Including the case of building from tarball source.

fmt code

config.example.toml

@@ -48,7 +48,8 @@ change-id = 116881
 # We also currently only support this when building LLVM for the build triple.
 #
 # Set this to `"if-unchanged"` to only download if the llvm-project have not 
-# been modified. (if no changes, the logic is the same as `"if-available"`)
+# been modified. (If there are no changes or if built from tarball source, 
+# the logic is the same as "if-available")
 #
 # Note that many of the LLVM options are not currently supported for
 # downloading. Currently only the "assertions" option can be toggled.

src/bootstrap/src/core/build_steps/setup.rs

@@ -147,8 +147,14 @@ impl Step for Profile {
     }
 
     fn run(self, builder: &Builder<'_>) {
-        if self == Profile::Codegen {
-            builder.update_submodule(&Path::new("src/llvm-project"));
+        // During ./x.py setup once you select the codegen profile.
+        // The submodule will be downloaded. It does not work in the
+        // tarball case since they don't include Git and submodules
+        // are already included.
+        if !builder.rust_info().is_from_tarball() {
+            if self == Profile::Codegen {
+                builder.update_submodule(&Path::new("src/llvm-project"));
+            }
         }
         setup(&builder.build.config, self)
     }

src/bootstrap/src/core/config/config.rs

@@ -2108,12 +2108,16 @@ impl Config {
                 llvm::is_ci_llvm_available(&self, asserts)
             }
             Some(StringOrBool::String(s)) if s == "if-unchanged" => {
-                if self
-                    .last_modified_commit(&["src/llvm-project"], "download-ci-llvm", true)
-                    .is_none()
-                {
-                    // there are some untracked changes in the the given paths.
-                    false
+                if !self.rust_info.is_from_tarball() {
+                    if self
+                        .last_modified_commit(&["src/llvm-project"], "download-ci-llvm", true)
+                        .is_none()
+                    {
+                        // there are some untracked changes in the the given paths.
+                        false
+                    } else {
+                        llvm::is_ci_llvm_available(&self, asserts)
+                    }
                 } else {
                     llvm::is_ci_llvm_available(&self, asserts)
                 }