From c637a84ad4f4446e6f6bbb1129632b20b42c6e3a Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Fri, 8 Nov 2024 16:14:02 +0100
Subject: [PATCH 1/2] Add finish_ongoing_codegen timer in join_codegen to match
 cg_llvm

---
 src/lib.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index aba0c28f6b8..19a1de53d1d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -241,6 +241,8 @@ fn join_codegen(
         sess: &Session,
         outputs: &OutputFilenames,
     ) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>) {
+        let _timer = sess.timer("finish_ongoing_codegen");
+
         ongoing_codegen.downcast::<driver::aot::OngoingCodegen>().unwrap().join(
             sess,
             outputs,

From 8a0053e9e16586e060612db44578038d3edb107e Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Fri, 8 Nov 2024 16:16:03 +0100
Subject: [PATCH 2/2] Use a BufWriter in emit_module to reduce syscall overhead

For the coercions rustc-perf benchmark without this commit reduces the
total amount of time it takes to emit the object file from 270ms to
27ms.
---
 src/driver/aot.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/driver/aot.rs b/src/driver/aot.rs
index 419efa90600..8eab73ad5f9 100644
--- a/src/driver/aot.rs
+++ b/src/driver/aot.rs
@@ -2,6 +2,7 @@
 //! standalone executable.
 
 use std::fs::{self, File};
+use std::io::BufWriter;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::thread::JoinHandle;
@@ -397,14 +398,19 @@ fn emit_module(
     }
 
     let tmp_file = output_filenames.temp_path(OutputType::Object, Some(&name));
-    let mut file = match File::create(&tmp_file) {
+    let file = match File::create(&tmp_file) {
         Ok(file) => file,
         Err(err) => return Err(format!("error creating object file: {}", err)),
     };
 
+    let mut file = BufWriter::new(file);
     if let Err(err) = object.write_stream(&mut file) {
         return Err(format!("error writing object file: {}", err));
     }
+    let file = match file.into_inner() {
+        Ok(file) => file,
+        Err(err) => return Err(format!("error writing object file: {}", err)),
+    };
 
     prof.artifact_size("object_file", &*name, file.metadata().unwrap().len());