Auto merge of rust-lang#133345 - GuillaumeGomez:stop-cloning-context, r=<try>

Stop cloning `Context` so much

This is a first step for rust-lang#82381.

It's already big enough so I'll continue in a follow-up once this PR is merged. Next step will be to get rid of `SharedContext` by inlining it directly into `Context`.

cc `@camelid`
r? `@notriddle`

Author: bors

src/librustdoc/formats/renderer.rs

@@ -1,5 +1,5 @@
+use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_middle::ty::TyCtxt;
-use tracing::debug;
 
 use crate::clean;
 use crate::config::RenderOptions;
@@ -17,6 +17,7 @@ pub(crate) trait FormatRenderer<'tcx>: Sized {
     ///
     /// This is true for html, and false for json. See #80664
     const RUN_ON_MODULE: bool;
+    type InfoType;
 
     /// Sets up any state required for the renderer. When this is called the cache has already been
     /// populated.
@@ -28,7 +29,8 @@ pub(crate) trait FormatRenderer<'tcx>: Sized {
     ) -> Result<(Self, clean::Crate), Error>;
 
     /// Make a new renderer to render a child of the item currently being rendered.
-    fn make_child_renderer(&self) -> Self;
+    fn make_child_renderer(&mut self) -> Self::InfoType;
+    fn set_back_info(&mut self, _info: Self::InfoType);
 
     /// Renders a single non-module item. This means no recursive sub-item rendering is required.
     fn item(&mut self, item: clean::Item) -> Result<(), Error>;
@@ -47,6 +49,40 @@ pub(crate) trait FormatRenderer<'tcx>: Sized {
     fn cache(&self) -> &Cache;
 }
 
+fn run_format_inner<'tcx, T: FormatRenderer<'tcx>>(
+    cx: &mut T,
+    item: clean::Item,
+    prof: &SelfProfilerRef,
+) -> Result<(), Error> {
+    if item.is_mod() && T::RUN_ON_MODULE {
+        // modules are special because they add a namespace. We also need to
+        // recurse into the items of the module as well.
+        let _timer =
+            prof.generic_activity_with_arg("render_mod_item", item.name.unwrap().to_string());
+
+        cx.mod_item_in(&item)?;
+        let (clean::StrippedItem(box clean::ModuleItem(module)) | clean::ModuleItem(module)) =
+            item.inner.kind
+        else {
+            unreachable!()
+        };
+        for it in module.items {
+            let info = cx.make_child_renderer();
+            run_format_inner(cx, it, prof)?;
+            cx.set_back_info(info);
+        }
+
+        cx.mod_item_out()?;
+    // FIXME: checking `item.name.is_some()` is very implicit and leads to lots of special
+    // cases. Use an explicit match instead.
+    } else if let Some(item_name) = item.name
+        && !item.is_extern_crate()
+    {
+        prof.generic_activity_with_arg("render_item", item_name.as_str()).run(|| cx.item(item))?;
+    }
+    Ok(())
+}
+
 /// Main method for rendering a crate.
 pub(crate) fn run_format<'tcx, T: FormatRenderer<'tcx>>(
     krate: clean::Crate,
@@ -66,36 +102,8 @@ pub(crate) fn run_format<'tcx, T: FormatRenderer<'tcx>>(
     }
 
     // Render the crate documentation
-    let mut work = vec![(format_renderer.make_child_renderer(), krate.module)];
-
-    while let Some((mut cx, item)) = work.pop() {
-        if item.is_mod() && T::RUN_ON_MODULE {
-            // modules are special because they add a namespace. We also need to
-            // recurse into the items of the module as well.
-            let _timer =
-                prof.generic_activity_with_arg("render_mod_item", item.name.unwrap().to_string());
-
-            cx.mod_item_in(&item)?;
-            let (clean::StrippedItem(box clean::ModuleItem(module)) | clean::ModuleItem(module)) =
-                item.inner.kind
-            else {
-                unreachable!()
-            };
-            for it in module.items {
-                debug!("Adding {:?} to worklist", it.name);
-                work.push((cx.make_child_renderer(), it));
-            }
-
-            cx.mod_item_out()?;
-        // FIXME: checking `item.name.is_some()` is very implicit and leads to lots of special
-        // cases. Use an explicit match instead.
-        } else if let Some(item_name) = item.name
-            && !item.is_extern_crate()
-        {
-            prof.generic_activity_with_arg("render_item", item_name.as_str())
-                .run(|| cx.item(item))?;
-        }
-    }
+    run_format_inner(&mut format_renderer, krate.module, prof)?;
+
     prof.verbose_generic_activity_with_arg("renderer_after_krate", T::descr())
         .run(|| format_renderer.after_krate())
 }

src/librustdoc/html/markdown.rs

@@ -32,7 +32,6 @@ use std::iter::Peekable;
 use std::ops::{ControlFlow, Range};
 use std::path::PathBuf;
 use std::str::{self, CharIndices};
-use std::sync::OnceLock;
 
 use pulldown_cmark::{
     BrokenLink, CodeBlockKind, CowStr, Event, LinkType, Options, Parser, Tag, TagEnd, html,
@@ -1886,12 +1885,10 @@ pub(crate) fn rust_code_blocks(md: &str, extra_info: &ExtraInfo<'_>) -> Vec<Rust
 #[derive(Clone, Default, Debug)]
 pub struct IdMap {
     map: FxHashMap<Cow<'static, str>, usize>,
+    defined_ids: FxHashMap<Cow<'static, str>, usize>,
     existing_footnotes: usize,
 }
 
-// The map is pre-initialized and cloned each time to avoid reinitializing it repeatedly.
-static DEFAULT_ID_MAP: OnceLock<FxHashMap<Cow<'static, str>, usize>> = OnceLock::new();
-
 fn init_id_map() -> FxHashMap<Cow<'static, str>, usize> {
     let mut map = FxHashMap::default();
     // This is the list of IDs used in JavaScript.
@@ -1948,7 +1945,7 @@ fn init_id_map() -> FxHashMap<Cow<'static, str>, usize> {
 
 impl IdMap {
     pub fn new() -> Self {
-        IdMap { map: DEFAULT_ID_MAP.get_or_init(init_id_map).clone(), existing_footnotes: 0 }
+        IdMap { map: FxHashMap::default(), defined_ids: init_id_map(), existing_footnotes: 0 }
     }
 
     pub(crate) fn derive<S: AsRef<str> + ToString>(&mut self, candidate: S) -> String {
@@ -1973,4 +1970,9 @@ impl IdMap {
         closure(self, &mut existing_footnotes);
         self.existing_footnotes = existing_footnotes;
     }
+
+    pub(crate) fn clear(&mut self) {
+        self.map = self.defined_ids.clone();
+        self.existing_footnotes = 0;
+    }
 }

src/librustdoc/html/render/context.rs

@@ -49,10 +49,6 @@ pub(crate) struct Context<'tcx> {
     /// The current destination folder of where HTML artifacts should be placed.
     /// This changes as the context descends into the module hierarchy.
     pub(crate) dst: PathBuf,
-    /// A flag, which when `true`, will render pages which redirect to the
-    /// real location of an item. This is used to allow external links to
-    /// publicly reused items to redirect to the right location.
-    pub(super) render_redirect_pages: bool,
     /// Tracks section IDs for `Deref` targets so they match in both the main
     /// body and the sidebar.
     pub(super) deref_id_map: DefIdMap<String>,
@@ -64,21 +60,32 @@ pub(crate) struct Context<'tcx> {
     ///
     /// [#82381]: https://github.com/rust-lang/rust/issues/82381
     pub(crate) shared: Rc<SharedContext<'tcx>>,
+    /// Collection of all types with notable traits referenced in the current module.
+    pub(crate) types_with_notable_traits: FxIndexSet<clean::Type>,
+    /// Contains information that needs to be saved and reset after rendering an item which is
+    /// not a module.
+    pub(crate) info: ContextInfo,
+}
+
+#[derive(Clone, Copy)]
+pub(crate) struct ContextInfo {
+    /// A flag, which when `true`, will render pages which redirect to the
+    /// real location of an item. This is used to allow external links to
+    /// publicly reused items to redirect to the right location.
+    pub(super) render_redirect_pages: bool,
     /// This flag indicates whether source links should be generated or not. If
     /// the source files are present in the html rendering, then this will be
     /// `true`.
     pub(crate) include_sources: bool,
-    /// Collection of all types with notable traits referenced in the current module.
-    pub(crate) types_with_notable_traits: FxIndexSet<clean::Type>,
     /// Field used during rendering, to know if we're inside an inlined item.
     pub(crate) is_inside_inlined_module: bool,
 }
 
-// `Context` is cloned a lot, so we don't want the size to grow unexpectedly.
-#[cfg(all(not(windows), target_pointer_width = "64"))]
-rustc_data_structures::static_assert_size!(Context<'_>, 192);
-#[cfg(all(windows, target_pointer_width = "64"))]
-rustc_data_structures::static_assert_size!(Context<'_>, 200);
+impl ContextInfo {
+    fn new(include_sources: bool) -> Self {
+        Self { render_redirect_pages: false, include_sources, is_inside_inlined_module: false }
+    }
+}
 
 /// Shared mutable state used in [`Context`] and elsewhere.
 pub(crate) struct SharedContext<'tcx> {
@@ -174,14 +181,16 @@ impl<'tcx> Context<'tcx> {
     }
 
     fn render_item(&mut self, it: &clean::Item, is_module: bool) -> String {
-        let mut render_redirect_pages = self.render_redirect_pages;
+        let mut render_redirect_pages = self.info.render_redirect_pages;
         // If the item is stripped but inlined, links won't point to the item so no need to generate
         // a file for it.
         if it.is_stripped()
             && let Some(def_id) = it.def_id()
             && def_id.is_local()
         {
-            if self.is_inside_inlined_module || self.shared.cache.inlined_items.contains(&def_id) {
+            if self.info.is_inside_inlined_module
+                || self.shared.cache.inlined_items.contains(&def_id)
+            {
                 // For now we're forced to generate a redirect page for stripped items until
                 // `record_extern_fqn` correctly points to external items.
                 render_redirect_pages = true;
@@ -441,6 +450,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
     }
 
     const RUN_ON_MODULE: bool = true;
+    type InfoType = ContextInfo;
 
     fn init(
         krate: clean::Crate,
@@ -562,13 +572,11 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         let mut cx = Context {
             current: Vec::new(),
             dst,
-            render_redirect_pages: false,
             id_map,
             deref_id_map: Default::default(),
             shared: Rc::new(scx),
-            include_sources,
             types_with_notable_traits: FxIndexSet::default(),
-            is_inside_inlined_module: false,
+            info: ContextInfo::new(include_sources),
         };
 
         if emit_crate {
@@ -582,18 +590,15 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         Ok((cx, krate))
     }
 
-    fn make_child_renderer(&self) -> Self {
-        Self {
-            current: self.current.clone(),
-            dst: self.dst.clone(),
-            render_redirect_pages: self.render_redirect_pages,
-            deref_id_map: Default::default(),
-            id_map: IdMap::new(),
-            shared: Rc::clone(&self.shared),
-            include_sources: self.include_sources,
-            types_with_notable_traits: FxIndexSet::default(),
-            is_inside_inlined_module: self.is_inside_inlined_module,
-        }
+    fn make_child_renderer(&mut self) -> Self::InfoType {
+        self.deref_id_map.clear();
+        self.id_map.clear();
+        self.types_with_notable_traits.clear();
+        self.info
+    }
+
+    fn set_back_info(&mut self, info: Self::InfoType) {
+        self.info = info;
     }
 
     fn after_krate(&mut self) -> Result<(), Error> {
@@ -775,8 +780,8 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         // External crates will provide links to these structures, so
         // these modules are recursed into, but not rendered normally
         // (a flag on the context).
-        if !self.render_redirect_pages {
-            self.render_redirect_pages = item.is_stripped();
+        if !self.info.render_redirect_pages {
+            self.info.render_redirect_pages = item.is_stripped();
         }
         let item_name = item.name.unwrap();
         self.dst.push(&*item_name.as_str());
@@ -793,19 +798,19 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
                 self.shared.fs.write(joint_dst, buf)?;
             }
         }
-        if !self.is_inside_inlined_module {
+        if !self.info.is_inside_inlined_module {
             if let Some(def_id) = item.def_id()
                 && self.cache().inlined_items.contains(&def_id)
             {
-                self.is_inside_inlined_module = true;
+                self.info.is_inside_inlined_module = true;
             }
         } else if !self.cache().document_hidden && item.is_doc_hidden() {
             // We're not inside an inlined module anymore since this one cannot be re-exported.
-            self.is_inside_inlined_module = false;
+            self.info.is_inside_inlined_module = false;
         }
 
         // Render sidebar-items.js used throughout this module.
-        if !self.render_redirect_pages {
+        if !self.info.render_redirect_pages {
             let (clean::StrippedItem(box clean::ModuleItem(ref module))
             | clean::ModuleItem(ref module)) = item.kind
             else {
@@ -836,8 +841,8 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         // External crates will provide links to these structures, so
         // these modules are recursed into, but not rendered normally
         // (a flag on the context).
-        if !self.render_redirect_pages {
-            self.render_redirect_pages = item.is_stripped();
+        if !self.info.render_redirect_pages {
+            self.info.render_redirect_pages = item.is_stripped();
         }
 
         let buf = self.render_item(&item, false);
@@ -850,7 +855,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             let joint_dst = self.dst.join(file_name);
             self.shared.fs.write(joint_dst, buf)?;
 
-            if !self.render_redirect_pages {
+            if !self.info.render_redirect_pages {
                 self.shared.all.borrow_mut().append(full_path(self, &item), &item_type);
             }
             // If the item is a macro, redirect from the old macro URL (with !)

src/librustdoc/html/render/print_item.rs

@@ -223,7 +223,7 @@ pub(super) fn print_item(cx: &mut Context<'_>, item: &clean::Item, buf: &mut Buf
     // this page, and this link will be auto-clicked. The `id` attribute is
     // used to find the link to auto-click.
     let src_href =
-        if cx.include_sources && !item.is_primitive() { cx.src_href(item) } else { None };
+        if cx.info.include_sources && !item.is_primitive() { cx.src_href(item) } else { None };
 
     let path_components = if item.is_primitive() || item.is_keyword() {
         vec![]

src/librustdoc/html/render/write_shared.rs

@@ -104,7 +104,7 @@ pub(crate) fn write_shared(
             &cx.shared.style_files,
             cx.shared.layout.css_file_extension.as_deref(),
             &cx.shared.resource_suffix,
-            cx.include_sources,
+            cx.info.include_sources,
         )?;
         match &opt.index_page {
             Some(index_page) if opt.enable_index_page => {

src/librustdoc/html/sources.rs

@@ -124,7 +124,7 @@ struct SourceCollector<'a, 'tcx> {
 
 impl DocVisitor<'_> for SourceCollector<'_, '_> {
     fn visit_item(&mut self, item: &clean::Item) {
-        if !self.cx.include_sources {
+        if !self.cx.info.include_sources {
             return;
         }
 
@@ -146,7 +146,7 @@ impl DocVisitor<'_> for SourceCollector<'_, '_> {
             // something like that), so just don't include sources for the
             // entire crate. The other option is maintaining this mapping on a
             // per-file basis, but that's probably not worth it...
-            self.cx.include_sources = match self.emit_source(&filename, file_span) {
+            self.cx.info.include_sources = match self.emit_source(&filename, file_span) {
                 Ok(()) => true,
                 Err(e) => {
                     self.cx.shared.tcx.dcx().span_err(

src/librustdoc/json/mod.rs

@@ -137,6 +137,7 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
     }
 
     const RUN_ON_MODULE: bool = false;
+    type InfoType = ();
 
     fn init(
         krate: clean::Crate,
@@ -161,9 +162,8 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
         ))
     }
 
-    fn make_child_renderer(&self) -> Self {
-        self.clone()
-    }
+    fn make_child_renderer(&mut self) -> Self::InfoType {}
+    fn set_back_info(&mut self, _info: Self::InfoType) {}
 
     /// Inserts an item into the index. This should be used rather than directly calling insert on
     /// the hashmap because certain items (traits and types) need to have their mappings for trait