From 1af1c2de36d39c5e24846d74f1ae549499bab70d Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Thu, 19 Oct 2017 20:02:46 -0700
Subject: [PATCH 1/2] rustbuild: Compile rustc with ThinLTO

This commit enables ThinLTO for the compiler as well as multiple codegen units.
This is intended to get the benefits of parallel codegen while also avoiding
any major loss of perf. Finally this commit is also intended as further testing
for #45320 and shaking out bugs.
---
 src/bootstrap/bin/rustc.rs |  3 +++
 src/bootstrap/builder.rs   | 14 ++++++++++++--
 src/bootstrap/config.rs    |  7 +++----
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index aeeda85e924ef..16a23eb364a38 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -175,6 +175,9 @@ fn main() {
         if let Ok(s) = env::var("RUSTC_CODEGEN_UNITS") {
             cmd.arg("-C").arg(format!("codegen-units={}", s));
         }
+        if stage != "0" && env::var("RUSTC_THINLTO").is_ok() {
+            cmd.arg("-Ccodegen-units=16").arg("-Zthinlto");
+        }
 
         // Emit save-analysis info.
         if env::var("RUSTC_SAVE_ANALYSIS") == Ok("api".to_string()) {
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 6480b5a619c03..5891925f7f798 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -471,8 +471,6 @@ impl<'a> Builder<'a> {
              .env("RUSTC", self.out.join("bootstrap/debug/rustc"))
              .env("RUSTC_REAL", self.rustc(compiler))
              .env("RUSTC_STAGE", stage.to_string())
-             .env("RUSTC_CODEGEN_UNITS",
-                  self.config.rust_codegen_units.to_string())
              .env("RUSTC_DEBUG_ASSERTIONS",
                   self.config.rust_debug_assertions.to_string())
              .env("RUSTC_SYSROOT", self.sysroot(compiler))
@@ -486,6 +484,10 @@ impl<'a> Builder<'a> {
              })
              .env("TEST_MIRI", self.config.test_miri.to_string());
 
+        if let Some(n) = self.config.rust_codegen_units {
+            cargo.env("RUSTC_CODEGEN_UNITS", n.to_string());
+        }
+
         if let Some(host_linker) = self.build.linker(compiler.host) {
             cargo.env("RUSTC_HOST_LINKER", host_linker);
         }
@@ -618,6 +620,14 @@ impl<'a> Builder<'a> {
         // FIXME: cargo bench does not accept `--release`
         if self.config.rust_optimize && cmd != "bench" {
             cargo.arg("--release");
+
+            if mode != Mode::Libstd &&
+               self.config.rust_codegen_units.is_none() &&
+               self.build.is_rust_llvm(compiler.host)
+
+            {
+                cargo.env("RUSTC_THINLTO", "1");
+            }
         }
         if self.config.locked_deps {
             cargo.arg("--locked");
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index d6c83e3acfc8a..66e5efcea4e80 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -81,7 +81,7 @@ pub struct Config {
 
     // rust codegen options
     pub rust_optimize: bool,
-    pub rust_codegen_units: u32,
+    pub rust_codegen_units: Option<u32>,
     pub rust_debug_assertions: bool,
     pub rust_debuginfo: bool,
     pub rust_debuginfo_lines: bool,
@@ -307,7 +307,6 @@ impl Config {
         config.submodules = true;
         config.docs = true;
         config.rust_rpath = true;
-        config.rust_codegen_units = 1;
         config.channel = "dev".to_string();
         config.codegen_tests = true;
         config.ignore_git = false;
@@ -470,8 +469,8 @@ impl Config {
             config.musl_root = rust.musl_root.clone().map(PathBuf::from);
 
             match rust.codegen_units {
-                Some(0) => config.rust_codegen_units = num_cpus::get() as u32,
-                Some(n) => config.rust_codegen_units = n,
+                Some(0) => config.rust_codegen_units = Some(num_cpus::get() as u32),
+                Some(n) => config.rust_codegen_units = Some(n),
                 None => {}
             }
         }

From d01427f53e81a24e1c49d1672f37d4809c04a004 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Fri, 20 Oct 2017 11:40:04 -0700
Subject: [PATCH 2/2] [test] Add some `#[inline]` to `HashMap`

---
 src/libstd/collections/hash/map.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index 3c0fa0860d394..d96a4f40d3f8e 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1113,6 +1113,7 @@ impl<K, V, S> HashMap<K, V, S>
     /// assert_eq!(map.get(&2), None);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[inline]
     pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
         where K: Borrow<Q>,
               Q: Hash + Eq
@@ -2554,6 +2555,7 @@ impl<K, S, Q: ?Sized> super::Recover<Q> for HashMap<K, (), S>
 {
     type Key = K;
 
+    #[inline]
     fn get(&self, key: &Q) -> Option<&K> {
         self.search(key).into_occupied_bucket().map(|bucket| bucket.into_refs().0)
     }
@@ -2566,6 +2568,7 @@ impl<K, S, Q: ?Sized> super::Recover<Q> for HashMap<K, (), S>
         self.search_mut(key).into_occupied_bucket().map(|bucket| pop_internal(bucket).0)
     }
 
+    #[inline]
     fn replace(&mut self, key: K) -> Option<K> {
         self.reserve(1);