Skip codegen_crate call in check mode

compiler/rustc_codegen_cranelift/src/driver/aot.rs

@@ -671,18 +671,7 @@ pub(crate) fn run_aot(tcx: TyCtxt<'_>) -> Box<OngoingCodegen> {
     }
     .to_owned();
 
-    let cgus = if tcx.sess.opts.output_types.should_codegen() {
-        tcx.collect_and_partition_mono_items(()).codegen_units
-    } else {
-        // If only `--emit metadata` is used, we shouldn't perform any codegen.
-        // Also `tcx.collect_and_partition_mono_items` may panic in that case.
-        return Box::new(OngoingCodegen {
-            modules: vec![],
-            allocator_module: None,
-            crate_info: CrateInfo::new(tcx, target_cpu),
-            concurrency_limiter: ConcurrencyLimiter::new(0),
-        });
-    };
+    let cgus = tcx.collect_and_partition_mono_items(()).codegen_units;
 
     if tcx.dep_graph.is_fully_enabled() {
         for cgu in cgus {

compiler/rustc_codegen_cranelift/src/driver/jit.rs

@@ -33,9 +33,7 @@ fn create_jit_module(tcx: TyCtxt<'_>) -> (UnwindModule<JITModule>, CodegenCx) {
 }
 
 pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_args: Vec<String>) -> ! {
-    if !tcx.sess.opts.output_types.should_codegen() {
-        tcx.dcx().fatal("JIT mode doesn't work with `cargo check`");
-    }
+    // FIXME error on check mode or crate types other than bin in CodegenBackend::init()
 
     if !tcx.crate_types().contains(&rustc_session::config::CrateType::Executable) {
         tcx.dcx().fatal("can't jit non-executable crate");

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -1274,13 +1274,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
         })
         .expect("failed to spawn helper thread");
 
-    let ol =
-        if tcx.sess.opts.unstable_opts.no_codegen || !tcx.sess.opts.output_types.should_codegen() {
-            // If we know that we won’t be doing codegen, create target machines without optimisation.
-            config::OptLevel::No
-        } else {
-            tcx.backend_optimization_level(())
-        };
+    let ol = tcx.backend_optimization_level(());
     let backend_features = tcx.global_backend_features(());
 
     let remark_dir = if let Some(ref dir) = sess.opts.unstable_opts.remark_dir {

compiler/rustc_codegen_ssa/src/base.rs

@@ -684,17 +684,6 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
     tcx: TyCtxt<'_>,
     target_cpu: String,
 ) -> OngoingCodegen<B> {
-    // Skip crate items and just output metadata in -Z no-codegen mode.
-    if tcx.sess.opts.unstable_opts.no_codegen || !tcx.sess.opts.output_types.should_codegen() {
-        let ongoing_codegen = start_async_codegen(backend, tcx, target_cpu, None);
-
-        ongoing_codegen.codegen_finished(tcx);
-
-        ongoing_codegen.check_for_errors(tcx.sess);
-
-        return ongoing_codegen;
-    }
-
     if tcx.sess.target.need_explicit_cpu && tcx.sess.opts.cg.target_cpu.is_none() {
         // The target has no default cpu, but none is set explicitly
         tcx.dcx().emit_fatal(errors::CpuRequired);

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);