Split join_codegen_and_link() into two steps

src/librustc_codegen_llvm/lib.rs

@@ -29,7 +29,7 @@ use rustc::dep_graph::WorkProduct;
 use rustc_codegen_ssa::back::lto::{LtoModuleCodegen, SerializedModule, ThinModule};
 use rustc_codegen_ssa::back::write::{CodegenContext, FatLTOInput, ModuleConfig};
 use rustc_codegen_ssa::traits::*;
-use rustc_codegen_ssa::CompiledModule;
+use rustc_codegen_ssa::{CodegenResults, CompiledModule};
 use rustc_errors::{FatalError, Handler};
 use std::any::Any;
 use std::ffi::CStr;
@@ -39,7 +39,7 @@ use syntax::expand::allocator::AllocatorKind;
 
 use rustc::dep_graph::DepGraph;
 use rustc::middle::cstore::{EncodedMetadata, MetadataLoaderDyn};
-use rustc::session::config::{OptLevel, OutputFilenames, OutputType, PrintRequest};
+use rustc::session::config::{OptLevel, OutputFilenames, PrintRequest};
 use rustc::session::Session;
 use rustc::ty::{self, TyCtxt};
 use rustc::util::common::ErrorReported;
@@ -270,13 +270,12 @@ impl CodegenBackend for LlvmCodegenBackend {
         )
     }
 
-    fn join_codegen_and_link(
+    fn join_codegen(
         &self,
         ongoing_codegen: Box<dyn Any>,
         sess: &Session,
         dep_graph: &DepGraph,
-        outputs: &OutputFilenames,
-    ) -> Result<(), ErrorReported> {
+    ) -> Result<Box<dyn Any>, ErrorReported> {
         let (codegen_results, work_products) = ongoing_codegen
             .downcast::<rustc_codegen_ssa::back::write::OngoingCodegen<LlvmCodegenBackend>>()
             .expect("Expected LlvmCodegenBackend's OngoingCodegen, found Box<Any>")
@@ -291,14 +290,18 @@ impl CodegenBackend for LlvmCodegenBackend {
 
         sess.compile_status()?;
 
-        if !sess
-            .opts
-            .output_types
-            .keys()
-            .any(|&i| i == OutputType::Exe || i == OutputType::Metadata)
-        {
-            return Ok(());
-        }
+        Ok(Box::new(codegen_results))
+    }
+
+    fn link(
+        &self,
+        sess: &Session,
+        codegen_results: Box<dyn Any>,
+        outputs: &OutputFilenames,
+    ) -> Result<(), ErrorReported> {
+        let codegen_results = codegen_results
+            .downcast::<CodegenResults>()
+            .expect("Expected CodegenResults, found Box<Any>");
 
         if sess.opts.debugging_opts.no_link {
             // FIXME: use a binary format to encode the `.rlink` file

src/librustc_codegen_utils/codegen_backend.rs

@@ -43,11 +43,22 @@ pub trait CodegenBackend {
     /// # Panics
     ///
     /// Panics when the passed `Box<dyn Any>` was not returned by `codegen_backend`.
-    fn join_codegen_and_link(
+    fn join_codegen(
         &self,
         ongoing_codegen: Box<dyn Any>,
         sess: &Session,
         dep_graph: &DepGraph,
+    ) -> Result<Box<dyn Any>, ErrorReported>;
+
+    /// This is called on the returned `Box<dyn Any>` from `join_codegen`
+    ///
+    /// # Panics
+    ///
+    /// Panics when the passed `Box<dyn Any>` was not returned by `join_codegen`.
+    fn link(
+        &self,
+        sess: &Session,
+        codegen_results: Box<dyn Any>,
         outputs: &OutputFilenames,
     ) -> Result<(), ErrorReported>;
 }

src/librustc_interface/queries.rs

@@ -310,19 +310,22 @@ pub struct Linker {
 
 impl Linker {
     pub fn link(self) -> Result<()> {
-        let r = self
-            .codegen_backend
-            .join_codegen_and_link(
-                self.ongoing_codegen,
-                &self.sess,
-                &self.dep_graph,
-                &self.prepare_outputs,
-            )
-            .map_err(|_| ErrorReported);
+        let codegen_results =
+            self.codegen_backend.join_codegen(self.ongoing_codegen, &self.sess, &self.dep_graph)?;
         let prof = self.sess.prof.clone();
         let dep_graph = self.dep_graph;
         prof.generic_activity("drop_dep_graph").run(move || drop(dep_graph));
-        r
+
+        if !self
+            .sess
+            .opts
+            .output_types
+            .keys()
+            .any(|&i| i == OutputType::Exe || i == OutputType::Metadata)
+        {
+            return Ok(());
+        }
+        self.codegen_backend.link(&self.sess, codegen_results, &self.prepare_outputs)
     }
 }
 

src/test/run-make-fulldeps/hotplug_codegen_backend/the_backend.rs

@@ -71,18 +71,28 @@ impl CodegenBackend for TheBackend {
         Box::new(tcx.crate_name(LOCAL_CRATE) as Symbol)
     }
 
-    fn join_codegen_and_link(
+    fn join_codegen(
         &self,
         ongoing_codegen: Box<dyn Any>,
-        sess: &Session,
+        _sess: &Session,
         _dep_graph: &DepGraph,
+    ) -> Result<Box<dyn Any>, ErrorReported> {
+        let crate_name = ongoing_codegen.downcast::<Symbol>()
+            .expect("in join_codegen: ongoing_codegen is not a Symbol");
+        Ok(crate_name)
+    }
+
+    fn link(
+        &self,
+        sess: &Session,
+        codegen_results: Box<dyn Any>,
         outputs: &OutputFilenames,
     ) -> Result<(), ErrorReported> {
         use std::io::Write;
         use rustc::session::config::CrateType;
         use rustc_codegen_utils::link::out_filename;
-        let crate_name = ongoing_codegen.downcast::<Symbol>()
-            .expect("in join_codegen_and_link: ongoing_codegen is not a Symbol");
+        let crate_name = codegen_results.downcast::<Symbol>()
+            .expect("in link: codegen_results is not a Symbol");
         for &crate_type in sess.opts.crate_types.iter() {
             if crate_type != CrateType::Rlib {
                 sess.fatal(&format!("Crate type is {:?}", crate_type));