Rollup merge of #73034 - doctorn:nomangle-inline-linkage, r=matthewjasper

Export `#[inline]` fns with extern indicators

In ancient history (#36280) we stopped `#[inline]` fns being codegened if they weren't used. However,

- #72944
- #72463

observe that when writing something like

```rust
#![crate_type = "cdylib"]

#[no_mangle]
#[inline]
pub extern "C" fn foo() {
    // ...
}
```

we really _do_ want `foo` to be codegened. This change makes this the case.

Resolves #72944, resolves #72463 (and maybe some more)

1 files changed, 6 insertions, 4 deletions

diff --git a/src/librustc_codegen_ssa/back/symbol_export.rs b/src/librustc_codegen_ssa/back/symbol_export.rs
index 970d13b30c0..98f7da8361c 100644
--- a/src/librustc_codegen_ssa/back/symbol_export.rs
+++ b/src/librustc_codegen_ssa/back/symbol_export.rs
@@ -89,10 +89,12 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, cnum: CrateNum) -> DefIdMap<
                 | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) => {
                     let def_id = tcx.hir().local_def_id(hir_id);
                     let generics = tcx.generics_of(def_id);
-                    if !generics.requires_monomorphization(tcx) &&
-                        // Functions marked with #[inline] are only ever codegened
-                        // with "internal" linkage and are never exported.
-                        !Instance::mono(tcx, def_id.to_def_id()).def.generates_cgu_internal_copy(tcx)
+                    if !generics.requires_monomorphization(tcx)
+                        // Functions marked with #[inline] are codegened with "internal"
+                        // linkage and are not exported unless marked with an extern
+                        // inidicator
+                        && (!Instance::mono(tcx, def_id.to_def_id()).def.generates_cgu_internal_copy(tcx)
+                            || tcx.codegen_fn_attrs(def_id.to_def_id()).contains_extern_indicator())
                     {
                         Some(def_id)
                     } else {