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sess/cg: re-introduce split dwarf kind

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In #79570, `-Z split-dwarf-kind={none,single,split}` was replaced by `-C
split-debuginfo={off,packed,unpacked}`. `-C split-debuginfo`'s packed
and unpacked aren't exact parallels to single and split, respectively.

On Unix, `-C split-debuginfo=packed` will put debuginfo into object
files and package debuginfo into a DWARF package file (`.dwp`) and
`-C split-debuginfo=unpacked` will put debuginfo into dwarf object files
and won't package it.

In the initial implementation of Split DWARF, split mode wrote sections
which did not require relocation into a DWARF object (`.dwo`) file which
was ignored by the linker and then packaged those DWARF objects into
DWARF packages (`.dwp`). In single mode, sections which did not require
relocation were written into object files but ignored by the linker and
were not packaged. However, both split and single modes could be
packaged or not, the primary difference in behaviour was where the
debuginfo sections that did not require link-time relocation were
written (in a DWARF object or the object file).

This commit re-introduces a `-Z split-dwarf-kind` flag, which can be
used to pick between split and single modes when `-C split-debuginfo` is
used to enable Split DWARF (either packed or unpacked).

Signed-off-by: David Wood <david.wood@huawei.com>
This commit is contained in:
David Wood 2021-10-08 16:10:17 +00:00
parent f1ce0e6a00
commit 08ed338f56
8 changed files with 184 additions and 61 deletions
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35
compiler/rustc_codegen_llvm/src/back/write.rs
View file

@ -23,7 +23,7 @@ use rustc_errors::{FatalError, Handler, Level};
use rustc_fs_util::{link_or_copy, path_to_c_string};
use rustc_middle::bug;
use rustc_middle::ty::TyCtxt;
use rustc_session::config::{self, Lto, OutputType, Passes, SwitchWithOptPath};
use rustc_session::config::{self, Lto, OutputType, Passes, SplitDwarfKind, SwitchWithOptPath};
use rustc_session::Session;
use rustc_span::symbol::sym;
use rustc_span::InnerSpan;
@ -106,7 +106,11 @@ 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(()).split_dwarf_path(tcx.sess.split_debuginfo(), Some(mod_name))
tcx.output_filenames(()).split_dwarf_path(
tcx.sess.split_debuginfo(),
tcx.sess.opts.debugging_opts.split_dwarf_kind,
Some(mod_name),
)
} else {
None
};
@ -892,17 +896,18 @@ 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_debuginfo {
// Don't change how DWARF is emitted in single mode (or when disabled).
SplitDebuginfo::Off | SplitDebuginfo::Packed => None,
// Emit (a subset of the) DWARF into a separate file in split mode.
SplitDebuginfo::Unpacked => {
if cgcx.target_can_use_split_dwarf {
Some(dwo_out.as_path())
} else {
None
}
}
let dwo_out = match (cgcx.split_debuginfo, cgcx.split_dwarf_kind) {
// Don't change how DWARF is emitted when disabled.
(SplitDebuginfo::Off, _) => None,
// Don't provide a DWARF object path if split debuginfo is enabled but this is
// a platform that doesn't support Split DWARF.
_ if !cgcx.target_can_use_split_dwarf => None,
// Don't provide a DWARF object path in single mode, sections will be written
// into the object as normal but ignored by linker.
(_, SplitDwarfKind::Single) => None,
// Emit (a subset of the) DWARF into a separate dwarf object file in split
// mode.
(_, SplitDwarfKind::Split) => Some(dwo_out.as_path()),
};
with_codegen(tm, llmod, config.no_builtins, |cpm| {
@ -939,7 +944,9 @@ pub(crate) unsafe fn codegen(
Ok(module.into_compiled_module(
config.emit_obj != EmitObj::None,
cgcx.target_can_use_split_dwarf && cgcx.split_debuginfo == SplitDebuginfo::Unpacked,
cgcx.target_can_use_split_dwarf
&& cgcx.split_debuginfo != SplitDebuginfo::Off
&& cgcx.split_dwarf_kind == SplitDwarfKind::Split,
config.emit_bc,
&cgcx.output_filenames,
))