make reachable_set ref-counted

Once it is computed, no need to deep clone the set.

src/librustc/middle/reachable.rs

@@ -18,6 +18,7 @@
 use hir::map as hir_map;
 use hir::def::Def;
 use hir::def_id::{DefId, CrateNum};
+use std::rc::Rc;
 use ty::{self, TyCtxt};
 use ty::maps::Providers;
 use middle::privacy;
@@ -362,11 +363,11 @@ impl<'a, 'tcx: 'a> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a,
     }
 }
 
-pub fn find_reachable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> NodeSet {
+pub fn find_reachable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Rc<NodeSet> {
     ty::queries::reachable_set::get(tcx, DUMMY_SP, LOCAL_CRATE)
 }
 
-fn reachable_set<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> NodeSet {
+fn reachable_set<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) -> Rc<NodeSet> {
     debug_assert!(crate_num == LOCAL_CRATE);
 
     let access_levels = &ty::queries::privacy_access_levels::get(tcx, DUMMY_SP, LOCAL_CRATE);
@@ -411,7 +412,7 @@ fn reachable_set<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) ->
     reachable_context.propagate();
 
     // Return the set of reachable symbols.
-    reachable_context.reachable_symbols
+    Rc::new(reachable_context.reachable_symbols)
 }
 
 pub fn provide(providers: &mut Providers) {

src/librustc/ty/maps.rs

@@ -451,7 +451,7 @@ define_maps! { <'tcx>
     /// Performs the privacy check and computes "access levels".
     pub privacy_access_levels: PrivacyAccessLevels(CrateNum) -> Rc<AccessLevels>,
 
-    pub reachable_set: reachability_dep_node(CrateNum) -> NodeSet,
+    pub reachable_set: reachability_dep_node(CrateNum) -> Rc<NodeSet>,
 
     pub mir_shims: mir_shim(ty::InstanceDef<'tcx>) -> &'tcx RefCell<mir::Mir<'tcx>>
 }

src/librustc/ty/mod.rs

@@ -114,7 +114,7 @@ mod sty;
 #[derive(Clone)]
 pub struct CrateAnalysis {
     pub access_levels: Rc<AccessLevels>,
-    pub reachable: NodeSet,
+    pub reachable: Rc<NodeSet>,
     pub name: String,
     pub glob_map: Option<hir::GlobMap>,
 }

src/librustc_driver/driver.rs

@@ -810,7 +810,7 @@ pub fn phase_2_configure_and_expand<F>(sess: &Session,
         defs: resolver.definitions,
         analysis: ty::CrateAnalysis {
             access_levels: Rc::new(AccessLevels::default()),
-            reachable: NodeSet(),
+            reachable: Rc::new(NodeSet()),
             name: crate_name.to_string(),
             glob_map: if resolver.make_glob_map { Some(resolver.glob_map) } else { None },
         },

src/librustc_trans/base.rs

@@ -1012,8 +1012,8 @@ fn iter_functions(llmod: llvm::ModuleRef) -> ValueIter {
 ///
 /// This list is later used by linkers to determine the set of symbols needed to
 /// be exposed from a dynamic library and it's also encoded into the metadata.
-pub fn find_exported_symbols(tcx: TyCtxt, reachable: NodeSet) -> NodeSet {
-    reachable.into_iter().filter(|&id| {
+pub fn find_exported_symbols(tcx: TyCtxt, reachable: &NodeSet) -> NodeSet {
+    reachable.iter().cloned().filter(|&id| {
         // Next, we want to ignore some FFI functions that are not exposed from
         // this crate. Reachable FFI functions can be lumped into two
         // categories:
@@ -1065,7 +1065,7 @@ pub fn trans_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let krate = tcx.hir.krate();
 
     let ty::CrateAnalysis { reachable, .. } = analysis;
-    let exported_symbols = find_exported_symbols(tcx, reachable);
+    let exported_symbols = find_exported_symbols(tcx, &reachable);
 
     let check_overflow = tcx.sess.overflow_checks();