Install libgccjit into the compiler's sysroot when the GCC codegen backend is enabled

Author: Kobzol

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

@@ -18,7 +18,7 @@ use serde_derive::Deserialize;
 #[cfg(feature = "tracing")]
 use tracing::{instrument, span};
 
-use crate::core::build_steps::gcc::{Gcc, add_cg_gcc_cargo_flags};
+use crate::core::build_steps::gcc::{Gcc, GccOutput, add_cg_gcc_cargo_flags};
 use crate::core::build_steps::tool::{RustcPrivateCompilers, SourceType, copy_lld_artifacts};
 use crate::core::build_steps::{dist, llvm};
 use crate::core::builder;
@@ -1543,13 +1543,22 @@ impl Step for RustcLink {
     }
 }
 
+/// Output of the `compile::GccCodegenBackend` step.
+/// It includes the path to the libgccjit library on which this backend depends.
+#[derive(Clone)]
+pub struct GccCodegenBackendOutput {
+    stamp: BuildStamp,
+    gcc: GccOutput,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct GccCodegenBackend {
     compilers: RustcPrivateCompilers,
 }
 
 impl Step for GccCodegenBackend {
-    type Output = BuildStamp;
+    type Output = GccCodegenBackendOutput;
+
     const ONLY_HOSTS: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
@@ -1584,6 +1593,8 @@ impl Step for GccCodegenBackend {
             &CodegenBackendKind::Gcc,
         );
 
+        let gcc = builder.ensure(Gcc { target });
+
         if builder.config.keep_stage.contains(&build_compiler.stage) {
             trace!("`keep-stage` requested");
             builder.info(
@@ -1592,7 +1603,7 @@ impl Step for GccCodegenBackend {
             );
             // Codegen backends are linked separately from this step today, so we don't do
             // anything here.
-            return stamp;
+            return GccCodegenBackendOutput { stamp, gcc };
         }
 
         let mut cargo = builder::Cargo::new(
@@ -1606,13 +1617,16 @@ impl Step for GccCodegenBackend {
         cargo.arg("--manifest-path").arg(builder.src.join("compiler/rustc_codegen_gcc/Cargo.toml"));
         rustc_cargo_env(builder, &mut cargo, target);
 
-        let gcc = builder.ensure(Gcc { target });
         add_cg_gcc_cargo_flags(&mut cargo, &gcc);
 
         let _guard =
             builder.msg(Kind::Build, "codegen backend gcc", Mode::Codegen, build_compiler, target);
         let files = run_cargo(builder, cargo, vec![], &stamp, vec![], false, false);
-        write_codegen_backend_stamp(stamp, files, builder.config.dry_run())
+
+        GccCodegenBackendOutput {
+            stamp: write_codegen_backend_stamp(stamp, files, builder.config.dry_run()),
+            gcc,
+        }
     }
 
     fn metadata(&self) -> Option<StepMetadata> {
@@ -2191,53 +2205,6 @@ impl Step for Assemble {
         );
         build_compiler.stage = actual_stage;
 
-        let mut codegen_backend_stamps = vec![];
-        {
-            #[cfg(feature = "tracing")]
-            let _codegen_backend_span =
-                span!(tracing::Level::DEBUG, "building requested codegen backends").entered();
-
-            for backend in builder.config.enabled_codegen_backends(target_compiler.host) {
-                // FIXME: this is a horrible hack used to make `x check` work when other codegen
-                // backends are enabled.
-                // `x check` will check stage 1 rustc, which copies its rmetas to the stage0 sysroot.
-                // Then it checks codegen backends, which correctly use these rmetas.
-                // Then it needs to check std, but for that it needs to build stage 1 rustc.
-                // This copies the build rmetas into the stage0 sysroot, effectively poisoning it,
-                // because we then have both check and build rmetas in the same sysroot.
-                // That would be fine on its own. However, when another codegen backend is enabled,
-                // then building stage 1 rustc implies also building stage 1 codegen backend (even if
-                // it isn't used for anything). And since that tries to use the poisoned
-                // rmetas, it fails to build.
-                // We don't actually need to build rustc-private codegen backends for checking std,
-                // so instead we skip that.
-                // Note: this would be also an issue for other rustc-private tools, but that is "solved"
-                // by check::Std being last in the list of checked things (see
-                // `Builder::get_step_descriptions`).
-                if builder.kind == Kind::Check && builder.top_stage == 1 {
-                    continue;
-                }
-
-                let prepare_compilers = || {
-                    RustcPrivateCompilers::from_build_and_target_compiler(
-                        build_compiler,
-                        target_compiler,
-                    )
-                };
-
-                let stamp = match backend {
-                    CodegenBackendKind::Cranelift => {
-                        builder.ensure(CraneliftCodegenBackend { compilers: prepare_compilers() })
-                    }
-                    CodegenBackendKind::Gcc => {
-                        builder.ensure(GccCodegenBackend { compilers: prepare_compilers() })
-                    }
-                    CodegenBackendKind::Llvm | CodegenBackendKind::Custom(_) => continue,
-                };
-                codegen_backend_stamps.push(stamp);
-            }
-        }
-
         let stage = target_compiler.stage;
         let host = target_compiler.host;
         let (host_info, dir_name) = if build_compiler.host == host {
@@ -2296,9 +2263,56 @@ impl Step for Assemble {
             }
         }
 
-        debug!("copying codegen backends to sysroot");
-        for stamp in codegen_backend_stamps {
-            copy_codegen_backends_to_sysroot(builder, stamp, target_compiler);
+        {
+            #[cfg(feature = "tracing")]
+            let _codegen_backend_span =
+                span!(tracing::Level::DEBUG, "building requested codegen backends").entered();
+
+            for backend in builder.config.enabled_codegen_backends(target_compiler.host) {
+                // FIXME: this is a horrible hack used to make `x check` work when other codegen
+                // backends are enabled.
+                // `x check` will check stage 1 rustc, which copies its rmetas to the stage0 sysroot.
+                // Then it checks codegen backends, which correctly use these rmetas.
+                // Then it needs to check std, but for that it needs to build stage 1 rustc.
+                // This copies the build rmetas into the stage0 sysroot, effectively poisoning it,
+                // because we then have both check and build rmetas in the same sysroot.
+                // That would be fine on its own. However, when another codegen backend is enabled,
+                // then building stage 1 rustc implies also building stage 1 codegen backend (even if
+                // it isn't used for anything). And since that tries to use the poisoned
+                // rmetas, it fails to build.
+                // We don't actually need to build rustc-private codegen backends for checking std,
+                // so instead we skip that.
+                // Note: this would be also an issue for other rustc-private tools, but that is "solved"
+                // by check::Std being last in the list of checked things (see
+                // `Builder::get_step_descriptions`).
+                if builder.kind == Kind::Check && builder.top_stage == 1 {
+                    continue;
+                }
+
+                let prepare_compilers = || {
+                    RustcPrivateCompilers::from_build_and_target_compiler(
+                        build_compiler,
+                        target_compiler,
+                    )
+                };
+
+                match backend {
+                    CodegenBackendKind::Cranelift => {
+                        let stamp = builder
+                            .ensure(CraneliftCodegenBackend { compilers: prepare_compilers() });
+                        copy_codegen_backends_to_sysroot(builder, stamp, target_compiler);
+                    }
+                    CodegenBackendKind::Gcc => {
+                        let output =
+                            builder.ensure(GccCodegenBackend { compilers: prepare_compilers() });
+                        copy_codegen_backends_to_sysroot(builder, output.stamp, target_compiler);
+                        // Also copy libgccjit to the library sysroot, so that it is available for
+                        // the codegen backend.
+                        output.gcc.install_to(builder, &rustc_libdir);
+                    }
+                    CodegenBackendKind::Llvm | CodegenBackendKind::Custom(_) => continue,
+                }
+            }
         }
 
         if builder.config.lld_enabled {

src/bootstrap/src/core/build_steps/gcc.rs

@@ -12,6 +12,7 @@ use std::fs;
 use std::path::{Path, PathBuf};
 use std::sync::OnceLock;
 
+use crate::FileType;
 use crate::core::builder::{Builder, Cargo, Kind, RunConfig, ShouldRun, Step};
 use crate::core::config::TargetSelection;
 use crate::utils::build_stamp::{BuildStamp, generate_smart_stamp_hash};
@@ -28,6 +29,18 @@ pub struct GccOutput {
     pub libgccjit: PathBuf,
 }
 
+impl GccOutput {
+    /// Install the required libgccjit library file(s) to the specified `path`.
+    pub fn install_to(&self, builder: &Builder<'_>, directory: &Path) {
+        let dst = directory.join(self.libgccjit.file_name().unwrap());
+        builder.install(&self.libgccjit, directory, FileType::NativeLibrary);
+        // FIXME: try to remove the alias, it shouldn't be needed
+        // We just have to teach rustc_codegen_gcc to link to libgccjit.so directly, instead of
+        // linking to libgccjit.so.0.
+        create_lib_alias(builder, &dst);
+    }
+}
+
 impl Step for Gcc {
     type Output = GccOutput;