Skip codegen_crate call in check mode

compiler/rustc_interface/src/passes.rs

@@ -8,6 +8,7 @@ use std::{env, fs, iter};
 use rustc_ast as ast;
 use rustc_attr_parsing::{AttributeParser, ShouldEmit};
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_codegen_ssa::{CodegenResults, CrateInfo};
 use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{AppendOnlyIndexVec, FreezeLock, WorkerLocal};
@@ -1236,7 +1237,21 @@ pub(crate) fn start_codegen<'tcx>(
 
     let metadata = rustc_metadata::fs::encode_and_write_metadata(tcx);
 
-    let codegen = tcx.sess.time("codegen_crate", move || codegen_backend.codegen_crate(tcx));
+    let codegen = tcx.sess.time("codegen_crate", move || {
+        if tcx.sess.opts.unstable_opts.no_codegen || !tcx.sess.opts.output_types.should_codegen() {
+            // Skip crate items and just output metadata in -Z no-codegen mode.
+            tcx.sess.dcx().abort_if_errors();
+
+            // Linker::link will skip join_codegen in case of a CodegenResults Any value.
+            Box::new(CodegenResults {
+                modules: vec![],
+                allocator_module: None,
+                crate_info: CrateInfo::new(tcx, "<dummy cpu>".to_owned()),
+            })
+        } else {
+            codegen_backend.codegen_crate(tcx)
+        }
+    });
 
     info!("Post-codegen\n{:?}", tcx.debug_stats());
 

compiler/rustc_interface/src/queries.rs

@@ -3,6 +3,7 @@ use std::sync::Arc;
 
 use rustc_codegen_ssa::CodegenResults;
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_data_structures::indexmap::IndexMap;
 use rustc_data_structures::svh::Svh;
 use rustc_errors::timings::TimingSection;
 use rustc_hir::def_id::LOCAL_CRATE;
@@ -46,7 +47,14 @@ impl Linker {
 
     pub fn link(self, sess: &Session, codegen_backend: &dyn CodegenBackend) {
         let (codegen_results, mut work_products) = sess.time("finish_ongoing_codegen", || {
-            codegen_backend.join_codegen(self.ongoing_codegen, sess, &self.output_filenames)
+            match self.ongoing_codegen.downcast::<CodegenResults>() {
+                // This was a check only build
+                Ok(codegen_results) => (*codegen_results, IndexMap::default()),
+
+                Err(ongoing_codegen) => {
+                    codegen_backend.join_codegen(ongoing_codegen, sess, &self.output_filenames)
+                }
+            }
         });
         sess.timings.end_section(sess.dcx(), TimingSection::Codegen);