bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #117962 - weihanglo:debug-name-table, r=wesleywiser

Browse source 
fix: stop emitting `.debug_pubnames` and `.debug_pubtypes`

A continuation of #94181.
Fixes #48762
MCP can be found in <https://github.com/rust-lang/compiler-team/issues/688>.

`.debug_pubnames` and `.debug_pubtypes` are poorly designed and people
seldom use them. However, they take a considerable portion of size in
the final binary. This tells LLVM stop emitting those sections on
DWARFv4 or lower. DWARFv5 use `.debug_names` which is more concise
in size and performant for name lookup.

Some other no-really-useful personal notes:

<details><summary>Details</summary>
<p>

## Pepole saying they are not useful

* https://github.com/rust-lang/rust/issues/48762
* https://rust-lang.zulipchat.com/#narrow/stream/317568-t-compiler.2Fwg-debugging/topic/investigating.20debuginfo.20size/near/342713604
* `DwarfCompileUnit::hasDwarfPubSections()` — f633f325a1/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp (L1477-L1494)
* clang default to no debug name table when no option provided — f633f325a1/clang/lib/Frontend/CompilerInvocation.cpp (L1819-L1824)
* GCC explicitly says GDB doesn't use pub sections (`TARGET_WANT_DEBUG_PUB_SECTIONS` only be true on Darwin) — 5d2a360f0a/gcc/target.def (L6985-L6990) and 319b460545/gold/dwarf_reader.h (L424-L427)
* Probably the only place that makes use of pub section in lldb — 725115d7bb/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp (L2117-L2135)

* "The -gsplit-dwarf option requires -ggnu-pubnames." — 5d2a360f0a/gcc/opts.cc (L1205)

* LLVM: Always emit `.debug_names` with dwarf 5 for Apple platforms — https://reviews.llvm.org/D118754

</p>
</details>
This commit is contained in:
bors 2023-12-11 22:32:08 +00:00
commit e2a3c9b3f0
5 changed files with 73 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

25
compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
View file

@ -697,6 +697,25 @@ static DICompileUnit::DebugEmissionKind fromRust(LLVMRustDebugEmissionKind Kind)
}
}
enum class LLVMRustDebugNameTableKind {
Default,
GNU,
None,
};
static DICompileUnit::DebugNameTableKind fromRust(LLVMRustDebugNameTableKind Kind) {
switch (Kind) {
case LLVMRustDebugNameTableKind::Default:
return DICompileUnit::DebugNameTableKind::Default;
case LLVMRustDebugNameTableKind::GNU:
return DICompileUnit::DebugNameTableKind::GNU;
case LLVMRustDebugNameTableKind::None:
return DICompileUnit::DebugNameTableKind::None;
default:
report_fatal_error("bad DebugNameTableKind.");
}
}
enum class LLVMRustChecksumKind {
None,
MD5,
@ -765,13 +784,15 @@ extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateCompileUnit(
const char *Flags, unsigned RuntimeVer,
const char *SplitName, size_t SplitNameLen,
LLVMRustDebugEmissionKind Kind,
uint64_t DWOId, bool SplitDebugInlining) {
uint64_t DWOId, bool SplitDebugInlining,
LLVMRustDebugNameTableKind TableKind) {
auto *File = unwrapDI<DIFile>(FileRef);
return wrap(Builder->createCompileUnit(Lang, File, StringRef(Producer, ProducerLen),
isOptimized, Flags, RuntimeVer,
StringRef(SplitName, SplitNameLen),
fromRust(Kind), DWOId, SplitDebugInlining));
fromRust(Kind), DWOId, SplitDebugInlining,
false, fromRust(TableKind)));
}
extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateFile(