Rollup merge of #93969 - bjorn3:codegen_backend_dep_info, r=pnkfelix

Only add codegen backend to dep info if -Zbinary-dep-depinfo is used

I am currently migrating the cg_clif build system from using a binary linked to the codegen backend as rustc replacement to passing `-Zcodegen-backend` instead. Without this PR this would force cargo to rebuild the sysroot on any change to the codegen backend even if I explicitly specify that I want it to be preserved, which would make development of cg_clif a lot slower. If you still want to have changes to the codegen backend invalidate the cargo build cache you can explicitly specify `-Zbinary-dep-depinfo`.

cc ``@eddyb`` as the codegen backend was initially added to the depinfo for rust-gpu.

1 files changed, 8 insertions, 4 deletions

diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 2a01b677e33..08987dff660 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -629,11 +629,15 @@ fn write_out_deps(
         });
         files.extend(extra_tracked_files);
 
-        if let Some(ref backend) = sess.opts.debugging_opts.codegen_backend {
-            files.push(backend.to_string());
-        }
-
         if sess.binary_dep_depinfo() {
+            if let Some(ref backend) = sess.opts.debugging_opts.codegen_backend {
+                if backend.contains('.') {
+                    // If the backend name contain a `.`, it is the path to an external dynamic
+                    // library. If not, it is not a path.
+                    files.push(backend.to_string());
+                }
+            }
+
             boxed_resolver.borrow_mut().access(|resolver| {
                 for cnum in resolver.cstore().crates_untracked() {
                     let source = resolver.cstore().crate_source_untracked(cnum);