::FileNotFound(ident, default_path)),
         (true, true) => {
-            let mut err = struct_span_err!(
-                sess.span_diagnostic,
-                span,
-                E0761,
-                "file for module `{}` found at both {} and {}",
-                mod_name,
-                default_path_str,
-                secondary_path_str,
-            );
-            err.help("delete or rename one of them to remove the ambiguity");
-            Err(err)
+            Err(ModError::MultipleCandidates(ident, default_path_str, secondary_path_str))
         }
-    };
+    }
+}
 
-    ModulePath { name: mod_name, path_exists: default_exists || secondary_exists, result }
+impl ModError<'_> {
+    fn report(self, sess: &Session, span: Span) {
+        let diag = &sess.parse_sess.span_diagnostic;
+        match self {
+            ModError::CircularInclusion(file_paths) => {
+                let mut msg = String::from("circular modules: ");
+                for file_path in &file_paths {
+                    msg.push_str(&file_path.display().to_string());
+                    msg.push_str(" -> ");
+                }
+                msg.push_str(&file_paths[0].display().to_string());
+                diag.struct_span_err(span, &msg)
+            }
+            ModError::ModInBlock(ident) => {
+                let msg = "cannot declare a non-inline module inside a block unless it has a path attribute";
+                let mut err = diag.struct_span_err(span, msg);
+                if let Some(ident) = ident {
+                    let note =
+                        format!("maybe `use` the module `{}` instead of redeclaring it", ident);
+                    err.span_note(span, &note);
+                }
+                err
+            }
+            ModError::FileNotFound(ident, default_path) => {
+                let mut err = struct_span_err!(
+                    diag,
+                    span,
+                    E0583,
+                    "file not found for module `{}`",
+                    ident,
+                );
+                err.help(&format!(
+                    "to create the module `{}`, create file \"{}\"",
+                    ident,
+                    default_path.display(),
+                ));
+                err
+            }
+            ModError::MultipleCandidates(ident, default_path_short, secondary_path_short) => {
+                let mut err = struct_span_err!(
+                    diag,
+                    span,
+                    E0761,
+                    "file for module `{}` found at both {} and {}",
+                    ident,
+                    default_path_short,
+                    secondary_path_short,
+                );
+                err.help("delete or rename one of them to remove the ambiguity");
+                err
+            }
+            ModError::ParserError(err) => err,
+        }.emit()
+    }
 }
diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index 8ee995a59d80d..95ae6a1ac9a26 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/compiler/rustc_feature/src/active.rs
@@ -644,6 +644,9 @@ declare_features! (
     /// Allows associated types in inherent impls.
     (active, inherent_associated_types, "1.52.0", Some(8995), None),
 
+    /// Allows `extern "C-unwind" fn` to enable unwinding across ABI boundaries.
+    (active, c_unwind, "1.52.0", Some(74990), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 5217066bbefde..94be7a03a932b 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -302,8 +302,10 @@ fn configure_and_expand_inner<'a>(
             ..rustc_expand::expand::ExpansionConfig::default(crate_name.to_string())
         };
 
-        let extern_mod_loaded = |k: &ast::Crate, ident: Ident| {
-            pre_expansion_lint(sess, lint_store, k, &*ident.name.as_str())
+        let extern_mod_loaded = |ident: Ident, attrs, items, span| {
+            let krate = ast::Crate { attrs, items, span, proc_macros: vec![] };
+            pre_expansion_lint(sess, lint_store, &krate, &ident.name.as_str());
+            (krate.attrs, krate.items)
         };
         let mut ecx = ExtCtxt::new(&sess, cfg, &mut resolver, Some(&extern_mod_loaded));
 
@@ -988,7 +990,7 @@ fn encode_and_write_metadata(
             .unwrap_or_else(|err| tcx.sess.fatal(&format!("couldn't create a temp dir: {}", err)));
         let metadata_tmpdir = MaybeTempDir::new(metadata_tmpdir, tcx.sess.opts.cg.save_temps);
         let metadata_filename = emit_metadata(tcx.sess, &metadata, &metadata_tmpdir);
-        if let Err(e) = fs::rename(&metadata_filename, &out_filename) {
+        if let Err(e) = util::non_durable_rename(&metadata_filename, &out_filename) {
             tcx.sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
         }
         if tcx.sess.opts.json_artifact_notifications {
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 798996263c700..0a30eda1ec406 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -694,6 +694,24 @@ pub fn build_output_filenames(
     }
 }
 
+#[cfg(not(target_os = "linux"))]
+pub fn non_durable_rename(src: &Path, dst: &Path) -> std::io::Result<()> {
+    std::fs::rename(src, dst)
+}
+
+/// This function attempts to bypass the auto_da_alloc heuristic implemented by some filesystems
+/// such as btrfs and ext4. When renaming over a file that already exists then they will "helpfully"
+/// write back the source file before committing the rename in case a developer forgot some of
+/// the fsyncs in the open/write/fsync(file)/rename/fsync(dir) dance for atomic file updates.
+///
+/// To avoid triggering this heuristic we delete the destination first, if it exists.
+/// The cost of an extra syscall is much lower than getting descheduled for the sync IO.
+#[cfg(target_os = "linux")]
+pub fn non_durable_rename(src: &Path, dst: &Path) -> std::io::Result<()> {
+    let _ = std::fs::remove_file(dst);
+    std::fs::rename(src, dst)
+}
+
 // Note: Also used by librustdoc, see PR #43348. Consider moving this struct elsewhere.
 //
 // FIXME: Currently the `everybody_loops` transformation is not applied to:
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 6d2ab0e5f5a80..814581a6cf171 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -2562,6 +2562,7 @@ fn fn_can_unwind(
     panic_strategy: PanicStrategy,
     codegen_fn_attr_flags: CodegenFnAttrFlags,
     call_conv: Conv,
+    abi: SpecAbi,
 ) -> bool {
     if panic_strategy != PanicStrategy::Unwind {
         // In panic=abort mode we assume nothing can unwind anywhere, so
@@ -2586,17 +2587,34 @@ fn fn_can_unwind(
             //
             //  2. A Rust item using a non-Rust ABI (like `extern "C" fn foo() { ... }`).
             //
-            // Foreign items (case 1) are assumed to not unwind; it is
-            // UB otherwise. (At least for now; see also
-            // rust-lang/rust#63909 and Rust RFC 2753.)
-            //
-            // Items defined in Rust with non-Rust ABIs (case 2) are also
-            // not supposed to unwind. Whether this should be enforced
-            // (versus stating it is UB) and *how* it would be enforced
-            // is currently under discussion; see rust-lang/rust#58794.
-            //
-            // In either case, we mark item as explicitly nounwind.
-            false
+            // In both of these cases, we should refer to the ABI to determine whether or not we
+            // should unwind. See Rust RFC 2945 for more information on this behavior, here:
+            // https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
+            use SpecAbi::*;
+            match abi {
+                C { unwind } | Stdcall { unwind } | System { unwind } | Thiscall { unwind } => {
+                    unwind
+                }
+                Cdecl
+                | Fastcall
+                | Vectorcall
+                | Aapcs
+                | Win64
+                | SysV64
+                | PtxKernel
+                | Msp430Interrupt
+                | X86Interrupt
+                | AmdGpuKernel
+                | EfiApi
+                | AvrInterrupt
+                | AvrNonBlockingInterrupt
+                | CCmseNonSecureCall
+                | RustIntrinsic
+                | PlatformIntrinsic
+                | Unadjusted => false,
+                // In the `if` above, we checked for functions with the Rust calling convention.
+                Rust | RustCall => unreachable!(),
+            }
         }
     }
 }
@@ -2654,14 +2672,14 @@ where
             RustIntrinsic | PlatformIntrinsic | Rust | RustCall => Conv::Rust,
 
             // It's the ABI's job to select this, not ours.
-            System => bug!("system abi should be selected elsewhere"),
+            System { .. } => bug!("system abi should be selected elsewhere"),
             EfiApi => bug!("eficall abi should be selected elsewhere"),
 
-            Stdcall => Conv::X86Stdcall,
+            Stdcall { .. } => Conv::X86Stdcall,
             Fastcall => Conv::X86Fastcall,
             Vectorcall => Conv::X86VectorCall,
-            Thiscall => Conv::X86ThisCall,
-            C => Conv::C,
+            Thiscall { .. } => Conv::X86ThisCall,
+            C { .. } => Conv::C,
             Unadjusted => Conv::C,
             Win64 => Conv::X86_64Win64,
             SysV64 => Conv::X86_64SysV,
@@ -2823,7 +2841,12 @@ where
             c_variadic: sig.c_variadic,
             fixed_count: inputs.len(),
             conv,
-            can_unwind: fn_can_unwind(cx.tcx().sess.panic_strategy(), codegen_fn_attr_flags, conv),
+            can_unwind: fn_can_unwind(
+                cx.tcx().sess.panic_strategy(),
+                codegen_fn_attr_flags,
+                conv,
+                sig.abi,
+            ),
         };
         fn_abi.adjust_for_abi(cx, sig.abi);
         debug!("FnAbi::new_internal = {:?}", fn_abi);
diff --git a/compiler/rustc_mir/src/interpret/terminator.rs b/compiler/rustc_mir/src/interpret/terminator.rs
index 0807949a2d91b..4aa1360d53539 100644
--- a/compiler/rustc_mir/src/interpret/terminator.rs
+++ b/compiler/rustc_mir/src/interpret/terminator.rs
@@ -248,9 +248,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             };
             if normalize_abi(caller_abi) != normalize_abi(callee_abi) {
                 throw_ub_format!(
-                    "calling a function with ABI {:?} using caller ABI {:?}",
-                    callee_abi,
-                    caller_abi
+                    "calling a function with ABI {} using caller ABI {}",
+                    callee_abi.name(),
+                    caller_abi.name()
                 )
             }
         }
diff --git a/compiler/rustc_mir_build/src/build/mod.rs b/compiler/rustc_mir_build/src/build/mod.rs
index b928458df8ee4..3ac9c631d031e 100644
--- a/compiler/rustc_mir_build/src/build/mod.rs
+++ b/compiler/rustc_mir_build/src/build/mod.rs
@@ -548,7 +548,7 @@ macro_rules! unpack {
     }};
 }
 
-fn should_abort_on_panic(tcx: TyCtxt<'_>, fn_def_id: LocalDefId, _abi: Abi) -> bool {
+fn should_abort_on_panic(tcx: TyCtxt<'_>, fn_def_id: LocalDefId, abi: Abi) -> bool {
     // Validate `#[unwind]` syntax regardless of platform-specific panic strategy.
     let attrs = &tcx.get_attrs(fn_def_id.to_def_id());
     let unwind_attr = attr::find_unwind_attr(&tcx.sess, attrs);
@@ -558,12 +558,42 @@ fn should_abort_on_panic(tcx: TyCtxt<'_>, fn_def_id: LocalDefId, _abi: Abi) -> b
         return false;
     }
 
-    // This is a special case: some functions have a C abi but are meant to
-    // unwind anyway. Don't stop them.
     match unwind_attr {
-        None => false, // FIXME(#58794); should be `!(abi == Abi::Rust || abi == Abi::RustCall)`
+        // If an `#[unwind]` attribute was found, we should adhere to it.
         Some(UnwindAttr::Allowed) => false,
         Some(UnwindAttr::Aborts) => true,
+        // If no attribute was found and the panic strategy is `unwind`, then we should examine
+        // the function's ABI string to determine whether it should abort upon panic.
+        None => {
+            use Abi::*;
+            match abi {
+                // In the case of ABI's that have an `-unwind` equivalent, check whether the ABI
+                // permits unwinding. If so, we should not abort. Otherwise, we should.
+                C { unwind } | Stdcall { unwind } | System { unwind } | Thiscall { unwind } => {
+                    !unwind
+                }
+                // Rust and `rust-call` functions are allowed to unwind, and should not abort.
+                Rust | RustCall => false,
+                // Other ABI's should abort.
+                Cdecl
+                | Fastcall
+                | Vectorcall
+                | Aapcs
+                | Win64
+                | SysV64
+                | PtxKernel
+                | Msp430Interrupt
+                | X86Interrupt
+                | AmdGpuKernel
+                | EfiApi
+                | AvrInterrupt
+                | AvrNonBlockingInterrupt
+                | CCmseNonSecureCall
+                | RustIntrinsic
+                | PlatformIntrinsic
+                | Unadjusted => true,
+            }
+        }
     }
 }
 
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index ed971951b0f76..6cc649c1180c5 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -576,7 +576,8 @@ impl CheckAttrVisitor<'tcx> {
                             sym::masked,
                             sym::no_default_passes, // deprecated
                             sym::no_inline,
-                            sym::passes, // deprecated
+                            sym::passes,  // deprecated
+                            sym::plugins, // removed, but rustdoc warns about it itself
                             sym::primitive,
                             sym::spotlight,
                             sym::test,
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 81b38347414e8..592773bfe1b44 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -13,7 +13,6 @@ use rustc_span::hygiene::ExpnId;
 use rustc_span::source_map::{FilePathMapping, SourceMap};
 use rustc_span::{MultiSpan, Span, Symbol};
 
-use std::path::PathBuf;
 use std::str;
 
 /// The set of keys (and, optionally, values) that define the compilation
@@ -122,8 +121,6 @@ pub struct ParseSess {
     pub missing_fragment_specifiers: Lock<FxHashMap<Span, NodeId>>,
     /// Places where raw identifiers were used. This is used for feature-gating raw identifiers.
     pub raw_identifier_spans: Lock<Vec<Span>>,
-    /// Used to determine and report recursive module inclusions.
-    pub included_mod_stack: Lock<Vec<PathBuf>>,
     source_map: Lrc<SourceMap>,
     pub buffered_lints: Lock<Vec<BufferedEarlyLint>>,
     /// Contains the spans of block expressions that could have been incomplete based on the
@@ -157,7 +154,6 @@ impl ParseSess {
             edition: ExpnId::root().expn_data().edition,
             missing_fragment_specifiers: Default::default(),
             raw_identifier_spans: Lock::new(Vec::new()),
-            included_mod_stack: Lock::new(vec![]),
             source_map,
             buffered_lints: Lock::new(vec![]),
             ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 9663760cba189..9d249279e01c7 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -330,6 +330,7 @@ symbols! {
         bridge,
         bswap,
         c_str,
+        c_unwind,
         c_variadic,
         call,
         call_mut,
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index bbf7ecc39cfd9..12c0a147990fa 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -440,7 +440,7 @@ impl Printer<'tcx> for SymbolMangler<'tcx> {
                     }
                     match sig.abi {
                         Abi::Rust => {}
-                        Abi::C => cx.push("KC"),
+                        Abi::C { unwind: false } => cx.push("KC"),
                         abi => {
                             cx.push("K");
                             let name = abi.name();
diff --git a/compiler/rustc_target/src/spec/abi.rs b/compiler/rustc_target/src/spec/abi.rs
index 65e8a4e8db2ad..17eb33b8f2eaa 100644
--- a/compiler/rustc_target/src/spec/abi.rs
+++ b/compiler/rustc_target/src/spec/abi.rs
@@ -8,24 +8,21 @@ mod tests;
 #[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Debug)]
 #[derive(HashStable_Generic, Encodable, Decodable)]
 pub enum Abi {
-    // N.B., this ordering MUST match the AbiDatas array below.
-    // (This is ensured by the test indices_are_correct().)
-
     // Multiplatform / generic ABIs
     //
     // These ABIs come first because every time we add a new ABI, we
     // have to re-bless all the hashing tests. These are used in many
     // places, so giving them stable values reduces test churn. The
     // specific values are meaningless.
-    Rust = 0,
-    C = 1,
+    Rust,
+    C { unwind: bool },
 
     // Single platform ABIs
     Cdecl,
-    Stdcall,
+    Stdcall { unwind: bool },
     Fastcall,
     Vectorcall,
-    Thiscall,
+    Thiscall { unwind: bool },
     Aapcs,
     Win64,
     SysV64,
@@ -39,7 +36,7 @@ pub enum Abi {
     CCmseNonSecureCall,
 
     // Multiplatform / generic ABIs
-    System,
+    System { unwind: bool },
     RustIntrinsic,
     RustCall,
     PlatformIntrinsic,
@@ -61,13 +58,16 @@ pub struct AbiData {
 const AbiDatas: &[AbiData] = &[
     // Cross-platform ABIs
     AbiData { abi: Abi::Rust, name: "Rust", generic: true },
-    AbiData { abi: Abi::C, name: "C", generic: true },
+    AbiData { abi: Abi::C { unwind: false }, name: "C", generic: true },
+    AbiData { abi: Abi::C { unwind: true }, name: "C-unwind", generic: true },
     // Platform-specific ABIs
     AbiData { abi: Abi::Cdecl, name: "cdecl", generic: false },
-    AbiData { abi: Abi::Stdcall, name: "stdcall", generic: false },
+    AbiData { abi: Abi::Stdcall { unwind: false }, name: "stdcall", generic: false },
+    AbiData { abi: Abi::Stdcall { unwind: true }, name: "stdcall-unwind", generic: false },
     AbiData { abi: Abi::Fastcall, name: "fastcall", generic: false },
     AbiData { abi: Abi::Vectorcall, name: "vectorcall", generic: false },
-    AbiData { abi: Abi::Thiscall, name: "thiscall", generic: false },
+    AbiData { abi: Abi::Thiscall { unwind: false }, name: "thiscall", generic: false },
+    AbiData { abi: Abi::Thiscall { unwind: true }, name: "thiscall-unwind", generic: false },
     AbiData { abi: Abi::Aapcs, name: "aapcs", generic: false },
     AbiData { abi: Abi::Win64, name: "win64", generic: false },
     AbiData { abi: Abi::SysV64, name: "sysv64", generic: false },
@@ -84,7 +84,8 @@ const AbiDatas: &[AbiData] = &[
     },
     AbiData { abi: Abi::CCmseNonSecureCall, name: "C-cmse-nonsecure-call", generic: false },
     // Cross-platform ABIs
-    AbiData { abi: Abi::System, name: "system", generic: true },
+    AbiData { abi: Abi::System { unwind: false }, name: "system", generic: true },
+    AbiData { abi: Abi::System { unwind: true }, name: "system-unwind", generic: true },
     AbiData { abi: Abi::RustIntrinsic, name: "rust-intrinsic", generic: true },
     AbiData { abi: Abi::RustCall, name: "rust-call", generic: true },
     AbiData { abi: Abi::PlatformIntrinsic, name: "platform-intrinsic", generic: true },
@@ -103,7 +104,52 @@ pub fn all_names() -> Vec<&'static str> {
 impl Abi {
     #[inline]
     pub fn index(self) -> usize {
-        self as usize
+        // N.B., this ordering MUST match the AbiDatas array above.
+        // (This is ensured by the test indices_are_correct().)
+        use Abi::*;
+        let i = match self {
+            // Cross-platform ABIs
+            Rust => 0,
+            C { unwind: false } => 1,
+            C { unwind: true } => 2,
+            // Platform-specific ABIs
+            Cdecl => 3,
+            Stdcall { unwind: false } => 4,
+            Stdcall { unwind: true } => 5,
+            Fastcall => 6,
+            Vectorcall => 7,
+            Thiscall { unwind: false } => 8,
+            Thiscall { unwind: true } => 9,
+            Aapcs => 10,
+            Win64 => 11,
+            SysV64 => 12,
+            PtxKernel => 13,
+            Msp430Interrupt => 14,
+            X86Interrupt => 15,
+            AmdGpuKernel => 16,
+            EfiApi => 17,
+            AvrInterrupt => 18,
+            AvrNonBlockingInterrupt => 19,
+            CCmseNonSecureCall => 20,
+            // Cross-platform ABIs
+            System { unwind: false } => 21,
+            System { unwind: true } => 22,
+            RustIntrinsic => 23,
+            RustCall => 24,
+            PlatformIntrinsic => 25,
+            Unadjusted => 26,
+        };
+        debug_assert!(
+            AbiDatas
+                .iter()
+                .enumerate()
+                .find(|(_, AbiData { abi, .. })| *abi == self)
+                .map(|(index, _)| index)
+                .expect("abi variant has associated data")
+                == i,
+            "Abi index did not match `AbiDatas` ordering"
+        );
+        i
     }
 
     #[inline]
@@ -122,6 +168,8 @@ impl Abi {
 
 impl fmt::Display for Abi {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "\"{}\"", self.name())
+        match self {
+            abi => write!(f, "\"{}\"", abi.name()),
+        }
     }
 }
diff --git a/compiler/rustc_target/src/spec/arm_base.rs b/compiler/rustc_target/src/spec/arm_base.rs
index b74d80dc6bb2b..01f573313c97f 100644
--- a/compiler/rustc_target/src/spec/arm_base.rs
+++ b/compiler/rustc_target/src/spec/arm_base.rs
@@ -2,5 +2,14 @@ use crate::spec::abi::Abi;
 
 // All the calling conventions trigger an assertion(Unsupported calling convention) in llvm on arm
 pub fn unsupported_abis() -> Vec<Abi> {
-    vec![Abi::Stdcall, Abi::Fastcall, Abi::Vectorcall, Abi::Thiscall, Abi::Win64, Abi::SysV64]
+    vec![
+        Abi::Stdcall { unwind: false },
+        Abi::Stdcall { unwind: true },
+        Abi::Fastcall,
+        Abi::Vectorcall,
+        Abi::Thiscall { unwind: false },
+        Abi::Thiscall { unwind: true },
+        Abi::Win64,
+        Abi::SysV64,
+    ]
 }
diff --git a/compiler/rustc_target/src/spec/mipsel_unknown_none.rs b/compiler/rustc_target/src/spec/mipsel_unknown_none.rs
index 0f9d3c3de1543..110c8dd80ea77 100644
--- a/compiler/rustc_target/src/spec/mipsel_unknown_none.rs
+++ b/compiler/rustc_target/src/spec/mipsel_unknown_none.rs
@@ -23,10 +23,12 @@ pub fn target() -> Target {
             panic_strategy: PanicStrategy::Abort,
             relocation_model: RelocModel::Static,
             unsupported_abis: vec![
-                Abi::Stdcall,
+                Abi::Stdcall { unwind: false },
+                Abi::Stdcall { unwind: true },
                 Abi::Fastcall,
                 Abi::Vectorcall,
-                Abi::Thiscall,
+                Abi::Thiscall { unwind: false },
+                Abi::Thiscall { unwind: true },
                 Abi::Win64,
                 Abi::SysV64,
             ],
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 039e9a8b2745f..85e7c74472f16 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -679,7 +679,7 @@ supported_targets! {
     ("thumbv7neon-linux-androideabi", thumbv7neon_linux_androideabi),
     ("aarch64-linux-android", aarch64_linux_android),
 
-    ("x86_64-linux-kernel", x86_64_linux_kernel),
+    ("x86_64-unknown-none-linuxkernel", x86_64_unknown_none_linuxkernel),
 
     ("aarch64-unknown-freebsd", aarch64_unknown_freebsd),
     ("armv6-unknown-freebsd", armv6_unknown_freebsd),
@@ -777,7 +777,8 @@ supported_targets! {
 
     ("aarch64-unknown-hermit", aarch64_unknown_hermit),
     ("x86_64-unknown-hermit", x86_64_unknown_hermit),
-    ("x86_64-unknown-hermit-kernel", x86_64_unknown_hermit_kernel),
+
+    ("x86_64-unknown-none-hermitkernel", x86_64_unknown_none_hermitkernel),
 
     ("riscv32i-unknown-none-elf", riscv32i_unknown_none_elf),
     ("riscv32imc-unknown-none-elf", riscv32imc_unknown_none_elf),
@@ -1282,24 +1283,31 @@ impl Target {
     /// Given a function ABI, turn it into the correct ABI for this target.
     pub fn adjust_abi(&self, abi: Abi) -> Abi {
         match abi {
-            Abi::System => {
+            Abi::System { unwind } => {
                 if self.is_like_windows && self.arch == "x86" {
-                    Abi::Stdcall
+                    Abi::Stdcall { unwind }
                 } else {
-                    Abi::C
+                    Abi::C { unwind }
                 }
             }
             // These ABI kinds are ignored on non-x86 Windows targets.
             // See https://docs.microsoft.com/en-us/cpp/cpp/argument-passing-and-naming-conventions
             // and the individual pages for __stdcall et al.
-            Abi::Stdcall | Abi::Fastcall | Abi::Vectorcall | Abi::Thiscall => {
-                if self.is_like_windows && self.arch != "x86" { Abi::C } else { abi }
+            Abi::Stdcall { unwind } | Abi::Thiscall { unwind } => {
+                if self.is_like_windows && self.arch != "x86" { Abi::C { unwind } } else { abi }
+            }
+            Abi::Fastcall | Abi::Vectorcall => {
+                if self.is_like_windows && self.arch != "x86" {
+                    Abi::C { unwind: false }
+                } else {
+                    abi
+                }
             }
             Abi::EfiApi => {
                 if self.arch == "x86_64" {
                     Abi::Win64
                 } else {
-                    Abi::C
+                    Abi::C { unwind: false }
                 }
             }
             abi => abi,
diff --git a/compiler/rustc_target/src/spec/nvptx64_nvidia_cuda.rs b/compiler/rustc_target/src/spec/nvptx64_nvidia_cuda.rs
index 3c9c7d578fbd4..15d8e4843f976 100644
--- a/compiler/rustc_target/src/spec/nvptx64_nvidia_cuda.rs
+++ b/compiler/rustc_target/src/spec/nvptx64_nvidia_cuda.rs
@@ -49,10 +49,12 @@ pub fn target() -> Target {
             // create the tests for this.
             unsupported_abis: vec![
                 Abi::Cdecl,
-                Abi::Stdcall,
+                Abi::Stdcall { unwind: false },
+                Abi::Stdcall { unwind: true },
                 Abi::Fastcall,
                 Abi::Vectorcall,
-                Abi::Thiscall,
+                Abi::Thiscall { unwind: false },
+                Abi::Thiscall { unwind: true },
                 Abi::Aapcs,
                 Abi::Win64,
                 Abi::SysV64,
diff --git a/compiler/rustc_target/src/spec/riscv_base.rs b/compiler/rustc_target/src/spec/riscv_base.rs
index 64cf890037e51..5bcbb2e621bd0 100644
--- a/compiler/rustc_target/src/spec/riscv_base.rs
+++ b/compiler/rustc_target/src/spec/riscv_base.rs
@@ -5,10 +5,12 @@ use crate::spec::abi::Abi;
 pub fn unsupported_abis() -> Vec<Abi> {
     vec![
         Abi::Cdecl,
-        Abi::Stdcall,
+        Abi::Stdcall { unwind: false },
+        Abi::Stdcall { unwind: true },
         Abi::Fastcall,
         Abi::Vectorcall,
-        Abi::Thiscall,
+        Abi::Thiscall { unwind: false },
+        Abi::Thiscall { unwind: true },
         Abi::Aapcs,
         Abi::Win64,
         Abi::SysV64,
diff --git a/compiler/rustc_target/src/spec/x86_64_unknown_hermit_kernel.rs b/compiler/rustc_target/src/spec/x86_64_unknown_none_hermitkernel.rs
similarity index 91%
rename from compiler/rustc_target/src/spec/x86_64_unknown_hermit_kernel.rs
rename to compiler/rustc_target/src/spec/x86_64_unknown_none_hermitkernel.rs
index 9fcfe4e6c14bf..a357def190b83 100644
--- a/compiler/rustc_target/src/spec/x86_64_unknown_hermit_kernel.rs
+++ b/compiler/rustc_target/src/spec/x86_64_unknown_none_hermitkernel.rs
@@ -10,7 +10,7 @@ pub fn target() -> Target {
     base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
-        llvm_target: "x86_64-unknown-hermit".to_string(),
+        llvm_target: "x86_64-unknown-none-elf".to_string(),
         pointer_width: 64,
         data_layout: "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
             .to_string(),
diff --git a/compiler/rustc_target/src/spec/x86_64_linux_kernel.rs b/compiler/rustc_target/src/spec/x86_64_unknown_none_linuxkernel.rs
similarity index 76%
rename from compiler/rustc_target/src/spec/x86_64_linux_kernel.rs
rename to compiler/rustc_target/src/spec/x86_64_unknown_none_linuxkernel.rs
index 43e683ddbcc84..68d80205e1472 100644
--- a/compiler/rustc_target/src/spec/x86_64_linux_kernel.rs
+++ b/compiler/rustc_target/src/spec/x86_64_unknown_none_linuxkernel.rs
@@ -14,8 +14,11 @@ pub fn target() -> Target {
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m64".to_string());
 
     Target {
-        // FIXME: Some dispute, the linux-on-clang folks think this should use "Linux"
-        llvm_target: "x86_64-elf".to_string(),
+        // FIXME: Some dispute, the linux-on-clang folks think this should use
+        // "Linux". We disagree because running *on* Linux is nothing like
+        // running *as" linux, and historically the "os" component as has always
+        // been used to mean the "on" part.
+        llvm_target: "x86_64-unknown-none-elf".to_string(),
         pointer_width: 64,
         data_layout: "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
             .to_string(),
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index 3881d55ef9169..a175da3270638 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -2666,7 +2666,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
         } else if tcx.sess.check_name(attr, sym::used) {
             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
         } else if tcx.sess.check_name(attr, sym::cmse_nonsecure_entry) {
-            if tcx.fn_sig(id).abi() != abi::Abi::C {
+            if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
                 struct_span_err!(
                     tcx.sess,
                     attr.span,
diff --git a/compiler/rustc_typeck/src/collect/type_of.rs b/compiler/rustc_typeck/src/collect/type_of.rs
index e6f771cfd5372..3f2f244e44fd2 100644
--- a/compiler/rustc_typeck/src/collect/type_of.rs
+++ b/compiler/rustc_typeck/src/collect/type_of.rs
@@ -722,11 +722,12 @@ fn infer_placeholder_type(
                 format!("{}: {}", item_ident, ty),
                 Applicability::MachineApplicable,
             )
-            .emit();
+            .emit_unless(ty.references_error());
         }
         None => {
             let mut diag = bad_placeholder_type(tcx, vec![span]);
-            if !matches!(ty.kind(), ty::Error(_)) {
+
+            if !ty.references_error() {
                 diag.span_suggestion(
                     span,
                     "replace `_` with the correct type",
@@ -734,6 +735,7 @@ fn infer_placeholder_type(
                     Applicability::MaybeIncorrect,
                 );
             }
+
             diag.emit();
         }
     }
diff --git a/compiler/rustc_typeck/src/lib.rs b/compiler/rustc_typeck/src/lib.rs
index 6ddc26efeae35..fb864c5b4a7d7 100644
--- a/compiler/rustc_typeck/src/lib.rs
+++ b/compiler/rustc_typeck/src/lib.rs
@@ -118,14 +118,19 @@ use astconv::AstConv;
 use bounds::Bounds;
 
 fn require_c_abi_if_c_variadic(tcx: TyCtxt<'_>, decl: &hir::FnDecl<'_>, abi: Abi, span: Span) {
-    if decl.c_variadic && !(abi == Abi::C || abi == Abi::Cdecl) {
-        let mut err = struct_span_err!(
-            tcx.sess,
-            span,
-            E0045,
-            "C-variadic function must have C or cdecl calling convention"
-        );
-        err.span_label(span, "C-variadics require C or cdecl calling convention").emit();
+    match (decl.c_variadic, abi) {
+        // The function has the correct calling convention, or isn't a "C-variadic" function.
+        (false, _) | (true, Abi::C { .. }) | (true, Abi::Cdecl) => {}
+        // The function is a "C-variadic" function with an incorrect calling convention.
+        (true, _) => {
+            let mut err = struct_span_err!(
+                tcx.sess,
+                span,
+                E0045,
+                "C-variadic function must have C or cdecl calling convention"
+            );
+            err.span_label(span, "C-variadics require C or cdecl calling convention").emit();
+        }
     }
 }
 
diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index afea8aa8ff262..634ed87b0910e 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -846,6 +846,12 @@ extern "rust-intrinsic" {
     /// destination value, then forgets the original. It's equivalent to C's
     /// `memcpy` under the hood, just like `transmute_copy`.
     ///
+    /// Because `transmute` is a by-value operation, alignment of the *transmuted values
+    /// themselves* is not a concern. As with any other function, the compiler already ensures
+    /// both `T` and `U` are properly aligned. However, when transmuting values that *point
+    /// elsewhere* (such as pointers, references, boxes…), the caller has to ensure proper
+    /// alignment of the pointed-to values.
+    ///
     /// `transmute` is **incredibly** unsafe. There are a vast number of ways to
     /// cause [undefined behavior][ub] with this function. `transmute` should be
     /// the absolute last resort.
@@ -965,7 +971,13 @@ extern "rust-intrinsic" {
     /// assert_eq!(b"Rust", &[82, 117, 115, 116]);
     /// ```
     ///
-    /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`:
+    /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`.
+    ///
+    /// To transmute the inner type of the contents of a container, you must make sure to not
+    /// violate any of the container's invariants. For `Vec`, this means that both the size
+    /// *and alignment* of the inner types have to match. Other containers might rely on the
+    /// size of the type, alignment, or even the `TypeId`, in which case transmuting wouldn't
+    /// be possible at all without violating the container invariants.
     ///
     /// ```
     /// let store = [0, 1, 2, 3];
@@ -991,14 +1003,11 @@ extern "rust-intrinsic" {
     ///
     /// let v_clone = v_orig.clone();
     ///
-    /// // The no-copy, unsafe way, still using transmute, but not relying on the data layout.
-    /// // Like the first approach, this reuses the `Vec` internals.
-    /// // Therefore, the new inner type must have the
-    /// // exact same size, *and the same alignment*, as the old type.
-    /// // The same caveats exist for this method as transmute, for
-    /// // the original inner type (`&i32`) to the converted inner type
-    /// // (`Option<&i32>`), so read the nomicon pages linked above and also
-    /// // consult the [`from_raw_parts`] documentation.
+    /// // This is the proper no-copy, unsafe way of "transmuting" a `Vec`, without relying on the
+    /// // data layout. Instead of literally calling `transmute`, we perform a pointer cast, but
+    /// // in terms of converting the original inner type (`&i32`) to the new one (`Option<&i32>`),
+    /// // this has all the same caveats. Besides the information provided above, also consult the
+    /// // [`from_raw_parts`] documentation.
     /// let v_from_raw = unsafe {
     // FIXME Update this when vec_into_raw_parts is stabilized
     ///     // Ensure the original vector is not dropped.
diff --git a/library/core/src/iter/adapters/zip.rs b/library/core/src/iter/adapters/zip.rs
index 817fc2a51e981..ea7a809c6badb 100644
--- a/library/core/src/iter/adapters/zip.rs
+++ b/library/core/src/iter/adapters/zip.rs
@@ -13,9 +13,10 @@ use crate::iter::{InPlaceIterable, SourceIter, TrustedLen};
 pub struct Zip<A, B> {
     a: A,
     b: B,
-    // index and len are only used by the specialized version of zip
+    // index, len and a_len are only used by the specialized version of zip
     index: usize,
     len: usize,
+    a_len: usize,
 }
 impl<A: Iterator, B: Iterator> Zip<A, B> {
     pub(in crate::iter) fn new(a: A, b: B) -> Zip<A, B> {
@@ -110,6 +111,7 @@ where
             b,
             index: 0, // unused
             len: 0,   // unused
+            a_len: 0, // unused
         }
     }
 
@@ -184,8 +186,9 @@ where
     B: TrustedRandomAccess + Iterator,
 {
     fn new(a: A, b: B) -> Self {
-        let len = cmp::min(a.size(), b.size());
-        Zip { a, b, index: 0, len }
+        let a_len = a.size();
+        let len = cmp::min(a_len, b.size());
+        Zip { a, b, index: 0, len, a_len }
     }
 
     #[inline]
@@ -197,7 +200,7 @@ where
             unsafe {
                 Some((self.a.__iterator_get_unchecked(i), self.b.__iterator_get_unchecked(i)))
             }
-        } else if A::MAY_HAVE_SIDE_EFFECT && self.index < self.a.size() {
+        } else if A::MAY_HAVE_SIDE_EFFECT && self.index < self.a_len {
             let i = self.index;
             self.index += 1;
             self.len += 1;
@@ -262,6 +265,7 @@ where
                     for _ in 0..sz_a - self.len {
                         self.a.next_back();
                     }
+                    self.a_len = self.len;
                 }
                 let sz_b = self.b.size();
                 if B::MAY_HAVE_SIDE_EFFECT && sz_b > self.len {
@@ -273,6 +277,7 @@ where
         }
         if self.index < self.len {
             self.len -= 1;
+            self.a_len -= 1;
             let i = self.len;
             // SAFETY: `i` is smaller than the previous value of `self.len`,
             // which is also smaller than or equal to `self.a.len()` and `self.b.len()`
diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index bcd2b207c4f6f..e3c812a047c8c 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -150,7 +150,7 @@
 use crate::iter::{FromIterator, FusedIterator, TrustedLen};
 use crate::pin::Pin;
 use crate::{
-    convert, fmt, hint, mem,
+    fmt, hint, mem,
     ops::{self, Deref, DerefMut},
 };
 
@@ -1275,7 +1275,8 @@ impl<T, E> Option<Result<T, E>> {
     /// ```
     #[inline]
     #[stable(feature = "transpose_result", since = "1.33.0")]
-    pub fn transpose(self) -> Result<Option<T>, E> {
+    #[rustc_const_unstable(feature = "const_option", issue = "67441")]
+    pub const fn transpose(self) -> Result<Option<T>, E> {
         match self {
             Some(Ok(x)) => Ok(Some(x)),
             Some(Err(e)) => Err(e),
@@ -1750,7 +1751,11 @@ impl<T> Option<Option<T>> {
     /// ```
     #[inline]
     #[stable(feature = "option_flattening", since = "1.40.0")]
-    pub fn flatten(self) -> Option<T> {
-        self.and_then(convert::identity)
+    #[rustc_const_unstable(feature = "const_option", issue = "67441")]
+    pub const fn flatten(self) -> Option<T> {
+        match self {
+            Some(inner) => inner,
+            None => None,
+        }
     }
 }
diff --git a/library/core/src/result.rs b/library/core/src/result.rs
index 7c48b8e41c621..2ce8a703c123e 100644
--- a/library/core/src/result.rs
+++ b/library/core/src/result.rs
@@ -1233,7 +1233,8 @@ impl<T, E> Result<Option<T>, E> {
     /// ```
     #[inline]
     #[stable(feature = "transpose_result", since = "1.33.0")]
-    pub fn transpose(self) -> Option<Result<T, E>> {
+    #[rustc_const_unstable(feature = "const_result", issue = "82814")]
+    pub const fn transpose(self) -> Option<Result<T, E>> {
         match self {
             Ok(Some(x)) => Some(Ok(x)),
             Ok(None) => None,
diff --git a/library/core/tests/iter/adapters/zip.rs b/library/core/tests/iter/adapters/zip.rs
index a597710392952..000c15f72c886 100644
--- a/library/core/tests/iter/adapters/zip.rs
+++ b/library/core/tests/iter/adapters/zip.rs
@@ -265,3 +265,26 @@ fn test_issue_82282() {
         panic!();
     }
 }
+
+#[test]
+fn test_issue_82291() {
+    use std::cell::Cell;
+
+    let mut v1 = [()];
+    let v2 = [()];
+
+    let called = Cell::new(0);
+
+    let mut zip = v1
+        .iter_mut()
+        .map(|r| {
+            called.set(called.get() + 1);
+            r
+        })
+        .zip(&v2);
+
+    zip.next_back();
+    assert_eq!(called.get(), 1);
+    zip.next();
+    assert_eq!(called.get(), 1);
+}
diff --git a/library/unwind/src/lib.rs b/library/unwind/src/lib.rs
index d145c6767ec26..be5e56c71e36f 100644
--- a/library/unwind/src/lib.rs
+++ b/library/unwind/src/lib.rs
@@ -15,7 +15,7 @@ cfg_if::cfg_if! {
         target_os = "none",
     ))] {
         // These "unix" family members do not have unwinder.
-        // Note this also matches x86_64-linux-kernel.
+        // Note this also matches x86_64-unknown-none-linuxkernel.
     } else if #[cfg(any(
         unix,
         windows,
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index d3b88c019f019..611117788da88 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -217,13 +217,13 @@ target | std | host | notes
 `thumbv4t-none-eabi` | * |  | ARMv4T T32
 `x86_64-apple-ios-macabi` | ✓ |  | Apple Catalyst on x86_64
 `x86_64-apple-tvos` | * | | x86 64-bit tvOS
-`x86_64-linux-kernel` | * |  | Linux kernel modules
+`x86_64-unknown-none-linuxkernel` | * |  | Linux kernel modules
 `x86_64-sun-solaris` | ? |  | Deprecated target for 64-bit Solaris 10/11, illumos
 `x86_64-pc-windows-msvc` | ✓ |  | 64-bit Windows XP support
 `x86_64-unknown-dragonfly` | ✓ | ✓ | 64-bit DragonFlyBSD
 `x86_64-unknown-haiku` | ✓ | ✓ | 64-bit Haiku
 `x86_64-unknown-hermit` | ? |  |
-`x86_64-unknown-hermit-kernel` | ? |  | HermitCore kernel
+`x86_64-unknown-none-hermitkernel` | ? |  | HermitCore kernel
 `x86_64-unknown-l4re-uclibc` | ? |  |
 `x86_64-unknown-openbsd` | ✓ | ✓ | 64-bit OpenBSD
 `x86_64-unknown-uefi` | ? |  |
diff --git a/src/doc/unstable-book/src/language-features/c-unwind.md b/src/doc/unstable-book/src/language-features/c-unwind.md
new file mode 100644
index 0000000000000..2801d9b5e7778
--- /dev/null
+++ b/src/doc/unstable-book/src/language-features/c-unwind.md
@@ -0,0 +1,15 @@
+# `c_unwind`
+
+The tracking issue for this feature is: [#74990]
+
+[#74990]: https://github.com/rust-lang/rust/issues/74990
+
+------------------------
+
+Introduces four new ABI strings: "C-unwind", "stdcall-unwind",
+"thiscall-unwind", and "system-unwind". These enable unwinding from other
+languages (such as C++) into Rust frames and from Rust into other languages.
+
+See [RFC 2945] for more information.
+
+[RFC 2945]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index de6942968ea0d..43cddc06320b8 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -658,9 +658,8 @@ fn check_deprecated_options(matches: &getopts::Matches, diag: &rustc_errors::Han
             {
                 continue;
             }
-            let mut err =
-                diag.struct_warn(&format!("the '{}' flag is considered deprecated", flag));
-            err.warn(
+            let mut err = diag.struct_warn(&format!("the `{}` flag is deprecated", flag));
+            err.note(
                 "see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
                  for more information",
             );
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 9cb0649b314f5..e9c32396e8459 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -22,7 +22,7 @@ use rustc_session::DiagnosticOutput;
 use rustc_session::Session;
 use rustc_span::source_map;
 use rustc_span::symbol::sym;
-use rustc_span::DUMMY_SP;
+use rustc_span::{Span, DUMMY_SP};
 
 use std::cell::RefCell;
 use std::collections::hash_map::Entry;
@@ -76,7 +76,7 @@ crate struct DocContext<'tcx> {
     ///
     /// See `collect_intra_doc_links::traits_implemented_by` for more details.
     /// `map<module, set<trait>>`
-    crate module_trait_cache: RefCell<FxHashMap<DefId, FxHashSet<DefId>>>,
+    crate module_trait_cache: FxHashMap<DefId, FxHashSet<DefId>>,
     /// This same cache is used throughout rustdoc, including in [`crate::html::render`].
     crate cache: Cache,
     /// Used by [`clean::inline`] to tell if an item has already been inlined.
@@ -169,13 +169,13 @@ impl<'tcx> DocContext<'tcx> {
 
     /// Like `hir().local_def_id_to_hir_id()`, but skips calling it on fake DefIds.
     /// (This avoids a slice-index-out-of-bounds panic.)
-    crate fn as_local_hir_id(&self, def_id: DefId) -> Option<HirId> {
+    crate fn as_local_hir_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<HirId> {
         if MAX_DEF_IDX.with(|m| {
             m.borrow().get(&def_id.krate).map(|&idx| idx <= def_id.index).unwrap_or(false)
         }) {
             None
         } else {
-            def_id.as_local().map(|def_id| self.tcx.hir().local_def_id_to_hir_id(def_id))
+            def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
         }
     }
 }
@@ -389,7 +389,7 @@ crate fn run_global_ctxt(
     tcx: TyCtxt<'_>,
     resolver: Rc<RefCell<interface::BoxedResolver>>,
     mut default_passes: passes::DefaultPassOption,
-    mut manual_passes: Vec<String>,
+    manual_passes: Vec<String>,
     render_options: RenderOptions,
     output_format: OutputFormat,
 ) -> (clean::Crate, RenderOptions, Cache) {
@@ -450,7 +450,7 @@ crate fn run_global_ctxt(
             .cloned()
             .filter(|trait_def_id| tcx.trait_is_auto(*trait_def_id))
             .collect(),
-        module_trait_cache: RefCell::new(FxHashMap::default()),
+        module_trait_cache: FxHashMap::default(),
         cache: Cache::new(access_levels, render_options.document_private),
         inlined: FxHashSet::default(),
         output_format,
@@ -479,7 +479,7 @@ crate fn run_global_ctxt(
                 https://doc.rust-lang.org/nightly/rustdoc/how-to-write-documentation.html";
             tcx.struct_lint_node(
                 crate::lint::MISSING_CRATE_LEVEL_DOCS,
-                ctxt.as_local_hir_id(m.def_id).unwrap(),
+                DocContext::as_local_hir_id(tcx, m.def_id).unwrap(),
                 |lint| {
                     let mut diag =
                         lint.build("no documentation found for this crate's top-level module");
@@ -490,21 +490,44 @@ crate fn run_global_ctxt(
         }
     }
 
-    fn report_deprecated_attr(name: &str, diag: &rustc_errors::Handler) {
-        let mut msg = diag
-            .struct_warn(&format!("the `#![doc({})]` attribute is considered deprecated", name));
-        msg.warn(
+    fn report_deprecated_attr(name: &str, diag: &rustc_errors::Handler, sp: Span) {
+        let mut msg =
+            diag.struct_span_warn(sp, &format!("the `#![doc({})]` attribute is deprecated", name));
+        msg.note(
             "see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
              for more information",
         );
 
         if name == "no_default_passes" {
             msg.help("you may want to use `#![doc(document_private_items)]`");
+        } else if name.starts_with("plugins") {
+            msg.warn("`#![doc(plugins = \"...\")]` no longer functions; see CVE-2018-1000622 <https://nvd.nist.gov/vuln/detail/CVE-2018-1000622>");
         }
 
         msg.emit();
     }
 
+    let parse_pass = |name: &str, sp: Option<Span>| {
+        if let Some(pass) = passes::find_pass(name) {
+            Some(ConditionalPass::always(pass))
+        } else {
+            let msg = &format!("ignoring unknown pass `{}`", name);
+            let mut warning = if let Some(sp) = sp {
+                tcx.sess.struct_span_warn(sp, msg)
+            } else {
+                tcx.sess.struct_warn(msg)
+            };
+            if name == "collapse-docs" {
+                warning.note("the `collapse-docs` pass was removed in #80261 <https://github.com/rust-lang/rust/pull/80261>");
+            }
+            warning.emit();
+            None
+        }
+    };
+
+    let mut manual_passes: Vec<_> =
+        manual_passes.into_iter().flat_map(|name| parse_pass(&name, None)).collect();
+
     // Process all of the crate attributes, extracting plugin metadata along
     // with the passes which we are supposed to run.
     for attr in krate.module.as_ref().unwrap().attrs.lists(sym::doc) {
@@ -513,29 +536,25 @@ crate fn run_global_ctxt(
         let name = attr.name_or_empty();
         if attr.is_word() {
             if name == sym::no_default_passes {
-                report_deprecated_attr("no_default_passes", diag);
+                report_deprecated_attr("no_default_passes", diag, attr.span());
                 if default_passes == passes::DefaultPassOption::Default {
                     default_passes = passes::DefaultPassOption::None;
                 }
             }
         } else if let Some(value) = attr.value_str() {
-            let sink = match name {
+            match name {
                 sym::passes => {
-                    report_deprecated_attr("passes = \"...\"", diag);
-                    &mut manual_passes
+                    report_deprecated_attr("passes = \"...\"", diag, attr.span());
                 }
                 sym::plugins => {
-                    report_deprecated_attr("plugins = \"...\"", diag);
-                    eprintln!(
-                        "WARNING: `#![doc(plugins = \"...\")]` \
-                         no longer functions; see CVE-2018-1000622"
-                    );
+                    report_deprecated_attr("plugins = \"...\"", diag, attr.span());
                     continue;
                 }
                 _ => continue,
             };
             for name in value.as_str().split_whitespace() {
-                sink.push(name.to_string());
+                let span = attr.name_value_literal_span().unwrap_or(attr.span());
+                manual_passes.extend(parse_pass(name, Some(span)));
             }
         }
 
@@ -544,17 +563,7 @@ crate fn run_global_ctxt(
         }
     }
 
-    let passes = passes::defaults(default_passes).iter().copied().chain(
-        manual_passes.into_iter().flat_map(|name| {
-            if let Some(pass) = passes::find_pass(&name) {
-                Some(ConditionalPass::always(pass))
-            } else {
-                error!("unknown pass {}, skipping", name);
-                None
-            }
-        }),
-    );
-
+    let passes = passes::defaults(default_passes).iter().copied().chain(manual_passes);
     info!("Executing passes");
 
     for p in passes {
diff --git a/src/librustdoc/passes/check_code_block_syntax.rs b/src/librustdoc/passes/check_code_block_syntax.rs
index c85490864ec70..98886139f3088 100644
--- a/src/librustdoc/passes/check_code_block_syntax.rs
+++ b/src/librustdoc/passes/check_code_block_syntax.rs
@@ -48,9 +48,12 @@ impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
         let buffer = buffer.borrow();
 
         if buffer.has_errors || is_empty {
-            let mut diag = if let Some(sp) =
-                super::source_span_for_markdown_range(self.cx, &dox, &code_block.range, &item.attrs)
-            {
+            let mut diag = if let Some(sp) = super::source_span_for_markdown_range(
+                self.cx.tcx,
+                &dox,
+                &code_block.range,
+                &item.attrs,
+            ) {
                 let (warning_message, suggest_using_text) = if buffer.has_errors {
                     ("could not parse code block as Rust code", true)
                 } else {
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 38efecb393b79..ec5994b762b8a 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -484,13 +484,13 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
     /// Resolves a string as a path within a particular namespace. Returns an
     /// optional URL fragment in the case of variants and methods.
     fn resolve<'path>(
-        &self,
+        &mut self,
         path_str: &'path str,
         ns: Namespace,
         module_id: DefId,
         extra_fragment: &Option<String>,
     ) -> Result<(Res, Option<String>), ErrorKind<'path>> {
-        let cx = &self.cx;
+        let tcx = self.cx.tcx;
 
         if let Some(res) = self.resolve_path(path_str, ns, module_id) {
             match res {
@@ -498,7 +498,9 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                 // item a separate function.
                 Res::Def(DefKind::AssocFn | DefKind::AssocConst, _) => assert_eq!(ns, ValueNS),
                 Res::Def(DefKind::AssocTy, _) => assert_eq!(ns, TypeNS),
-                Res::Def(DefKind::Variant, _) => return handle_variant(cx, res, extra_fragment),
+                Res::Def(DefKind::Variant, _) => {
+                    return handle_variant(self.cx, res, extra_fragment);
+                }
                 // Not a trait item; just return what we found.
                 Res::Primitive(ty) => {
                     if extra_fragment.is_some() {
@@ -565,13 +567,12 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
             ) => {
                 debug!("looking for associated item named {} for item {:?}", item_name, did);
                 // Checks if item_name belongs to `impl SomeItem`
-                let assoc_item = cx
-                    .tcx
+                let assoc_item = tcx
                     .inherent_impls(did)
                     .iter()
                     .flat_map(|&imp| {
-                        cx.tcx.associated_items(imp).find_by_name_and_namespace(
-                            cx.tcx,
+                        tcx.associated_items(imp).find_by_name_and_namespace(
+                            tcx,
                             Ident::with_dummy_span(item_name),
                             ns,
                             imp,
@@ -587,7 +588,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                     // something like [`ambi_fn`](<SomeStruct as SomeTrait>::ambi_fn)
                     .or_else(|| {
                         let kind =
-                            resolve_associated_trait_item(did, module_id, item_name, ns, &self.cx);
+                            resolve_associated_trait_item(did, module_id, item_name, ns, self.cx);
                         debug!("got associated item kind {:?}", kind);
                         kind
                     });
@@ -611,7 +612,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                     debug!("looking for variants or fields named {} for {:?}", item_name, did);
                     // FIXME(jynelson): why is this different from
                     // `variant_field`?
-                    match cx.tcx.type_of(did).kind() {
+                    match tcx.type_of(did).kind() {
                         ty::Adt(def, _) => {
                             let field = if def.is_enum() {
                                 def.all_fields().find(|item| item.ident.name == item_name)
@@ -652,10 +653,9 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                     None
                 }
             }
-            Res::Def(DefKind::Trait, did) => cx
-                .tcx
+            Res::Def(DefKind::Trait, did) => tcx
                 .associated_items(did)
-                .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, did)
+                .find_by_name_and_namespace(tcx, Ident::with_dummy_span(item_name), ns, did)
                 .map(|item| {
                     let kind = match item.kind {
                         ty::AssocKind::Const => "associatedconstant",
@@ -699,7 +699,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
     /// This returns the `Res` even if it was erroneous for some reason
     /// (such as having invalid URL fragments or being in the wrong namespace).
     fn check_full_res(
-        &self,
+        &mut self,
         ns: Namespace,
         path_str: &str,
         module_id: DefId,
@@ -733,7 +733,7 @@ fn resolve_associated_trait_item(
     module: DefId,
     item_name: Symbol,
     ns: Namespace,
-    cx: &DocContext<'_>,
+    cx: &mut DocContext<'_>,
 ) -> Option<(ty::AssocKind, DefId)> {
     // FIXME: this should also consider blanket impls (`impl<T> X for T`). Unfortunately
     // `get_auto_trait_and_blanket_impls` is broken because the caching behavior is wrong. In the
@@ -758,10 +758,10 @@ fn resolve_associated_trait_item(
 ///
 /// NOTE: this cannot be a query because more traits could be available when more crates are compiled!
 /// So it is not stable to serialize cross-crate.
-fn traits_implemented_by(cx: &DocContext<'_>, type_: DefId, module: DefId) -> FxHashSet<DefId> {
-    let mut cache = cx.module_trait_cache.borrow_mut();
-    let in_scope_traits = cache.entry(module).or_insert_with(|| {
-        cx.enter_resolver(|resolver| {
+fn traits_implemented_by(cx: &mut DocContext<'_>, type_: DefId, module: DefId) -> FxHashSet<DefId> {
+    let mut resolver = cx.resolver.borrow_mut();
+    let in_scope_traits = cx.module_trait_cache.entry(module).or_insert_with(|| {
+        resolver.access(|resolver| {
             let parent_scope = &ParentScope::module(resolver.get_module(module), resolver);
             resolver
                 .traits_in_scope(None, parent_scope, SyntaxContext::root(), None)
@@ -771,13 +771,14 @@ fn traits_implemented_by(cx: &DocContext<'_>, type_: DefId, module: DefId) -> Fx
         })
     });
 
-    let ty = cx.tcx.type_of(type_);
+    let tcx = cx.tcx;
+    let ty = tcx.type_of(type_);
     let iter = in_scope_traits.iter().flat_map(|&trait_| {
         trace!("considering explicit impl for trait {:?}", trait_);
 
         // Look at each trait implementation to see if it's an impl for `did`
-        cx.tcx.find_map_relevant_impl(trait_, ty, |impl_| {
-            let trait_ref = cx.tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
+        tcx.find_map_relevant_impl(trait_, ty, |impl_| {
+            let trait_ref = tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
             // Check if these are the same type.
             let impl_type = trait_ref.self_ty();
             trace!(
@@ -1146,7 +1147,7 @@ impl LinkCollector<'_, '_> {
                 suggest_disambiguator(resolved, diag, path_str, dox, sp, &ori_link.range);
             };
             report_diagnostic(
-                self.cx,
+                self.cx.tcx,
                 BROKEN_INTRA_DOC_LINKS,
                 &msg,
                 &item,
@@ -1220,7 +1221,7 @@ impl LinkCollector<'_, '_> {
                         && !self.cx.tcx.features().intra_doc_pointers
                     {
                         let span = super::source_span_for_markdown_range(
-                            self.cx,
+                            self.cx.tcx,
                             dox,
                             &ori_link.range,
                             &item.attrs,
@@ -1308,7 +1309,7 @@ impl LinkCollector<'_, '_> {
     /// After parsing the disambiguator, resolve the main part of the link.
     // FIXME(jynelson): wow this is just so much
     fn resolve_with_disambiguator(
-        &self,
+        &mut self,
         key: &ResolutionInfo,
         diag: DiagnosticInfo<'_>,
     ) -> Option<(Res, Option<String>)> {
@@ -1674,7 +1675,7 @@ impl Suggestion {
 /// parameter of the callback will contain it, and the primary span of the diagnostic will be set
 /// to it.
 fn report_diagnostic(
-    cx: &DocContext<'_>,
+    tcx: TyCtxt<'_>,
     lint: &'static Lint,
     msg: &str,
     item: &Item,
@@ -1682,7 +1683,7 @@ fn report_diagnostic(
     link_range: &Range<usize>,
     decorate: impl FnOnce(&mut DiagnosticBuilder<'_>, Option<rustc_span::Span>),
 ) {
-    let hir_id = match cx.as_local_hir_id(item.def_id) {
+    let hir_id = match DocContext::as_local_hir_id(tcx, item.def_id) {
         Some(hir_id) => hir_id,
         None => {
             // If non-local, no need to check anything.
@@ -1694,10 +1695,10 @@ fn report_diagnostic(
     let attrs = &item.attrs;
     let sp = span_of_attrs(attrs).unwrap_or(item.source.span());
 
-    cx.tcx.struct_span_lint_hir(lint, hir_id, sp, |lint| {
+    tcx.struct_span_lint_hir(lint, hir_id, sp, |lint| {
         let mut diag = lint.build(msg);
 
-        let span = super::source_span_for_markdown_range(cx, dox, link_range, attrs);
+        let span = super::source_span_for_markdown_range(tcx, dox, link_range, attrs);
 
         if let Some(sp) = span {
             diag.set_span(sp);
@@ -1732,7 +1733,7 @@ fn report_diagnostic(
 /// handled earlier. For example, if passed `Item::Crate(std)` and `path_str`
 /// `std::io::Error::x`, this will resolve `std::io::Error`.
 fn resolution_failure(
-    collector: &LinkCollector<'_, '_>,
+    collector: &mut LinkCollector<'_, '_>,
     item: &Item,
     path_str: &str,
     disambiguator: Option<Disambiguator>,
@@ -1742,7 +1743,7 @@ fn resolution_failure(
 ) {
     let tcx = collector.cx.tcx;
     report_diagnostic(
-        collector.cx,
+        tcx,
         BROKEN_INTRA_DOC_LINKS,
         &format!("unresolved link to `{}`", path_str),
         item,
@@ -1973,7 +1974,7 @@ fn anchor_failure(
         ),
     };
 
-    report_diagnostic(cx, BROKEN_INTRA_DOC_LINKS, &msg, item, dox, &link_range, |diag, sp| {
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, item, dox, &link_range, |diag, sp| {
         if let Some(sp) = sp {
             diag.span_label(sp, "contains invalid anchor");
         }
@@ -2013,7 +2014,7 @@ fn ambiguity_error(
         }
     }
 
-    report_diagnostic(cx, BROKEN_INTRA_DOC_LINKS, &msg, item, dox, &link_range, |diag, sp| {
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, item, dox, &link_range, |diag, sp| {
         if let Some(sp) = sp {
             diag.span_label(sp, "ambiguous link");
         } else {
@@ -2066,7 +2067,7 @@ fn privacy_error(cx: &DocContext<'_>, item: &Item, path_str: &str, dox: &str, li
     let msg =
         format!("public documentation for `{}` links to private item `{}`", item_name, path_str);
 
-    report_diagnostic(cx, PRIVATE_INTRA_DOC_LINKS, &msg, item, dox, &link.range, |diag, sp| {
+    report_diagnostic(cx.tcx, PRIVATE_INTRA_DOC_LINKS, &msg, item, dox, &link.range, |diag, sp| {
         if let Some(sp) = sp {
             diag.span_label(sp, "this item is private");
         }
diff --git a/src/librustdoc/passes/doc_test_lints.rs b/src/librustdoc/passes/doc_test_lints.rs
index 2fa9179515de1..951258db9e2a2 100644
--- a/src/librustdoc/passes/doc_test_lints.rs
+++ b/src/librustdoc/passes/doc_test_lints.rs
@@ -82,7 +82,7 @@ crate fn should_have_doc_example(cx: &DocContext<'_>, item: &clean::Item) -> boo
 }
 
 crate fn look_for_tests<'tcx>(cx: &DocContext<'tcx>, dox: &str, item: &Item) {
-    let hir_id = match cx.as_local_hir_id(item.def_id) {
+    let hir_id = match DocContext::as_local_hir_id(cx.tcx, item.def_id) {
         Some(hir_id) => hir_id,
         None => {
             // If non-local, no need to check anything.
diff --git a/src/librustdoc/passes/html_tags.rs b/src/librustdoc/passes/html_tags.rs
index 27e669aa44fc0..23364b6fec9d1 100644
--- a/src/librustdoc/passes/html_tags.rs
+++ b/src/librustdoc/passes/html_tags.rs
@@ -167,7 +167,8 @@ fn extract_tags(
 
 impl<'a, 'tcx> DocFolder for InvalidHtmlTagsLinter<'a, 'tcx> {
     fn fold_item(&mut self, item: Item) -> Option<Item> {
-        let hir_id = match self.cx.as_local_hir_id(item.def_id) {
+        let tcx = self.cx.tcx;
+        let hir_id = match DocContext::as_local_hir_id(tcx, item.def_id) {
             Some(hir_id) => hir_id,
             None => {
                 // If non-local, no need to check anything.
@@ -176,13 +177,13 @@ impl<'a, 'tcx> DocFolder for InvalidHtmlTagsLinter<'a, 'tcx> {
         };
         let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
         if !dox.is_empty() {
-            let cx = &self.cx;
             let report_diag = |msg: &str, range: &Range<usize>| {
-                let sp = match super::source_span_for_markdown_range(cx, &dox, range, &item.attrs) {
+                let sp = match super::source_span_for_markdown_range(tcx, &dox, range, &item.attrs)
+                {
                     Some(sp) => sp,
                     None => span_of_attrs(&item.attrs).unwrap_or(item.source.span()),
                 };
-                cx.tcx.struct_span_lint_hir(crate::lint::INVALID_HTML_TAGS, hir_id, sp, |lint| {
+                tcx.struct_span_lint_hir(crate::lint::INVALID_HTML_TAGS, hir_id, sp, |lint| {
                     lint.build(msg).emit()
                 });
             };
diff --git a/src/librustdoc/passes/mod.rs b/src/librustdoc/passes/mod.rs
index 5813732facb6e..4c639c8496db3 100644
--- a/src/librustdoc/passes/mod.rs
+++ b/src/librustdoc/passes/mod.rs
@@ -1,6 +1,7 @@
 //! Contains information about "passes", used to modify crate information during the documentation
 //! process.
 
+use rustc_middle::ty::TyCtxt;
 use rustc_span::{InnerSpan, Span, DUMMY_SP};
 use std::ops::Range;
 
@@ -167,7 +168,7 @@ crate fn span_of_attrs(attrs: &clean::Attributes) -> Option<Span> {
 /// attributes are not all sugared doc comments. It's difficult to calculate the correct span in
 /// that case due to escaping and other source features.
 crate fn source_span_for_markdown_range(
-    cx: &DocContext<'_>,
+    tcx: TyCtxt<'_>,
     markdown: &str,
     md_range: &Range<usize>,
     attrs: &clean::Attributes,
@@ -179,7 +180,7 @@ crate fn source_span_for_markdown_range(
         return None;
     }
 
-    let snippet = cx.sess().source_map().span_to_snippet(span_of_attrs(attrs)?).ok()?;
+    let snippet = tcx.sess.source_map().span_to_snippet(span_of_attrs(attrs)?).ok()?;
 
     let starting_line = markdown[..md_range.start].matches('\n').count();
     let ending_line = starting_line + markdown[md_range.start..md_range.end].matches('\n').count();
diff --git a/src/librustdoc/passes/non_autolinks.rs b/src/librustdoc/passes/non_autolinks.rs
index 09a1959fa113c..16ad940c62717 100644
--- a/src/librustdoc/passes/non_autolinks.rs
+++ b/src/librustdoc/passes/non_autolinks.rs
@@ -60,7 +60,7 @@ crate fn check_non_autolinks(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
 
 impl<'a, 'tcx> DocFolder for NonAutolinksLinter<'a, 'tcx> {
     fn fold_item(&mut self, item: Item) -> Option<Item> {
-        let hir_id = match self.cx.as_local_hir_id(item.def_id) {
+        let hir_id = match DocContext::as_local_hir_id(self.cx.tcx, item.def_id) {
             Some(hir_id) => hir_id,
             None => {
                 // If non-local, no need to check anything.
@@ -70,7 +70,7 @@ impl<'a, 'tcx> DocFolder for NonAutolinksLinter<'a, 'tcx> {
         let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
         if !dox.is_empty() {
             let report_diag = |cx: &DocContext<'_>, msg: &str, url: &str, range: Range<usize>| {
-                let sp = super::source_span_for_markdown_range(cx, &dox, &range, &item.attrs)
+                let sp = super::source_span_for_markdown_range(cx.tcx, &dox, &range, &item.attrs)
                     .or_else(|| span_of_attrs(&item.attrs))
                     .unwrap_or(item.source.span());
                 cx.tcx.struct_span_lint_hir(crate::lint::NON_AUTOLINKS, hir_id, sp, |lint| {
diff --git a/src/test/codegen/unwind-abis/c-unwind-abi-panic-abort.rs b/src/test/codegen/unwind-abis/c-unwind-abi-panic-abort.rs
new file mode 100644
index 0000000000000..afd65ff6741a6
--- /dev/null
+++ b/src/test/codegen/unwind-abis/c-unwind-abi-panic-abort.rs
@@ -0,0 +1,18 @@
+// compile-flags: -C panic=abort -C opt-level=0
+
+// Test that `nounwind` atributes are applied to `C-unwind` extern functions when the
+// code is compiled with `panic=abort`.  We disable optimizations above to prevent LLVM from
+// inferring the attribute.
+
+#![crate_type = "lib"]
+#![feature(c_unwind)]
+
+// CHECK: @rust_item_that_can_unwind() unnamed_addr #0 {
+#[no_mangle]
+pub extern "C-unwind" fn rust_item_that_can_unwind() {
+}
+
+// Now, make sure that the LLVM attributes for this functions are correct.  First, make
+// sure that the first item is correctly marked with the `nounwind` attribute:
+//
+// CHECK: attributes #0 = { {{.*}}nounwind{{.*}} }
diff --git a/src/test/codegen/unwind-abis/c-unwind-abi.rs b/src/test/codegen/unwind-abis/c-unwind-abi.rs
new file mode 100644
index 0000000000000..f157653675322
--- /dev/null
+++ b/src/test/codegen/unwind-abis/c-unwind-abi.rs
@@ -0,0 +1,29 @@
+// compile-flags: -C opt-level=0
+
+// Test that `nounwind` atributes are correctly applied to exported `C` and `C-unwind` extern
+// functions. `C-unwind` functions MUST NOT have this attribute. We disable optimizations above
+// to prevent LLVM from inferring the attribute.
+
+#![crate_type = "lib"]
+#![feature(c_unwind)]
+
+// CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
+#[no_mangle]
+pub extern "C" fn rust_item_that_cannot_unwind() {
+}
+
+// CHECK: @rust_item_that_can_unwind() unnamed_addr #1 {
+#[no_mangle]
+pub extern "C-unwind" fn rust_item_that_can_unwind() {
+}
+
+// Now, make some assertions that the LLVM attributes for these functions are correct.  First, make
+// sure that the first item is correctly marked with the `nounwind` attribute:
+//
+// CHECK: attributes #0 = { {{.*}}nounwind{{.*}} }
+//
+// Next, let's assert that the second item, which CAN unwind, does not have this attribute.
+//
+// CHECK: attributes #1 = {
+// CHECK-NOT: nounwind
+// CHECK: }
diff --git a/src/test/codegen/unwind-abis/stdcall-unwind-abi.rs b/src/test/codegen/unwind-abis/stdcall-unwind-abi.rs
new file mode 100644
index 0000000000000..ed804ca278d2d
--- /dev/null
+++ b/src/test/codegen/unwind-abis/stdcall-unwind-abi.rs
@@ -0,0 +1,32 @@
+// compile-flags: -C opt-level=0
+// ignore-arm stdcall isn't supported
+// ignore-aarch64 stdcall isn't supported
+// ignore-riscv64 stdcall isn't supported
+
+// Test that `nounwind` atributes are correctly applied to exported `stdcall` and `stdcall-unwind`
+// extern functions. `stdcall-unwind` functions MUST NOT have this attribute. We disable
+// optimizations above to prevent LLVM from inferring the attribute.
+
+#![crate_type = "lib"]
+#![feature(c_unwind)]
+
+// CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
+#[no_mangle]
+pub extern "stdcall" fn rust_item_that_cannot_unwind() {
+}
+
+// CHECK: @rust_item_that_can_unwind() unnamed_addr #1 {
+#[no_mangle]
+pub extern "stdcall-unwind" fn rust_item_that_can_unwind() {
+}
+
+// Now, make some assertions that the LLVM attributes for these functions are correct.  First, make
+// sure that the first item is correctly marked with the `nounwind` attribute:
+//
+// CHECK: attributes #0 = { {{.*}}nounwind{{.*}} }
+//
+// Next, let's assert that the second item, which CAN unwind, does not have this attribute.
+//
+// CHECK: attributes #1 = {
+// CHECK-NOT: nounwind
+// CHECK: }
diff --git a/src/test/codegen/unwind-abis/system-unwind-abi.rs b/src/test/codegen/unwind-abis/system-unwind-abi.rs
new file mode 100644
index 0000000000000..c4d51328352c0
--- /dev/null
+++ b/src/test/codegen/unwind-abis/system-unwind-abi.rs
@@ -0,0 +1,29 @@
+// compile-flags: -C opt-level=0
+
+// Test that `nounwind` atributes are correctly applied to exported `system` and `system-unwind`
+// extern functions. `system-unwind` functions MUST NOT have this attribute. We disable
+// optimizations above to prevent LLVM from inferring the attribute.
+
+#![crate_type = "lib"]
+#![feature(c_unwind)]
+
+// CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
+#[no_mangle]
+pub extern "system" fn rust_item_that_cannot_unwind() {
+}
+
+// CHECK: @rust_item_that_can_unwind() unnamed_addr #1 {
+#[no_mangle]
+pub extern "system-unwind" fn rust_item_that_can_unwind() {
+}
+
+// Now, make some assertions that the LLVM attributes for these functions are correct.  First, make
+// sure that the first item is correctly marked with the `nounwind` attribute:
+//
+// CHECK: attributes #0 = { {{.*}}nounwind{{.*}} }
+//
+// Next, let's assert that the second item, which CAN unwind, does not have this attribute.
+//
+// CHECK: attributes #1 = {
+// CHECK-NOT: nounwind
+// CHECK: }
diff --git a/src/test/codegen/unwind-abis/thiscall-unwind-abi.rs b/src/test/codegen/unwind-abis/thiscall-unwind-abi.rs
new file mode 100644
index 0000000000000..aaa63ae55c3ac
--- /dev/null
+++ b/src/test/codegen/unwind-abis/thiscall-unwind-abi.rs
@@ -0,0 +1,33 @@
+// compile-flags: -C opt-level=0
+// ignore-arm thiscall isn't supported
+// ignore-aarch64 thiscall isn't supported
+// ignore-riscv64 thiscall isn't supported
+
+// Test that `nounwind` atributes are correctly applied to exported `thiscall` and
+// `thiscall-unwind` extern functions. `thiscall-unwind` functions MUST NOT have this attribute. We
+// disable optimizations above to prevent LLVM from inferring the attribute.
+
+#![crate_type = "lib"]
+#![feature(abi_thiscall)]
+#![feature(c_unwind)]
+
+// CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
+#[no_mangle]
+pub extern "thiscall" fn rust_item_that_cannot_unwind() {
+}
+
+// CHECK: @rust_item_that_can_unwind() unnamed_addr #1 {
+#[no_mangle]
+pub extern "thiscall-unwind" fn rust_item_that_can_unwind() {
+}
+
+// Now, make some assertions that the LLVM attributes for these functions are correct.  First, make
+// sure that the first item is correctly marked with the `nounwind` attribute:
+//
+// CHECK: attributes #0 = { {{.*}}nounwind{{.*}} }
+//
+// Next, let's assert that the second item, which CAN unwind, does not have this attribute.
+//
+// CHECK: attributes #1 = {
+// CHECK-NOT: nounwind
+// CHECK: }
diff --git a/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/Makefile b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/Makefile
new file mode 100644
index 0000000000000..a8515c533af57
--- /dev/null
+++ b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/Makefile
@@ -0,0 +1,30 @@
+-include ../tools.mk
+
+all: archive
+	# Compile `main.rs`, which will link into our library, and run it.
+	$(RUSTC) main.rs
+	$(call RUN,main)
+
+ifdef IS_MSVC
+archive: add.o panic.o
+	# Now, create an archive using these two objects.
+	$(AR) crus $(TMPDIR)/add.lib $(TMPDIR)/add.o $(TMPDIR)/panic.o
+else
+archive: add.o panic.o
+	# Now, create an archive using these two objects.
+	$(AR) crus $(TMPDIR)/libadd.a $(TMPDIR)/add.o $(TMPDIR)/panic.o
+endif
+
+# Compile `panic.rs` into an object file.
+#
+# Note that we invoke `rustc` directly, so we may emit an object rather
+# than an archive. We'll do that later.
+panic.o:
+	$(BARE_RUSTC) $(RUSTFLAGS)  \
+		--out-dir $(TMPDIR) \
+		--emit=obj panic.rs
+
+# Compile `add.c` into an object file.
+add.o:
+	$(call COMPILE_OBJ,$(TMPDIR)/add.o,add.c)
+
diff --git a/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/add.c b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/add.c
new file mode 100644
index 0000000000000..444359451f6ec
--- /dev/null
+++ b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/add.c
@@ -0,0 +1,12 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+
+// An external function, defined in Rust.
+extern void panic_if_greater_than_10(unsigned x);
+
+unsigned add_small_numbers(unsigned a, unsigned b) {
+    unsigned c = a + b;
+    panic_if_greater_than_10(c);
+    return c;
+}
diff --git a/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/main.rs b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/main.rs
new file mode 100644
index 0000000000000..78a71219c7811
--- /dev/null
+++ b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/main.rs
@@ -0,0 +1,35 @@
+//! A test for calling `C-unwind` functions across foreign function boundaries.
+//!
+//! This test triggers a panic in a Rust library that our foreign function invokes. This shows
+//! that we can unwind through the C code in that library, and catch the underlying panic.
+#![feature(c_unwind)]
+
+use std::panic::{catch_unwind, AssertUnwindSafe};
+
+fn main() {
+    // Call `add_small_numbers`, passing arguments that will NOT trigger a panic.
+    let (a, b) = (9, 1);
+    let c = unsafe { add_small_numbers(a, b) };
+    assert_eq!(c, 10);
+
+    // Call `add_small_numbers`, passing arguments that will trigger a panic, and catch it.
+    let caught_unwind = catch_unwind(AssertUnwindSafe(|| {
+        let (a, b) = (10, 1);
+        let _c = unsafe { add_small_numbers(a, b) };
+        unreachable!("should have unwound instead of returned");
+    }));
+
+    // Assert that we did indeed panic, then unwrap and downcast the panic into the sum.
+    assert!(caught_unwind.is_err());
+    let panic_obj = caught_unwind.unwrap_err();
+    let msg = panic_obj.downcast_ref::<String>().unwrap();
+    assert_eq!(msg, "11");
+}
+
+#[link(name = "add", kind = "static")]
+extern "C-unwind" {
+    /// An external function, defined in C.
+    ///
+    /// Returns the sum of two numbers, or panics if the sum is greater than 10.
+    fn add_small_numbers(a: u32, b: u32) -> u32;
+}
diff --git a/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/panic.rs b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/panic.rs
new file mode 100644
index 0000000000000..a99a04d5c6f4b
--- /dev/null
+++ b/src/test/run-make-fulldeps/c-unwind-abi-catch-lib-panic/panic.rs
@@ -0,0 +1,12 @@
+#![crate_type = "staticlib"]
+#![feature(c_unwind)]
+
+/// This function will panic if `x` is greater than 10.
+///
+/// This function is called by `add_small_numbers`.
+#[no_mangle]
+pub extern "C-unwind" fn panic_if_greater_than_10(x: u32) {
+    if x > 10 {
+        panic!("{}", x); // That is too big!
+    }
+}
diff --git a/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/Makefile b/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/Makefile
new file mode 100644
index 0000000000000..9553b7aeeb983
--- /dev/null
+++ b/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/Makefile
@@ -0,0 +1,5 @@
+-include ../tools.mk
+
+all: $(call NATIVE_STATICLIB,add)
+	$(RUSTC) main.rs
+	$(call RUN,main) || exit 1
diff --git a/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/add.c b/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/add.c
new file mode 100644
index 0000000000000..444359451f6ec
--- /dev/null
+++ b/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/add.c
@@ -0,0 +1,12 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+
+// An external function, defined in Rust.
+extern void panic_if_greater_than_10(unsigned x);
+
+unsigned add_small_numbers(unsigned a, unsigned b) {
+    unsigned c = a + b;
+    panic_if_greater_than_10(c);
+    return c;
+}
diff --git a/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/main.rs b/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/main.rs
new file mode 100644
index 0000000000000..15d38d7216058
--- /dev/null
+++ b/src/test/run-make-fulldeps/c-unwind-abi-catch-panic/main.rs
@@ -0,0 +1,44 @@
+//! A test for calling `C-unwind` functions across foreign function boundaries.
+//!
+//! This test triggers a panic when calling a foreign function that calls *back* into Rust.
+#![feature(c_unwind)]
+
+use std::panic::{catch_unwind, AssertUnwindSafe};
+
+fn main() {
+    // Call `add_small_numbers`, passing arguments that will NOT trigger a panic.
+    let (a, b) = (9, 1);
+    let c = unsafe { add_small_numbers(a, b) };
+    assert_eq!(c, 10);
+
+    // Call `add_small_numbers`, passing arguments that will trigger a panic, and catch it.
+    let caught_unwind = catch_unwind(AssertUnwindSafe(|| {
+        let (a, b) = (10, 1);
+        let _c = unsafe { add_small_numbers(a, b) };
+        unreachable!("should have unwound instead of returned");
+    }));
+
+    // Assert that we did indeed panic, then unwrap and downcast the panic into the sum.
+    assert!(caught_unwind.is_err());
+    let panic_obj = caught_unwind.unwrap_err();
+    let msg = panic_obj.downcast_ref::<String>().unwrap();
+    assert_eq!(msg, "11");
+}
+
+#[link(name = "add", kind = "static")]
+extern "C-unwind" {
+    /// An external function, defined in C.
+    ///
+    /// Returns the sum of two numbers, or panics if the sum is greater than 10.
+    fn add_small_numbers(a: u32, b: u32) -> u32;
+}
+
+/// This function will panic if `x` is greater than 10.
+///
+/// This function is called by `add_small_numbers`.
+#[no_mangle]
+pub extern "C-unwind" fn panic_if_greater_than_10(x: u32) {
+    if x > 10 {
+        panic!("{}", x); // That is too big!
+    }
+}
diff --git a/src/test/rustdoc-ui/deprecated-attrs.rs b/src/test/rustdoc-ui/deprecated-attrs.rs
index ca626afbe5359..5febc5eb9cd54 100644
--- a/src/test/rustdoc-ui/deprecated-attrs.rs
+++ b/src/test/rustdoc-ui/deprecated-attrs.rs
@@ -1,7 +1,17 @@
 // check-pass
+// compile-flags: --passes unknown-pass
+// error-pattern: ignoring unknown pass `unknown-pass`
 
-#![doc(no_default_passes, passes = "unindent-comments")]
-
-struct SomeStruct;
-
-pub struct OtherStruct;
+#![doc(no_default_passes)]
+//~^ WARNING attribute is deprecated
+//~| NOTE see issue #44136
+//~| HELP use `#![doc(document_private_items)]`
+#![doc(passes = "collapse-docs unindent-comments")]
+//~^ WARNING attribute is deprecated
+//~| NOTE see issue #44136
+//~| WARNING ignoring unknown pass
+//~| NOTE `collapse-docs` pass was removed
+#![doc(plugins = "xxx")]
+//~^ WARNING attribute is deprecated
+//~| NOTE see issue #44136
+//~| WARNING no longer functions; see CVE
diff --git a/src/test/rustdoc-ui/deprecated-attrs.stderr b/src/test/rustdoc-ui/deprecated-attrs.stderr
index f68fb46744805..b855cedf5223e 100644
--- a/src/test/rustdoc-ui/deprecated-attrs.stderr
+++ b/src/test/rustdoc-ui/deprecated-attrs.stderr
@@ -1,11 +1,42 @@
-warning: the `#![doc(no_default_passes)]` attribute is considered deprecated
+warning: the `passes` flag is deprecated
    |
-   = warning: see issue #44136 <https://github.com/rust-lang/rust/issues/44136> for more information
+   = note: see issue #44136 <https://github.com/rust-lang/rust/issues/44136> for more information
+
+warning: ignoring unknown pass `unknown-pass`
+
+warning: the `#![doc(no_default_passes)]` attribute is deprecated
+  --> $DIR/deprecated-attrs.rs:5:8
+   |
+LL | #![doc(no_default_passes)]
+   |        ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #44136 <https://github.com/rust-lang/rust/issues/44136> for more information
    = help: you may want to use `#![doc(document_private_items)]`
 
-warning: the `#![doc(passes = "...")]` attribute is considered deprecated
+warning: the `#![doc(passes = "...")]` attribute is deprecated
+  --> $DIR/deprecated-attrs.rs:9:8
+   |
+LL | #![doc(passes = "collapse-docs unindent-comments")]
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #44136 <https://github.com/rust-lang/rust/issues/44136> for more information
+
+warning: ignoring unknown pass `collapse-docs`
+  --> $DIR/deprecated-attrs.rs:9:17
+   |
+LL | #![doc(passes = "collapse-docs unindent-comments")]
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the `collapse-docs` pass was removed in #80261 <https://github.com/rust-lang/rust/pull/80261>
+
+warning: the `#![doc(plugins = "...")]` attribute is deprecated
+  --> $DIR/deprecated-attrs.rs:14:8
+   |
+LL | #![doc(plugins = "xxx")]
+   |        ^^^^^^^^^^^^^^^
    |
-   = warning: see issue #44136 <https://github.com/rust-lang/rust/issues/44136> for more information
+   = note: see issue #44136 <https://github.com/rust-lang/rust/issues/44136> for more information
+   = warning: `#![doc(plugins = "...")]` no longer functions; see CVE-2018-1000622 <https://nvd.nist.gov/vuln/detail/CVE-2018-1000622>
 
-warning: 2 warnings emitted
+warning: 5 warnings emitted
 
diff --git a/src/test/ui/allocator/no_std-alloc-error-handler-custom.rs b/src/test/ui/allocator/no_std-alloc-error-handler-custom.rs
index 4d40c7d0d2237..c9b4abbfd3fd3 100644
--- a/src/test/ui/allocator/no_std-alloc-error-handler-custom.rs
+++ b/src/test/ui/allocator/no_std-alloc-error-handler-custom.rs
@@ -7,7 +7,7 @@
 // compile-flags:-C panic=abort
 // aux-build:helper.rs
 
-#![feature(start, rustc_private, new_uninit, panic_info_message)]
+#![feature(start, rustc_private, new_uninit, panic_info_message, lang_items)]
 #![feature(alloc_error_handler)]
 #![no_std]
 
@@ -84,6 +84,13 @@ fn panic(panic_info: &core::panic::PanicInfo) -> ! {
     }
 }
 
+// Because we are compiling this code with `-C panic=abort`, this wouldn't normally be needed.
+// However, `core` and `alloc` are both compiled with `-C panic=unwind`, which means that functions
+// in these libaries will refer to `rust_eh_personality` if LLVM can not *prove* the contents won't
+// unwind. So, for this test case we will define the symbol.
+#[lang = "eh_personality"]
+extern fn rust_eh_personality() {}
+
 #[derive(Debug)]
 struct Page([[u64; 32]; 16]);
 
diff --git a/src/test/ui/allocator/no_std-alloc-error-handler-default.rs b/src/test/ui/allocator/no_std-alloc-error-handler-default.rs
index 4f8c44f1763c8..d6cd4a6af855f 100644
--- a/src/test/ui/allocator/no_std-alloc-error-handler-default.rs
+++ b/src/test/ui/allocator/no_std-alloc-error-handler-default.rs
@@ -8,7 +8,7 @@
 // aux-build:helper.rs
 // gate-test-default_alloc_error_handler
 
-#![feature(start, rustc_private, new_uninit, panic_info_message)]
+#![feature(start, rustc_private, new_uninit, panic_info_message, lang_items)]
 #![feature(default_alloc_error_handler)]
 #![no_std]
 
@@ -71,6 +71,13 @@ fn panic(panic_info: &core::panic::PanicInfo) -> ! {
     }
 }
 
+// Because we are compiling this code with `-C panic=abort`, this wouldn't normally be needed.
+// However, `core` and `alloc` are both compiled with `-C panic=unwind`, which means that functions
+// in these libaries will refer to `rust_eh_personality` if LLVM can not *prove* the contents won't
+// unwind. So, for this test case we will define the symbol.
+#[lang = "eh_personality"]
+extern fn rust_eh_personality() {}
+
 #[derive(Debug)]
 struct Page([[u64; 32]; 16]);
 
diff --git a/src/test/ui/codemap_tests/unicode.stderr b/src/test/ui/codemap_tests/unicode.stderr
index 61c3f4f1c9847..b7ba4fa46d92b 100644
--- a/src/test/ui/codemap_tests/unicode.stderr
+++ b/src/test/ui/codemap_tests/unicode.stderr
@@ -4,7 +4,7 @@ error[E0703]: invalid ABI: found `路濫狼á́́`
 LL | extern "路濫狼á́́" fn foo() {}
    |        ^^^^^^^^^ invalid ABI
    |
-   = help: valid ABIs: Rust, C, cdecl, stdcall, fastcall, vectorcall, thiscall, aapcs, win64, sysv64, ptx-kernel, msp430-interrupt, x86-interrupt, amdgpu-kernel, efiapi, avr-interrupt, avr-non-blocking-interrupt, C-cmse-nonsecure-call, system, rust-intrinsic, rust-call, platform-intrinsic, unadjusted
+   = help: valid ABIs: Rust, C, C-unwind, cdecl, stdcall, stdcall-unwind, fastcall, vectorcall, thiscall, thiscall-unwind, aapcs, win64, sysv64, ptx-kernel, msp430-interrupt, x86-interrupt, amdgpu-kernel, efiapi, avr-interrupt, avr-non-blocking-interrupt, C-cmse-nonsecure-call, system, system-unwind, rust-intrinsic, rust-call, platform-intrinsic, unadjusted
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/directory_ownership/macro-expanded-mod.rs b/src/test/ui/directory_ownership/macro-expanded-mod.rs
index 9cb159603a8c5..fa81769e5a800 100644
--- a/src/test/ui/directory_ownership/macro-expanded-mod.rs
+++ b/src/test/ui/directory_ownership/macro-expanded-mod.rs
@@ -2,7 +2,7 @@
 
 macro_rules! mod_decl {
     ($i:ident) => {
-        mod $i; //~ ERROR Cannot declare a non-inline module inside a block
+        mod $i; //~ ERROR cannot declare a non-inline module inside a block
     };
 }
 
diff --git a/src/test/ui/directory_ownership/macro-expanded-mod.stderr b/src/test/ui/directory_ownership/macro-expanded-mod.stderr
index f90419247c92b..4039728e18ac3 100644
--- a/src/test/ui/directory_ownership/macro-expanded-mod.stderr
+++ b/src/test/ui/directory_ownership/macro-expanded-mod.stderr
@@ -1,4 +1,4 @@
-error: Cannot declare a non-inline module inside a block unless it has a path attribute
+error: cannot declare a non-inline module inside a block unless it has a path attribute
   --> $DIR/macro-expanded-mod.rs:5:9
    |
 LL |         mod $i;
diff --git a/src/test/ui/directory_ownership/non-inline-mod-restriction.rs b/src/test/ui/directory_ownership/non-inline-mod-restriction.rs
index af31b8a49281f..de4f816656cc4 100644
--- a/src/test/ui/directory_ownership/non-inline-mod-restriction.rs
+++ b/src/test/ui/directory_ownership/non-inline-mod-restriction.rs
@@ -1,5 +1,5 @@
 // Test that non-inline modules are not allowed inside blocks.
 
 fn main() {
-    mod foo; //~ ERROR Cannot declare a non-inline module inside a block
+    mod foo; //~ ERROR cannot declare a non-inline module inside a block
 }
diff --git a/src/test/ui/directory_ownership/non-inline-mod-restriction.stderr b/src/test/ui/directory_ownership/non-inline-mod-restriction.stderr
index d034942ca5d4c..64189bee43f6e 100644
--- a/src/test/ui/directory_ownership/non-inline-mod-restriction.stderr
+++ b/src/test/ui/directory_ownership/non-inline-mod-restriction.stderr
@@ -1,4 +1,4 @@
-error: Cannot declare a non-inline module inside a block unless it has a path attribute
+error: cannot declare a non-inline module inside a block unless it has a path attribute
   --> $DIR/non-inline-mod-restriction.rs:4:5
    |
 LL |     mod foo;
diff --git a/src/test/ui/modules/path-no-file-name.rs b/src/test/ui/modules/path-no-file-name.rs
new file mode 100644
index 0000000000000..f62cd2a9eb4e4
--- /dev/null
+++ b/src/test/ui/modules/path-no-file-name.rs
@@ -0,0 +1,7 @@
+// normalize-stderr-test: "\.:.*\(" -> ".: $$ACCESS_DENIED_MSG ("
+// normalize-stderr-test: "os error \d+" -> "os error $$ACCESS_DENIED_CODE"
+
+#[path = "."]
+mod m; //~ ERROR couldn't read
+
+fn main() {}
diff --git a/src/test/ui/modules/path-no-file-name.stderr b/src/test/ui/modules/path-no-file-name.stderr
new file mode 100644
index 0000000000000..32a213c68f654
--- /dev/null
+++ b/src/test/ui/modules/path-no-file-name.stderr
@@ -0,0 +1,8 @@
+error: couldn't read $DIR/.: $ACCESS_DENIED_MSG (os error $ACCESS_DENIED_CODE)
+  --> $DIR/path-no-file-name.rs:5:1
+   |
+LL | mod m;
+   | ^^^^^^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/parser/circular_modules_main.rs b/src/test/ui/parser/circular_modules_main.rs
index 1ae36a1f7605e..d4b47efe68158 100644
--- a/src/test/ui/parser/circular_modules_main.rs
+++ b/src/test/ui/parser/circular_modules_main.rs
@@ -1,10 +1,12 @@
+// error-pattern: circular modules
+
 #[path = "circular_modules_hello.rs"]
-mod circular_modules_hello; //~ ERROR: circular modules
+mod circular_modules_hello;
 
 pub fn hi_str() -> String {
     "Hi!".to_string()
 }
 
 fn main() {
-    circular_modules_hello::say_hello(); //~ ERROR cannot find function `say_hello` in module
+    circular_modules_hello::say_hello();
 }
diff --git a/src/test/ui/parser/circular_modules_main.stderr b/src/test/ui/parser/circular_modules_main.stderr
index 5d4db8c31a2c3..ee45f65a3bd5a 100644
--- a/src/test/ui/parser/circular_modules_main.stderr
+++ b/src/test/ui/parser/circular_modules_main.stderr
@@ -1,18 +1,18 @@
-error: circular modules: $DIR/circular_modules_hello.rs -> $DIR/circular_modules_main.rs -> $DIR/circular_modules_hello.rs
-  --> $DIR/circular_modules_main.rs:2:1
+error: circular modules: $DIR/circular_modules_main.rs -> $DIR/circular_modules_hello.rs -> $DIR/circular_modules_main.rs
+  --> $DIR/circular_modules_hello.rs:4:1
    |
-LL | mod circular_modules_hello;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | mod circular_modules_main;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0425]: cannot find function `say_hello` in module `circular_modules_hello`
-  --> $DIR/circular_modules_main.rs:9:29
+error[E0425]: cannot find function `hi_str` in module `circular_modules_main`
+  --> $DIR/circular_modules_hello.rs:7:43
    |
-LL |     circular_modules_hello::say_hello();
-   |                             ^^^^^^^^^ not found in `circular_modules_hello`
+LL |     println!("{}", circular_modules_main::hi_str());
+   |                                           ^^^^^^ not found in `circular_modules_main`
    |
 help: consider importing this function
    |
-LL | use circular_modules_hello::say_hello;
+LL | use hi_str;
    |
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/parser/issue-8537.stderr b/src/test/ui/parser/issue-8537.stderr
index 3f63c08021098..85e2b77d867b9 100644
--- a/src/test/ui/parser/issue-8537.stderr
+++ b/src/test/ui/parser/issue-8537.stderr
@@ -4,7 +4,7 @@ error[E0703]: invalid ABI: found `invalid-ab_isize`
 LL |   "invalid-ab_isize"
    |   ^^^^^^^^^^^^^^^^^^ invalid ABI
    |
-   = help: valid ABIs: Rust, C, cdecl, stdcall, fastcall, vectorcall, thiscall, aapcs, win64, sysv64, ptx-kernel, msp430-interrupt, x86-interrupt, amdgpu-kernel, efiapi, avr-interrupt, avr-non-blocking-interrupt, C-cmse-nonsecure-call, system, rust-intrinsic, rust-call, platform-intrinsic, unadjusted
+   = help: valid ABIs: Rust, C, C-unwind, cdecl, stdcall, stdcall-unwind, fastcall, vectorcall, thiscall, thiscall-unwind, aapcs, win64, sysv64, ptx-kernel, msp430-interrupt, x86-interrupt, amdgpu-kernel, efiapi, avr-interrupt, avr-non-blocking-interrupt, C-cmse-nonsecure-call, system, system-unwind, rust-intrinsic, rust-call, platform-intrinsic, unadjusted
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/item-free-const-no-body-semantic-fail.rs b/src/test/ui/parser/item-free-const-no-body-semantic-fail.rs
index 613b3c9856171..15a15a207b1ca 100644
--- a/src/test/ui/parser/item-free-const-no-body-semantic-fail.rs
+++ b/src/test/ui/parser/item-free-const-no-body-semantic-fail.rs
@@ -4,4 +4,3 @@ fn main() {}
 
 const A: u8; //~ ERROR free constant item without body
 const B; //~ ERROR free constant item without body
-//~^ ERROR missing type for `const` item
diff --git a/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr b/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr
index 4e97229fa1a41..aa75e5cee01d4 100644
--- a/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr
+++ b/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr
@@ -14,11 +14,5 @@ LL | const B;
    |        |
    |        help: provide a definition for the constant: `= <expr>;`
 
-error: missing type for `const` item
-  --> $DIR/item-free-const-no-body-semantic-fail.rs:6:7
-   |
-LL | const B;
-   |       ^ help: provide a type for the item: `B: [type error]`
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/parser/item-free-static-no-body-semantic-fail.rs b/src/test/ui/parser/item-free-static-no-body-semantic-fail.rs
index 780479e3d26ac..61d3eab24d8c7 100644
--- a/src/test/ui/parser/item-free-static-no-body-semantic-fail.rs
+++ b/src/test/ui/parser/item-free-static-no-body-semantic-fail.rs
@@ -4,8 +4,6 @@ fn main() {}
 
 static A: u8; //~ ERROR free static item without body
 static B; //~ ERROR free static item without body
-//~^ ERROR missing type for `static` item
 
 static mut C: u8; //~ ERROR free static item without body
 static mut D; //~ ERROR free static item without body
-//~^ ERROR missing type for `static mut` item
diff --git a/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr b/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr
index 60b7bb34c698b..7b408323674de 100644
--- a/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr
+++ b/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr
@@ -15,7 +15,7 @@ LL | static B;
    |         help: provide a definition for the static: `= <expr>;`
 
 error: free static item without body
-  --> $DIR/item-free-static-no-body-semantic-fail.rs:9:1
+  --> $DIR/item-free-static-no-body-semantic-fail.rs:8:1
    |
 LL | static mut C: u8;
    | ^^^^^^^^^^^^^^^^-
@@ -23,24 +23,12 @@ LL | static mut C: u8;
    |                 help: provide a definition for the static: `= <expr>;`
 
 error: free static item without body
-  --> $DIR/item-free-static-no-body-semantic-fail.rs:10:1
+  --> $DIR/item-free-static-no-body-semantic-fail.rs:9:1
    |
 LL | static mut D;
    | ^^^^^^^^^^^^-
    |             |
    |             help: provide a definition for the static: `= <expr>;`
 
-error: missing type for `static` item
-  --> $DIR/item-free-static-no-body-semantic-fail.rs:6:8
-   |
-LL | static B;
-   |        ^ help: provide a type for the item: `B: [type error]`
-
-error: missing type for `static mut` item
-  --> $DIR/item-free-static-no-body-semantic-fail.rs:10:12
-   |
-LL | static mut D;
-   |            ^ help: provide a type for the item: `D: [type error]`
-
-error: aborting due to 6 previous errors
+error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/symbol-names/impl1.rs b/src/test/ui/symbol-names/impl1.rs
index 24bdf6d669e88..a352d255c782d 100644
--- a/src/test/ui/symbol-names/impl1.rs
+++ b/src/test/ui/symbol-names/impl1.rs
@@ -3,8 +3,8 @@
 // revisions: legacy v0
 //[legacy]compile-flags: -Z symbol-mangling-version=legacy
     //[v0]compile-flags: -Z symbol-mangling-version=v0
-//[legacy]normalize-stderr-32bit: "hee444285569b39c2" -> "SYMBOL_HASH"
-//[legacy]normalize-stderr-64bit: "h310ea0259fc3d32d" -> "SYMBOL_HASH"
+//[legacy]normalize-stderr-32bit: "h13cfe136e83a9196" -> "SYMBOL_HASH"
+//[legacy]normalize-stderr-64bit: "hd949d7797008991f" -> "SYMBOL_HASH"
 
 #![feature(auto_traits, rustc_attrs)]
 #![allow(dead_code)]
diff --git a/src/test/ui/typeck/issue-79040.rs b/src/test/ui/typeck/issue-79040.rs
new file mode 100644
index 0000000000000..af2a9c1ba87ef
--- /dev/null
+++ b/src/test/ui/typeck/issue-79040.rs
@@ -0,0 +1,5 @@
+fn main() {
+    const FOO = "hello" + 1; //~ ERROR cannot add `{integer}` to `&str`
+    //~^ ERROR cannot add `{integer}` to `&str`
+    println!("{}", FOO);
+}
diff --git a/src/test/ui/typeck/issue-79040.stderr b/src/test/ui/typeck/issue-79040.stderr
new file mode 100644
index 0000000000000..32049e5d96860
--- /dev/null
+++ b/src/test/ui/typeck/issue-79040.stderr
@@ -0,0 +1,19 @@
+error[E0369]: cannot add `{integer}` to `&str`
+  --> $DIR/issue-79040.rs:2:25
+   |
+LL |     const FOO = "hello" + 1;
+   |                 ------- ^ - {integer}
+   |                 |
+   |                 &str
+
+error[E0369]: cannot add `{integer}` to `&str`
+  --> $DIR/issue-79040.rs:2:25
+   |
+LL |     const FOO = "hello" + 1;
+   |                 ------- ^ - {integer}
+   |                 |
+   |                 &str
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0369`.
diff --git a/src/test/ui/unwind-abis/feature-gate-c-unwind-enabled.rs b/src/test/ui/unwind-abis/feature-gate-c-unwind-enabled.rs
new file mode 100644
index 0000000000000..6ff5dbda2d560
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-c-unwind-enabled.rs
@@ -0,0 +1,12 @@
+// Test that the "C-unwind" ABI is feature-gated, and *can* be used when the
+// `c_unwind` feature gate is enabled.
+
+// check-pass
+
+#![feature(c_unwind)]
+
+extern "C-unwind" fn f() {}
+
+fn main() {
+    f();
+}
diff --git a/src/test/ui/unwind-abis/feature-gate-c-unwind.rs b/src/test/ui/unwind-abis/feature-gate-c-unwind.rs
new file mode 100644
index 0000000000000..f02a368d4e097
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-c-unwind.rs
@@ -0,0 +1,9 @@
+// Test that the "C-unwind" ABI is feature-gated, and cannot be used when the
+// `c_unwind` feature gate is not used.
+
+extern "C-unwind" fn f() {}
+//~^ ERROR C-unwind ABI is experimental and subject to change [E0658]
+
+fn main() {
+    f();
+}
diff --git a/src/test/ui/unwind-abis/feature-gate-c-unwind.stderr b/src/test/ui/unwind-abis/feature-gate-c-unwind.stderr
new file mode 100644
index 0000000000000..f4c785a235f67
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-c-unwind.stderr
@@ -0,0 +1,12 @@
+error[E0658]: C-unwind ABI is experimental and subject to change
+  --> $DIR/feature-gate-c-unwind.rs:4:8
+   |
+LL | extern "C-unwind" fn f() {}
+   |        ^^^^^^^^^^
+   |
+   = note: see issue #74990 <https://github.com/rust-lang/rust/issues/74990> for more information
+   = help: add `#![feature(c_unwind)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/unwind-abis/feature-gate-stdcall-unwind.rs b/src/test/ui/unwind-abis/feature-gate-stdcall-unwind.rs
new file mode 100644
index 0000000000000..7d4dc8c9343f1
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-stdcall-unwind.rs
@@ -0,0 +1,13 @@
+// ignore-arm stdcall isn't supported
+// ignore-aarch64 stdcall isn't supported
+// ignore-riscv64 stdcall isn't supported
+
+// Test that the "stdcall-unwind" ABI is feature-gated, and cannot be used when
+// the `c_unwind` feature gate is not used.
+
+extern "stdcall-unwind" fn f() {}
+//~^ ERROR stdcall-unwind ABI is experimental and subject to change [E0658]
+
+fn main() {
+    f();
+}
diff --git a/src/test/ui/unwind-abis/feature-gate-stdcall-unwind.stderr b/src/test/ui/unwind-abis/feature-gate-stdcall-unwind.stderr
new file mode 100644
index 0000000000000..e3d569f464f87
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-stdcall-unwind.stderr
@@ -0,0 +1,12 @@
+error[E0658]: stdcall-unwind ABI is experimental and subject to change
+  --> $DIR/feature-gate-stdcall-unwind.rs:8:8
+   |
+LL | extern "stdcall-unwind" fn f() {}
+   |        ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #74990 <https://github.com/rust-lang/rust/issues/74990> for more information
+   = help: add `#![feature(c_unwind)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/unwind-abis/feature-gate-system-unwind.rs b/src/test/ui/unwind-abis/feature-gate-system-unwind.rs
new file mode 100644
index 0000000000000..26c2de4e81767
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-system-unwind.rs
@@ -0,0 +1,9 @@
+// Test that the "system-unwind" ABI is feature-gated, and cannot be used when
+// the `c_unwind` feature gate is not used.
+
+extern "system-unwind" fn f() {}
+//~^ ERROR system-unwind ABI is experimental and subject to change [E0658]
+
+fn main() {
+    f();
+}
diff --git a/src/test/ui/unwind-abis/feature-gate-system-unwind.stderr b/src/test/ui/unwind-abis/feature-gate-system-unwind.stderr
new file mode 100644
index 0000000000000..87877336475b4
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-system-unwind.stderr
@@ -0,0 +1,12 @@
+error[E0658]: system-unwind ABI is experimental and subject to change
+  --> $DIR/feature-gate-system-unwind.rs:4:8
+   |
+LL | extern "system-unwind" fn f() {}
+   |        ^^^^^^^^^^^^^^^
+   |
+   = note: see issue #74990 <https://github.com/rust-lang/rust/issues/74990> for more information
+   = help: add `#![feature(c_unwind)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/unwind-abis/feature-gate-thiscall-unwind.rs b/src/test/ui/unwind-abis/feature-gate-thiscall-unwind.rs
new file mode 100644
index 0000000000000..2f4cefccc1967
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-thiscall-unwind.rs
@@ -0,0 +1,13 @@
+// ignore-arm thiscall isn't supported
+// ignore-aarch64 thiscall isn't supported
+// ignore-riscv64 thiscall isn't supported
+
+// Test that the "thiscall-unwind" ABI is feature-gated, and cannot be used when
+// the `c_unwind` feature gate is not used.
+
+extern "thiscall-unwind" fn f() {}
+//~^ ERROR thiscall-unwind ABI is experimental and subject to change [E0658]
+
+fn main() {
+    f();
+}
diff --git a/src/test/ui/unwind-abis/feature-gate-thiscall-unwind.stderr b/src/test/ui/unwind-abis/feature-gate-thiscall-unwind.stderr
new file mode 100644
index 0000000000000..b103bb8d56585
--- /dev/null
+++ b/src/test/ui/unwind-abis/feature-gate-thiscall-unwind.stderr
@@ -0,0 +1,12 @@
+error[E0658]: thiscall-unwind ABI is experimental and subject to change
+  --> $DIR/feature-gate-thiscall-unwind.rs:8:8
+   |
+LL | extern "thiscall-unwind" fn f() {}
+   |        ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #74990 <https://github.com/rust-lang/rust/issues/74990> for more information
+   = help: add `#![feature(c_unwind)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.