bootstrap: Build LLVM with ThinLTO on Linux64.

Author: michaelwoerister

src/bootstrap/compile.rs

@@ -35,7 +35,6 @@ use util::{exe, libdir, is_dylib, CiEnv};
 use {Compiler, Mode};
 use native;
 use tool;
-
 use cache::{INTERNER, Interned};
 use builder::{Step, RunConfig, ShouldRun, Builder};
 
@@ -635,20 +634,28 @@ impl Step for CodegenBackend {
             return;
         }
 
-        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "build");
+        let mut cargo = builder.cargo(compiler, Mode::Librustc, target, "rustc");
         let mut features = builder.rustc_features().to_string();
         cargo.arg("--manifest-path")
             .arg(builder.src.join("src/librustc_codegen_llvm/Cargo.toml"));
         rustc_cargo_env(builder, &mut cargo);
 
         features += &build_codegen_backend(&builder, &mut cargo, &compiler, target, backend);
+        cargo.arg("--features").arg(features);
 
         let tmp_stamp = builder.cargo_out(compiler, Mode::Librustc, target)
             .join(".tmp.stamp");
 
+        if builder.config.llvm_thin_lto {
+            cargo.deferred_arg("--")
+                 .deferred_arg("-Clink-arg=-fuse-ld=lld")
+                 .deferred_arg("-Clink-arg=-flto=thin")
+                 .deferred_arg("-Clink-arg=-O2");
+        }
+
         let _folder = builder.fold_output(|| format!("stage{}-rustc_codegen_llvm", compiler.stage));
         let files = run_cargo(builder,
-                              cargo.arg("--features").arg(features),
+                              &mut cargo,
                               &tmp_stamp,
                               false);
         if builder.config.dry_run {

src/bootstrap/config.rs

@@ -79,6 +79,7 @@ pub struct Config {
     pub llvm_assertions: bool,
     pub llvm_optimize: bool,
     pub llvm_release_debuginfo: bool,
+    pub llvm_thin_lto: bool,
     pub llvm_version_check: bool,
     pub llvm_static_stdcpp: bool,
     pub llvm_link_shared: bool,
@@ -246,6 +247,7 @@ struct Llvm {
     assertions: Option<bool>,
     optimize: Option<bool>,
     release_debuginfo: Option<bool>,
+    thin_lto: Option<bool>,
     version_check: Option<bool>,
     static_libstdcpp: Option<bool>,
     targets: Option<String>,
@@ -501,6 +503,7 @@ impl Config {
             llvm_assertions = llvm.assertions;
             set(&mut config.llvm_optimize, llvm.optimize);
             set(&mut config.llvm_release_debuginfo, llvm.release_debuginfo);
+            set(&mut config.llvm_thin_lto, llvm.thin_lto);
             set(&mut config.llvm_version_check, llvm.version_check);
             set(&mut config.llvm_static_stdcpp, llvm.static_libstdcpp);
             set(&mut config.llvm_link_shared, llvm.link_shared);

src/bootstrap/native.rs

@@ -154,6 +154,11 @@ impl Step for Llvm {
            .define("LLVM_TARGET_ARCH", target.split('-').next().unwrap())
            .define("LLVM_DEFAULT_TARGET_TRIPLE", target);
 
+        if builder.config.llvm_thin_lto {
+            cfg.define("LLVM_ENABLE_LTO", "Thin")
+               .define("LLVM_ENABLE_LLD", "ON");
+        }
+
         // By default, LLVM will automatically find OCaml and, if it finds it,
         // install the LLVM bindings in LLVM_OCAML_INSTALL_PATH, which defaults
         // to /usr/bin/ocaml.

src/ci/docker/dist-x86_64-linux/Dockerfile

@@ -93,7 +93,9 @@ ENV RUST_CONFIGURE_ARGS \
       --enable-sanitizers \
       --enable-profiler \
       --enable-compiler-docs \
-      --set target.x86_64-unknown-linux-gnu.linker=clang
+      --set target.x86_64-unknown-linux-gnu.linker=clang \
+      --set target.x86_64-unknown-linux-gnu.ar=/rustroot/bin/llvm-ar \
+      --set target.x86_64-unknown-linux-gnu.ranlib=/rustroot/bin/llvm-ranlib
 ENV SCRIPT python2.7 ../x.py dist --host $HOSTS --target $HOSTS
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang