1 files changed, 72 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/middle/exported_symbols.rs b/compiler/rustc_middle/src/middle/exported_symbols.rs
new file mode 100644
index 000000000..631fd09ec
--- /dev/null
+++ b/compiler/rustc_middle/src/middle/exported_symbols.rs
@@ -0,0 +1,72 @@
+use crate::ty::subst::SubstsRef;
+use crate::ty::{self, Ty, TyCtxt};
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
+use rustc_macros::HashStable;
+
+/// The SymbolExportLevel of a symbols specifies from which kinds of crates
+/// the symbol will be exported. `C` symbols will be exported from any
+/// kind of crate, including cdylibs which export very few things.
+/// `Rust` will only be exported if the crate produced is a Rust
+/// dylib.
+#[derive(Eq, PartialEq, Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)]
+pub enum SymbolExportLevel {
+    C,
+    Rust,
+}
+
+impl SymbolExportLevel {
+    pub fn is_below_threshold(self, threshold: SymbolExportLevel) -> bool {
+        threshold == SymbolExportLevel::Rust // export everything from Rust dylibs
+          || self == SymbolExportLevel::C
+    }
+}
+
+/// Kind of exported symbols.
+#[derive(Eq, PartialEq, Debug, Copy, Clone, Encodable, Decodable, HashStable)]
+pub enum SymbolExportKind {
+    Text,
+    Data,
+    Tls,
+}
+
+/// The `SymbolExportInfo` of a symbols specifies symbol-related information
+/// that is relevant to code generation and linking.
+#[derive(Eq, PartialEq, Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)]
+pub struct SymbolExportInfo {
+    pub level: SymbolExportLevel,
+    pub kind: SymbolExportKind,
+    pub used: bool,
+}
+
+#[derive(Eq, PartialEq, Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)]
+pub enum ExportedSymbol<'tcx> {
+    NonGeneric(DefId),
+    Generic(DefId, SubstsRef<'tcx>),
+    DropGlue(Ty<'tcx>),
+    NoDefId(ty::SymbolName<'tcx>),
+}
+
+impl<'tcx> ExportedSymbol<'tcx> {
+    /// This is the symbol name of an instance if it is instantiated in the
+    /// local crate.
+    pub fn symbol_name_for_local_instance(&self, tcx: TyCtxt<'tcx>) -> ty::SymbolName<'tcx> {
+        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::DropGlue(ty) => {
+                tcx.symbol_name(ty::Instance::resolve_drop_in_place(tcx, ty))
+            }
+            ExportedSymbol::NoDefId(symbol_name) => symbol_name,
+        }
+    }
+}
+
+pub fn metadata_symbol_name(tcx: TyCtxt<'_>) -> String {
+    format!(
+        "rust_metadata_{}_{:08x}",
+        tcx.crate_name(LOCAL_CRATE),
+        tcx.sess.local_stable_crate_id().to_u64(),
+    )
+}