cleanup

Author: ZuseZ4

src/bootstrap/configure.py

@@ -120,7 +120,11 @@ def v(*args):
 o("llvm-assertions", "llvm.assertions", "build LLVM with assertions")
 o("llvm-enzyme", "llvm.enzyme", "build LLVM with enzyme")
 o("llvm-offload", "llvm.offload", "build LLVM with gpu offload support")
-o("llvm-offload-clang-dir", "llvm.offload-clang-dir", "pass the absolute directory of ClangConfig.cmake")
+o(
+        "llvm-offload-clang-dir",
+        "llvm.offload-clang-dir",
+        "pass the absolute directory of ClangConfig.cmake",
+)
 o("llvm-plugins", "llvm.plugins", "build LLVM with plugin interface")
 o("debug-assertions", "rust.debug-assertions", "build with debugging assertions")
 o(

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

@@ -891,6 +891,17 @@ fn get_var(var_base: &str, host: &str, target: &str) -> Option<OsString> {
         .or_else(|| env::var_os(var_base))
 }
 
+// FIXME(offload): In an ideal world, we would just enable the offload runtime in our previous LLVM
+// build step. For now, we still depend on the openmp runtime since we use some of it's API, so we
+// build both. However, when building those runtimes as part of the LLVM step, then LLVM's cmake
+// implicitely assumes that Clang has also been build and will try to use it. In the Rust CI, we
+// don't always build clang (due to compile times), but instead use a slightly older external clang.
+// LLVM tries to remove this build dependency of offload/openmp on Clang for LLVM-22, so in the
+// future we might be able to integrate this step into the LLVM step. For now, we instead introduce
+// a Clang_DIR bootstrap option, which allows us tell CMake to use an external clang for these two
+// runtimes. This external clang will try to use it's own (older) include dirs when building our
+// in-tree LLVM submodule, which will cause build failures. To prevent those, we now also
+// explicitely set our include dirs.
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct OmpOffload {
     pub target: TargetSelection,
@@ -918,11 +929,17 @@ impl Step for OmpOffload {
 
         let LlvmResult { host_llvm_config, .. } = builder.ensure(Llvm { target: self.target });
 
+        // Running cmake twice in the same folder is known to cause issues, like deleting existing
+        // binaries. We therefore write our offload artifacts into it's own subfolder. We use a
+        // subfolder, so that all the logic that processes our build artifacts (hopefully) also
+        // automatically manages our artifacts in the subfolder.
         let out_dir = builder.llvm_out(target).join("offload-outdir");
         if std::fs::exists(&out_dir).is_ok_and(|x| x == false) {
             std::fs::DirBuilder::new().create(&out_dir).unwrap();
             dbg!("Created out subdir!");
         }
+
+        // Offload/OpenMP are just subfolders of LLVM, so we can use the LLVM sha.
         static STAMP_HASH_MEMO: OnceLock<String> = OnceLock::new();
         let smart_stamp_hash = STAMP_HASH_MEMO.get_or_init(|| {
             generate_smart_stamp_hash(
@@ -960,32 +977,16 @@ impl Step for OmpOffload {
         configure_cmake(builder, target, &mut cfg, true, LdFlags::default(), &[]);
 
         // Re-use the same flags as llvm to control the level of debug information
-        // generated by Enzyme.
-        // FIXME(ZuseZ4): Find a nicer way to use Enzyme Debug builds.
+        // generated for offload.
         let profile = match (builder.config.llvm_optimize, builder.config.llvm_release_debuginfo) {
             (false, _) => "Debug",
             (true, false) => "Release",
             (true, true) => "RelWithDebInfo",
         };
         trace!(?profile);
 
-        //let cc = if let Some(p) = &builder.build.config.llvm_offload_cc {
-        //    //p.clone()
-        //    builder.cc(target)
-        //} else {
-        //    builder.cc(target)
-        //};
-        //let cxx = if let Some(p) = &builder.build.config.llvm_offload_cxx {
-        //    //p.clone()
-        //    builder.cxx(target).unwrap()
-        //} else {
-        //    builder.cxx(target).unwrap()
-        //};
-        let root = if let Some(p) = &builder.build.config.llvm_root_offload {
-            p.clone()
-        } else {
-            builder.llvm_out(target).join("build")
-        };
+        // OpenMP/Offload builds currently (LLVM-21) still depend on Clang, although there are
+        // intentions to loosen this requirement for LLVM-22. If we were to
         let clang_dir = if !builder.config.llvm_clang {
             // We must have an external clang to use.
             assert!(&builder.build.config.llvm_clang_dir.is_some());
@@ -995,17 +996,18 @@ impl Step for OmpOffload {
             None
         };
 
+        // FIXME(offload): Once we move from OMP to Offload (Ol) APIs, we should drop the openmp
+        // runtime to simplify our build. We should also re-evaluate the LLVM_Root and try to get
+        // rid of the Clang_DIR, once we upgrade to LLVM-22.
         cfg.out_dir(&out_dir)
             .profile(profile)
             .env("LLVM_CONFIG_REAL", &host_llvm_config)
             .define("LLVM_ENABLE_ASSERTIONS", "ON")
             .define("LLVM_ENABLE_RUNTIMES", "openmp;offload")
             .define("LLVM_INCLUDE_TESTS", "OFF")
             .define("OFFLOAD_INCLUDE_TESTS", "OFF")
-            //.define("CMAKE_C_COMPILER", cc)
-            //.define("CMAKE_CXX_COMPILER", cxx)
             .define("OPENMP_STANDALONE_BUILD", "ON")
-            .define("LLVM_ROOT", root)
+            .define("LLVM_ROOT", builder.llvm_out(target).join("build"))
             .define("LLVM_DIR", builder.llvm_out(target).join("lib").join("cmake").join("llvm"));
         if let Some(p) = clang_dir {
             cfg.define("Clang_DIR", p);

src/bootstrap/src/core/config/config.rs

@@ -169,9 +169,6 @@ pub struct Config {
     pub llvm_link_jobs: Option<u32>,
     pub llvm_version_suffix: Option<String>,
     pub llvm_use_linker: Option<String>,
-    pub llvm_offload_cc: Option<PathBuf>,
-    pub llvm_offload_cxx: Option<PathBuf>,
-    pub llvm_root_offload: Option<PathBuf>,
     pub llvm_clang_dir: Option<PathBuf>,
     pub llvm_allow_old_toolchain: bool,
     pub llvm_polly: bool,
@@ -607,9 +604,6 @@ impl Config {
             ldflags: llvm_ldflags,
             use_libcxx: llvm_use_libcxx,
             use_linker: llvm_use_linker,
-            offload_cc: llvm_offload_cc,
-            offload_cxx: llvm_offload_cxx,
-            root_offload: llvm_root_offload,
             clang_dir: llvm_clang_dir,
             allow_old_toolchain: llvm_allow_old_toolchain,
             offload: llvm_offload,
@@ -1377,7 +1371,6 @@ impl Config {
             llvm_enable_warnings: llvm_enable_warnings.unwrap_or(false),
             llvm_enzyme: llvm_enzyme.unwrap_or(false),
             llvm_experimental_targets,
-            llvm_root_offload: llvm_root_offload.map(PathBuf::from),
             llvm_from_ci,
             llvm_ldflags,
             llvm_libunwind_default: rust_llvm_libunwind
@@ -1392,8 +1385,6 @@ impl Config {
                     .or((!llvm_from_ci && llvm_thin_lto.unwrap_or(false)).then_some(true)),
             ),
             llvm_offload: llvm_offload.unwrap_or(false),
-            llvm_offload_cc: llvm_offload_cc.map(PathBuf::from),
-            llvm_offload_cxx: llvm_offload_cxx.map(PathBuf::from),
             llvm_optimize: llvm_optimize.unwrap_or(true),
             llvm_plugins: llvm_plugin.unwrap_or(false),
             llvm_polly: llvm_polly.unwrap_or(false),

src/bootstrap/src/core/config/toml/llvm.rs

@@ -32,9 +32,6 @@ define_config! {
         ldflags: Option<String> = "ldflags",
         use_libcxx: Option<bool> = "use-libcxx",
         use_linker: Option<String> = "use-linker",
-        offload_cc: Option<String> = "offload-cc",
-        offload_cxx: Option<String> = "offload-cxx",
-        root_offload: Option<String> = "root-offload",
         clang_dir: Option<String> = "offload-clang-dir",
         allow_old_toolchain: Option<bool> = "allow-old-toolchain",
         offload: Option<bool> = "offload",
@@ -114,9 +111,6 @@ pub fn check_incompatible_options_for_ci_llvm(
         ldflags,
         use_libcxx,
         use_linker,
-        offload_cc: _,
-        offload_cxx: _,
-        root_offload: _,
         clang_dir: _,
         allow_old_toolchain,
         offload,