diff --git a/src/librustc_codegen_llvm/back/archive.rs b/src/librustc_codegen_llvm/back/archive.rs
index 68d3f90cd3991..e169cfc4cc829 100644
--- a/src/librustc_codegen_llvm/back/archive.rs
+++ b/src/librustc_codegen_llvm/back/archive.rs
@@ -9,7 +9,9 @@ use std::str;
 
 use crate::llvm::archive_ro::{ArchiveRO, Child};
 use crate::llvm::{self, ArchiveKind};
-use rustc_codegen_ssa::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION};
+use rustc_codegen_ssa::{
+    METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, looks_like_rust_object_file
+};
 use rustc_codegen_ssa::back::archive::{ArchiveBuilder, find_library};
 use rustc::session::Session;
 use syntax::symbol::Symbol;
@@ -141,7 +143,7 @@ impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
             }
 
             // Don't include Rust objects if LTO is enabled
-            if lto && fname.starts_with(&obj_start) && fname.ends_with(".o") {
+            if lto && looks_like_rust_object_file(fname) {
                 return true
             }
 
diff --git a/src/librustc_codegen_ssa/back/link.rs b/src/librustc_codegen_ssa/back/link.rs
index 1c5d3b1a890ee..a2b50ea8e2bf7 100644
--- a/src/librustc_codegen_ssa/back/link.rs
+++ b/src/librustc_codegen_ssa/back/link.rs
@@ -3,7 +3,7 @@
 
 use rustc::session::{Session, filesearch};
 use rustc::session::config::{
-    self, RUST_CGU_EXT, DebugInfo, OutputFilenames, OutputType, PrintRequest, Sanitizer
+    self, DebugInfo, OutputFilenames, OutputType, PrintRequest, Sanitizer
 };
 use rustc::session::search_paths::PathKind;
 use rustc::middle::dependency_format::Linkage;
@@ -15,7 +15,8 @@ use rustc_fs_util::fix_windows_verbatim_for_gcc;
 use rustc_target::spec::{PanicStrategy, RelroLevel, LinkerFlavor};
 use syntax::symbol::Symbol;
 
-use crate::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, CrateInfo, CodegenResults};
+use crate::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, CrateInfo,
+    looks_like_rust_object_file, CodegenResults};
 use super::archive::ArchiveBuilder;
 use super::command::Command;
 use super::linker::Linker;
@@ -1549,23 +1550,9 @@ fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
                 let canonical = f.replace("-", "_");
                 let canonical_name = name.replace("-", "_");
 
-                // Look for `.rcgu.o` at the end of the filename to conclude
-                // that this is a Rust-related object file.
-                fn looks_like_rust(s: &str) -> bool {
-                    let path = Path::new(s);
-                    let ext = path.extension().and_then(|s| s.to_str());
-                    if ext != Some(OutputType::Object.extension()) {
-                        return false
-                    }
-                    let ext2 = path.file_stem()
-                        .and_then(|s| Path::new(s).extension())
-                        .and_then(|s| s.to_str());
-                    ext2 == Some(RUST_CGU_EXT)
-                }
-
                 let is_rust_object =
                     canonical.starts_with(&canonical_name) &&
-                    looks_like_rust(&f);
+                    looks_like_rust_object_file(&f);
 
                 // If we've been requested to skip all native object files
                 // (those not generated by the rust compiler) then we can skip
diff --git a/src/librustc_codegen_ssa/lib.rs b/src/librustc_codegen_ssa/lib.rs
index 0221a04b04518..dd75883f97deb 100644
--- a/src/librustc_codegen_ssa/lib.rs
+++ b/src/librustc_codegen_ssa/lib.rs
@@ -22,9 +22,9 @@
 #[macro_use] extern crate rustc;
 #[macro_use] extern crate syntax;
 
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use rustc::dep_graph::WorkProduct;
-use rustc::session::config::{OutputFilenames, OutputType};
+use rustc::session::config::{OutputFilenames, OutputType, RUST_CGU_EXT};
 use rustc::middle::lang_items::LangItem;
 use rustc::hir::def_id::CrateNum;
 use rustc::ty::query::Providers;
@@ -62,6 +62,7 @@ pub struct ModuleCodegen<M> {
 pub const METADATA_FILENAME: &str = "rust.metadata.bin";
 pub const RLIB_BYTECODE_EXTENSION: &str = "bc.z";
 
+
 impl<M> ModuleCodegen<M> {
     pub fn into_compiled_module(self,
                             emit_obj: bool,
@@ -166,3 +167,22 @@ pub fn provide_extern(providers: &mut Providers<'_>) {
     crate::back::symbol_export::provide_extern(providers);
     crate::base::provide_both(providers);
 }
+
+/// Checks if the given filename ends with the `.rcgu.o` extension that `rustc`
+/// uses for the object files it generates.
+pub fn looks_like_rust_object_file(filename: &str) -> bool {
+    let path = Path::new(filename);
+    let ext = path.extension().and_then(|s| s.to_str());
+    if ext != Some(OutputType::Object.extension()) {
+        // The file name does not end with ".o", so it can't be an object file.
+        return false
+    }
+
+    // Strip the ".o" at the end
+    let ext2 = path.file_stem()
+        .and_then(|s| Path::new(s).extension())
+        .and_then(|s| s.to_str());
+
+    // Check if the "inner" extension
+    ext2 == Some(RUST_CGU_EXT)
+}