Move reachable.rs to librustc_passes.

1 files changed, 0 insertions, 437 deletions

diff --git a/src/librustc/middle/reachable.rs b/src/librustc/middle/reachable.rs
deleted file mode 100644
index c6598f2d328..00000000000
--- a/src/librustc/middle/reachable.rs
+++ /dev/null
@@ -1,437 +0,0 @@
-// Finds items that are externally reachable, to determine which items
-// need to have their metadata (and possibly their AST) serialized.
-// All items that can be referred to through an exported name are
-// reachable, and when a reachable thing is inline or generic, it
-// makes all other generics or inline functions that it references
-// reachable as well.
-
-use crate::hir::def::{DefKind, Res};
-use crate::hir::def_id::{CrateNum, DefId};
-use crate::hir::Node;
-use crate::hir::{CodegenFnAttrFlags, CodegenFnAttrs};
-use crate::middle::privacy;
-use crate::session::config;
-use crate::ty::query::Providers;
-use crate::ty::{self, TyCtxt};
-use crate::util::nodemap::{FxHashSet, HirIdSet};
-use rustc_data_structures::sync::Lrc;
-
-use crate::hir;
-use crate::hir::def_id::LOCAL_CRATE;
-use crate::hir::intravisit;
-use crate::hir::intravisit::{NestedVisitorMap, Visitor};
-use crate::hir::itemlikevisit::ItemLikeVisitor;
-use rustc_macros::HashStable;
-use rustc_target::spec::abi::Abi;
-
-// Returns true if the given item must be inlined because it may be
-// monomorphized or it was marked with `#[inline]`. This will only return
-// true for functions.
-fn item_might_be_inlined(tcx: TyCtxt<'tcx>, item: &hir::Item<'_>, attrs: CodegenFnAttrs) -> bool {
-    if attrs.requests_inline() {
-        return true;
-    }
-
-    match item.kind {
-        hir::ItemKind::Fn(ref sig, ..) if sig.header.is_const() => {
-            return true;
-        }
-        hir::ItemKind::Impl(..) | hir::ItemKind::Fn(..) => {
-            let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
-            generics.requires_monomorphization(tcx)
-        }
-        _ => false,
-    }
-}
-
-fn method_might_be_inlined(
-    tcx: TyCtxt<'_>,
-    impl_item: &hir::ImplItem<'_>,
-    impl_src: DefId,
-) -> bool {
-    let codegen_fn_attrs = tcx.codegen_fn_attrs(impl_item.hir_id.owner_def_id());
-    let generics = tcx.generics_of(tcx.hir().local_def_id(impl_item.hir_id));
-    if codegen_fn_attrs.requests_inline() || generics.requires_monomorphization(tcx) {
-        return true;
-    }
-    if let hir::ImplItemKind::Method(method_sig, _) = &impl_item.kind {
-        if method_sig.header.is_const() {
-            return true;
-        }
-    }
-    if let Some(impl_hir_id) = tcx.hir().as_local_hir_id(impl_src) {
-        match tcx.hir().find(impl_hir_id) {
-            Some(Node::Item(item)) => item_might_be_inlined(tcx, &item, codegen_fn_attrs),
-            Some(..) | None => span_bug!(impl_item.span, "impl did is not an item"),
-        }
-    } else {
-        span_bug!(impl_item.span, "found a foreign impl as a parent of a local method")
-    }
-}
-
-// Information needed while computing reachability.
-struct ReachableContext<'a, 'tcx> {
-    // The type context.
-    tcx: TyCtxt<'tcx>,
-    tables: &'a ty::TypeckTables<'tcx>,
-    // The set of items which must be exported in the linkage sense.
-    reachable_symbols: HirIdSet,
-    // A worklist of item IDs. Each item ID in this worklist will be inlined
-    // and will be scanned for further references.
-    worklist: Vec<hir::HirId>,
-    // Whether any output of this compilation is a library
-    any_library: bool,
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for ReachableContext<'a, 'tcx> {
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
-        NestedVisitorMap::None
-    }
-
-    fn visit_nested_body(&mut self, body: hir::BodyId) {
-        let old_tables = self.tables;
-        self.tables = self.tcx.body_tables(body);
-        let body = self.tcx.hir().body(body);
-        self.visit_body(body);
-        self.tables = old_tables;
-    }
-
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
-        let res = match expr.kind {
-            hir::ExprKind::Path(ref qpath) => Some(self.tables.qpath_res(qpath, expr.hir_id)),
-            hir::ExprKind::MethodCall(..) => self
-                .tables
-                .type_dependent_def(expr.hir_id)
-                .map(|(kind, def_id)| Res::Def(kind, def_id)),
-            _ => None,
-        };
-
-        match res {
-            Some(Res::Local(hir_id)) => {
-                self.reachable_symbols.insert(hir_id);
-            }
-            Some(res) => {
-                if let Some((hir_id, def_id)) = res.opt_def_id().and_then(|def_id| {
-                    self.tcx.hir().as_local_hir_id(def_id).map(|hir_id| (hir_id, def_id))
-                }) {
-                    if self.def_id_represents_local_inlined_item(def_id) {
-                        self.worklist.push(hir_id);
-                    } else {
-                        match res {
-                            // If this path leads to a constant, then we need to
-                            // recurse into the constant to continue finding
-                            // items that are reachable.
-                            Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => {
-                                self.worklist.push(hir_id);
-                            }
-
-                            // If this wasn't a static, then the destination is
-                            // surely reachable.
-                            _ => {
-                                self.reachable_symbols.insert(hir_id);
-                            }
-                        }
-                    }
-                }
-            }
-            _ => {}
-        }
-
-        intravisit::walk_expr(self, expr)
-    }
-}
-
-impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
-    // Returns true if the given def ID represents a local item that is
-    // eligible for inlining and false otherwise.
-    fn def_id_represents_local_inlined_item(&self, def_id: DefId) -> bool {
-        let hir_id = match self.tcx.hir().as_local_hir_id(def_id) {
-            Some(hir_id) => hir_id,
-            None => {
-                return false;
-            }
-        };
-
-        match self.tcx.hir().find(hir_id) {
-            Some(Node::Item(item)) => match item.kind {
-                hir::ItemKind::Fn(..) => {
-                    item_might_be_inlined(self.tcx, &item, self.tcx.codegen_fn_attrs(def_id))
-                }
-                _ => false,
-            },
-            Some(Node::TraitItem(trait_method)) => match trait_method.kind {
-                hir::TraitItemKind::Const(_, ref default) => default.is_some(),
-                hir::TraitItemKind::Method(_, hir::TraitMethod::Provided(_)) => true,
-                hir::TraitItemKind::Method(_, hir::TraitMethod::Required(_))
-                | hir::TraitItemKind::Type(..) => false,
-            },
-            Some(Node::ImplItem(impl_item)) => {
-                match impl_item.kind {
-                    hir::ImplItemKind::Const(..) => true,
-                    hir::ImplItemKind::Method(..) => {
-                        let attrs = self.tcx.codegen_fn_attrs(def_id);
-                        let generics = self.tcx.generics_of(def_id);
-                        if generics.requires_monomorphization(self.tcx) || attrs.requests_inline() {
-                            true
-                        } else {
-                            let impl_did = self.tcx.hir().get_parent_did(hir_id);
-                            // Check the impl. If the generics on the self
-                            // type of the impl require inlining, this method
-                            // does too.
-                            let impl_hir_id = self.tcx.hir().as_local_hir_id(impl_did).unwrap();
-                            match self.tcx.hir().expect_item(impl_hir_id).kind {
-                                hir::ItemKind::Impl(..) => {
-                                    let generics = self.tcx.generics_of(impl_did);
-                                    generics.requires_monomorphization(self.tcx)
-                                }
-                                _ => false,
-                            }
-                        }
-                    }
-                    hir::ImplItemKind::OpaqueTy(..) | hir::ImplItemKind::TyAlias(_) => false,
-                }
-            }
-            Some(_) => false,
-            None => false, // This will happen for default methods.
-        }
-    }
-
-    // Step 2: Mark all symbols that the symbols on the worklist touch.
-    fn propagate(&mut self) {
-        let mut scanned = FxHashSet::default();
-        while let Some(search_item) = self.worklist.pop() {
-            if !scanned.insert(search_item) {
-                continue;
-            }
-
-            if let Some(ref item) = self.tcx.hir().find(search_item) {
-                self.propagate_node(item, search_item);
-            }
-        }
-    }
-
-    fn propagate_node(&mut self, node: &Node<'tcx>, search_item: hir::HirId) {
-        if !self.any_library {
-            // If we are building an executable, only explicitly extern
-            // types need to be exported.
-            if let Node::Item(item) = *node {
-                let reachable = if let hir::ItemKind::Fn(ref sig, ..) = item.kind {
-                    sig.header.abi != Abi::Rust
-                } else {
-                    false
-                };
-                let def_id = self.tcx.hir().local_def_id(item.hir_id);
-                let codegen_attrs = self.tcx.codegen_fn_attrs(def_id);
-                let is_extern = codegen_attrs.contains_extern_indicator();
-                let std_internal =
-                    codegen_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL);
-                if reachable || is_extern || std_internal {
-                    self.reachable_symbols.insert(search_item);
-                }
-            }
-        } else {
-            // If we are building a library, then reachable symbols will
-            // continue to participate in linkage after this product is
-            // produced. In this case, we traverse the ast node, recursing on
-            // all reachable nodes from this one.
-            self.reachable_symbols.insert(search_item);
-        }
-
-        match *node {
-            Node::Item(item) => {
-                match item.kind {
-                    hir::ItemKind::Fn(.., body) => {
-                        let def_id = self.tcx.hir().local_def_id(item.hir_id);
-                        if item_might_be_inlined(self.tcx, &item, self.tcx.codegen_fn_attrs(def_id))
-                        {
-                            self.visit_nested_body(body);
-                        }
-                    }
-
-                    // Reachable constants will be inlined into other crates
-                    // unconditionally, so we need to make sure that their
-                    // contents are also reachable.
-                    hir::ItemKind::Const(_, init) => {
-                        self.visit_nested_body(init);
-                    }
-
-                    // These are normal, nothing reachable about these
-                    // inherently and their children are already in the
-                    // worklist, as determined by the privacy pass
-                    hir::ItemKind::ExternCrate(_)
-                    | hir::ItemKind::Use(..)
-                    | hir::ItemKind::OpaqueTy(..)
-                    | hir::ItemKind::TyAlias(..)
-                    | hir::ItemKind::Static(..)
-                    | hir::ItemKind::Mod(..)
-                    | hir::ItemKind::ForeignMod(..)
-                    | hir::ItemKind::Impl(..)
-                    | hir::ItemKind::Trait(..)
-                    | hir::ItemKind::TraitAlias(..)
-                    | hir::ItemKind::Struct(..)
-                    | hir::ItemKind::Enum(..)
-                    | hir::ItemKind::Union(..)
-                    | hir::ItemKind::GlobalAsm(..) => {}
-                }
-            }
-            Node::TraitItem(trait_method) => {
-                match trait_method.kind {
-                    hir::TraitItemKind::Const(_, None)
-                    | hir::TraitItemKind::Method(_, hir::TraitMethod::Required(_)) => {
-                        // Keep going, nothing to get exported
-                    }
-                    hir::TraitItemKind::Const(_, Some(body_id))
-                    | hir::TraitItemKind::Method(_, hir::TraitMethod::Provided(body_id)) => {
-                        self.visit_nested_body(body_id);
-                    }
-                    hir::TraitItemKind::Type(..) => {}
-                }
-            }
-            Node::ImplItem(impl_item) => match impl_item.kind {
-                hir::ImplItemKind::Const(_, body) => {
-                    self.visit_nested_body(body);
-                }
-                hir::ImplItemKind::Method(_, body) => {
-                    let did = self.tcx.hir().get_parent_did(search_item);
-                    if method_might_be_inlined(self.tcx, impl_item, did) {
-                        self.visit_nested_body(body)
-                    }
-                }
-                hir::ImplItemKind::OpaqueTy(..) | hir::ImplItemKind::TyAlias(_) => {}
-            },
-            Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., body, _, _), .. }) => {
-                self.visit_nested_body(body);
-            }
-            // Nothing to recurse on for these
-            Node::ForeignItem(_)
-            | Node::Variant(_)
-            | Node::Ctor(..)
-            | Node::Field(_)
-            | Node::Ty(_)
-            | Node::MacroDef(_) => {}
-            _ => {
-                bug!(
-                    "found unexpected node kind in worklist: {} ({:?})",
-                    self.tcx.hir().node_to_string(search_item),
-                    node,
-                );
-            }
-        }
-    }
-}
-
-// Some methods from non-exported (completely private) trait impls still have to be
-// reachable if they are called from inlinable code. Generally, it's not known until
-// monomorphization if a specific trait impl item can be reachable or not. So, we
-// conservatively mark all of them as reachable.
-// FIXME: One possible strategy for pruning the reachable set is to avoid marking impl
-// items of non-exported traits (or maybe all local traits?) unless their respective
-// trait items are used from inlinable code through method call syntax or UFCS, or their
-// trait is a lang item.
-struct CollectPrivateImplItemsVisitor<'a, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    access_levels: &'a privacy::AccessLevels,
-    worklist: &'a mut Vec<hir::HirId>,
-}
-
-impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a, 'tcx> {
-    fn visit_item(&mut self, item: &hir::Item<'_>) {
-        // Anything which has custom linkage gets thrown on the worklist no
-        // matter where it is in the crate, along with "special std symbols"
-        // which are currently akin to allocator symbols.
-        let def_id = self.tcx.hir().local_def_id(item.hir_id);
-        let codegen_attrs = self.tcx.codegen_fn_attrs(def_id);
-        if codegen_attrs.contains_extern_indicator()
-            || codegen_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
-        {
-            self.worklist.push(item.hir_id);
-        }
-
-        // We need only trait impls here, not inherent impls, and only non-exported ones
-        if let hir::ItemKind::Impl(.., Some(ref trait_ref), _, ref impl_item_refs) = item.kind {
-            if !self.access_levels.is_reachable(item.hir_id) {
-                self.worklist.extend(impl_item_refs.iter().map(|ii_ref| ii_ref.id.hir_id));
-
-                let trait_def_id = match trait_ref.path.res {
-                    Res::Def(DefKind::Trait, def_id) => def_id,
-                    _ => unreachable!(),
-                };
-
-                if !trait_def_id.is_local() {
-                    return;
-                }
-
-                let provided_trait_methods = self.tcx.provided_trait_methods(trait_def_id);
-                self.worklist.reserve(provided_trait_methods.len());
-                for default_method in provided_trait_methods {
-                    let hir_id = self.tcx.hir().as_local_hir_id(default_method.def_id).unwrap();
-                    self.worklist.push(hir_id);
-                }
-            }
-        }
-    }
-
-    fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
-
-    fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {
-        // processed in visit_item above
-    }
-}
-
-// We introduce a new-type here, so we can have a specialized HashStable
-// implementation for it.
-#[derive(Clone, HashStable)]
-pub struct ReachableSet(pub Lrc<HirIdSet>);
-
-fn reachable_set(tcx: TyCtxt<'_>, crate_num: CrateNum) -> ReachableSet {
-    debug_assert!(crate_num == LOCAL_CRATE);
-
-    let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
-
-    let any_library = tcx.sess.crate_types.borrow().iter().any(|ty| {
-        *ty == config::CrateType::Rlib
-            || *ty == config::CrateType::Dylib
-            || *ty == config::CrateType::ProcMacro
-    });
-    let mut reachable_context = ReachableContext {
-        tcx,
-        tables: &ty::TypeckTables::empty(None),
-        reachable_symbols: Default::default(),
-        worklist: Vec::new(),
-        any_library,
-    };
-
-    // Step 1: Seed the worklist with all nodes which were found to be public as
-    //         a result of the privacy pass along with all local lang items and impl items.
-    //         If other crates link to us, they're going to expect to be able to
-    //         use the lang items, so we need to be sure to mark them as
-    //         exported.
-    reachable_context.worklist.extend(access_levels.map.iter().map(|(id, _)| *id));
-    for item in tcx.lang_items().items().iter() {
-        if let Some(did) = *item {
-            if let Some(hir_id) = tcx.hir().as_local_hir_id(did) {
-                reachable_context.worklist.push(hir_id);
-            }
-        }
-    }
-    {
-        let mut collect_private_impl_items = CollectPrivateImplItemsVisitor {
-            tcx,
-            access_levels,
-            worklist: &mut reachable_context.worklist,
-        };
-        tcx.hir().krate().visit_all_item_likes(&mut collect_private_impl_items);
-    }
-
-    // Step 2: Mark all symbols that the symbols on the worklist touch.
-    reachable_context.propagate();
-
-    debug!("Inline reachability shows: {:?}", reachable_context.reachable_symbols);
-
-    // Return the set of reachable symbols.
-    ReachableSet(Lrc::new(reachable_context.reachable_symbols))
-}
-
-pub fn provide(providers: &mut Providers<'_>) {
-    *providers = Providers { reachable_set, ..*providers };
-}