[Proof of concept] Build shared LLVM lib for gnullvm

src/bootstrap/src/core/build_steps/dist.rs

@@ -35,7 +35,7 @@ use crate::utils::build_stamp::{self, BuildStamp};
 use crate::utils::channel::{self, Info};
 use crate::utils::exec::{BootstrapCommand, command};
 use crate::utils::helpers::{
-    exe, is_dylib, move_file, t, target_supports_cranelift_backend, timeit,
+    exe, is_dylib, libdir, move_file, t, target_supports_cranelift_backend, timeit,
 };
 use crate::utils::tarball::{GeneratedTarball, OverlayKind, Tarball};
 use crate::{CodegenBackendKind, Compiler, DependencyType, FileType, LLVM_TOOLS, Mode, trace};
@@ -2518,7 +2518,7 @@ fn maybe_install_llvm(
     }
 }
 
-/// Maybe add libLLVM.so to the target lib-dir for linking.
+/// Maybe add libLLVM.so to the target runtime lib-dir.
 #[cfg_attr(
     feature = "tracing",
     instrument(
@@ -2533,7 +2533,7 @@ fn maybe_install_llvm(
     ),
 )]
 pub fn maybe_install_llvm_target(builder: &Builder<'_>, target: TargetSelection, sysroot: &Path) {
-    let dst_libdir = sysroot.join("lib/rustlib").join(target).join("lib");
+    let dst_libdir = sysroot.join("lib/rustlib").join(target).join(libdir(target));
     // We do not need to copy LLVM files into the sysroot if it is not
     // dynamically linked; it is already included into librustc_llvm
     // statically.
@@ -2557,7 +2557,8 @@ pub fn maybe_install_llvm_target(builder: &Builder<'_>, target: TargetSelection,
     ),
 )]
 pub fn maybe_install_llvm_runtime(builder: &Builder<'_>, target: TargetSelection, sysroot: &Path) {
-    let dst_libdir = sysroot.join(builder.sysroot_libdir_relative(Compiler::new(1, target)));
+    let dst_libdir =
+        sysroot.join(builder.sysroot_runtime_libdir_relative(Compiler::new(1, target)));
     // We do not need to copy LLVM files into the sysroot if it is not
     // dynamically linked; it is already included into librustc_llvm
     // statically.

src/bootstrap/src/core/builder/mod.rs

@@ -1363,6 +1363,25 @@ Alternatively, you can set `build.local-rebuild=true` and use a stage0 compiler
         }
     }
 
+    /// Returns the compiler's relative runtime libdir where shared libraries are found for a
+    /// compiler's sysroot.
+    ///
+    /// For example this returns `lib` on Unix and `bin` on Windows.
+    pub fn sysroot_runtime_libdir_relative(&self, compiler: Compiler) -> PathBuf {
+        let adjust_path = |path: &Path| -> PathBuf {
+            if compiler.host.is_windows() || compiler.host.contains("cygwin") {
+                path.parent().expect("original path should point to `lib` already").join("bin")
+            } else {
+                path.to_owned()
+            }
+        };
+        match self.config.libdir_relative() {
+            Some(relative_libdir) if compiler.stage >= 1 => adjust_path(relative_libdir),
+            _ if compiler.stage == 0 => adjust_path(&self.build.initial_relative_libdir),
+            _ => PathBuf::from(libdir(compiler.host)),
+        }
+    }
+
     pub fn rustc_lib_paths(&self, compiler: Compiler) -> Vec<PathBuf> {
         let mut dylib_dirs = vec![self.rustc_libdir(compiler)];
 

src/ci/github-actions/jobs.yml

@@ -691,6 +691,7 @@ auto:
         --target=aarch64-pc-windows-gnullvm,i686-pc-windows-gnullvm
         --enable-full-tools
         --enable-profiler
+        --enable-llvm-link-shared
       DIST_REQUIRE_ALL_TOOLS: 1
       CODEGEN_BACKENDS: llvm,cranelift
       CC_i686_pc_windows_gnullvm: i686-w64-mingw32-clang
@@ -703,6 +704,7 @@ auto:
         --build=x86_64-pc-windows-gnullvm
         --enable-full-tools
         --enable-profiler
+        --enable-llvm-link-shared
       DIST_REQUIRE_ALL_TOOLS: 1
       CODEGEN_BACKENDS: llvm,cranelift
     <<: *job-windows