Distinguish "has patches" from "in-tree" again

Fixes #102560

Author: jyn514

src/bootstrap/compile.rs

@@ -352,12 +352,17 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
     let compiler_builtins_c_feature = if builder.config.optimized_compiler_builtins {
         if !builder.is_rust_llvm(target) {
             panic!(
-                "need a managed LLVM submodule for optimized intrinsics support; unset `llvm-config` or `optimized-compiler-builtins`"
+                "LLVM must have the Rust project's patched sources to support using it for `compiler-builtins`; unset `llvm-config` or `optimized-compiler-builtins`"
             );
         }
 
         builder.update_submodule(&Path::new("src").join("llvm-project"));
         let compiler_builtins_root = builder.src.join("src/llvm-project/compiler-rt");
+        if !compiler_builtins_root.exists() {
+            panic!(
+                "needed LLVM sources available to build `compiler-rt`, but they weren't present; consider enabling `build.submodules = true`"
+            );
+        }
         // Note that `libprofiler_builtins/build.rs` also computes this so if
         // you're changing something here please also change that.
         cargo.env("RUST_COMPILER_RT_ROOT", &compiler_builtins_root);

src/bootstrap/dist.rs

@@ -25,6 +25,7 @@ use crate::builder::{Builder, Kind, RunConfig, ShouldRun, Step};
 use crate::cache::{Interned, INTERNER};
 use crate::channel;
 use crate::compile;
+use crate::config::Target;
 use crate::config::TargetSelection;
 use crate::doc::DocumentationFormat;
 use crate::llvm;
@@ -1964,20 +1965,29 @@ 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 !builder.is_rust_llvm(target) {
-        // 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 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.
+    let should_install_llvm = match builder.config.target_config.get(&target) {
         // If the LLVM is coming from ourselves (just from CI) though, we
         // still want to install it, as it otherwise won't be available.
+        Some(Target { llvm_config: Some(_), .. }) => {
+            builder.config.llvm_from_ci && target == builder.config.build
+        }
+        Some(Target { llvm_config: None, .. }) | None => true,
+    };
+
+    if !should_install_llvm {
         return false;
     }
 

src/bootstrap/lib.rs

@@ -863,18 +863,19 @@ 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 our custom, patched, version of LLVM.
     ///
-    /// If no custom `llvm-config` was specified then Rust's llvm will be used.
+    /// 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 pre-built version of LLVM, but the user has promised that pre-built version has our patches.
             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()
+            // We're using pre-built LLVM and the user hasn't promised the patches match.
+            // This only has our patches if it's our managed, CI-built LLVM.
+            Some(Target { llvm_config: Some(_), .. }) => {
+                self.config.llvm_from_ci && target == self.config.build
             }
-            None => true,
+            Some(Target { llvm_config: None, llvm_has_rust_patches: None, .. }) | None => true,
         }
     }