WIP

.github/workflows/main.yml

@@ -169,7 +169,9 @@ jobs:
     - name: Configure extra test environment
       run: echo CARGO_CONTAINER_TESTS=1 >> $GITHUB_ENV
       if: matrix.os == 'ubuntu-latest'
-    - run: cargo test -p cargo
+    - run: |
+        export PATH="$(basename $(rustc --print target-libdir)/bin):$PATH"
+        cargo test -p cargo -- pgo
     - name: Clear intermediate test output
       run: ci/clean-test-output.sh
 

crates/cargo-test-macro/src/lib.rs

@@ -137,6 +137,18 @@ pub fn cargo_test(attr: TokenStream, item: TokenStream) -> TokenStream {
                 let command = &s[9..];
                 set_ignore!(!has_command(command), "{command} not installed");
             }
+            s if s.starts_with("requires=") => {
+                let command = &s[9..];
+                let Ok(command) = command.parse::<Literal>() else {
+                    panic!("expected a string literal for `requires`, got: {command}");
+                };
+                let command = command.to_string();
+                let Some(command) = command.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
+                else {
+                    panic!("expected a string literal for `requires`, got: {command}");
+                };
+                set_ignore!(!has_command(command), "{command} not installed");
+            }
             s if s.starts_with(">=1.") => {
                 requires_reason = true;
                 let min_minor = s[4..].parse().unwrap();
@@ -274,13 +286,16 @@ fn check_command(command_path: &Path, args: &[&str]) -> bool {
             //   environments like Docker. Consider installing it if Cargo
             //   gains more hg support, but otherwise it isn't critical.
             // * lldb is not pre-installed on Ubuntu and Windows, so skip.
-            if is_ci() && !matches!(command_name.as_str(), "hg" | "lldb") {
+            if is_ci() && !matches!(command_name.as_str(), "hg" | "lldb" | "lldb-profdata") {
                 panic!("expected command `{command_name}` to be somewhere in PATH: {e}",);
             }
             return false;
         }
     };
     if !output.status.success() {
+        if command_name.as_str() == "llvm-profdata" {
+            return true;
+        }
         panic!(
             "expected command `{command_name}` to be runnable, got error {}:\n\
             stderr:{}\n\

src/cargo/core/compiler/build_runner/compilation_files.rs

@@ -708,6 +708,7 @@ fn compute_metadata(
     let c_metadata = UnitHash(c_metadata_hasher.finish());
     let c_extra_filename = UnitHash(c_extra_filename_hasher.finish());
     let unit_id = c_extra_filename;
+    // let c_metadata = c_extra_filename;
 
     let c_extra_filename = use_extra_filename.then_some(c_extra_filename);
 

tests/testsuite/main.rs

@@ -136,6 +136,7 @@ mod package_features;
 mod patch;
 mod path;
 mod paths;
+mod pgo;
 mod pkgid;
 mod precise_pre_release;
 mod proc_macro;

tests/testsuite/pgo.rs

@@ -0,0 +1,115 @@
+//! Test if PGO works.
+
+use std::path::PathBuf;
+use std::process::Command;
+
+use cargo_test_support::prelude::*;
+use cargo_test_support::project;
+use cargo_test_support::str;
+
+fn llvm_profdata() -> Option<PathBuf> {
+    let output = Command::new("rustc")
+        .arg("--print=target-libdir")
+        .output()
+        .expect("rustc to run");
+    assert!(output.status.success());
+    let mut libdir = PathBuf::from(String::from_utf8(output.stdout).unwrap());
+    assert!(libdir.pop());
+    let mut bin = libdir.join("bin").join("llvm-profdata");
+    bin.exists().then(|| bin.clone()).or_else(|| {
+        bin.set_extension("exe");
+        bin.exists().then_some(bin)
+    })
+}
+
+#[cargo_test]
+fn pgo_works() {
+    let Some(llvm_profdata) = llvm_profdata() else {
+        return;
+    };
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            edition = "2021"
+            "#,
+        )
+        .file(
+            "src/main.rs",
+            r#"
+                fn fibonacci(n: u64) -> u64 {
+                    match n {
+                        0 => 0,
+                        1 => 1,
+                        _ => fibonacci(n - 1) + fibonacci(n - 2),
+                    }
+                }
+
+                fn main() {
+                    for i in [15, 20, 25] {
+                        let _ = fibonacci(i);
+                    }
+                }
+            "#,
+        )
+        .build();
+
+    let target_dir = p.build_dir();
+    let release_bin = target_dir.join("release").join("foo");
+    let pgo_data_dir = target_dir.join("pgo-data");
+    let profdata_path = target_dir.join("merged.profdata");
+
+    // Build the instrumented binary
+    p.cargo("build --release")
+        .env(
+            "RUSTFLAGS",
+            format!("-Cprofile-generate={}", pgo_data_dir.display()),
+        )
+        .run();
+    // Run the instrumented binary
+    cargo_test_support::execs()
+        .with_process_builder(cargo_test_support::process(release_bin))
+        .run();
+
+    cargo_test_support::process(llvm_profdata)
+        .arg("merge")
+        .arg("-o")
+        .arg(&profdata_path)
+        .arg(pgo_data_dir)
+        .status()
+        .unwrap();
+
+#[cfg(target_os = "macos")]
+let stderr = str![[r#"
+[COMPILING] foo v0.0.0 ([ROOT]/foo)
+[RUNNING] `rustc [..]-Cprofile-use=[ROOT]/foo/target/merged.profdata -Cllvm-args=-pgo-warn-missing-function`
+[WARNING] [..] no profile data available for function [..]
+
+[WARNING] `foo` (bin "foo") generated 1 warning
+[FINISHED] `release` profile [optimized] target(s) in [ELAPSED]s
+
+"#]];
+
+#[cfg(not(target_os = "macos"))]
+let stderr = str![[r#"
+[COMPILING] foo v0.0.0 ([ROOT]/foo)
+[RUNNING] `rustc [..]-Cprofile-use=[ROOT]/foo/target/merged.profdata -Cllvm-args=-pgo-warn-missing-function`
+[FINISHED] `release` profile [optimized] target(s) in [ELAPSED]s
+
+"#]];
+
+    // Use merged profdata during optimization.
+    p.cargo("build --release -v")
+        .env(
+            "RUSTFLAGS",
+            format!(
+                "-Cprofile-use={} -Cllvm-args=-pgo-warn-missing-function",
+                profdata_path.display()
+            ),
+        )
+        .with_stderr_data(stderr)
+        .run();
+}