rustc: Stabilize -Zrun-dsymutil as -Csplit-debuginfo

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -732,10 +732,7 @@ pub unsafe fn optimize_thin_module(
     let diag_handler = cgcx.create_diag_handler();
 
     let module_name = &thin_module.shared.module_names[thin_module.idx];
-    let split_dwarf_file = cgcx
-        .output_filenames
-        .split_dwarf_filename(cgcx.split_dwarf_kind, Some(module_name.to_str().unwrap()));
-    let tm_factory_config = TargetMachineFactoryConfig { split_dwarf_file };
+    let tm_factory_config = TargetMachineFactoryConfig::new(cgcx, module_name.to_str().unwrap());
     let tm =
         (cgcx.tm_factory)(tm_factory_config).map_err(|e| write::llvm_err(&diag_handler, &e))?;
 

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -23,13 +23,11 @@ use rustc_fs_util::{link_or_copy, path_to_c_string};
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
-use rustc_session::config::{
-    self, Lto, OutputType, Passes, SanitizerSet, SplitDwarfKind, SwitchWithOptPath,
-};
+use rustc_session::config::{self, Lto, OutputType, Passes, SanitizerSet, SwitchWithOptPath};
 use rustc_session::Session;
 use rustc_span::symbol::sym;
 use rustc_span::InnerSpan;
-use rustc_target::spec::{CodeModel, RelocModel};
+use rustc_target::spec::{CodeModel, RelocModel, SplitDebuginfo};
 use tracing::debug;
 
 use libc::{c_char, c_int, c_uint, c_void, size_t};
@@ -93,9 +91,12 @@ 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 = tcx
-        .output_filenames(LOCAL_CRATE)
-        .split_dwarf_filename(tcx.sess.opts.debugging_opts.split_dwarf, Some(mod_name));
+    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))
+    } else {
+        None
+    };
     let config = TargetMachineFactoryConfig { split_dwarf_file };
     target_machine_factory(&tcx.sess, tcx.backend_optimization_level(LOCAL_CRATE))(config)
         .unwrap_or_else(|err| llvm_err(tcx.sess.diagnostic(), &err).raise())
@@ -838,11 +839,17 @@ pub(crate) unsafe fn codegen(
                     .generic_activity_with_arg("LLVM_module_codegen_emit_obj", &module.name[..]);
 
                 let dwo_out = cgcx.output_filenames.temp_path_dwo(module_name);
-                let dwo_out = match cgcx.split_dwarf_kind {
+                let dwo_out = match cgcx.split_debuginfo {
                     // Don't change how DWARF is emitted in single mode (or when disabled).
-                    SplitDwarfKind::None | SplitDwarfKind::Single => None,
+                    SplitDebuginfo::Off | SplitDebuginfo::Packed => None,
                     // Emit (a subset of the) DWARF into a separate file in split mode.
-                    SplitDwarfKind::Split => Some(dwo_out.as_path()),
+                    SplitDebuginfo::Unpacked => {
+                        if cgcx.target_can_use_split_dwarf {
+                            Some(dwo_out.as_path())
+                        } else {
+                            None
+                        }
+                    }
                 };
 
                 with_codegen(tm, llmod, config.no_builtins, |cpm| {
@@ -880,7 +887,7 @@ pub(crate) unsafe fn codegen(
 
     Ok(module.into_compiled_module(
         config.emit_obj != EmitObj::None,
-        cgcx.split_dwarf_kind == SplitDwarfKind::Split,
+        cgcx.target_can_use_split_dwarf && cgcx.split_debuginfo == SplitDebuginfo::Unpacked,
         config.emit_bc,
         &cgcx.output_filenames,
     ))

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -996,10 +996,13 @@ pub fn compile_unit_metadata(
     let flags = "\0";
 
     let out_dir = &tcx.output_filenames(LOCAL_CRATE).out_directory;
-    let split_name = tcx
-        .output_filenames(LOCAL_CRATE)
-        .split_dwarf_filename(tcx.sess.opts.debugging_opts.split_dwarf, Some(codegen_unit_name))
-        .unwrap_or_default();
+    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))
+    } else {
+        None
+    }
+    .unwrap_or_default();
     let out_dir = out_dir.to_str().unwrap();
     let split_name = split_name.to_str().unwrap();
 

compiler/rustc_codegen_llvm/src/lib.rs

@@ -351,12 +351,7 @@ impl ModuleLlvm {
         unsafe {
             let llcx = llvm::LLVMRustContextCreate(cgcx.fewer_names);
             let llmod_raw = back::lto::parse_module(llcx, name, buffer, handler)?;
-
-            let split_dwarf_file = cgcx
-                .output_filenames
-                .split_dwarf_filename(cgcx.split_dwarf_kind, Some(name.to_str().unwrap()));
-            let tm_factory_config = TargetMachineFactoryConfig { split_dwarf_file };
-
+            let tm_factory_config = TargetMachineFactoryConfig::new(&cgcx, name.to_str().unwrap());
             let tm = match (cgcx.tm_factory)(tm_factory_config) {
                 Ok(m) => m,
                 Err(e) => {

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -14,7 +14,7 @@ use rustc_session::utils::NativeLibKind;
 use rustc_session::{filesearch, Session};
 use rustc_span::symbol::Symbol;
 use rustc_target::spec::crt_objects::{CrtObjects, CrtObjectsFallback};
-use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor};
+use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor, SplitDebuginfo};
 use rustc_target::spec::{PanicStrategy, RelocModel, RelroLevel, Target};
 
 use super::archive::ArchiveBuilder;
@@ -99,9 +99,6 @@ pub fn link_binary<'a, B: ArchiveBuilder<'a>>(
                         path.as_ref(),
                         target_cpu,
                     );
-                    if sess.opts.debugging_opts.split_dwarf == config::SplitDwarfKind::Split {
-                        link_dwarf_object(sess, &out_filename);
-                    }
                 }
             }
             if sess.opts.json_artifact_notifications {
@@ -828,29 +825,43 @@ fn link_natively<'a, B: ArchiveBuilder<'a>>(
         }
     }
 
-    // On macOS, debuggers need this utility to get run to do some munging of
-    // the symbols. Note, though, that if the object files are being preserved
-    // for their debug information there's no need for us to run dsymutil.
-    if sess.target.is_like_osx
-        && sess.opts.debuginfo != DebugInfo::None
-        && !preserve_objects_for_their_debuginfo(sess)
-    {
-        let prog = Command::new("dsymutil").arg(out_filename).output();
-        match prog {
-            Ok(prog) => {
-                if !prog.status.success() {
-                    let mut output = prog.stderr.clone();
-                    output.extend_from_slice(&prog.stdout);
-                    sess.struct_warn(&format!(
-                        "processing debug info with `dsymutil` failed: {}",
-                        prog.status
-                    ))
-                    .note(&escape_string(&output))
-                    .emit();
+    match sess.split_debuginfo() {
+        // If split debug information is disabled or located in individual files
+        // there's nothing to do here.
+        SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
+
+        // If packed split-debuginfo is requested, but the final compilation
+        // doesn't actually have any debug information, then we skip this step.
+        SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
+
+        // On macOS the external `dsymutil` tool is used to create the packed
+        // debug information. Note that this will read debug information from
+        // the objects on the filesystem which we'll clean up later.
+        SplitDebuginfo::Packed if sess.target.is_like_osx => {
+            let prog = Command::new("dsymutil").arg(out_filename).output();
+            match prog {
+                Ok(prog) => {
+                    if !prog.status.success() {
+                        let mut output = prog.stderr.clone();
+                        output.extend_from_slice(&prog.stdout);
+                        sess.struct_warn(&format!(
+                            "processing debug info with `dsymutil` failed: {}",
+                            prog.status
+                        ))
+                        .note(&escape_string(&output))
+                        .emit();
+                    }
                 }
+                Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
             }
-            Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
         }
+
+        // On MSVC packed debug information is produced by the linker itself so
+        // there's no need to do anything else here.
+        SplitDebuginfo::Packed if sess.target.is_like_msvc => {}
+
+        // ... and otherwise we're processing a `*.dwp` packed dwarf file.
+        SplitDebuginfo::Packed => link_dwarf_object(sess, &out_filename),
     }
 }
 
@@ -1050,28 +1061,9 @@ fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
         return false;
     }
 
-    // Single mode keeps debuginfo in the same object file, but in such a way that it it skipped
-    // by the linker - so it's expected that when codegen units are linked together that this
-    // debuginfo would be lost without keeping around the temps.
-    if sess.opts.debugging_opts.split_dwarf == config::SplitDwarfKind::Single {
-        return true;
-    }
-
-    // If we're on OSX then the equivalent of split dwarf is turned on by
-    // default. The final executable won't actually have any debug information
-    // except it'll have pointers to elsewhere. Historically we've always run
-    // `dsymutil` to "link all the dwarf together" but this is actually sort of
-    // a bummer for incremental compilation! (the whole point of split dwarf is
-    // that you don't do this sort of dwarf link).
-    //
-    // Basically as a result this just means that if we're on OSX and we're
-    // *not* running dsymutil then the object files are the only source of truth
-    // for debug information, so we must preserve them.
-    if sess.target.is_like_osx {
-        return !sess.opts.debugging_opts.run_dsymutil;
-    }
-
-    false
+    // "unpacked" split debuginfo means that we leave object files as the
+    // debuginfo is found in the original object files themselves
+    sess.split_debuginfo() == SplitDebuginfo::Unpacked
 }
 
 pub fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -282,6 +282,20 @@ pub struct TargetMachineFactoryConfig {
     pub split_dwarf_file: Option<PathBuf>,
 }
 
+impl TargetMachineFactoryConfig {
+    pub fn new(
+        cgcx: &CodegenContext<impl WriteBackendMethods>,
+        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))
+        } else {
+            None
+        };
+        TargetMachineFactoryConfig { split_dwarf_file }
+    }
+}
+
 pub type TargetMachineFactoryFn<B> = Arc<
     dyn Fn(TargetMachineFactoryConfig) -> Result<<B as WriteBackendMethods>::TargetMachine, String>
         + Send
@@ -311,10 +325,11 @@ pub struct CodegenContext<B: WriteBackendMethods> {
     pub tm_factory: TargetMachineFactoryFn<B>,
     pub msvc_imps_needed: bool,
     pub is_pe_coff: bool,
+    pub target_can_use_split_dwarf: bool,
     pub target_pointer_width: u32,
     pub target_arch: String,
     pub debuginfo: config::DebugInfo,
-    pub split_dwarf_kind: config::SplitDwarfKind,
+    pub split_debuginfo: rustc_target::spec::SplitDebuginfo,
 
     // Number of cgus excluding the allocator/metadata modules
     pub total_cgus: usize,
@@ -1035,10 +1050,11 @@ fn start_executing_work<B: ExtraBackendMethods>(
         total_cgus,
         msvc_imps_needed: msvc_imps_needed(tcx),
         is_pe_coff: tcx.sess.target.is_like_windows,
+        target_can_use_split_dwarf: tcx.sess.target_can_use_split_dwarf(),
         target_pointer_width: tcx.sess.target.pointer_width,
         target_arch: tcx.sess.target.arch.clone(),
         debuginfo: tcx.sess.opts.debuginfo,
-        split_dwarf_kind: tcx.sess.opts.debugging_opts.split_dwarf,
+        split_debuginfo: tcx.sess.split_debuginfo(),
     };
 
     // This is the "main loop" of parallel work happening for parallel codegen.

compiler/rustc_interface/src/tests.rs

@@ -17,7 +17,7 @@ use rustc_span::edition::{Edition, DEFAULT_EDITION};
 use rustc_span::symbol::sym;
 use rustc_span::SourceFileHashAlgorithm;
 use rustc_target::spec::{CodeModel, LinkerFlavor, MergeFunctions, PanicStrategy};
-use rustc_target::spec::{RelocModel, RelroLevel, TlsModel};
+use rustc_target::spec::{RelocModel, RelroLevel, SplitDebuginfo, TlsModel};
 use std::collections::{BTreeMap, BTreeSet};
 use std::iter::FromIterator;
 use std::path::PathBuf;
@@ -446,6 +446,7 @@ fn test_codegen_options_tracking_hash() {
     tracked!(profile_use, Some(PathBuf::from("abc")));
     tracked!(relocation_model, Some(RelocModel::Pic));
     tracked!(soft_float, true);
+    tracked!(split_debuginfo, Some(SplitDebuginfo::Packed));
     tracked!(target_cpu, Some(String::from("abc")));
     tracked!(target_feature, String::from("all the features, all of them"));
 }
@@ -579,7 +580,6 @@ fn test_debugging_options_tracking_hash() {
     tracked!(relax_elf_relocations, Some(true));
     tracked!(relro_level, Some(RelroLevel::Full));
     tracked!(report_delayed_bugs, true);
-    tracked!(run_dsymutil, false);
     tracked!(sanitizer, SanitizerSet::ADDRESS);
     tracked!(sanitizer_memory_track_origins, 2);
     tracked!(sanitizer_recover, SanitizerSet::ADDRESS);

compiler/rustc_session/src/config.rs

@@ -13,7 +13,7 @@ use rustc_data_structures::impl_stable_hash_via_hash;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 
 use rustc_target::abi::{Align, TargetDataLayout};
-use rustc_target::spec::{Target, TargetTriple};
+use rustc_target::spec::{SplitDebuginfo, Target, TargetTriple};
 
 use crate::parse::CrateConfig;
 use rustc_feature::UnstableFeatures;
@@ -221,23 +221,6 @@ pub enum DebugInfo {
     Full,
 }
 
-/// Some debuginfo requires link-time relocation and some does not. LLVM can partition the debuginfo
-/// into sections depending on whether or not it requires link-time relocation. Split DWARF
-/// provides a mechanism which allows the linker to skip the sections which don't require link-time
-/// relocation - either by putting those sections into DWARF object files, or keeping them in the
-/// object file in such a way that the linker will skip them.
-#[derive(Clone, Copy, Debug, PartialEq, Hash)]
-pub enum SplitDwarfKind {
-    /// Disabled.
-    None,
-    /// Sections which do not require relocation are written into the object file but ignored
-    /// by the linker.
-    Single,
-    /// Sections which do not require relocation are written into a DWARF object (`.dwo`) file,
-    /// which is skipped by the linker by virtue of being a different file.
-    Split,
-}
-
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
 #[derive(Encodable, Decodable)]
 pub enum OutputType {
@@ -635,30 +618,30 @@ impl OutputFilenames {
     /// mode is being used, which is the logic that this function is intended to encapsulate.
     pub fn split_dwarf_filename(
         &self,
-        split_dwarf_kind: SplitDwarfKind,
+        split_debuginfo_kind: SplitDebuginfo,
         cgu_name: Option<&str>,
     ) -> Option<PathBuf> {
-        self.split_dwarf_path(split_dwarf_kind, cgu_name)
+        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(
         &self,
-        split_dwarf_kind: SplitDwarfKind,
+        split_debuginfo_kind: SplitDebuginfo,
         cgu_name: Option<&str>,
     ) -> Option<PathBuf> {
         let obj_out = self.temp_path(OutputType::Object, cgu_name);
         let dwo_out = self.temp_path_dwo(cgu_name);
-        match split_dwarf_kind {
-            SplitDwarfKind::None => None,
+        match split_debuginfo_kind {
+            SplitDebuginfo::Off => None,
             // Single mode doesn't change how DWARF is emitted, but does add Split DWARF attributes
             // (pointing at the path which is being determined here). Use the path to the current
             // object file.
-            SplitDwarfKind::Single => Some(obj_out),
+            SplitDebuginfo::Packed => Some(obj_out),
             // Split mode emits the DWARF into a different file, use that path.
-            SplitDwarfKind::Split => Some(dwo_out),
+            SplitDebuginfo::Unpacked => Some(dwo_out),
         }
     }
 }
@@ -1910,6 +1893,15 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
 
     let pretty = parse_pretty(matches, &debugging_opts, error_format);
 
+    if !debugging_opts.unstable_options
+        && !target_triple.triple().contains("apple")
+        && cg.split_debuginfo.is_some()
+    {
+        {
+            early_error(error_format, "`-Csplit-debuginfo` is unstable on this platform");
+        }
+    }
+
     Options {
         crate_types,
         optimize: opt_level,
@@ -2191,7 +2183,7 @@ crate mod dep_tracking {
     use rustc_feature::UnstableFeatures;
     use rustc_span::edition::Edition;
     use rustc_target::spec::{CodeModel, MergeFunctions, PanicStrategy, RelocModel};
-    use rustc_target::spec::{RelroLevel, TargetTriple, TlsModel};
+    use rustc_target::spec::{RelroLevel, SplitDebuginfo, TargetTriple, TlsModel};
     use std::collections::hash_map::DefaultHasher;
     use std::collections::BTreeMap;
     use std::hash::Hash;
@@ -2263,6 +2255,7 @@ crate mod dep_tracking {
     impl_dep_tracking_hash_via_hash!(TargetTriple);
     impl_dep_tracking_hash_via_hash!(Edition);
     impl_dep_tracking_hash_via_hash!(LinkerPluginLto);
+    impl_dep_tracking_hash_via_hash!(Option<SplitDebuginfo>);
     impl_dep_tracking_hash_via_hash!(SwitchWithOptPath);
     impl_dep_tracking_hash_via_hash!(Option<SymbolManglingVersion>);
     impl_dep_tracking_hash_via_hash!(Option<SourceFileHashAlgorithm>);