Set path of the compile unit to the source directory

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -93,7 +93,7 @@ pub fn create_informational_target_machine(sess: &Session) -> &'static mut llvm:
 pub fn create_target_machine(tcx: TyCtxt<'_>, mod_name: &str) -> &'static mut llvm::TargetMachine {
     let split_dwarf_file = if tcx.sess.target_can_use_split_dwarf() {
         tcx.output_filenames(LOCAL_CRATE)
-            .split_dwarf_filename(tcx.sess.split_debuginfo(), Some(mod_name))
+            .split_dwarf_path(tcx.sess.split_debuginfo(), Some(mod_name))
     } else {
         None
     };

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -979,7 +979,7 @@ pub fn compile_unit_metadata(
     // The OSX linker has an idiosyncrasy where it will ignore some debuginfo
     // if multiple object files with the same `DW_AT_name` are linked together.
     // As a workaround we generate unique names for each object file. Those do
-    // not correspond to an actual source file but that should be harmless.
+    // not correspond to an actual source file but that is harmless.
     if tcx.sess.target.is_like_osx {
         name_in_debuginfo.push("@");
         name_in_debuginfo.push(codegen_unit_name);
@@ -992,17 +992,17 @@ pub fn compile_unit_metadata(
     let producer = format!("clang LLVM ({})", rustc_producer);
 
     let name_in_debuginfo = name_in_debuginfo.to_string_lossy();
+    let work_dir = tcx.sess.working_dir.0.to_string_lossy();
     let flags = "\0";
-
     let out_dir = &tcx.output_filenames(LOCAL_CRATE).out_directory;
     let split_name = if tcx.sess.target_can_use_split_dwarf() {
         tcx.output_filenames(LOCAL_CRATE)
-            .split_dwarf_filename(tcx.sess.split_debuginfo(), Some(codegen_unit_name))
+            .split_dwarf_path(tcx.sess.split_debuginfo(), Some(codegen_unit_name))
+            .map(|f| out_dir.join(f))
     } else {
         None
     }
     .unwrap_or_default();
-    let out_dir = out_dir.to_str().unwrap();
     let split_name = split_name.to_str().unwrap();
 
     // FIXME(#60020):
@@ -1024,12 +1024,12 @@ pub fn compile_unit_metadata(
     assert!(tcx.sess.opts.debuginfo != DebugInfo::None);
 
     unsafe {
-        let file_metadata = llvm::LLVMRustDIBuilderCreateFile(
+        let compile_unit_file = llvm::LLVMRustDIBuilderCreateFile(
             debug_context.builder,
             name_in_debuginfo.as_ptr().cast(),
             name_in_debuginfo.len(),
-            out_dir.as_ptr().cast(),
-            out_dir.len(),
+            work_dir.as_ptr().cast(),
+            work_dir.len(),
             llvm::ChecksumKind::None,
             ptr::null(),
             0,
@@ -1038,12 +1038,15 @@ pub fn compile_unit_metadata(
         let unit_metadata = llvm::LLVMRustDIBuilderCreateCompileUnit(
             debug_context.builder,
             DW_LANG_RUST,
-            file_metadata,
+            compile_unit_file,
             producer.as_ptr().cast(),
             producer.len(),
             tcx.sess.opts.optimize != config::OptLevel::No,
             flags.as_ptr().cast(),
             0,
+            // NB: this doesn't actually have any perceptible effect, it seems. LLVM will instead
+            // put the path supplied to `MCSplitDwarfFile` into the debug info of the final
+            // output(s).
             split_name.as_ptr().cast(),
             split_name.len(),
             kind,

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -288,7 +288,7 @@ impl TargetMachineFactoryConfig {
         module_name: &str,
     ) -> TargetMachineFactoryConfig {
         let split_dwarf_file = if cgcx.target_can_use_split_dwarf {
-            cgcx.output_filenames.split_dwarf_filename(cgcx.split_debuginfo, Some(module_name))
+            cgcx.output_filenames.split_dwarf_path(cgcx.split_debuginfo, Some(module_name))
         } else {
             None
         };

compiler/rustc_session/src/config.rs

@@ -667,17 +667,6 @@ impl OutputFilenames {
         path
     }
 
-    /// Returns the name of the Split DWARF file - this can differ depending on which Split DWARF
-    /// mode is being used, which is the logic that this function is intended to encapsulate.
-    pub fn split_dwarf_filename(
-        &self,
-        split_debuginfo_kind: SplitDebuginfo,
-        cgu_name: Option<&str>,
-    ) -> Option<PathBuf> {
-        self.split_dwarf_path(split_debuginfo_kind, cgu_name)
-            .map(|path| path.strip_prefix(&self.out_directory).unwrap_or(&path).to_path_buf())
-    }
-
     /// Returns the path for the Split DWARF file - this can differ depending on which Split DWARF
     /// mode is being used, which is the logic that this function is intended to encapsulate.
     pub fn split_dwarf_path(

src/test/codegen/debug-compile-unit-path.rs

@@ -0,0 +1,9 @@
+// compile-flags: -g --remap-path-prefix={{cwd}}=/cwd/ --remap-path-prefix={{src-base}}=/base/
+// ignore-tidy-linelength
+//
+// Ensure that we remap the compile unit directory and that we set it to the compilers current
+// working directory and not something else.
+#![crate_type="rlib"]
+
+// CHECK-DAG: [[FILE:![0-9]*]] = !DIFile(filename: "/base/debug-compile-unit-path.rs{{.*}}", directory: "/cwd/")
+// CHECK-DAG: {{![0-9]*}} = distinct !DICompileUnit({{.*}}file: [[FILE]]

src/test/run-make-fulldeps/split-debuginfo/Makefile

@@ -1,5 +1,7 @@
 -include ../tools.mk
 
+# min-llvm-version: 11.0
+
 all: off packed unpacked
 
 ifeq ($(UNAME),Darwin)

src/test/run-make-fulldeps/split-dwarf/Makefile

@@ -1,6 +1,7 @@
 -include ../tools.mk
 
 # only-linux
+# min-llvm-version: 11.0
 
 all:
 	$(RUSTC) -Z unstable-options -C split-debuginfo=packed foo.rs -g