Rollup merge of rust-lang#77765 - amshafer:master, r=petrochenkov

Add LLVM flags to limit DWARF version to 2 on BSD

This has been a thorn in my side for a while, I can finally generate flamegraphs of rust programs on bsd again. This fixes dtrace profiling on freebsd, I think it might help with lldb as well but I can't test that because my current rust-lldb setup is messed up.

I'm limiting the dwarf version to 2 on all bsd's (netbsd/openbsd/freebsd) since it looks like this applies to all of them, but I have only tested on freebsd.

Let me know if there's anything I can improve!

---
Currently on FreeBSD dtrace profiling does not work and shows jumbled/incorrect
symbols in the backtraces. FreeBSD does not support the latest versions of DWARF
in dtrace (and lldb?) yet, and needs to be limited to DWARF2 in the same way as macos.

This adds an is_like_bsd flag since it was missing. NetBSD/OpenBSD/FreeBSD all
match this.

This effectively copies rust-lang#11864 but targets FreeBSD instead of macos.

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -120,10 +120,8 @@ pub fn finalize(cx: &CodegenCx<'_, '_>) {
         // for macOS to understand. For more info see #11352
         // This can be overridden using --llvm-opts -dwarf-version,N.
         // Android has the same issue (#22398)
-        if cx.sess().target.target.options.is_like_osx
-            || cx.sess().target.target.options.is_like_android
-        {
-            llvm::LLVMRustAddModuleFlag(cx.llmod, "Dwarf Version\0".as_ptr().cast(), 2)
+        if let Some(version) = cx.sess().target.target.options.dwarf_version {
+            llvm::LLVMRustAddModuleFlag(cx.llmod, "Dwarf Version\0".as_ptr().cast(), version)
         }
 
         // Indicate that we want CodeView debug information on MSVC

compiler/rustc_target/src/spec/android_base.rs

@@ -9,6 +9,7 @@ pub fn opts() -> TargetOptions {
         .unwrap()
         .push("-Wl,--allow-multiple-definition".to_string());
     base.is_like_android = true;
+    base.dwarf_version = Some(2);
     base.position_independent_executables = true;
     base.has_elf_tls = false;
     base.requires_uwtable = true;

compiler/rustc_target/src/spec/apple_base.rs

@@ -23,6 +23,7 @@ pub fn opts() -> TargetOptions {
         executables: true,
         target_family: Some("unix".to_string()),
         is_like_osx: true,
+        dwarf_version: Some(2),
         has_rpath: true,
         dll_prefix: "lib".to_string(),
         dll_suffix: ".dylib".to_string(),

compiler/rustc_target/src/spec/dragonfly_base.rs

@@ -24,6 +24,7 @@ pub fn opts() -> TargetOptions {
         pre_link_args: args,
         position_independent_executables: true,
         relro_level: RelroLevel::Full,
+        dwarf_version: Some(2),
         ..Default::default()
     }
 }

compiler/rustc_target/src/spec/freebsd_base.rs

@@ -26,6 +26,7 @@ pub fn opts() -> TargetOptions {
         eliminate_frame_pointer: false, // FIXME 43575
         relro_level: RelroLevel::Full,
         abi_return_struct_as_int: true,
+        dwarf_version: Some(2),
         ..Default::default()
     }
 }

compiler/rustc_target/src/spec/mod.rs

@@ -816,6 +816,9 @@ pub struct TargetOptions {
     pub is_like_emscripten: bool,
     /// Whether the target toolchain is like Fuchsia's.
     pub is_like_fuchsia: bool,
+    /// Version of DWARF to use if not using the default.
+    /// Useful because some platforms (osx, bsd) only want up to DWARF2.
+    pub dwarf_version: Option<u32>,
     /// Whether the linker support GNU-like arguments such as -O. Defaults to false.
     pub linker_is_gnu: bool,
     /// The MinGW toolchain has a known issue that prevents it from correctly
@@ -1012,6 +1015,7 @@ impl Default for TargetOptions {
             is_like_emscripten: false,
             is_like_msvc: false,
             is_like_fuchsia: false,
+            dwarf_version: None,
             linker_is_gnu: false,
             allows_weak_linkage: true,
             has_rpath: false,
@@ -1165,6 +1169,15 @@ impl Target {
                     base.options.$key_name = s;
                 }
             } );
+            ($key_name:ident, Option<u32>) => ( {
+                let name = (stringify!($key_name)).replace("_", "-");
+                if let Some(s) = obj.find(&name).and_then(Json::as_u64) {
+                    if s < 1 || s > 5 {
+                        return Err("Not a valid DWARF version number".to_string());
+                    }
+                    base.options.$key_name = Some(s as u32);
+                }
+            } );
             ($key_name:ident, Option<u64>) => ( {
                 let name = (stringify!($key_name)).replace("_", "-");
                 if let Some(s) = obj.find(&name).and_then(Json::as_u64) {
@@ -1417,6 +1430,7 @@ impl Target {
         key!(is_like_emscripten, bool);
         key!(is_like_android, bool);
         key!(is_like_fuchsia, bool);
+        key!(dwarf_version, Option<u32>);
         key!(linker_is_gnu, bool);
         key!(allows_weak_linkage, bool);
         key!(has_rpath, bool);
@@ -1654,6 +1668,7 @@ impl ToJson for Target {
         target_option_val!(is_like_emscripten);
         target_option_val!(is_like_android);
         target_option_val!(is_like_fuchsia);
+        target_option_val!(dwarf_version);
         target_option_val!(linker_is_gnu);
         target_option_val!(allows_weak_linkage);
         target_option_val!(has_rpath);

compiler/rustc_target/src/spec/netbsd_base.rs

@@ -24,6 +24,7 @@ pub fn opts() -> TargetOptions {
         position_independent_executables: true,
         relro_level: RelroLevel::Full,
         use_ctors_section: true,
+        dwarf_version: Some(2),
         ..Default::default()
     }
 }

compiler/rustc_target/src/spec/openbsd_base.rs

@@ -26,6 +26,7 @@ pub fn opts() -> TargetOptions {
         position_independent_executables: true,
         eliminate_frame_pointer: false, // FIXME 43575
         relro_level: RelroLevel::Full,
+        dwarf_version: Some(2),
         ..Default::default()
     }
 }