fix(trim-paths): remove SO symbols when unsplit-debuginfo specified

`SO` (`N_SO`) debug symbols are always embedded in the executables
on macOS even when debuginfo is splitted. Here is a hack that when
the scope of `unsplit-debuginfo` is present, we trim them before passing
the rustc working directory to LLVM when creating `DIFile`.
(After all `SO` symbols are are sort of "unsplit" debuginfo")

Author: weihanglo

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -853,7 +853,18 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
 
     use rustc_session::RemapFileNameExt;
     let name_in_debuginfo = name_in_debuginfo.to_string_lossy();
-    let work_dir = tcx.sess.opts.working_dir.for_codegen(tcx.sess).to_string_lossy();
+    let work_dir = if tcx.sess.target.is_like_osx {
+        // `SO` (`N_SO`) debug symbols are always embedded in the executables on macOS even when
+        // debuginfo is splitted. Here is a hack that when the scope of `unsplit-debuginfo` is
+        // present, we trim them. (They are sort of "unsplit" debuginfo")
+        use rustc_session::config::RemapPathScopeComponents;
+        tcx.sess.opts.working_dir.for_scope(tcx.sess, RemapPathScopeComponents::UNSPLIT_DEBUGINFO)
+    } else {
+        tcx.sess.opts.working_dir.for_codegen(tcx.sess)
+    }
+    .to_string_lossy();
+    debug!(?work_dir);
+
     let flags = "\0";
     let output_filenames = tcx.output_filenames(());
     let split_name = if tcx.sess.target_can_use_split_dwarf() {

tests/run-make/split-debuginfo/Makefile

@@ -24,7 +24,7 @@ packed-remapped-scope:
 		-Z remap-path-scope=object foo.rs -g
 	ls $(TMPDIR)/*.o && exit 1 || exit 0
 	[ -d $(TMPDIR)/foo.dSYM ]
-	dsymutil -s $(TMPDIR)/foo | grep 'N_SO' | grep $(HERE) || exit 1 # expected behavior is (! grep ...)
+	dsymutil -s $(TMPDIR)/foo | grep 'N_SO' | (! grep $(HERE)) || exit 1
 	# As of 2023-12, `OSO` should be the only thing that cannot be trimmed. See rust-lang/rust#116948
 	dsymutil -s $(TMPDIR)/foo | grep 'N_OSO' | grep $(TMPDIR) || exit 1 # expected behavior is (! grep ...)
 	rm -rf $(TMPDIR)/foo.dSYM
@@ -56,7 +56,7 @@ unpacked-remapped-scope:
 		-Z remap-path-scope=object foo.rs -g
 	ls $(TMPDIR)/*.o
 	[ ! -d $(TMPDIR)/foo.dSYM ]
-	dsymutil -s $(TMPDIR)/foo | grep 'N_SO' | (grep $(HERE)) || exit 1 # expected behavior is (! grep ...)
+	dsymutil -s $(TMPDIR)/foo | grep 'N_SO' | (! grep $(HERE)) || exit 1
 	# As of 2023-12, `OSO` should be the only thing that cannot be trimmed. See rust-lang/rust#116948
 	dsymutil -s $(TMPDIR)/foo | grep 'N_OSO' | (grep $(TMPDIR)) || exit 1 # expected behavior is (! grep ...)
 	rm $(TMPDIR)/*.o