add and document a new is_system_llvm abstraction

rust-lang · jyn514 · Dec 25, 2023 · Dec 25, 2023 · Dec 25, 2023 · b3ebe50664bbc5be6db6dc6ddb320e28105d37ba
commit b3ebe50664bbc5be6db6dc6ddb320e28105d37ba
diff --git a/src/bootstrap/src/core/build_steps/dist.rs b/src/bootstrap/src/core/build_steps/dist.rs
@@ -2042,23 2042,24 @@ fn install_llvm_file(builder: &Builder<'_>, source: &Path, destination: &Path) {
 ///
 /// Returns whether the files were actually copied.
 fn maybe_install_llvm(builder: &Builder<'_>, target: TargetSelection, dst_libdir: &Path) -> bool {
- if let Some(config) = builder.config.target_config.get(&target) {
- if config.llvm_config.is_some() && !builder.config.llvm_from_ci {
- // If the LLVM was externally provided, then we don't currently copy
- // artifacts into the sysroot. This is not necessarily the right
- // choice (in particular, it will require the LLVM dylib to be in
- // the linker's load path at runtime), but the common use case for
- // external LLVMs is distribution provided LLVMs, and in that case
- // they're usually in the standard search path (e.g., /usr/lib) and
- // copying them here is going to cause problems as we may end up
- // with the wrong files and isn't what distributions want.
- //
- // This behavior may be revisited in the future though.
- //
- // If the LLVM is coming from ourselves (just from CI) though, we
- // still want to install it, as it otherwise won't be available.
- return false;
- }
  // If the LLVM was externally provided, then we don't currently copy
  // artifacts into the sysroot. This is not necessarily the right
  // choice (in particular, it will require the LLVM dylib to be in
  // the linker's load path at runtime), but the common use case for
  // external LLVMs is distribution provided LLVMs, and in that case
  // they're usually in the standard search path (e.g., /usr/lib) and
  // copying them here is going to cause problems as we may end up
  // with the wrong files and isn't what distributions want.
  //
  // This behavior may be revisited in the future though.
  //
  // NOTE: this intentionally doesn't use `is_rust_llvm`; whether this is patched or not doesn't matter,
  // we only care if the shared object itself is managed by bootstrap.
  //
  // If the LLVM is coming from ourselves (just from CI) though, we
  // still want to install it, as it otherwise won't be available.
  if builder.is_system_llvm(target) {
  return false;
  }
 
  // On macOS, rustc (and LLVM tools) link to an unversioned libLLVM.dylib

diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
@@ -1848,6 1848,8 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
  llvm_components_passed = true;
  }
  if !builder.is_rust_llvm(target) {
  // FIXME: missing Rust patches is not the same as being system llvm; we should rename the flag at some point.
  // Inspecting the tests with `// no-system-llvm` in src/test *looks* like this is doing the right thing, though.
  cmd.arg("--system-llvm");
  }
 

diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
@@ -1810,7 1810,14 @@ impl Config {
  }
  target.llvm_config = Some(config.src.join(s));
  }
- target.llvm_has_rust_patches = cfg.llvm_has_rust_patches;
  if let Some(patches) = cfg.llvm_has_rust_patches {
  assert_eq!(
  config.submodules,
  Some(false),
  "cannot set `llvm-has-rust-patches` for a managed submodule (set `build.submodules = false` if you want to apply patches)"
  );
  target.llvm_has_rust_patches = Some(patches);
  }
  if let Some(ref s) = cfg.llvm_filecheck {
  target.llvm_filecheck = Some(config.src.join(s));
  }

diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
@@ -823,18 823,34 @@ impl Build {
  INTERNER.intern_path(self.out.join(&*target.triple).join("md-doc"))
  }
 
- /// Returns `true` if no custom `llvm-config` is set for the specified target.
  /// Returns `true` if this is an external version of LLVM not managed by bootstrap.
  /// In particular, we expect llvm sources to be available when this is false.
  ///
- /// If no custom `llvm-config` was specified then Rust's llvm will be used.
  /// NOTE: this is not the same as `!is_rust_llvm` when `llvm_has_patches` is set.
  fn is_system_llvm(&self, target: TargetSelection) -> bool {
  match self.config.target_config.get(&target) {
  Some(Target { llvm_config: Some(_), .. }) => {
  let ci_llvm = self.config.llvm_from_ci && target == self.config.build;
  !ci_llvm
  }
  // We're building from the in-tree src/llvm-project sources.
  Some(Target { llvm_config: None, .. }) => false,
  None => false,
  }
  }
 
  /// Returns `true` if this is our custom, patched, version of LLVM.
  ///
  /// This does not necessarily imply that we're managing the `llvm-project` submodule.
  fn is_rust_llvm(&self, target: TargetSelection) -> bool {
  match self.config.target_config.get(&target) {
  // We're using a user-controlled version of LLVM. The user has explicitly told us whether the version has our patches.
  // (They might be wrong, but that's not a supported use-case.)
  // In particular, this tries to support `submodules = false` and `patches = false`, for using a newer version of LLVM that's not through `rust-lang/llvm-project`.
  Some(Target { llvm_has_rust_patches: Some(patched), .. }) => *patched,
- Some(Target { llvm_config, .. }) => {
- // If the user set llvm-config we assume Rust is not patched,
- // but first check to see if it was configured by llvm-from-ci.
- (self.config.llvm_from_ci && target == self.config.build) || llvm_config.is_none()
- }
- None => true,
  // The user hasn't promised the patches match.
  // This only has our patches if it's downloaded from CI or built from source.
  _ => !self.is_system_llvm(target),
  }
  }