[wip] Add projection query for upstream drop-glue instances.

src/librustc/query/mod.rs

@@ -783,6 +783,11 @@ rustc_queries! {
         }
         query upstream_monomorphizations_for(_: DefId)
             -> Option<&'tcx FxHashMap<SubstsRef<'tcx>, CrateNum>> {}
+
+        query upstream_drop_glue_for(substs: SubstsRef<'tcx>) -> Option<CrateNum> {
+            desc { "available upstream drop-glue for `{:?}`", substs }
+            no_force
+        }
     }
 
     Other {

src/librustc/ty/instance.rs

@@ -4,7 +4,7 @@ use crate::traits;
 use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
 use rustc_hir::def::Namespace;
-use rustc_hir::def_id::DefId;
+use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_macros::HashStable;
 use rustc_target::spec::abi::Abi;
 
@@ -91,6 +91,38 @@ impl<'tcx> Instance<'tcx> {
         let ty = tcx.type_of(self.def.def_id());
         tcx.subst_and_normalize_erasing_regions(self.substs, param_env, &ty)
     }
+
+    pub fn upstream_monomorphization(&self, tcx: TyCtxt<'tcx>) -> Option<CrateNum> {
+        // If we are not in share generics mode, we don't link to upstream
+        // monomorphizations but always instantiate our own internal versions
+        // instead.
+        if !tcx.sess.opts.share_generics() {
+            return None;
+        }
+
+        // If this instance has non-erasable parameters, it cannot be a shared
+        // monomorphization. Non-generic instances are already handled above
+        // by `is_reachable_non_generic()`.
+        if self.substs.non_erasable_generics().next().is_none() {
+            return None;
+        }
+
+        if self.def_id().is_local() {
+            return None;
+        }
+
+        match self.def {
+            InstanceDef::Item(def_id) => {
+                tcx
+                    .upstream_monomorphizations_for(def_id)
+                    .and_then(|monos| monos.get(&self.substs).cloned())
+            }
+            InstanceDef::DropGlue(_, Some(_)) => {
+                tcx.upstream_drop_glue_for(self.substs)
+            }
+            _ => None,
+        }
+    }
 }
 
 impl<'tcx> InstanceDef<'tcx> {

src/librustc/ty/query/keys.rs

@@ -116,6 +116,15 @@ impl Key for (DefId, SimplifiedType) {
     }
 }
 
+impl<'tcx> Key for SubstsRef<'tcx> {
+    fn query_crate(&self) -> CrateNum {
+        LOCAL_CRATE
+    }
+    fn default_span(&self, _: TyCtxt<'_>) -> Span {
+        DUMMY_SP
+    }
+}
+
 impl<'tcx> Key for (DefId, SubstsRef<'tcx>) {
     fn query_crate(&self) -> CrateNum {
         self.0.krate

src/librustc_codegen_llvm/callee.rs

@@ -130,12 +130,7 @@ pub fn get_fn(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) -> &'ll Value
                     } else {
                         // This is a monomorphization of a generic function
                         // defined in an upstream crate.
-                        if cx
-                            .tcx
-                            .upstream_monomorphizations_for(instance_def_id)
-                            .map(|set| set.contains_key(instance.substs))
-                            .unwrap_or(false)
-                        {
+                        if instance.upstream_monomorphization(tcx).is_some() {
                             // This is instantiated in another crate. It cannot
                             // be `hidden`.
                         } else {

src/librustc_codegen_ssa/back/symbol_export.rs

@@ -321,6 +321,17 @@ fn upstream_monomorphizations_for_provider(
     tcx.upstream_monomorphizations(LOCAL_CRATE).get(&def_id)
 }
 
+fn upstream_drop_glue_for_provider<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    substs: SubstsRef<'tcx>,
+) -> Option<CrateNum> {
+    if let Some(def_id) = tcx.lang_items().drop_in_place_fn() {
+        tcx.upstream_monomorphizations(LOCAL_CRATE).get(&def_id).and_then(|monos| monos.get(&substs).cloned())
+    } else {
+        None
+    }
+}
+
 fn is_unreachable_local_definition_provider(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
     if let Some(hir_id) = tcx.hir().as_local_hir_id(def_id) {
         !tcx.reachable_set(LOCAL_CRATE).contains(&hir_id)
@@ -335,6 +346,7 @@ pub fn provide(providers: &mut Providers<'_>) {
     providers.exported_symbols = exported_symbols_provider_local;
     providers.upstream_monomorphizations = upstream_monomorphizations_provider;
     providers.is_unreachable_local_definition = is_unreachable_local_definition_provider;
+    providers.upstream_drop_glue_for = upstream_drop_glue_for_provider;
 }
 
 pub fn provide_extern(providers: &mut Providers<'_>) {

src/librustc_codegen_utils/symbol_names.rs

@@ -129,26 +129,8 @@ fn symbol_name_provider(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> ty::Symb
         //
         // For generics we might find re-usable upstream instances. For anything
         // else we rely on their being a local copy available.
-
         if is_generic(instance.substs) {
-            let def_id = instance.def_id();
-
-            if !def_id.is_local() && tcx.sess.opts.share_generics() {
-                // If we are re-using a monomorphization from another crate,
-                // we have to compute the symbol hash accordingly.
-                let upstream_monomorphizations = tcx.upstream_monomorphizations_for(def_id);
-
-                upstream_monomorphizations
-                    .and_then(|monos| monos.get(&instance.substs).cloned())
-                    // If there is no instance available upstream, there'll be
-                    // one in the current crate.
-                    .unwrap_or(LOCAL_CRATE)
-            } else {
-                // For generic functions defined in the current crate, there
-                // can be no upstream instances. Also, if we don't share
-                // generics, we'll instantiate a local copy too.
-                LOCAL_CRATE
-            }
+            instance.upstream_monomorphization(tcx).unwrap_or(LOCAL_CRATE)
         } else {
             // For non-generic things that need to avoid naming conflicts, we
             // always instantiate a copy in the local crate.

src/librustc_mir/monomorphize/collector.rs

@@ -737,8 +737,8 @@ fn should_monomorphize_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: &Instance<'tcx
         return true;
     }
 
-    if tcx.is_reachable_non_generic(def_id)
-        || is_available_upstream_generic(tcx, def_id, instance.substs)
+    if tcx.is_reachable_non_generic(def_id) ||
+        instance.upstream_monomorphization(tcx).is_some()
     {
         // We can link to the item in question, no instance needed
         // in this crate.
@@ -750,34 +750,6 @@ fn should_monomorphize_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: &Instance<'tcx
     }
 
     return true;
-
-    fn is_available_upstream_generic<'tcx>(
-        tcx: TyCtxt<'tcx>,
-        def_id: DefId,
-        substs: SubstsRef<'tcx>,
-    ) -> bool {
-        debug_assert!(!def_id.is_local());
-
-        // If we are not in share generics mode, we don't link to upstream
-        // monomorphizations but always instantiate our own internal versions
-        // instead.
-        if !tcx.sess.opts.share_generics() {
-            return false;
-        }
-
-        // If this instance has non-erasable parameters, it cannot be a shared
-        // monomorphization. Non-generic instances are already handled above
-        // by `is_reachable_non_generic()`.
-        if substs.non_erasable_generics().next().is_none() {
-            return false;
-        }
-
-        // Take a look at the available monomorphizations listed in the metadata
-        // of upstream crates.
-        tcx.upstream_monomorphizations_for(def_id)
-            .map(|set| set.contains_key(substs))
-            .unwrap_or(false)
-    }
 }
 
 /// For a given pair of source and target type that occur in an unsizing coercion,