Auto merge of rust-lang#125642 - khuey:zstd, r=<try>

Enable zstd for debug compression.

Set LLVM_ENABLE_ZSTD alongside LLVM_ENABLE_ZLIB so that --compress-debug-sections=zstd is an option.

See rust-lang#120953

try-job: x86_64-gnu

Author: bors

compiler/rustc_llvm/build.rs

@@ -259,15 +259,32 @@ fn main() {
     cmd.args(&components);
 
     for lib in output(&mut cmd).split_whitespace() {
+        let mut is_static = false;
         let name = if let Some(stripped) = lib.strip_prefix("-l") {
             stripped
         } else if let Some(stripped) = lib.strip_prefix('-') {
             stripped
         } else if Path::new(lib).exists() {
             // On MSVC llvm-config will print the full name to libraries, but
             // we're only interested in the name part
-            let name = Path::new(lib).file_name().unwrap().to_str().unwrap();
-            name.trim_end_matches(".lib")
+            // On Unix when we get a static library llvm-config will print the
+            // full name and we *are* interested in the path, but we need to
+            // handle it separately. For example, when statically linking to
+            // libzstd llvm-config will output something like
+            //   -lrt -ldl -lm -lz /usr/local/lib/libzstd.a -lxml2
+            // and we transform the zstd part into
+            //   cargo:rustc-link-search-native=/usr/local/lib
+            //   cargo:rustc-link-lib=static=zstd
+            let path = Path::new(lib);
+            if lib.ends_with(".a") {
+                is_static = true;
+                println!("cargo:rustc-link-search=native={}", path.parent().unwrap().display());
+                let name = path.file_stem().unwrap().to_str().unwrap();
+                name.trim_start_matches("lib")
+            } else {
+                let name = path.file_name().unwrap().to_str().unwrap();
+                name.trim_end_matches(".lib")
+            }
         } else if lib.ends_with(".lib") {
             // Some MSVC libraries just come up with `.lib` tacked on, so chop
             // that off
@@ -285,7 +302,13 @@ fn main() {
             continue;
         }
 
-        let kind = if name.starts_with("LLVM") { llvm_kind } else { "dylib" };
+        let kind = if name.starts_with("LLVM") {
+            llvm_kind
+        } else if is_static {
+            "static"
+        } else {
+            "dylib"
+        };
         println!("cargo:rustc-link-lib={kind}={name}");
     }
 

src/bootstrap/download-ci-llvm-stamp

@@ -1,4 +1,4 @@
 Change this file to make users of the `download-ci-llvm` configuration download
 a new version of LLVM from CI, even if the LLVM submodule hasn’t changed.
 
-Last change is for: https://github.com/rust-lang/rust/pull/126298
+Last change is for: https://github.com/rust-lang/rust/pull/125642

src/bootstrap/src/core/build_steps/llvm.rs

@@ -377,15 +377,6 @@ impl Step for Llvm {
             cfg.define("LLVM_PROFDATA_FILE", path);
         }
 
-        // Disable zstd to avoid a dependency on libzstd.so.
-        cfg.define("LLVM_ENABLE_ZSTD", "OFF");
-
-        if !target.is_windows() {
-            cfg.define("LLVM_ENABLE_ZLIB", "ON");
-        } else {
-            cfg.define("LLVM_ENABLE_ZLIB", "OFF");
-        }
-
         // Are we compiling for iOS/tvOS/watchOS/visionOS?
         if target.contains("apple-ios")
             || target.contains("apple-tvos")
@@ -833,6 +824,16 @@ fn configure_llvm(builder: &Builder<'_>, target: TargetSelection, cfg: &mut cmak
         }
     }
 
+    // Libraries for ELF section compression.
+    if !target.is_windows() {
+        cfg.define("LLVM_ENABLE_ZLIB", "ON");
+        cfg.define("LLVM_ENABLE_ZSTD", "ON");
+        cfg.define("LLVM_USE_STATIC_ZSTD", "TRUE");
+    } else {
+        cfg.define("LLVM_ENABLE_ZLIB", "OFF");
+        cfg.define("LLVM_ENABLE_ZSTD", "OFF");
+    }
+
     if let Some(ref linker) = builder.config.llvm_use_linker {
         cfg.define("LLVM_USE_LINKER", linker);
     }

tests/run-make/rust-lld-compress-debug-sections/main.rs

@@ -0,0 +1,4 @@
+// Test linking using `cc` with `rust-lld`, using the unstable CLI described in MCP 510
+// see https://github.com/rust-lang/compiler-team/issues/510 for more info
+
+fn main() {}

tests/run-make/rust-lld-compress-debug-sections/rmake.rs

@@ -0,0 +1,39 @@
+// Checks the `compress-debug-sections` option on rust-lld.
+
+//@ needs-rust-lld
+//@ only-linux
+//@ ignore-cross-compile
+
+// FIXME: This test isn't comprehensive and isn't covering all possible combinations.
+
+use run_make_support::{assert_contains, cmd, llvm_readobj, run_in_tmpdir, rustc};
+
+fn check_compression(compression: &str, to_find: &str) {
+    run_in_tmpdir(|| {
+        let out = rustc()
+            .arg("-Zlinker-features=+lld")
+            .arg("-Clink-self-contained=+linker")
+            .arg("-Zunstable-options")
+            .arg("-Cdebuginfo=full")
+            .link_arg(&format!("-Wl,--compress-debug-sections={compression}"))
+            .input("main.rs")
+            .run_unchecked();
+        let stderr = out.stderr_utf8();
+        if stderr.is_empty() {
+            llvm_readobj().arg("-t").arg("main").run().assert_stdout_contains(to_find);
+        } else {
+            assert_contains(
+                stderr,
+                format!(
+                    "\
+LLVM was not built with LLVM_ENABLE_{to_find} or did not find {compression} at build time"
+                ),
+            );
+        }
+    });
+}
+
+fn main() {
+    check_compression("zlib", "ZLIB");
+    check_compression("zstd", "ZSTD");
+}