Rollup merge of rust-lang#57573 - Xanewok:querify-entry-fn, r=Zoxc

Querify `entry_fn`

Analogous to rust-lang#57570 but this will also require few fixups in Miri so I decided to separate that (and it seems [CI doesn't let us break tools anymore](rust-lang#57392 (comment))? Or was that because it was a rollup PR?)

r? @nikomatsakis

src/librustc/dep_graph/dep_node.rs

@@ -583,6 +583,7 @@ define_dep_nodes!( <'tcx>
     [] CheckImplItemWellFormed(DefId),
     [] ReachableNonGenerics(CrateNum),
     [] NativeLibraries(CrateNum),
+    [] EntryFn(CrateNum),
     [] PluginRegistrarFn(CrateNum),
     [] ProcMacroDeclsStatic(CrateNum),
     [input] CrateDisambiguator(CrateNum),

src/librustc/middle/dead.rs

@@ -409,7 +409,7 @@ fn create_and_seed_worklist<'a, 'tcx>(
         }
     }).chain(
         // Seed entry point
-        tcx.sess.entry_fn.borrow().map(|(id, _, _)| id)
+        tcx.entry_fn(LOCAL_CRATE).map(|(def_id, _)| tcx.hir().as_local_node_id(def_id).unwrap())
     ).collect::<Vec<_>>();
 
     // Seed implemented trait items

src/librustc/middle/entry.rs

@@ -1,5 +1,5 @@
 use hir::map as hir_map;
-use hir::def_id::{CRATE_DEF_INDEX};
+use hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, LOCAL_CRATE};
 use session::{config, Session};
 use session::config::EntryFnType;
 use syntax::ast::NodeId;
@@ -8,6 +8,8 @@ use syntax::entry::EntryPointType;
 use syntax_pos::Span;
 use hir::{Item, ItemKind, ImplItem, TraitItem};
 use hir::itemlikevisit::ItemLikeVisitor;
+use ty::TyCtxt;
+use ty::query::Providers;
 
 struct EntryContext<'a, 'tcx: 'a> {
     session: &'a Session,
@@ -45,36 +47,34 @@ impl<'a, 'tcx> ItemLikeVisitor<'tcx> for EntryContext<'a, 'tcx> {
     }
 }
 
-pub fn find_entry_point(session: &Session,
-                        hir_map: &hir_map::Map<'_>,
-                        crate_name: &str) {
-    let any_exe = session.crate_types.borrow().iter().any(|ty| {
+fn entry_fn(tcx: TyCtxt<'_, '_, '_>, cnum: CrateNum) -> Option<(DefId, EntryFnType)> {
+    assert_eq!(cnum, LOCAL_CRATE);
+
+    let any_exe = tcx.sess.crate_types.borrow().iter().any(|ty| {
         *ty == config::CrateType::Executable
     });
     if !any_exe {
         // No need to find a main function
-        session.entry_fn.set(None);
-        return
+        return None;
     }
 
     // If the user wants no main function at all, then stop here.
-    if attr::contains_name(&hir_map.krate().attrs, "no_main") {
-        session.entry_fn.set(None);
-        return
+    if attr::contains_name(&tcx.hir().krate().attrs, "no_main") {
+        return None;
     }
 
     let mut ctxt = EntryContext {
-        session,
-        map: hir_map,
+        session: tcx.sess,
+        map: tcx.hir(),
         main_fn: None,
         attr_main_fn: None,
         start_fn: None,
         non_main_fns: Vec::new(),
     };
 
-    hir_map.krate().visit_all_item_likes(&mut ctxt);
+    tcx.hir().krate().visit_all_item_likes(&mut ctxt);
 
-    configure_main(&mut ctxt, crate_name);
+    configure_main(tcx, &ctxt)
 }
 
 // Beware, this is duplicated in `libsyntax/entry.rs`, so make sure to keep
@@ -135,43 +135,58 @@ fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
                     .span_label(item.span, "multiple `start` functions")
                     .emit();
             }
-        },
-        EntryPointType::None => ()
+        }
+        EntryPointType::None => (),
     }
 }
 
-fn configure_main(this: &mut EntryContext<'_, '_>, crate_name: &str) {
-    if let Some((node_id, span)) = this.start_fn {
-        this.session.entry_fn.set(Some((node_id, span, EntryFnType::Start)));
-    } else if let Some((node_id, span)) = this.attr_main_fn {
-        this.session.entry_fn.set(Some((node_id, span, EntryFnType::Main)));
-    } else if let Some((node_id, span)) = this.main_fn {
-        this.session.entry_fn.set(Some((node_id, span, EntryFnType::Main)));
+fn configure_main(
+    tcx: TyCtxt<'_, '_, '_>,
+    visitor: &EntryContext<'_, '_>,
+) -> Option<(DefId, EntryFnType)> {
+    if let Some((node_id, _)) = visitor.start_fn {
+        Some((tcx.hir().local_def_id(node_id), EntryFnType::Start))
+    } else if let Some((node_id, _)) = visitor.attr_main_fn {
+        Some((tcx.hir().local_def_id(node_id), EntryFnType::Main))
+    } else if let Some((node_id, _)) = visitor.main_fn {
+        Some((tcx.hir().local_def_id(node_id), EntryFnType::Main))
     } else {
         // No main function
-        this.session.entry_fn.set(None);
-        let mut err = struct_err!(this.session, E0601,
-            "`main` function not found in crate `{}`", crate_name);
-        if !this.non_main_fns.is_empty() {
+        let mut err = struct_err!(tcx.sess, E0601,
+            "`main` function not found in crate `{}`", tcx.crate_name(LOCAL_CRATE));
+        if !visitor.non_main_fns.is_empty() {
             // There were some functions named 'main' though. Try to give the user a hint.
             err.note("the main function must be defined at the crate level \
                       but you have one or more functions named 'main' that are not \
                       defined at the crate level. Either move the definition or \
                       attach the `#[main]` attribute to override this behavior.");
-            for &(_, span) in &this.non_main_fns {
+            for &(_, span) in &visitor.non_main_fns {
                 err.span_note(span, "here is a function named 'main'");
             }
             err.emit();
-            this.session.abort_if_errors();
+            tcx.sess.abort_if_errors();
         } else {
-            if let Some(ref filename) = this.session.local_crate_source_file {
+            if let Some(ref filename) = tcx.sess.local_crate_source_file {
                 err.note(&format!("consider adding a `main` function to `{}`", filename.display()));
             }
-            if this.session.teach(&err.get_code().unwrap()) {
+            if tcx.sess.teach(&err.get_code().unwrap()) {
                 err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
                           to get started: https://doc.rust-lang.org/book/");
             }
             err.emit();
         }
+
+        None
     }
 }
+
+pub fn find_entry_point(tcx: TyCtxt<'_, '_, '_>) -> Option<(DefId, EntryFnType)> {
+    tcx.entry_fn(LOCAL_CRATE)
+}
+
+pub fn provide(providers: &mut Providers<'_>) {
+    *providers = Providers {
+        entry_fn,
+        ..*providers
+    };
+}

src/librustc/session/config.rs

@@ -649,15 +649,15 @@ impl Options {
     }
 }
 
-// The type of entry function, so
-// users can have their own entry
-// functions
-#[derive(Copy, Clone, PartialEq)]
+// The type of entry function, so users can have their own entry functions
+#[derive(Copy, Clone, PartialEq, Hash, Debug)]
 pub enum EntryFnType {
     Main,
     Start,
 }
 
+impl_stable_hash_via_hash!(EntryFnType);
+
 #[derive(Copy, PartialEq, PartialOrd, Clone, Ord, Eq, Hash, Debug)]
 pub enum CrateType {
     Executable,

src/librustc/session/mod.rs

@@ -67,8 +67,6 @@ pub struct Session {
     /// This is `None` if the host and target are the same.
     pub target_tlib_path: Option<SearchPath>,
     pub parse_sess: ParseSess,
-    /// For a library crate, this is always none
-    pub entry_fn: Once<Option<(NodeId, Span, config::EntryFnType)>>,
     pub sysroot: PathBuf,
     /// The name of the root source file of the crate, in the local file system.
     /// `None` means that there is no source file.
@@ -1173,8 +1171,6 @@ pub fn build_session_(
         host_tlib_path,
         target_tlib_path,
         parse_sess: p_s,
-        // For a library crate, this is always none
-        entry_fn: Once::new(),
         sysroot,
         local_crate_source_file,
         working_dir,

src/librustc/ty/query/config.rs

@@ -629,6 +629,12 @@ impl<'tcx> QueryDescription<'tcx> for queries::foreign_modules<'tcx> {
     }
 }
 
+impl<'tcx> QueryDescription<'tcx> for queries::entry_fn<'tcx> {
+    fn describe(_tcx: TyCtxt<'_, '_, '_>, _: CrateNum) -> Cow<'static, str> {
+        "looking up the entry function of a crate".into()
+    }
+}
+
 impl<'tcx> QueryDescription<'tcx> for queries::plugin_registrar_fn<'tcx> {
     fn describe(_tcx: TyCtxt<'_, '_, '_>, _: CrateNum) -> Cow<'static, str> {
         "looking up the plugin registrar for a crate".into()

src/librustc/ty/query/mod.rs

@@ -22,7 +22,7 @@ use mir::mono::CodegenUnit;
 use mir;
 use mir::interpret::GlobalId;
 use session::{CompileResult, CrateDisambiguator};
-use session::config::OutputFilenames;
+use session::config::{EntryFnType, OutputFilenames};
 use traits::{self, Vtable};
 use traits::query::{
     CanonicalPredicateGoal, CanonicalProjectionGoal,
@@ -476,6 +476,9 @@ define_queries! { <'tcx>
 
         [] fn foreign_modules: ForeignModules(CrateNum) -> Lrc<Vec<ForeignModule>>,
 
+        /// Identifies the entry-point (e.g. the `main` function) for a given
+        /// crate, returning `None` if there is no entry point (such as for library crates).
+        [] fn entry_fn: EntryFn(CrateNum) -> Option<(DefId, EntryFnType)>,
         [] fn plugin_registrar_fn: PluginRegistrarFn(CrateNum) -> Option<DefId>,
         [] fn proc_macro_decls_static: ProcMacroDeclsStatic(CrateNum) -> Option<DefId>,
         [] fn crate_disambiguator: CrateDisambiguator(CrateNum) -> CrateDisambiguator,

src/librustc/ty/query/plumbing.rs

@@ -1329,6 +1329,7 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::CheckImplItemWellFormed => { force!(check_impl_item_well_formed, def_id!()); }
         DepKind::ReachableNonGenerics => { force!(reachable_non_generics, krate!()); }
         DepKind::NativeLibraries => { force!(native_libraries, krate!()); }
+        DepKind::EntryFn => { force!(entry_fn, krate!()); }
         DepKind::PluginRegistrarFn => { force!(plugin_registrar_fn, krate!()); }
         DepKind::ProcMacroDeclsStatic => { force!(proc_macro_decls_static, krate!()); }
         DepKind::CrateDisambiguator => { force!(crate_disambiguator, krate!()); }

src/librustc_codegen_llvm/debuginfo/mod.rs

@@ -14,7 +14,7 @@ use llvm;
 use llvm::debuginfo::{DIFile, DIType, DIScope, DIBuilder, DISubprogram, DIArray, DIFlags,
     DILexicalBlock};
 use rustc::hir::CodegenFnAttrFlags;
-use rustc::hir::def_id::{DefId, CrateNum};
+use rustc::hir::def_id::{DefId, CrateNum, LOCAL_CRATE};
 use rustc::ty::subst::{Substs, UnpackedKind};
 
 use abi::Abi;
@@ -290,9 +290,8 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
         let mut flags = DIFlags::FlagPrototyped;
 
-        let local_id = self.tcx().hir().as_local_node_id(def_id);
-        if let Some((id, _, _)) = *self.sess().entry_fn.borrow() {
-            if local_id == Some(id) {
+        if let Some((id, _)) = self.tcx.entry_fn(LOCAL_CRATE) {
+            if id == def_id {
                 flags |= DIFlags::FlagMainSubprogram;
             }
         }

src/librustc_codegen_ssa/back/symbol_export.rs

@@ -194,7 +194,7 @@ fn exported_symbols_provider_local<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                  })
                                  .collect();
 
-    if tcx.sess.entry_fn.borrow().is_some() {
+    if tcx.entry_fn(LOCAL_CRATE).is_some() {
         let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new("main"));
 
         symbols.push((exported_symbol, SymbolExportLevel::C));

src/librustc_codegen_ssa/base.rs

@@ -441,10 +441,8 @@ pub fn codegen_instance<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
 pub fn maybe_create_entry_wrapper<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
     cx: &'a Bx::CodegenCx
 ) {
-    let (main_def_id, span) = match *cx.sess().entry_fn.borrow() {
-        Some((id, span, _)) => {
-            (cx.tcx().hir().local_def_id(id), span)
-        }
+    let (main_def_id, span) = match cx.tcx().entry_fn(LOCAL_CRATE) {
+        Some((def_id, _)) => { (def_id, cx.tcx().def_span(def_id)) },
         None => return,
     };
 
@@ -458,7 +456,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
 
     let main_llfn = cx.get_fn(instance);
 
-    let et = cx.sess().entry_fn.get().map(|e| e.2);
+    let et = cx.tcx().entry_fn(LOCAL_CRATE).map(|e| e.1);
     match et {
         Some(EntryFnType::Main) => create_entry_fn::<Bx>(cx, span, main_llfn, main_def_id, true),
         Some(EntryFnType::Start) => create_entry_fn::<Bx>(cx, span, main_llfn, main_def_id, false),

src/librustc_codegen_utils/lib.rs

@@ -31,6 +31,7 @@ extern crate syntax_pos;
 #[macro_use] extern crate rustc_data_structures;
 
 use rustc::ty::TyCtxt;
+use rustc::hir::def_id::LOCAL_CRATE;
 
 pub mod link;
 pub mod codegen_backend;
@@ -42,11 +43,9 @@ pub mod symbol_names_test;
 /// that actually test that compilation succeeds without
 /// reporting an error.
 pub fn check_for_rustc_errors_attr(tcx: TyCtxt) {
-    if let Some((id, span, _)) = *tcx.sess.entry_fn.borrow() {
-        let main_def_id = tcx.hir().local_def_id(id);
-
-        if tcx.has_attr(main_def_id, "rustc_error") {
-            tcx.sess.span_fatal(span, "compilation successful");
+    if let Some((def_id, _)) = tcx.entry_fn(LOCAL_CRATE) {
+        if tcx.has_attr(def_id, "rustc_error") {
+            tcx.sess.span_fatal(tcx.def_span(def_id), "compilation successful");
         }
     }
 }

src/librustc_driver/driver.rs

@@ -1149,6 +1149,7 @@ pub fn default_provide(providers: &mut ty::query::Providers) {
     rustc_passes::provide(providers);
     rustc_traits::provide(providers);
     middle::region::provide(providers);
+    middle::entry::provide(providers);
     cstore::provide(providers);
     lint::provide(providers);
 }
@@ -1183,10 +1184,6 @@ where
         rustc_incremental::load_query_result_cache(sess)
     });
 
-    time(sess, "looking for entry point", || {
-        middle::entry::find_entry_point(sess, &hir_map, name)
-    });
-
     let mut local_providers = ty::query::Providers::default();
     default_provide(&mut local_providers);
     codegen_backend.provide(&mut local_providers);
@@ -1216,6 +1213,10 @@ where
             // tcx available.
             time(sess, "dep graph tcx init", || rustc_incremental::dep_graph_tcx_init(tcx));
 
+            time(sess, "looking for entry point", || {
+                middle::entry::find_entry_point(tcx)
+            });
+
             time(sess, "looking for plugin registrar", || {
                 plugin::build::find_plugin_registrar(tcx)
             });