Pass --instrprof-atomic-counter-update-all only on old rustc

src/cargo.rs

@@ -25,7 +25,7 @@ pub(crate) struct Workspace {
     rustc: ProcessBuilder,
     pub(crate) target_for_config: cargo_config2::TargetTriple,
     pub(crate) target_for_cli: Option<String>,
-    pub(crate) nightly: bool,
+    pub(crate) rustc_version: RustcVersion,
     /// Whether `-C instrument-coverage` is available.
     pub(crate) stable_coverage: bool,
     /// Whether `-Z doctest-in-workspace` is needed.
@@ -50,14 +50,14 @@ impl Workspace {
         let target_for_config = target_for_config.pop().unwrap();
         let target_for_cli = config.build_target_for_cli(target)?.pop();
         let rustc = ProcessBuilder::from(config.rustc().clone());
-        let nightly = rustc_version(&rustc)?;
+        let rustc_version = rustc_version(&rustc)?;
 
-        if doctests && !nightly {
+        if doctests && !rustc_version.nightly {
             bail!("--doctests flag requires nightly toolchain; consider using `cargo +nightly llvm-cov`")
         }
         let stable_coverage =
             rustc.clone().args(["-C", "help"]).read()?.contains("instrument-coverage");
-        if !stable_coverage && !nightly {
+        if !stable_coverage && !rustc_version.nightly {
             bail!(
                 "cargo-llvm-cov requires rustc 1.60+; consider updating toolchain (`rustup update`)
                  or using nightly toolchain (`cargo +nightly llvm-cov`)"
@@ -100,7 +100,7 @@ impl Workspace {
             rustc,
             target_for_config,
             target_for_cli,
-            nightly,
+            rustc_version,
             stable_coverage,
             need_doctest_in_workspace,
         })
@@ -146,17 +146,33 @@ impl Workspace {
     }
 }
 
-fn rustc_version(rustc: &ProcessBuilder) -> Result<bool> {
+pub(crate) struct RustcVersion {
+    pub(crate) minor: u32,
+    pub(crate) nightly: bool,
+}
+
+fn rustc_version(rustc: &ProcessBuilder) -> Result<RustcVersion> {
     let mut cmd = rustc.clone();
     cmd.args(["--version", "--verbose"]);
     let verbose_version = cmd.read()?;
-    let version = verbose_version
+    let release = verbose_version
         .lines()
         .find_map(|line| line.strip_prefix("release: "))
         .ok_or_else(|| format_err!("unexpected version output from `{cmd}`: {verbose_version}"))?;
-    let (_version, channel) = version.split_once('-').unwrap_or_default();
+    let (version, channel) = release.split_once('-').unwrap_or_default();
+    let mut digits = version.splitn(3, '.');
+    let minor = (|| {
+        let major = digits.next()?.parse::<u32>().ok()?;
+        if major != 1 {
+            return None;
+        }
+        let minor = digits.next()?.parse::<u32>().ok()?;
+        let _patch = digits.next().unwrap_or("0").parse::<u32>().ok()?;
+        Some(minor)
+    })()
+    .ok_or_else(|| format_err!("unable to determine rustc version"))?;
     let nightly = channel == "nightly" || channel == "dev";
-    Ok(nightly)
+    Ok(RustcVersion { minor, nightly })
 }
 
 fn package_root(cargo: &OsStr, manifest_path: Option<&Utf8Path>) -> Result<Utf8PathBuf> {

src/main.rs

@@ -190,14 +190,18 @@ fn set_env(cx: &Context, env: &mut dyn EnvTarget, IsNextest(is_nextest): IsNexte
                 flags.push("codegen-units=1");
             }
         }
-        // Workaround for https://github.com/rust-lang/rust/issues/91092
-        // TODO: skip passing this on newer nightly that includes https://github.com/rust-lang/rust/pull/111469.
-        flags.push("-C");
-        flags.push("llvm-args=--instrprof-atomic-counter-update-all");
+        // Workaround for https://github.com/rust-lang/rust/issues/91092.
+        // Unnecessary since https://github.com/rust-lang/rust/pull/111469.
+        if cx.ws.rustc_version.nightly && cx.ws.rustc_version.minor <= 71
+            || !cx.ws.rustc_version.nightly && cx.ws.rustc_version.minor < 71
+        {
+            flags.push("-C");
+            flags.push("llvm-args=--instrprof-atomic-counter-update-all");
+        }
         if !cx.args.cov.no_cfg_coverage {
             flags.push("--cfg=coverage");
         }
-        if cx.ws.nightly && !cx.args.cov.no_cfg_coverage_nightly {
+        if cx.ws.rustc_version.nightly && !cx.args.cov.no_cfg_coverage_nightly {
             flags.push("--cfg=coverage_nightly");
         }
     }