From 1e0ad0c1d4fdca7a37221e05fd5e39739d9084f5 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@fb.com>
Date: Mon, 20 Jun 2022 16:26:51 -0700
Subject: [PATCH] Implement support for DWARF version 5.
DWARF version 5 brings a number of improvements over version 4. Quoting from
the announcement [1]:
> Version 5 incorporates improvements in many areas: better data compression,
> separation of debugging data from executable files, improved description of
> macros and source files, faster searching for symbols, improved debugging
> optimized code, as well as numerous improvements in functionality and
> performance.
On platforms where DWARF version 5 is supported (Linux, primarily), this commit
adds support for it behind a new `-Z dwarf-version=5` flag.
[1]: https://dwarfstd.org/Public_Review.php
---
.../rustc_codegen_llvm/src/debuginfo/mod.rs | 16 +++++++--------
compiler/rustc_interface/src/tests.rs | 1 +
compiler/rustc_session/src/options.rs | 2 ++
compiler/rustc_session/src/session.rs | 6 ++++++
.../rustc_target/src/spec/android_base.rs | 2 +-
compiler/rustc_target/src/spec/apple_base.rs | 2 +-
.../rustc_target/src/spec/dragonfly_base.rs | 2 +-
.../rustc_target/src/spec/freebsd_base.rs | 2 +-
compiler/rustc_target/src/spec/mod.rs | 14 ++++++-------
compiler/rustc_target/src/spec/netbsd_base.rs | 2 +-
.../rustc_target/src/spec/openbsd_base.rs | 2 +-
.../src/compiler-flags/dwarf-version.md | 9 +++++++++
src/test/assembly/dwarf5.rs | 20 +++++++++++++++++++
13 files changed, 59 insertions(+), 21 deletions(-)
create mode 100644 src/doc/unstable-book/src/compiler-flags/dwarf-version.md
create mode 100644 src/test/assembly/dwarf5.rs
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index 64ecbc82c560..730048d061b5 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -103,14 +103,14 @@ impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
// 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 let Some(version) = sess.target.dwarf_version {
- llvm::LLVMRustAddModuleFlag(
- self.llmod,
- llvm::LLVMModFlagBehavior::Warning,
- "Dwarf Version\0".as_ptr().cast(),
- version,
- )
- }
+ let dwarf_version =
+ sess.opts.debugging_opts.dwarf_version.unwrap_or(sess.target.default_dwarf_version);
+ llvm::LLVMRustAddModuleFlag(
+ self.llmod,
+ llvm::LLVMModFlagBehavior::Warning,
+ "Dwarf Version\0".as_ptr().cast(),
+ dwarf_version,
+ );
// Indicate that we want CodeView debug information on MSVC
if sess.target.is_like_msvc {
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 1bb79a0264dd..55827ff583af 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -733,6 +733,7 @@ fn test_debugging_options_tracking_hash() {
tracked!(dep_info_omit_d_target, true);
tracked!(drop_tracking, true);
tracked!(dual_proc_macros, true);
+ tracked!(dwarf_version, Some(5));
tracked!(fewer_names, Some(true));
tracked!(force_unstable_if_unmarked, true);
tracked!(fuel, Some(("abc".to_string(), 99)));
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index b617eb02eb6e..8f1057b793fa 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1272,6 +1272,8 @@ options! {
computed `block` spans (one span encompassing a block's terminator and \
all statements). If `-Z instrument-coverage` is also enabled, create \
an additional `.html` file showing the computed coverage spans."),
+ dwarf_version: Option<u32> = (None, parse_opt_number, [TRACKED],
+ "version of DWARF debug information to emit (default: 2 or 4, depending on platform)"),
emit_stack_sizes: bool = (false, parse_bool, [UNTRACKED],
"emit a section containing stack size metadata (default: no)"),
fewer_names: Option<bool> = (None, parse_opt_bool, [TRACKED],
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 1eee0c3163d4..1cccef2f64fe 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -1498,6 +1498,12 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
))
}
}
+
+ if let Some(dwarf_version) = sess.opts.debugging_opts.dwarf_version {
+ if dwarf_version > 5 {
+ sess.err(&format!("requested DWARF version {} is greater than 5", dwarf_version));
+ }
+ }
}
/// Holds data on the current incremental compilation session, if there is one.
diff --git a/compiler/rustc_target/src/spec/android_base.rs b/compiler/rustc_target/src/spec/android_base.rs
index c2b9d696776f..dc06597db6fd 100644
--- a/compiler/rustc_target/src/spec/android_base.rs
+++ b/compiler/rustc_target/src/spec/android_base.rs
@@ -3,7 +3,7 @@ use crate::spec::TargetOptions;
pub fn opts() -> TargetOptions {
let mut base = super::linux_base::opts();
base.os = "android".into();
- base.dwarf_version = Some(2);
+ base.default_dwarf_version = 2;
base.position_independent_executables = true;
base.has_thread_local = false;
// This is for backward compatibility, see https://github.com/rust-lang/rust/issues/49867
diff --git a/compiler/rustc_target/src/spec/apple_base.rs b/compiler/rustc_target/src/spec/apple_base.rs
index e8460a509e2b..713dc9a1f0ea 100644
--- a/compiler/rustc_target/src/spec/apple_base.rs
+++ b/compiler/rustc_target/src/spec/apple_base.rs
@@ -28,7 +28,7 @@ pub fn opts(os: &'static str) -> TargetOptions {
executables: true,
families: cvs!["unix"],
is_like_osx: true,
- dwarf_version: Some(2),
+ default_dwarf_version: 2,
frame_pointer: FramePointer::Always,
has_rpath: true,
dll_suffix: ".dylib".into(),
diff --git a/compiler/rustc_target/src/spec/dragonfly_base.rs b/compiler/rustc_target/src/spec/dragonfly_base.rs
index b59322d07f57..c1e469746cb4 100644
--- a/compiler/rustc_target/src/spec/dragonfly_base.rs
+++ b/compiler/rustc_target/src/spec/dragonfly_base.rs
@@ -9,7 +9,7 @@ pub fn opts() -> TargetOptions {
has_rpath: true,
position_independent_executables: true,
relro_level: RelroLevel::Full,
- dwarf_version: Some(2),
+ default_dwarf_version: 2,
..Default::default()
}
}
diff --git a/compiler/rustc_target/src/spec/freebsd_base.rs b/compiler/rustc_target/src/spec/freebsd_base.rs
index a7e0f9f70412..36312d26e370 100644
--- a/compiler/rustc_target/src/spec/freebsd_base.rs
+++ b/compiler/rustc_target/src/spec/freebsd_base.rs
@@ -10,7 +10,7 @@ pub fn opts() -> TargetOptions {
position_independent_executables: true,
relro_level: RelroLevel::Full,
abi_return_struct_as_int: true,
- dwarf_version: Some(2),
+ default_dwarf_version: 2,
..Default::default()
}
}
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index a08603da0409..48ccb10f2142 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1275,9 +1275,9 @@ pub struct TargetOptions {
pub is_like_msvc: bool,
/// Whether a target toolchain is like WASM.
pub is_like_wasm: bool,
- /// Version of DWARF to use if not using the default.
+ /// Default supported version of DWARF on this platform.
/// Useful because some platforms (osx, bsd) only want up to DWARF2.
- pub dwarf_version: Option<u32>,
+ pub default_dwarf_version: u32,
/// Whether the linker support GNU-like arguments such as -O. Defaults to true.
pub linker_is_gnu: bool,
/// The MinGW toolchain has a known issue that prevents it from correctly
@@ -1539,7 +1539,7 @@ impl Default for TargetOptions {
is_like_windows: false,
is_like_msvc: false,
is_like_wasm: false,
- dwarf_version: None,
+ default_dwarf_version: 4,
linker_is_gnu: true,
allows_weak_linkage: true,
has_rpath: false,
@@ -1778,13 +1778,13 @@ impl Target {
base.$key_name = s;
}
} );
- ($key_name:ident, Option<u32>) => ( {
+ ($key_name:ident, u32) => ( {
let name = (stringify!($key_name)).replace("_", "-");
if let Some(s) = obj.remove(&name).and_then(|b| b.as_u64()) {
if s < 1 || s > 5 {
return Err("Not a valid DWARF version number".into());
}
- base.$key_name = Some(s as u32);
+ base.$key_name = s as u32;
}
} );
($key_name:ident, Option<u64>) => ( {
@@ -2143,7 +2143,7 @@ impl Target {
key!(is_like_windows, bool);
key!(is_like_msvc, bool);
key!(is_like_wasm, bool);
- key!(dwarf_version, Option<u32>);
+ key!(default_dwarf_version, u32);
key!(linker_is_gnu, bool);
key!(allows_weak_linkage, bool);
key!(has_rpath, bool);
@@ -2387,7 +2387,7 @@ impl ToJson for Target {
target_option_val!(is_like_windows);
target_option_val!(is_like_msvc);
target_option_val!(is_like_wasm);
- target_option_val!(dwarf_version);
+ target_option_val!(default_dwarf_version);
target_option_val!(linker_is_gnu);
target_option_val!(allows_weak_linkage);
target_option_val!(has_rpath);
diff --git a/compiler/rustc_target/src/spec/netbsd_base.rs b/compiler/rustc_target/src/spec/netbsd_base.rs
index 69016d77cf97..40ef04ba0438 100644
--- a/compiler/rustc_target/src/spec/netbsd_base.rs
+++ b/compiler/rustc_target/src/spec/netbsd_base.rs
@@ -11,7 +11,7 @@ pub fn opts() -> TargetOptions {
position_independent_executables: true,
relro_level: RelroLevel::Full,
use_ctors_section: true,
- dwarf_version: Some(2),
+ default_dwarf_version: 2,
..Default::default()
}
}
diff --git a/compiler/rustc_target/src/spec/openbsd_base.rs b/compiler/rustc_target/src/spec/openbsd_base.rs
index bbd322bb6ce2..51cecdd47eab 100644
--- a/compiler/rustc_target/src/spec/openbsd_base.rs
+++ b/compiler/rustc_target/src/spec/openbsd_base.rs
@@ -11,7 +11,7 @@ pub fn opts() -> TargetOptions {
position_independent_executables: true,
frame_pointer: FramePointer::Always, // FIXME 43575: should be MayOmit...
relro_level: RelroLevel::Full,
- dwarf_version: Some(2),
+ default_dwarf_version: 2,
..Default::default()
}
}
diff --git a/src/doc/unstable-book/src/compiler-flags/dwarf-version.md b/src/doc/unstable-book/src/compiler-flags/dwarf-version.md
new file mode 100644
index 000000000000..c5e86f17df74
--- /dev/null
+++ b/src/doc/unstable-book/src/compiler-flags/dwarf-version.md
@@ -0,0 +1,9 @@
+## `dwarf-version`
+
+This option controls the version of DWARF that the compiler emits, on platforms
+that use DWARF to encode debug information. It takes one of the following
+values:
+
+* `2`: DWARF version 2 (the default on certain platforms, like macOS).
+* `4`: DWARF version 4 (the default on certain platforms, like Linux).
+* `5`: DWARF version 5.
diff --git a/src/test/assembly/dwarf5.rs b/src/test/assembly/dwarf5.rs
new file mode 100644
index 000000000000..f41e6bd55be7
--- /dev/null
+++ b/src/test/assembly/dwarf5.rs
@@ -0,0 +1,20 @@
+// Makes sure that `-Z dwarf-version=5` causes `rustc` to emit DWARF version 5.
+// assembly-output: emit-asm
+// compile-flags: -g --target x86_64-unknown-linux-gnu -Z dwarf-version=5
+// needs-llvm-components: x86
+
+#![feature(no_core, lang_items)]
+#![crate_type = "rlib"]
+#![no_core]
+
+#[lang = "sized"]
+trait Sized {}
+#[lang = "copy"]
+trait Copy {}
+
+pub fn wibble() {}
+
+// CHECK: .section .debug_info
+// CHECK-NOT: .short 2
+// CHECK-NOT: .short 4
+// CHECK: .short 5