Allow for re-using monomorphizations in upstream crates.

src/librustc/dep_graph/dep_node.rs

@@ -561,6 +561,7 @@ define_dep_nodes!( <'tcx>
     [] ImplParent(DefId),
     [] TraitOfItem(DefId),
     [] IsReachableNonGeneric(DefId),
+    [] IsUnreachableLocalDefinition(DefId),
     [] IsMirAvailable(DefId),
     [] ItemAttrs(DefId),
     [] TransFnAttrs(DefId),
@@ -648,15 +649,16 @@ define_dep_nodes!( <'tcx>
 
     [] InstanceDefSizeEstimate { instance_def: InstanceDef<'tcx> },
 
-    [] GetSymbolExportLevel(DefId),
-
     [] WasmCustomSections(CrateNum),
 
     [input] Features,
 
     [] ProgramClausesFor(DefId),
     [] WasmImportModuleMap(CrateNum),
     [] ForeignModules(CrateNum),
+
+    [] UpstreamMonomorphizations(CrateNum),
+    [] UpstreamMonomorphizationsFor(DefId),
 );
 
 trait DepNodeParams<'a, 'gcx: 'tcx + 'a, 'tcx: 'a> : fmt::Debug {

src/librustc/ich/impls_ty.rs

@@ -53,8 +53,21 @@ for &'gcx ty::Slice<T>
     }
 }
 
-impl<'a, 'gcx> HashStable<StableHashingContext<'a>>
-for ty::subst::Kind<'gcx> {
+impl<'a, 'gcx, T> ToStableHashKey<StableHashingContext<'a>> for &'gcx ty::Slice<T>
+    where T: HashStable<StableHashingContext<'a>>
+{
+    type KeyType = Fingerprint;
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &StableHashingContext<'a>) -> Fingerprint {
+        let mut hasher = StableHasher::new();
+        let mut hcx: StableHashingContext<'a> = hcx.clone();
+        self.hash_stable(&mut hcx, &mut hasher);
+        hasher.finish()
+    }
+}
+
+impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for ty::subst::Kind<'gcx> {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a>,
                                           hasher: &mut StableHasher<W>) {
@@ -67,6 +80,7 @@ for ty::subst::UnpackedKind<'gcx> {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a>,
                                           hasher: &mut StableHasher<W>) {
+        mem::discriminant(self).hash_stable(hcx, hasher);
         match self {
             ty::subst::UnpackedKind::Lifetime(lt) => lt.hash_stable(hcx, hasher),
             ty::subst::UnpackedKind::Type(ty) => ty.hash_stable(hcx, hasher),

src/librustc/middle/exported_symbols.rs

@@ -9,8 +9,13 @@
 // except according to those terms.
 
 use hir::def_id::{DefId, LOCAL_CRATE};
+use ich::StableHashingContext;
+use rustc_data_structures::stable_hasher::{StableHasher, HashStable,
+                                           StableHasherResult};
 use std::cmp;
+use std::mem;
 use ty;
+use ty::subst::Substs;
 
 /// The SymbolExportLevel of a symbols specifies from which kinds of crates
 /// the symbol will be exported. `C` symbols will be exported from any
@@ -40,56 +45,89 @@ impl SymbolExportLevel {
 }
 
 #[derive(Eq, PartialEq, Debug, Copy, Clone, RustcEncodable, RustcDecodable)]
-pub enum ExportedSymbol {
+pub enum ExportedSymbol<'tcx> {
     NonGeneric(DefId),
+    Generic(DefId, &'tcx Substs<'tcx>),
     NoDefId(ty::SymbolName),
 }
 
-impl ExportedSymbol {
-    pub fn symbol_name(&self, tcx: ty::TyCtxt) -> ty::SymbolName {
+impl<'tcx> ExportedSymbol<'tcx> {
+    pub fn symbol_name(&self,
+                       tcx: ty::TyCtxt<'_, 'tcx, '_>)
+                       -> ty::SymbolName {
         match *self {
             ExportedSymbol::NonGeneric(def_id) => {
                 tcx.symbol_name(ty::Instance::mono(tcx, def_id))
             }
+            ExportedSymbol::Generic(def_id, substs) => {
+                tcx.symbol_name(ty::Instance::new(def_id, substs))
+            }
             ExportedSymbol::NoDefId(symbol_name) => {
                 symbol_name
             }
         }
     }
 
-    pub fn compare_stable(&self, tcx: ty::TyCtxt, other: &ExportedSymbol) -> cmp::Ordering {
+    pub fn compare_stable(&self,
+                          tcx: ty::TyCtxt<'_, 'tcx, '_>,
+                          other: &ExportedSymbol<'tcx>)
+                          -> cmp::Ordering {
         match *self {
-            ExportedSymbol::NonGeneric(self_def_id) => {
-                match *other {
-                    ExportedSymbol::NonGeneric(other_def_id) => {
-                        tcx.def_path_hash(self_def_id).cmp(&tcx.def_path_hash(other_def_id))
-                    }
-                    ExportedSymbol::NoDefId(_) => {
-                        cmp::Ordering::Less
-                    }
+            ExportedSymbol::NonGeneric(self_def_id) => match *other {
+                ExportedSymbol::NonGeneric(other_def_id) => {
+                    tcx.def_path_hash(self_def_id).cmp(&tcx.def_path_hash(other_def_id))
+                }
+                ExportedSymbol::Generic(..) |
+                ExportedSymbol::NoDefId(_) => {
+                    cmp::Ordering::Less
+                }
+            }
+            ExportedSymbol::Generic(..) => match *other {
+                ExportedSymbol::NonGeneric(_) => {
+                    cmp::Ordering::Greater
+                }
+                ExportedSymbol::Generic(..) => {
+                    self.symbol_name(tcx).cmp(&other.symbol_name(tcx))
+                }
+                ExportedSymbol::NoDefId(_) => {
+                    cmp::Ordering::Less
                 }
             }
-            ExportedSymbol::NoDefId(self_symbol_name) => {
-                match *other {
-                    ExportedSymbol::NonGeneric(_) => {
-                        cmp::Ordering::Greater
-                    }
-                    ExportedSymbol::NoDefId(ref other_symbol_name) => {
-                        self_symbol_name.cmp(other_symbol_name)
-                    }
+            ExportedSymbol::NoDefId(self_symbol_name) => match *other {
+                ExportedSymbol::NonGeneric(_) |
+                ExportedSymbol::Generic(..) => {
+                    cmp::Ordering::Greater
+                }
+                ExportedSymbol::NoDefId(ref other_symbol_name) => {
+                    self_symbol_name.cmp(other_symbol_name)
                 }
             }
         }
     }
 }
 
-impl_stable_hash_for!(enum self::ExportedSymbol {
-    NonGeneric(def_id),
-    NoDefId(symbol_name)
-});
-
 pub fn metadata_symbol_name(tcx: ty::TyCtxt) -> String {
     format!("rust_metadata_{}_{}",
             tcx.original_crate_name(LOCAL_CRATE),
             tcx.crate_disambiguator(LOCAL_CRATE).to_fingerprint().to_hex())
 }
+
+impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for ExportedSymbol<'gcx> {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        mem::discriminant(self).hash_stable(hcx, hasher);
+        match *self {
+            ExportedSymbol::NonGeneric(def_id) => {
+                def_id.hash_stable(hcx, hasher);
+            }
+            ExportedSymbol::Generic(def_id, substs) => {
+                def_id.hash_stable(hcx, hasher);
+                substs.hash_stable(hcx, hasher);
+            }
+            ExportedSymbol::NoDefId(symbol_name) => {
+                symbol_name.hash_stable(hcx, hasher);
+            }
+        }
+    }
+}

src/librustc/session/config.rs

@@ -1304,6 +1304,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
           "embed LLVM bitcode in object files"),
     strip_debuginfo_if_disabled: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "tell the linker to strip debuginfo when building without debuginfo enabled."),
+    share_generics: Option<bool> = (None, parse_opt_bool, [TRACKED],
+          "make the current crate share its generic instantiations"),
 }
 
 pub fn default_lib_output() -> CrateType {

src/librustc/ty/context.rs

@@ -14,7 +14,8 @@ use dep_graph::DepGraph;
 use dep_graph::{DepNode, DepConstructor};
 use errors::DiagnosticBuilder;
 use session::Session;
-use session::config::{BorrowckMode, OutputFilenames};
+use session::config::{BorrowckMode, OutputFilenames, OptLevel};
+use session::config::CrateType::*;
 use middle;
 use hir::{TraitCandidate, HirId, ItemLocalId};
 use hir::def::{Def, Export};
@@ -1499,6 +1500,40 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             self.sess.opts.debugging_opts.mir_emit_validate > 0 ||
             self.use_mir()
     }
+
+    #[inline]
+    pub fn share_generics(self) -> bool {
+        match self.sess.opts.debugging_opts.share_generics {
+            Some(setting) => setting,
+            None => {
+                self.sess.opts.incremental.is_some() ||
+                match self.sess.opts.optimize {
+                    OptLevel::No   |
+                    OptLevel::Less |
+                    OptLevel::Size |
+                    OptLevel::SizeMin => true,
+                    OptLevel::Default    |
+                    OptLevel::Aggressive => false,
+                }
+            }
+        }
+    }
+
+    #[inline]
+    pub fn local_crate_exports_generics(self) -> bool {
+        debug_assert!(self.share_generics());
+
+        self.sess.crate_types.borrow().iter().any(|crate_type| {
+            match crate_type {
+                CrateTypeExecutable |
+                CrateTypeStaticlib  |
+                CrateTypeProcMacro  |
+                CrateTypeCdylib     => false,
+                CrateTypeRlib       |
+                CrateTypeDylib      => true,
+            }
+        })
+    }
 }
 
 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {

src/librustc/ty/maps/config.rs

@@ -131,6 +131,12 @@ impl<'tcx> QueryDescription<'tcx> for queries::coherent_trait<'tcx> {
     }
 }
 
+impl<'tcx> QueryDescription<'tcx> for queries::upstream_monomorphizations<'tcx> {
+    fn describe(_: TyCtxt, k: CrateNum) -> String {
+        format!("collecting available upstream monomorphizations `{:?}`", k)
+    }
+}
+
 impl<'tcx> QueryDescription<'tcx> for queries::crate_inherent_impls<'tcx> {
     fn describe(_: TyCtxt, k: CrateNum) -> String {
         format!("all inherent impls defined in crate `{:?}`", k)

src/librustc/ty/maps/mod.rs

@@ -319,9 +319,15 @@ define_maps! { <'tcx>
     //
     // Does not include external symbols that don't have a corresponding DefId,
     // like the compiler-generated `main` function and so on.
-    [] fn reachable_non_generics: ReachableNonGenerics(CrateNum) -> Lrc<DefIdSet>,
+    [] fn reachable_non_generics: ReachableNonGenerics(CrateNum)
+        -> Lrc<DefIdMap<SymbolExportLevel>>,
     [] fn is_reachable_non_generic: IsReachableNonGeneric(DefId) -> bool,
+    [] fn is_unreachable_local_definition: IsUnreachableLocalDefinition(DefId) -> bool,
 
+    [] fn upstream_monomorphizations: UpstreamMonomorphizations(CrateNum)
+        -> Lrc<DefIdMap<Lrc<FxHashMap<&'tcx Substs<'tcx>, CrateNum>>>>,
+    [] fn upstream_monomorphizations_for: UpstreamMonomorphizationsFor(DefId)
+        -> Option<Lrc<FxHashMap<&'tcx Substs<'tcx>, CrateNum>>>,
 
     [] fn native_libraries: NativeLibraries(CrateNum) -> Lrc<Vec<NativeLibrary>>,
 
@@ -381,11 +387,10 @@ define_maps! { <'tcx>
     [] fn all_crate_nums: all_crate_nums_node(CrateNum) -> Lrc<Vec<CrateNum>>,
 
     [] fn exported_symbols: ExportedSymbols(CrateNum)
-        -> Arc<Vec<(ExportedSymbol, SymbolExportLevel)>>,
+        -> Arc<Vec<(ExportedSymbol<'tcx>, SymbolExportLevel)>>,
     [] fn collect_and_partition_translation_items:
         collect_and_partition_translation_items_node(CrateNum)
         -> (Arc<DefIdSet>, Arc<Vec<Arc<CodegenUnit<'tcx>>>>),
-    [] fn symbol_export_level: GetSymbolExportLevel(DefId) -> SymbolExportLevel,
     [] fn is_translated_item: IsTranslatedItem(DefId) -> bool,
     [] fn codegen_unit: CodegenUnit(InternedString) -> Arc<CodegenUnit<'tcx>>,
     [] fn compile_codegen_unit: CompileCodegenUnit(InternedString) -> Stats,

src/librustc/ty/maps/plumbing.rs

@@ -1003,6 +1003,9 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::ImplParent => { force!(impl_parent, def_id!()); }
         DepKind::TraitOfItem => { force!(trait_of_item, def_id!()); }
         DepKind::IsReachableNonGeneric => { force!(is_reachable_non_generic, def_id!()); }
+        DepKind::IsUnreachableLocalDefinition => {
+            force!(is_unreachable_local_definition, def_id!());
+        }
         DepKind::IsMirAvailable => { force!(is_mir_available, def_id!()); }
         DepKind::ItemAttrs => { force!(item_attrs, def_id!()); }
         DepKind::TransFnAttrs => { force!(trans_fn_attrs, def_id!()); }
@@ -1087,13 +1090,19 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
 
         DepKind::TargetFeaturesWhitelist => { force!(target_features_whitelist, LOCAL_CRATE); }
 
-        DepKind::GetSymbolExportLevel => { force!(symbol_export_level, def_id!()); }
         DepKind::Features => { force!(features_query, LOCAL_CRATE); }
 
         DepKind::ProgramClausesFor => { force!(program_clauses_for, def_id!()); }
         DepKind::WasmCustomSections => { force!(wasm_custom_sections, krate!()); }
         DepKind::WasmImportModuleMap => { force!(wasm_import_module_map, krate!()); }
         DepKind::ForeignModules => { force!(foreign_modules, krate!()); }
+
+        DepKind::UpstreamMonomorphizations => {
+            force!(upstream_monomorphizations, krate!());
+        }
+        DepKind::UpstreamMonomorphizationsFor => {
+            force!(upstream_monomorphizations_for, def_id!());
+        }
     }
 
     true

src/librustc_metadata/cstore_impl.rs

@@ -186,9 +186,9 @@ provide! { <'tcx> tcx, def_id, other, cdata,
         let reachable_non_generics = tcx
             .exported_symbols(cdata.cnum)
             .iter()
-            .filter_map(|&(exported_symbol, _)| {
+            .filter_map(|&(exported_symbol, export_level)| {
                 if let ExportedSymbol::NonGeneric(def_id) = exported_symbol {
-                    return Some(def_id)
+                    return Some((def_id, export_level))
                 } else {
                     None
                 }
@@ -268,7 +268,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
             return Arc::new(Vec::new())
         }
 
-        Arc::new(cdata.exported_symbols())
+        Arc::new(cdata.exported_symbols(tcx))
     }
 
     wasm_custom_sections => { Lrc::new(cdata.wasm_custom_sections()) }

src/librustc_metadata/decoder.rs

@@ -1065,11 +1065,13 @@ impl<'a, 'tcx> CrateMetadata {
         arg_names.decode(self).collect()
     }
 
-    pub fn exported_symbols(&self) -> Vec<(ExportedSymbol, SymbolExportLevel)> {
-        self.root
-            .exported_symbols
-            .decode(self)
-            .collect()
+    pub fn exported_symbols(&self,
+                            tcx: TyCtxt<'a, 'tcx, 'tcx>)
+                            -> Vec<(ExportedSymbol<'tcx>, SymbolExportLevel)> {
+        let lazy_seq: LazySeq<(ExportedSymbol<'tcx>, SymbolExportLevel)> =
+            LazySeq::with_position_and_length(self.root.exported_symbols.position,
+                                              self.root.exported_symbols.len);
+        lazy_seq.decode((self, tcx)).collect()
     }
 
     pub fn wasm_custom_sections(&self) -> Vec<DefId> {

src/librustc_metadata/encoder.rs

@@ -1444,13 +1444,12 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
     // definition (as that's not defined in this crate).
     fn encode_exported_symbols(&mut self,
                                exported_symbols: &[(ExportedSymbol, SymbolExportLevel)])
-                               -> LazySeq<(ExportedSymbol, SymbolExportLevel)> {
-
+                               -> EncodedExportedSymbols {
         // The metadata symbol name is special. It should not show up in
         // downstream crates.
         let metadata_symbol_name = SymbolName::new(&metadata_symbol_name(self.tcx));
 
-        self.lazy_seq(exported_symbols
+        let lazy_seq = self.lazy_seq(exported_symbols
             .iter()
             .filter(|&&(ref exported_symbol, _)| {
                 match *exported_symbol {
@@ -1460,7 +1459,12 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
                     _ => true,
                 }
             })
-            .cloned())
+            .cloned());
+
+        EncodedExportedSymbols {
+            len: lazy_seq.len,
+            position: lazy_seq.position,
+        }
     }
 
     fn encode_wasm_custom_sections(&mut self, statics: &[DefId]) -> LazySeq<DefIndex> {