Add a test for #108030

Closes #108030.
This issue has been resolved in LLVM 17.

tests/run-make/lto-linkage-used-attr/Makefile

@@ -0,0 +1,9 @@
+include ../tools.mk
+
+# Verify that the impl_* symbols are preserved. #108030
+# only-x86_64-unknown-linux-gnu
+# min-llvm-version: 17
+
+all:
+	$(RUSTC) -Cdebuginfo=0 -Copt-level=3 lib.rs
+	$(RUSTC) -Clto=fat -Cdebuginfo=0 -Copt-level=3 main.rs

tests/run-make/lto-linkage-used-attr/lib.rs

@@ -0,0 +1,50 @@
+#![crate_type = "rlib"]
+#![crate_type = "cdylib"]
+
+#[macro_export]
+macro_rules! asm_func {
+    ($name:expr, $body:expr $(, $($args:tt)*)?) => {
+        core::arch::global_asm!(
+            concat!(
+                ".p2align 4\n",
+                ".hidden ", $name, "\n",
+                ".global ", $name, "\n",
+                ".type ", $name, ",@function\n",
+                $name, ":\n",
+                $body,
+                ".size ", $name, ",.-", $name,
+            )
+            $(, $($args)*)?
+        );
+    };
+}
+
+macro_rules! libcall_trampoline {
+    ($libcall:ident ; $libcall_impl:ident) => {
+        asm_func!(
+            stringify!($libcall),
+            concat!(
+                "
+                   .cfi_startproc simple
+                   .cfi_def_cfa_offset 0
+                    jmp {}
+                    .cfi_endproc
+                ",
+            ),
+            sym $libcall_impl
+        );
+    };
+}
+
+pub mod trampolines {
+    extern "C" {
+        pub fn table_fill_funcref();
+        pub fn table_fill_externref();
+    }
+
+    unsafe extern "C" fn impl_table_fill_funcref() {}
+    unsafe extern "C" fn impl_table_fill_externref() {}
+
+    libcall_trampoline!(table_fill_funcref ; impl_table_fill_funcref);
+    libcall_trampoline!(table_fill_externref ; impl_table_fill_externref);
+}

tests/run-make/lto-linkage-used-attr/main.rs

@@ -0,0 +1,10 @@
+extern crate lib;
+
+use lib::trampolines::*;
+
+fn main() {
+    unsafe {
+        table_fill_externref();
+        table_fill_funcref();
+    }
+}