Auto merge of #87297 - ZuseZ4:new_build_flags, r=Mark-Simulacrum

add two new build flags to build clang and enable llvm plugins

Based on the discussion here: https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Add.20configure.20flag.20to.20build.20clang/near/246439138

It allows building clang (which already is part of the llvm-project) based on the same llvm version which we use to build rustc.
It also allows enabling llvm's plugin interface, which is required for https://enzyme.mit.edu/.

There is no further integration beside of this basic build support.

Author: bors

config.toml.example

@@ -68,6 +68,9 @@ changelog-seen = 2
 # Indicates whether the LLVM assertions are enabled or not
 #assertions = false
 
+# Indicates whether the LLVM plugin is enabled or not
+#plugins = false
+
 # Indicates whether ccache is used when building LLVM
 #ccache = false
 # or alternatively ...
@@ -145,6 +148,9 @@ changelog-seen = 2
 # Whether to include the Polly optimizer.
 #polly = false
 
+# Whether to build the clang compiler.
+#clang = false
+
 # =============================================================================
 # General build configuration options
 # =============================================================================

src/bootstrap/config.rs

@@ -90,6 +90,7 @@ pub struct Config {
     // llvm codegen options
     pub llvm_skip_rebuild: bool,
     pub llvm_assertions: bool,
+    pub llvm_plugins: bool,
     pub llvm_optimize: bool,
     pub llvm_thin_lto: bool,
     pub llvm_release_debuginfo: bool,
@@ -104,6 +105,7 @@ pub struct Config {
     pub llvm_use_linker: Option<String>,
     pub llvm_allow_old_toolchain: bool,
     pub llvm_polly: bool,
+    pub llvm_clang: bool,
     pub llvm_from_ci: bool,
 
     pub use_lld: bool,
@@ -415,6 +417,7 @@ struct Llvm {
     thin_lto: Option<bool>,
     release_debuginfo: Option<bool>,
     assertions: Option<bool>,
+    plugins: Option<bool>,
     ccache: Option<StringOrBool>,
     version_check: Option<bool>,
     static_libstdcpp: Option<bool>,
@@ -432,6 +435,7 @@ struct Llvm {
     use_linker: Option<String>,
     allow_old_toolchain: Option<bool>,
     polly: Option<bool>,
+    clang: Option<bool>,
     download_ci_llvm: Option<StringOrBool>,
 }
 
@@ -702,6 +706,7 @@ impl Config {
         // Store off these values as options because if they're not provided
         // we'll infer default values for them later
         let mut llvm_assertions = None;
+        let mut llvm_plugins = None;
         let mut debug = None;
         let mut debug_assertions = None;
         let mut debug_assertions_std = None;
@@ -724,6 +729,7 @@ impl Config {
             }
             set(&mut config.ninja_in_file, llvm.ninja);
             llvm_assertions = llvm.assertions;
+            llvm_plugins = llvm.plugins;
             llvm_skip_rebuild = llvm_skip_rebuild.or(llvm.skip_rebuild);
             set(&mut config.llvm_optimize, llvm.optimize);
             set(&mut config.llvm_thin_lto, llvm.thin_lto);
@@ -744,6 +750,7 @@ impl Config {
             config.llvm_use_linker = llvm.use_linker.clone();
             config.llvm_allow_old_toolchain = llvm.allow_old_toolchain.unwrap_or(false);
             config.llvm_polly = llvm.polly.unwrap_or(false);
+            config.llvm_clang = llvm.clang.unwrap_or(false);
             config.llvm_from_ci = match llvm.download_ci_llvm {
                 Some(StringOrBool::String(s)) => {
                     assert!(s == "if-available", "unknown option `{}` for download-ci-llvm", s);
@@ -790,6 +797,8 @@ impl Config {
                 check_ci_llvm!(llvm.use_linker);
                 check_ci_llvm!(llvm.allow_old_toolchain);
                 check_ci_llvm!(llvm.polly);
+                check_ci_llvm!(llvm.clang);
+                check_ci_llvm!(llvm.plugins);
 
                 // CI-built LLVM can be either dynamic or static.
                 let ci_llvm = config.out.join(&*config.build.triple).join("ci-llvm");
@@ -952,6 +961,7 @@ impl Config {
 
         config.llvm_skip_rebuild = llvm_skip_rebuild.unwrap_or(false);
         config.llvm_assertions = llvm_assertions.unwrap_or(false);
+        config.llvm_plugins = llvm_plugins.unwrap_or(false);
         config.rust_optimize = optimize.unwrap_or(true);
 
         let default = debug == Some(true);

src/bootstrap/configure.py

@@ -57,6 +57,7 @@ def v(*args):
 o("profiler", "build.profiler", "build the profiler runtime")
 o("full-tools", None, "enable all tools")
 o("lld", "rust.lld", "build lld")
+o("clang", "llvm.clang", "build clang")
 o("missing-tools", "dist.missing-tools", "allow failures when building tools")
 o("use-libcxx", "llvm.use-libcxx", "build LLVM with libc++")
 o("control-flow-guard", "rust.control-flow-guard", "Enable Control Flow Guard")
@@ -72,6 +73,7 @@ def v(*args):
 o("optimize", "rust.optimize", "build optimized rust code")
 o("optimize-llvm", "llvm.optimize", "build optimized LLVM")
 o("llvm-assertions", "llvm.assertions", "build LLVM with assertions")
+o("llvm-plugins", "llvm.plugins", "build LLVM with plugin interface")
 o("debug-assertions", "rust.debug-assertions", "build with debugging assertions")
 o("llvm-release-debuginfo", "llvm.release-debuginfo", "build LLVM with debugger metadata")
 v("debuginfo-level", "rust.debuginfo-level", "debuginfo level for Rust code")

src/bootstrap/native.rs

@@ -169,10 +169,12 @@ impl Step for Llvm {
         };
 
         let assertions = if builder.config.llvm_assertions { "ON" } else { "OFF" };
+        let plugins = if builder.config.llvm_plugins { "ON" } else { "OFF" };
 
         cfg.out_dir(&out_dir)
             .profile(profile)
             .define("LLVM_ENABLE_ASSERTIONS", assertions)
+            .define("LLVM_ENABLE_PLUGINS", plugins)
             .define("LLVM_TARGETS_TO_BUILD", llvm_targets)
             .define("LLVM_EXPERIMENTAL_TARGETS_TO_BUILD", llvm_exp_targets)
             .define("LLVM_INCLUDE_EXAMPLES", "OFF")
@@ -265,6 +267,10 @@ impl Step for Llvm {
             enabled_llvm_projects.push("polly");
         }
 
+        if builder.config.llvm_clang {
+            enabled_llvm_projects.push("clang");
+        }
+
         // We want libxml to be disabled.
         // See https://github.com/rust-lang/rust/pull/50104
         cfg.define("LLVM_ENABLE_LIBXML2", "OFF");