bootstrap: Link LLVM tools dynamically in order to save time in ThinLTO builds.

Author: michaelwoerister

src/bootstrap/dist.rs

@@ -1929,16 +1929,37 @@ impl Step for LlvmTools {
         drop(fs::remove_dir_all(&image));
 
         // Prepare the image directory
-        let bindir = builder
+        let src_bindir = builder
             .llvm_out(target)
             .join("bin");
-        let dst = image.join("lib/rustlib")
-            .join(target)
-            .join("bin");
-        t!(fs::create_dir_all(&dst));
+        let dst_bindir = image.join("bin");
+        t!(fs::create_dir_all(&dst_bindir));
         for tool in LLVM_TOOLS {
-            let exe = bindir.join(exe(tool, &target));
-            builder.install(&exe, &dst, 0o755);
+            let exe = src_bindir.join(exe(tool, &target));
+            builder.install(&exe, &dst_bindir, 0o755);
+        }
+
+        // Maybe add libLLVM.so to the lib-dir. It will only have been built if
+        // LLVM tools are linked dynamically.
+        {
+            let src_libdir = builder
+                .llvm_out(target)
+                .join("lib");
+            let dst_libdir = image.join("lib");
+            t!(fs::create_dir_all(&dst_libdir));
+
+            // Usually libLLVM.so is a symlink to something like libLLVM-6.0.so.
+            // Since tools link to the latter rather than the former, we have to
+            // follow the symlink to find out what to distribute.
+            let llvm_dylib_path = src_libdir.join("libLLVM.so");
+            if llvm_dylib_path.exists() {
+                let llvm_dylib_path = llvm_dylib_path.canonicalize().unwrap_or_else(|e| {
+                    panic!("dist: Error calling canonicalize path `{}`: {}",
+                           llvm_dylib_path.display(), e);
+                });
+
+                builder.install(&llvm_dylib_path, &dst_libdir, 0o644);
+            }
         }
 
         // Prepare the overlay

src/bootstrap/lib.rs

@@ -1025,6 +1025,10 @@ impl Build {
         self.rust_version()
     }
 
+    fn llvm_link_tools_dynamically(&self, target: Interned<String>) -> bool {
+        (target.contains("linux-gnu") || target.contains("apple-darwin"))
+    }
+
     /// Returns the `version` string associated with this compiler for Rust
     /// itself.
     ///

src/bootstrap/native.rs

@@ -171,14 +171,10 @@ impl Step for Llvm {
 
         // This setting makes the LLVM tools link to the dynamic LLVM library,
         // which saves both memory during parallel links and overall disk space
-        // for the tools.  We don't distribute any of those tools, so this is
-        // just a local concern.  However, it doesn't work well everywhere.
-        //
-        // If we are shipping llvm tools then we statically link them LLVM
-        if (target.contains("linux-gnu") || target.contains("apple-darwin")) &&
-            !builder.config.llvm_tools_enabled &&
-            !want_lldb {
-                cfg.define("LLVM_LINK_LLVM_DYLIB", "ON");
+        // for the tools. We don't do this on every platform as it doesn't work
+        // equally well everywhere.
+        if builder.llvm_link_tools_dynamically(target) && !emscripten {
+            cfg.define("LLVM_LINK_LLVM_DYLIB", "ON");
         }
 
         // For distribution we want the LLVM tools to be *statically* linked to libstdc++

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

@@ -97,7 +97,7 @@ ENV RUST_CONFIGURE_ARGS \
       --set target.x86_64-unknown-linux-gnu.ar=/rustroot/bin/llvm-ar \
       --set target.x86_64-unknown-linux-gnu.ranlib=/rustroot/bin/llvm-ranlib \
       --set llvm.thin-lto=true
-ENV SCRIPT python2.7 ../x.py dist --host $HOSTS --target $HOSTS
+ENV SCRIPT python2.7 ../x.py dist --verbose --host $HOSTS --target $HOSTS
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
 
 # This is the only builder which will create source tarballs