Auto merge of #115704 - nebulark:s_object, r=nagisa

Pass name of object file to LLVM so it can correctly emit S_OBJNAME in pdb files on Windows

This should be the remaining fix to close https://github.com/rust-lang/rust/issues/96475
Setting ObjectFilenameForDebug in llvm::TargetOptions, so llvm it can emit S_OBJNAME  in pdb files on Windows.

Without a proper pdb parsing I am not able to add a unit test for this. The string is already appearing in the pdb file so I cannot just use grep.

`@rustbot` label: +A-debuginfo

compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs

@@ -37,6 +37,7 @@ impl OwnedTargetMachine {
         relax_elf_relocations: bool,
         use_init_array: bool,
         split_dwarf_file: &CStr,
+        output_obj_file: &CStr,
         debug_info_compression: &CStr,
         force_emulated_tls: bool,
         args_cstr_buff: &[u8],
@@ -68,6 +69,7 @@ impl OwnedTargetMachine {
                 relax_elf_relocations,
                 use_init_array,
                 split_dwarf_file.as_ptr(),
+                output_obj_file.as_ptr(),
                 debug_info_compression.as_ptr(),
                 force_emulated_tls,
                 args_cstr_buff.as_ptr() as *const c_char,

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -100,7 +100,7 @@ pub fn write_output_file<'ll>(
 }
 
 pub fn create_informational_target_machine(sess: &Session) -> OwnedTargetMachine {
-    let config = TargetMachineFactoryConfig { split_dwarf_file: None };
+    let config = TargetMachineFactoryConfig { split_dwarf_file: None, output_obj_file: None };
     // Can't use query system here quite yet because this function is invoked before the query
     // system/tcx is set up.
     let features = llvm_util::global_llvm_features(sess, false);
@@ -118,7 +118,11 @@ pub fn create_target_machine(tcx: TyCtxt<'_>, mod_name: &str) -> OwnedTargetMach
     } else {
         None
     };
-    let config = TargetMachineFactoryConfig { split_dwarf_file };
+
+    let output_obj_file =
+        Some(tcx.output_filenames(()).temp_path(OutputType::Object, Some(mod_name)));
+    let config = TargetMachineFactoryConfig { split_dwarf_file, output_obj_file };
+
     target_machine_factory(
         &tcx.sess,
         tcx.backend_optimization_level(()),
@@ -256,9 +260,13 @@ pub fn target_machine_factory(
     let debuginfo_compression = SmallCStr::new(&debuginfo_compression);
 
     Arc::new(move |config: TargetMachineFactoryConfig| {
-        let split_dwarf_file =
+        let path_to_cstring_helper = |path: Option<PathBuf>| -> CString {
-            path_mapping.map_prefix(config.split_dwarf_file.unwrap_or_default()).0;
+            let path = path_mapping.map_prefix(path.unwrap_or_default()).0;
-        let split_dwarf_file = CString::new(split_dwarf_file.to_str().unwrap()).unwrap();
+            CString::new(path.to_str().unwrap()).unwrap()
+        };
+
+        let split_dwarf_file = path_to_cstring_helper(config.split_dwarf_file);
+        let output_obj_file = path_to_cstring_helper(config.output_obj_file);
 
         OwnedTargetMachine::new(
             &triple,
@@ -279,6 +287,7 @@ pub fn target_machine_factory(
             relax_elf_relocations,
             use_init_array,
             &split_dwarf_file,
+            &output_obj_file,
             &debuginfo_compression,
             force_emulated_tls,
             &args_cstr_buff,

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2133,6 +2133,7 @@ extern "C" {
         RelaxELFRelocations: bool,
         UseInitArray: bool,
         SplitDwarfFile: *const c_char,
+        OutputObjFile: *const c_char,
         DebugInfoCompression: *const c_char,
         ForceEmulatedTls: bool,
         ArgsCstrBuff: *const c_char,

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -286,6 +286,10 @@ pub struct TargetMachineFactoryConfig {
     /// so the path to the dwarf object has to be provided when we create the target machine.
     /// This can be ignored by backends which do not need it for their Split DWARF support.
     pub split_dwarf_file: Option<PathBuf>,
+
+    /// The name of the output object file. Used for setting OutputFilenames in target options
+    /// so that LLVM can emit the CodeView S_OBJNAME record in pdb files
+    pub output_obj_file: Option<PathBuf>,
 }
 
 impl TargetMachineFactoryConfig {
@@ -302,7 +306,10 @@ impl TargetMachineFactoryConfig {
         } else {
             None
         };
-        TargetMachineFactoryConfig { split_dwarf_file }
+
+        let output_obj_file =
+            Some(cgcx.output_filenames.temp_path(OutputType::Object, Some(module_name)));
+        TargetMachineFactoryConfig { split_dwarf_file, output_obj_file }
     }
 }
 

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -416,6 +416,7 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
     bool RelaxELFRelocations,
     bool UseInitArray,
     const char *SplitDwarfFile,
+    const char *OutputObjFile,
     const char *DebugInfoCompression,
     bool ForceEmulatedTls,
     const char *ArgsCstrBuff, size_t ArgsCstrBuffLen) {
@@ -448,6 +449,9 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   if (SplitDwarfFile) {
       Options.MCOptions.SplitDwarfFile = SplitDwarfFile;
   }
+  if (OutputObjFile) {
+      Options.ObjectFilenameForDebug = OutputObjFile;
+  }
 #if LLVM_VERSION_GE(16, 0)
   if (!strcmp("zlib", DebugInfoCompression) && llvm::compression::zlib::isAvailable()) {
     Options.CompressDebugSections = DebugCompressionType::Zlib;