diff --git a/compiler/rustc_smir/src/rustc_internal/mod.rs b/compiler/rustc_smir/src/rustc_internal/mod.rs
index 1a9dea99f643f..581789d0be623 100644
--- a/compiler/rustc_smir/src/rustc_internal/mod.rs
+++ b/compiler/rustc_smir/src/rustc_internal/mod.rs
@@ -94,7 +94,7 @@ impl<'tcx> Tables<'tcx> {
         stable_mir::ty::Prov(self.create_alloc_id(aid))
     }
 
-    fn create_def_id(&mut self, did: DefId) -> stable_mir::DefId {
+    pub(super) fn create_def_id(&mut self, did: DefId) -> stable_mir::DefId {
         // FIXME: this becomes inefficient when we have too many ids
         for (i, &d) in self.def_ids.iter().enumerate() {
             if d == did {
diff --git a/compiler/rustc_smir/src/rustc_smir/mod.rs b/compiler/rustc_smir/src/rustc_smir/mod.rs
index 7d1122c2fd21d..330e356640668 100644
--- a/compiler/rustc_smir/src/rustc_smir/mod.rs
+++ b/compiler/rustc_smir/src/rustc_smir/mod.rs
@@ -1610,3 +1610,62 @@ impl<'tcx> Stable<'tcx> for DefKind {
         opaque(self)
     }
 }
+
+impl<'tcx> Stable<'tcx> for ty::Instance<'tcx> {
+    type T = stable_mir::ty::Instance;
+
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        let ty::Instance { def, args } = self;
+        stable_mir::ty::Instance { def: def.stable(tables), args: args.stable(tables) }
+    }
+}
+
+impl<'tcx> Stable<'tcx> for ty::InstanceDef<'tcx> {
+    type T = stable_mir::ty::InstanceDef;
+
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        use stable_mir::ty::InstanceDef::*;
+
+        match *self {
+            ty::InstanceDef::Item(did) => Item(tables.create_def_id(did)),
+            ty::InstanceDef::Intrinsic(did) => Intrinsic(tables.create_def_id(did)),
+            ty::InstanceDef::VTableShim(did) => VTableShim(tables.create_def_id(did)),
+            ty::InstanceDef::ReifyShim(did) => ReifyShim(tables.create_def_id(did)),
+            ty::InstanceDef::FnPtrShim(did, ty) => {
+                FnPtrShim(tables.create_def_id(did), tables.intern_ty(ty))
+            }
+            ty::InstanceDef::Virtual(did, vtable_idx) => {
+                Virtual(tables.create_def_id(did), vtable_idx)
+            }
+            ty::InstanceDef::ClosureOnceShim { call_once, track_caller } => {
+                ClosureOnceShim { call_once: tables.create_def_id(call_once), track_caller }
+            }
+            ty::InstanceDef::ThreadLocalShim(did) => ThreadLocalShim(tables.create_def_id(did)),
+            ty::InstanceDef::DropGlue(did, drop_glue) => {
+                DropGlue(tables.create_def_id(did), drop_glue.map(|ty| tables.intern_ty(ty)))
+            }
+            ty::InstanceDef::CloneShim(did, ty) => {
+                CloneShim(tables.create_def_id(did), tables.intern_ty(ty))
+            }
+            ty::InstanceDef::FnPtrAddrShim(did, ty) => {
+                FnPtrAddrShim(tables.create_def_id(did), tables.intern_ty(ty))
+            }
+        }
+    }
+}
+
+impl<'tcx> Stable<'tcx> for mir::mono::MonoItem<'tcx> {
+    type T = stable_mir::mir::mono::MonoItem;
+
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        use stable_mir::mir::mono::MonoItem::*;
+
+        match *self {
+            mir::mono::MonoItem::Fn(instance) => Fn(instance.stable(tables)),
+            mir::mono::MonoItem::Static(did) => Static(tables.create_def_id(did)),
+            mir::mono::MonoItem::GlobalAsm(iid) => {
+                GlobalAsm(opaque(tables.tcx.hir().item(iid).expect_global_asm()))
+            }
+        }
+    }
+}
diff --git a/compiler/stable_mir/src/mir.rs b/compiler/stable_mir/src/mir.rs
index a9dbc3463f80b..3138bb1ec832c 100644
--- a/compiler/stable_mir/src/mir.rs
+++ b/compiler/stable_mir/src/mir.rs
@@ -1,3 +1,4 @@
 mod body;
+pub mod mono;
 
 pub use body::*;
diff --git a/compiler/stable_mir/src/mir/mono.rs b/compiler/stable_mir/src/mir/mono.rs
new file mode 100644
index 0000000000000..fbff454d0e74f
--- /dev/null
+++ b/compiler/stable_mir/src/mir/mono.rs
@@ -0,0 +1,8 @@
+use crate::{ty::Instance, DefId, Opaque};
+
+#[derive(Clone, Debug)]
+pub enum MonoItem {
+    Fn(Instance),
+    Static(DefId),
+    GlobalAsm(Opaque),
+}
diff --git a/compiler/stable_mir/src/ty.rs b/compiler/stable_mir/src/ty.rs
index 6029e3c11adef..44eefbcc055fe 100644
--- a/compiler/stable_mir/src/ty.rs
+++ b/compiler/stable_mir/src/ty.rs
@@ -565,3 +565,24 @@ pub enum ImplPolarity {
     Negative,
     Reservation,
 }
+
+#[derive(Clone, Debug)]
+pub struct Instance {
+    pub def: InstanceDef,
+    pub args: GenericArgs,
+}
+
+#[derive(Clone, Debug)]
+pub enum InstanceDef {
+    Item(DefId),
+    Intrinsic(DefId),
+    VTableShim(DefId),
+    ReifyShim(DefId),
+    FnPtrShim(DefId, Ty),
+    Virtual(DefId, usize),
+    ClosureOnceShim { call_once: DefId, track_caller: bool },
+    ThreadLocalShim(DefId),
+    DropGlue(DefId, Option<Ty>),
+    CloneShim(DefId, Ty),
+    FnPtrAddrShim(DefId, Ty),
+}