Distribute LLVM bitcode linker as a preview component

Author: Kjetil Kjeka

Diff for: src/bootstrap/src/core/build_steps/dist.rs

@@ -1548,6 +1548,7 @@ impl Step for Extended {
             compiler: builder.compiler(stage, target),
             backend: "cranelift".to_string(),
         });
+        add_component!("llvm-bitcode-linker" => LlvmBitcodeLinker {compiler, target});
 
         let etc = builder.src.join("src/etc/installer");
 
@@ -2224,6 +2225,53 @@ impl Step for LlvmTools {
     }
 }
 
+#[derive(Debug, PartialOrd, Ord, Clone, Hash, PartialEq, Eq)]
+pub struct LlvmBitcodeLinker {
+    pub compiler: Compiler,
+    pub target: TargetSelection,
+}
+
+impl Step for LlvmBitcodeLinker {
+    type Output = Option<GeneratedTarball>;
+    const DEFAULT: bool = true;
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        let default = should_build_extended_tool(run.builder, "llvm-bitcode-linker");
+        run.alias("llvm-bitcode-linker").default_condition(default)
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(LlvmBitcodeLinker {
+            compiler: run.builder.compiler_for(
+                run.builder.top_stage,
+                run.builder.config.build,
+                run.target,
+            ),
+            target: run.target,
+        });
+    }
+
+    fn run(self, builder: &Builder<'_>) -> Option<GeneratedTarball> {
+        let compiler = self.compiler;
+        let target = self.target;
+
+        let llbc_linker =
+            builder.ensure(tool::LlvmBitcodeLinker { compiler, target, extra_features: vec![] });
+
+        let self_contained_bin_dir = format!("lib/rustlib/{}/bin/self-contained", target.triple);
+
+        // Prepare the image directory
+        let mut tarball = Tarball::new(builder, "llvm-bitcode-linker", &target.triple);
+        tarball.set_overlay(OverlayKind::LlvmBitcodeLinker);
+        tarball.is_preview(true);
+
+        tarball.add_file(llbc_linker, self_contained_bin_dir, 0o755);
+
+        Some(tarball.generate())
+    }
+}
+
 // Tarball intended for internal consumption to ease rustc/std development.
 //
 // Should not be considered stable by end users.

Diff for: src/bootstrap/src/core/build_steps/install.rs

@@ -300,6 +300,15 @@ install!((self, builder, _config),
             );
         }
     };
+    LlvmBitcodeLinker, alias = "llvm-bitcode-linker", Self::should_build(_config), only_hosts: true, {
+        if let Some(tarball) = builder.ensure(dist::LlvmBitcodeLinker { compiler: self.compiler, target: self.target }) {
+            install_sh(builder, "llvm-bitcode-linker", self.compiler.stage, Some(self.target), &tarball);
+        } else {
+            builder.info(
+                &format!("skipping llvm-bitcode-linker stage{} ({})", self.compiler.stage, self.target),
+            );
+        }
+    };
 );
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]

Diff for: src/bootstrap/src/core/build_steps/tool.rs

@@ -746,9 +746,11 @@ impl Step for LlvmBitcodeLinker {
             .join(exe(bin_name, self.compiler.host));
 
         if self.compiler.stage > 0 {
-            let bindir = builder.sysroot(self.compiler).join("bin");
-            t!(fs::create_dir_all(&bindir));
-            let bin_destination = bindir.join(exe(bin_name, self.compiler.host));
+            let bindir_self_contained = builder
+                .sysroot(self.compiler)
+                .join(format!("lib/rustlib/{}/bin/self-contained", self.target.triple));
+            t!(fs::create_dir_all(&bindir_self_contained));
+            let bin_destination = bindir_self_contained.join(exe(bin_name, self.compiler.host));
             builder.copy_link(&tool_out, &bin_destination);
             bin_destination
         } else {

Diff for: src/bootstrap/src/core/builder.rs

@@ -853,6 +853,7 @@ impl<'a> Builder<'a> {
                 dist::Clippy,
                 dist::Miri,
                 dist::LlvmTools,
+                dist::LlvmBitcodeLinker,
                 dist::RustDev,
                 dist::Bootstrap,
                 dist::Extended,

Diff for: src/bootstrap/src/utils/tarball.rs

@@ -20,6 +20,7 @@ pub(crate) enum OverlayKind {
     RLS,
     RustAnalyzer,
     RustcCodegenCranelift,
+    LlvmBitcodeLinker,
 }
 
 impl OverlayKind {
@@ -64,6 +65,12 @@ impl OverlayKind {
                 "compiler/rustc_codegen_cranelift/LICENSE-APACHE",
                 "compiler/rustc_codegen_cranelift/LICENSE-MIT",
             ],
+            OverlayKind::LlvmBitcodeLinker => &[
+                "COPYRIGHT",
+                "LICENSE-APACHE",
+                "LICENSE-MIT",
+                "src/tools/llvm-bitcode-linker/README.md",
+            ],
         }
     }
 
@@ -87,6 +94,7 @@ impl OverlayKind {
                 .rust_analyzer_info
                 .version(builder, &builder.release_num("rust-analyzer/crates/rust-analyzer")),
             OverlayKind::RustcCodegenCranelift => builder.rust_version(),
+            OverlayKind::LlvmBitcodeLinker => builder.rust_version(),
         }
     }
 }

Diff for: src/doc/unstable-book/src/compiler-flags/codegen-options.md

@@ -10,6 +10,10 @@ In addition to the stable set of linker flavors, the following unstable values a
 - `ptx`: use [`rust-ptx-linker`](https://github.com/denzp/rust-ptx-linker)
   for Nvidia NVPTX GPGPU support.
 - `bpf`: use [`bpf-linker`](https://github.com/alessandrod/bpf-linker) for eBPF support.
+- `llbc`: for linking in llvm bitcode. Install the preview rustup components`llvm-bitcode-linker`
+  and `llvm-tools` to use as a self-contained linker by passing
+  `-Zunstable-options -Clink-self-contained=+linker` together with `-Clinker-flavor=llbc`.
+  Can currently only be used for Nvidia NVPTX targets (`nvptx64-nvidia-cuda`).
 
 Additionally, a set of more precise linker flavors also exists, for example allowing targets to
 declare that they use the LLD linker by default. The following values are currently unstable, and

Diff for: src/tools/llvm-bitcode-linker/src/linker.rs

@@ -62,7 +62,7 @@ impl Session {
             .arg("-o")
             .arg(&self.link_path)
             .output()
-            .unwrap();
+            .context("An error occured when calling llvm-link. Make sure the llvm-tools component is installed.")?;
 
         if !llvm_link_output.status.success() {
             tracing::error!(
@@ -108,7 +108,9 @@ impl Session {
             opt_cmd.arg("--strip-debug");
         }
 
-        let opt_output = opt_cmd.output().unwrap();
+        let opt_output = opt_cmd.output().context(
+            "An error occured when calling opt. Make sure the llvm-tools component is installed.",
+        )?;
 
         if !opt_output.status.success() {
             tracing::error!(
@@ -133,8 +135,11 @@ impl Session {
             lcc_command.arg("--mcpu").arg(mcpu);
         }
 
-        let lcc_output =
-            lcc_command.arg(&self.opt_path).arg("-o").arg(&self.out_path).output().unwrap();
+        let lcc_output = lcc_command
+            .arg(&self.opt_path)
+            .arg("-o").arg(&self.out_path)
+            .output()
+            .context("An error occured when calling llc. Make sure the llvm-tools component is installed.")?;
 
         if !lcc_output.status.success() {
             tracing::error!(