WIP: Add PGO for apple darwin targets

src/bootstrap/src/core/build_steps/compile.rs

@@ -1388,12 +1388,19 @@ fn rustc_llvm_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetSelect
     // found. This is to avoid the linker errors about undefined references to
     // `__llvm_profile_instrument_memop` when linking `rustc_driver`.
     let mut llvm_linker_flags = String::new();
-    if builder.config.llvm_profile_generate && target.is_msvc() {
-        if let Some(ref clang_cl_path) = builder.config.llvm_clang_cl {
-            // Add clang's runtime library directory to the search path
-            let clang_rt_dir = get_clang_cl_resource_dir(builder, clang_cl_path);
-            llvm_linker_flags.push_str(&format!("-L{}", clang_rt_dir.display()));
+    if builder.config.llvm_profile_generate {
+        if target.is_msvc() {
+            if let Some(ref clang_cl_path) = builder.config.llvm_clang_cl {
+                // Add clang's runtime library directory to the search path
+                let clang_rt_dir = get_clang_cl_resource_dir(builder, clang_cl_path);
+                llvm_linker_flags.push_str(&format!("-L{}", clang_rt_dir.display()));
+            }
+        } else  {
+
+            llvm_linker_flags.push_str("-L/opt/homebrew/Cellar/llvm/20.1.2/lib/clang/20/lib/darwin -lclang_rt.profile_osx");
+
         }
+
     }
 
     // The config can also specify its own llvm linker flags.

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

@@ -1037,13 +1037,18 @@ impl Step for Lld {
         // when doing PGO on CI, cmake or clang-cl don't automatically link clang's
         // profiler runtime in. In that case, we need to manually ask cmake to do it, to avoid
         // linking errors, much like LLVM's cmake setup does in that situation.
-        if builder.config.llvm_profile_generate && target.is_msvc() {
-            if let Some(clang_cl_path) = builder.config.llvm_clang_cl.as_ref() {
-                // Find clang's runtime library directory and push that as a search path to the
-                // cmake linker flags.
-                let clang_rt_dir = get_clang_cl_resource_dir(builder, clang_cl_path);
-                ldflags.push_all(format!("/libpath:{}", clang_rt_dir.display()));
+        if builder.config.llvm_profile_generate  {
+            if target.is_msvc()  {
+                if let Some(clang_cl_path) = builder.config.llvm_clang_cl.as_ref() {
+                    // Find clang's runtime library directory and push that as a search path to the
+                    // cmake linker flags.
+                    let clang_rt_dir = get_clang_cl_resource_dir(builder, clang_cl_path);
+                    ldflags.push_all(format!("/libpath:{}", clang_rt_dir.display()));
+                }
+            } else {
+                ldflags.push_all("-L/opt/homebrew/Cellar/llvm/20.1.2/lib/clang/20/lib/darwin -lclang_rt.profile_osx");
             }
+
         }
 
         // LLD is built as an LLVM tool, but is distributed outside of the `llvm-tools` component,

src/ci/github-actions/jobs.yml

@@ -425,7 +425,7 @@ auto:
 
   - name: dist-aarch64-apple
     env:
-      SCRIPT: ./x.py dist bootstrap --include-default-paths --host=aarch64-apple-darwin --target=aarch64-apple-darwin
+      SCRIPT: ./x.py build --set rust.debug=true opt-dist && PGO_HOST=aarch64-apple-darwin ./build/aarch64-apple-darwin/stage0-tools-bin/opt-dist mac-ci -- python3 x.py dist bootstrap --include-default-paths
       RUST_CONFIGURE_ARGS: >-
         --enable-full-tools
         --enable-sanitizers

src/tools/opt-dist/src/main.rs

@@ -109,6 +109,10 @@ enum EnvironmentCmd {
         #[clap(flatten)]
         shared: SharedArgs,
     },
+    MacCi {
+        #[clap(flatten)]
+        shared: SharedArgs,
+    }
 }
 
 /// For a fast try build, we want to only build the bare minimum of components to get a
@@ -197,6 +201,27 @@ fn create_environment(args: Args) -> anyhow::Result<(Environment, Vec<String>)>
 
             (env, shared.build_args)
         }
+        EnvironmentCmd::MacCi { shared } => {
+            let target_triple =
+                std::env::var("PGO_HOST").expect("PGO_HOST environment variable missing");
+
+            let checkout_dir: Utf8PathBuf = std::env::current_dir()?.try_into()?;
+            let env = EnvironmentBuilder::default()
+                .host_tuple(target_triple)
+                .python_binary("python3".to_string())
+                .checkout_dir(checkout_dir.clone())
+                .host_llvm_dir("/opt/homebrew/Cellar/llvm/20.1.2".into())
+                .artifact_dir(checkout_dir.join("opt-artifacts"))
+                .build_dir(checkout_dir)
+                .shared_llvm(false)
+                .use_bolt(false)
+                .run_tests(false)
+                .skipped_tests(vec![])
+                .fast_try_build(is_fast_try_build)
+                .build()?;
+
+            (env, shared.build_args)
+        }
     };
     Ok((env, args))
 }