Don't attempt to do incr comp for the allocator shim

The allocator shim doesn't get reused and the allocator shim is just
under 2kb, so reusing it is likely more expensive than regenerating it.

Author: bjorn3

src/driver/aot.rs

@@ -38,12 +38,11 @@ pub(crate) struct OngoingCodegen {
     metadata_module: Option<CompiledModule>,
     metadata: EncodedMetadata,
     crate_info: CrateInfo,
-    work_products: FxHashMap<WorkProductId, WorkProduct>,
 }
 
 impl OngoingCodegen {
     pub(crate) fn join(self) -> (CodegenResults, FxHashMap<WorkProductId, WorkProduct>) {
-        let mut work_products = self.work_products;
+        let mut work_products = FxHashMap::default();
         let mut modules = vec![];
 
         for module_codegen_result in self.modules {
@@ -331,8 +330,6 @@ pub(crate) fn run_aot(
 
     tcx.sess.abort_if_errors();
 
-    let mut work_products = FxHashMap::default();
-
     let isa = crate::build_isa(tcx.sess, &backend_config);
     let mut allocator_module = make_module(tcx.sess, isa, "allocator_shim".to_string());
     assert_eq!(pointer_ty(tcx), allocator_module.target_config().pointer_type());
@@ -341,21 +338,27 @@ pub(crate) fn run_aot(
         crate::allocator::codegen(tcx, &mut allocator_module, &mut allocator_unwind_context);
 
     let allocator_module = if created_alloc_shim {
-        let ModuleCodegenResult { module_regular, module_global_asm, work_product } = emit_module(
-            tcx,
-            &backend_config,
-            "allocator_shim".to_string(),
-            ModuleKind::Allocator,
-            allocator_module,
-            None,
-            allocator_unwind_context,
-            None,
-        );
-        assert!(module_global_asm.is_none());
-        if let Some((id, product)) = work_product {
-            work_products.insert(id, product);
+        let name = "allocator_shim".to_owned();
+
+        let mut product = allocator_module.finish();
+        allocator_unwind_context.emit(&mut product);
+
+        let tmp_file = tcx.output_filenames(()).temp_path(OutputType::Object, Some(&name));
+        let obj = product.object.write().unwrap();
+
+        tcx.sess.prof.artifact_size("object_file", &*name, obj.len().try_into().unwrap());
+
+        if let Err(err) = std::fs::write(&tmp_file, obj) {
+            tcx.sess.fatal(&format!("error writing object file: {}", err));
         }
-        Some(module_regular)
+
+        Some(CompiledModule {
+            name,
+            kind: ModuleKind::Allocator,
+            object: Some(tmp_file),
+            dwarf_object: None,
+            bytecode: None,
+        })
     } else {
         None
     };
@@ -408,7 +411,6 @@ pub(crate) fn run_aot(
         metadata_module,
         metadata,
         crate_info: CrateInfo::new(tcx, target_cpu),
-        work_products,
     })
 }