From 75eaa452681e8008a24a7bd2ce8d44bad38d5a44 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jakub=20Ber=C3=A1nek?= Date: Wed, 31 Dec 2025 13:23:13 +0100 Subject: [PATCH] Allow building cg_gcc without building libgccjit --- src/bootstrap/src/core/build_steps/compile.rs | 106 ++++++++---------- 1 file changed, 47 insertions(+), 59 deletions(-) diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs index 762aeea9f451..adfb3c21d38e 100644 --- a/src/bootstrap/src/core/build_steps/compile.rs +++ b/src/bootstrap/src/core/build_steps/compile.rs @@ -19,7 +19,7 @@ use serde_derive::Deserialize; #[cfg(feature = "tracing")] use tracing::span; -use crate::core::build_steps::gcc::{Gcc, GccOutput, GccTargetPair, add_cg_gcc_cargo_flags}; +use crate::core::build_steps::gcc::{Gcc, GccOutput, GccTargetPair}; use crate::core::build_steps::tool::{RustcPrivateCompilers, SourceType, copy_lld_artifacts}; use crate::core::build_steps::{dist, llvm}; use crate::core::builder; @@ -1569,21 +1569,29 @@ impl Step for RustcLink { } /// Set of `libgccjit` dylibs that can be used by `cg_gcc` to compile code for a set of targets. +/// `libgccjit` requires a separate build for each `(host, target)` pair. +/// So if you are on linux-x64 and build for linux-aarch64, you will need at least: +/// - linux-x64 -> linux-x64 libgccjit (for building host code like proc macros) +/// - linux-x64 -> linux-aarch64 libgccjit (for the aarch64 target code) #[derive(Clone)] pub struct GccDylibSet { dylibs: BTreeMap, - host_pair: GccTargetPair, } impl GccDylibSet { - /// Returns the libgccjit.so dylib that corresponds to a host target on which `cg_gcc` will be - /// executed, and which will target the host. So e.g. if `cg_gcc` will be executed on - /// x86_64-unknown-linux-gnu, the host dylib will be for compilation pair - /// `(x86_64-unknown-linux-gnu, x86_64-unknown-linux-gnu)`. - fn host_dylib(&self) -> &GccOutput { - self.dylibs.get(&self.host_pair).unwrap_or_else(|| { - panic!("libgccjit.so was not built for host target {}", self.host_pair) - }) + /// Build a set of libgccjit dylibs that will be executed on `host` and will generate code for + /// each specified target. + pub fn build( + builder: &Builder<'_>, + host: TargetSelection, + targets: Vec, + ) -> Self { + let dylibs = targets + .iter() + .map(|t| GccTargetPair::for_target_pair(host, *t)) + .map(|target_pair| (target_pair, builder.ensure(Gcc { target_pair }))) + .collect(); + Self { dylibs } } /// Install the libgccjit dylibs to the corresponding target directories of the given compiler. @@ -1626,39 +1634,28 @@ impl GccDylibSet { /// Output of the `compile::GccCodegenBackend` step. /// -/// It contains paths to all built libgccjit libraries on which this backend depends here. +/// It contains a build stamp with the path to the built cg_gcc dylib. #[derive(Clone)] pub struct GccCodegenBackendOutput { stamp: BuildStamp, - dylib_set: GccDylibSet, } /// Builds the GCC codegen backend (`cg_gcc`). -/// The `cg_gcc` backend uses `libgccjit`, which requires a separate build for each -/// `host -> target` pair. So if you are on linux-x64 and build for linux-aarch64, -/// you will need at least: -/// - linux-x64 -> linux-x64 libgccjit (for building host code like proc macros) -/// - linux-x64 -> linux-aarch64 libgccjit (for the aarch64 target code) -/// -/// We model this by having a single cg_gcc for a given host target, which contains one -/// libgccjit per (host, target) pair. -/// Note that the host target is taken from `self.compilers.target_compiler.host`. +/// Note that this **does not** build libgccjit, which is a dependency of cg_gcc. +/// That has to be built separately, because a separate copy of libgccjit is required +/// for each (host, target) compilation pair. +/// cg_gcc goes to great lengths to ensure that it does not *directly* link to libgccjit, +/// so we respect that here and allow building cg_gcc without building libgccjit itself. #[derive(Debug, Clone, PartialEq, Eq, Hash)] pub struct GccCodegenBackend { compilers: RustcPrivateCompilers, - targets: Vec, + target: TargetSelection, } impl GccCodegenBackend { - /// Build `cg_gcc` that will run on host `H` (`compilers.target_compiler.host`) and will be - /// able to produce code target pairs (`H`, `T`) for all `T` from `targets`. - pub fn for_targets( - compilers: RustcPrivateCompilers, - mut targets: Vec, - ) -> Self { - // Sort targets to improve step cache hits - targets.sort(); - Self { compilers, targets } + /// Build `cg_gcc` that will run on the given host target. + pub fn for_target(compilers: RustcPrivateCompilers, target: TargetSelection) -> Self { + Self { compilers, target } } } @@ -1672,10 +1669,8 @@ impl Step for GccCodegenBackend { } fn make_run(run: RunConfig<'_>) { - // By default, build cg_gcc that will only be able to compile native code for the given - // host target. let compilers = RustcPrivateCompilers::new(run.builder, run.builder.top_stage, run.target); - run.builder.ensure(GccCodegenBackend { compilers, targets: vec![run.target] }); + run.builder.ensure(GccCodegenBackend::for_target(compilers, run.target)); } fn run(self, builder: &Builder<'_>) -> Self::Output { @@ -1689,18 +1684,6 @@ impl Step for GccCodegenBackend { &CodegenBackendKind::Gcc, ); - let dylib_set = GccDylibSet { - dylibs: self - .targets - .iter() - .map(|&target| { - let target_pair = GccTargetPair::for_target_pair(host, target); - (target_pair, builder.ensure(Gcc { target_pair })) - }) - .collect(), - host_pair: GccTargetPair::for_native_build(host), - }; - if builder.config.keep_stage.contains(&build_compiler.stage) { trace!("`keep-stage` requested"); builder.info( @@ -1709,7 +1692,7 @@ impl Step for GccCodegenBackend { ); // Codegen backends are linked separately from this step today, so we don't do // anything here. - return GccCodegenBackendOutput { stamp, dylib_set }; + return GccCodegenBackendOutput { stamp }; } let mut cargo = builder::Cargo::new( @@ -1723,15 +1706,12 @@ impl Step for GccCodegenBackend { cargo.arg("--manifest-path").arg(builder.src.join("compiler/rustc_codegen_gcc/Cargo.toml")); rustc_cargo_env(builder, &mut cargo, host); - add_cg_gcc_cargo_flags(&mut cargo, dylib_set.host_dylib()); - let _guard = builder.msg(Kind::Build, "codegen backend gcc", Mode::Codegen, build_compiler, host); let files = run_cargo(builder, cargo, vec![], &stamp, vec![], false, false); GccCodegenBackendOutput { stamp: write_codegen_backend_stamp(stamp, files, builder.config.dry_run()), - dylib_set, } } @@ -2457,12 +2437,18 @@ impl Step for Assemble { // GCC dylibs built below by taking a look at the current stage and whether // cg_gcc is used as the default codegen backend. + // First, the easy part: build cg_gcc let compilers = prepare_compilers(); + let cg_gcc = builder + .ensure(GccCodegenBackend::for_target(compilers, target_compiler.host)); + copy_codegen_backends_to_sysroot(builder, cg_gcc.stamp, target_compiler); + + // Then, the hard part: prepare all required libgccjit dylibs. // The left side of the target pairs below is implied. It has to match the - // host target on which cg_gcc will run, which is the host target of + // host target on which libgccjit will be used, which is the host target of // `target_compiler`. We only pass the right side of the target pairs to - // the `GccCodegenBackend` constructor. + // the `GccDylibSet` constructor. let mut targets = HashSet::new(); // Add all host targets, so that we are able to build host code in this // bootstrap invocation using cg_gcc. @@ -2477,14 +2463,16 @@ impl Step for Assemble { // host code (e.g. proc macros) using cg_gcc. targets.insert(compilers.target_compiler().host); - let output = builder.ensure(GccCodegenBackend::for_targets( - compilers, + // Now build all the required libgccjit dylibs + let dylib_set = GccDylibSet::build( + builder, + compilers.target_compiler().host, targets.into_iter().collect(), - )); - copy_codegen_backends_to_sysroot(builder, output.stamp, target_compiler); - // Also copy all requires libgccjit dylibs to the corresponding - // library sysroots, so that they are available for the codegen backend. - output.dylib_set.install_to(builder, target_compiler); + ); + + // And then copy all the dylibs to the corresponding + // library sysroots, so that they are available for cg_gcc. + dylib_set.install_to(builder, target_compiler); } CodegenBackendKind::Llvm | CodegenBackendKind::Custom(_) => continue, }