[llvm] [llvm][dwarfdump] Add --child-tags option to filter by DWARF tags (PR #165720)
Michael Buch via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 30 06:45:54 PDT 2025
https://github.com/Michael137 created https://github.com/llvm/llvm-project/pull/165720
This patch adds a new option `--child-tags` (`-t` for short), which makes dwarfdump only dump children whose DWARF tag is in the list of tags specified by the user.
Motivating examples are:
* dumping all global variables in a CU
* dumping all non-static data members of a structure
* dumping all module import declarations of a CU
* etc.
For tags not known to dwarfdump, we pretend that the tag wasn't specified.
Note, this flag only takes effect when `--show-children` is set (either explicitly or implicitly). We error out when trying to use the flag without dumping children.
Example:
```
$ builds/release/bin/llvm-dwarfdump -t DW_TAG_structure_type a.out.dSYM
...
0x0000000c: DW_TAG_compile_unit
DW_AT_producer ("clang version 22.0.0git (git at github.com:Michael137/llvm-project.git 737da3347c2fb01dd403420cf83e9b8fbea32618)")
DW_AT_language (DW_LANG_C11)
...
0x0000002a: DW_TAG_structure_type
DW_AT_APPLE_block (true)
DW_AT_byte_size (0x20)
0x00000067: DW_TAG_structure_type
DW_AT_APPLE_block (true)
DW_AT_name ("__block_descriptor")
DW_AT_byte_size (0x10)
...
```
```
$ builds/release/bin/llvm-dwarfdump -t DW_TAG_structure_type -t DW_TAG_member a.out.dSYM
...
0x0000000c: DW_TAG_compile_unit
DW_AT_producer ("clang version 22.0.0git (git at github.com:Michael137/llvm-project.git 737da3347c2fb01dd403420cf83e9b8fbea32618)")
DW_AT_language (DW_LANG_C11)
DW_AT_name ("macro.c")
...
0x0000002a: DW_TAG_structure_type
DW_AT_APPLE_block (true)
DW_AT_byte_size (0x20)
0x0000002c: DW_TAG_member
DW_AT_name ("__isa")
DW_AT_type (0x00000051 "void *")
DW_AT_data_member_location (0x00)
0x00000033: DW_TAG_member
DW_AT_name ("__flags")
DW_AT_type (0x00000052 "int")
DW_AT_data_member_location (0x08)
0x0000003a: DW_TAG_member
DW_AT_name ("__reserved")
DW_AT_type (0x00000052 "int")
DW_AT_data_member_location (0x0c)
0x00000041: DW_TAG_member
DW_AT_name ("__FuncPtr")
DW_AT_type (0x00000056 "void (*)(int)")
DW_AT_data_member_location (0x10)
0x00000048: DW_TAG_member
DW_AT_name ("__descriptor")
DW_AT_type (0x00000062 "__block_descriptor *")
DW_AT_alignment (8)
DW_AT_data_member_location (0x18)
0x00000067: DW_TAG_structure_type
DW_AT_APPLE_block (true)
DW_AT_name ("__block_descriptor")
DW_AT_byte_size (0x10)
0x0000006a: DW_TAG_member
DW_AT_name ("reserved")
DW_AT_type (0x00000079 "unsigned long")
DW_AT_data_member_location (0x00)
0x00000071: DW_TAG_member
DW_AT_name ("Size")
DW_AT_type (0x00000079 "unsigned long")
DW_AT_data_member_location (0x08)
...
```
>From 80328f1cc998a4779f14f92ed9f57684950c0d0e Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Tue, 21 Oct 2025 16:51:43 +0100
Subject: [PATCH] [llvm][dwarfdump] Add --child-tags option to filter by DWARF
tags
This patch adds a new option `--child-tags` (`-t` for short), which
makes dwarfdump only dump children whose DWARF tag is in the list of
tags specified by the user.
Motivating examples are:
* dumping all global variables in a CU
* dumping all non-static data members of a structure
* dumping all module import declarations of a CU
* etc.
For tags not known to dwarfdump, we pretend that the tag wasn't specified.
---
llvm/include/llvm/DebugInfo/DIContext.h | 2 ++
llvm/lib/DebugInfo/DWARF/DWARFDie.cpp | 4 +++-
llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp | 24 ++++++++++++++++++++
3 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/llvm/include/llvm/DebugInfo/DIContext.h b/llvm/include/llvm/DebugInfo/DIContext.h
index e7e87bbfebf38..32ce4520dbca7 100644
--- a/llvm/include/llvm/DebugInfo/DIContext.h
+++ b/llvm/include/llvm/DebugInfo/DIContext.h
@@ -202,6 +202,8 @@ struct DIDumpOptions {
bool ShowAddresses = true;
bool ShowChildren = false;
bool ShowParents = false;
+ /// List of DWARF tags to filter children by.
+ llvm::SmallVector<unsigned> ChildTagsFilter;
bool ShowForm = false;
bool SummarizeTypes = false;
bool Verbose = false;
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index db5cc37c93f90..7558fbda18459 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -676,7 +676,9 @@ void DWARFDie::dump(raw_ostream &OS, unsigned Indent,
DIDumpOptions ChildDumpOpts = DumpOpts;
ChildDumpOpts.ShowParents = false;
while (Child) {
- Child.dump(OS, Indent + 2, ChildDumpOpts);
+ if (DumpOpts.ChildTagsFilter.empty() ||
+ llvm::is_contained(DumpOpts.ChildTagsFilter, Child.getTag()))
+ Child.dump(OS, Indent + 2, ChildDumpOpts);
Child = Child.getSibling();
}
}
diff --git a/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp b/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp
index 79f05278c329d..eb5f8b4af95a6 100644
--- a/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp
+++ b/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp
@@ -14,6 +14,7 @@
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVectorExtras.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/DebugInfo/DIContext.h"
#include "llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h"
@@ -241,6 +242,15 @@ static opt<bool>
cat(DwarfDumpCategory));
static alias ShowParentsAlias("p", desc("Alias for --show-parents."),
aliasopt(ShowParents), cl::NotHidden);
+
+static list<std::string>
+ ChildTags("child-tags",
+ desc("When --show-children is specified, show only DIEs with the "
+ "specified DWARF tags."),
+ value_desc("list of DWARF tags"), cat(DwarfDumpCategory));
+static alias TagsAlias("t", desc("Alias for --child-tags."),
+ aliasopt(ChildTags), cl::NotHidden);
+
static opt<bool>
ShowForm("show-form",
desc("Show DWARF form types after the DWARF attribute types."),
@@ -329,6 +339,13 @@ static cl::extrahelp
/// @}
//===----------------------------------------------------------------------===//
+static llvm::SmallVector<unsigned>
+makeTagVector(const list<std::string> &TagStrings) {
+ return llvm::map_to_vector(TagStrings, [](const std::string &Tag) {
+ return llvm::dwarf::getTag(Tag);
+ });
+}
+
static void error(Error Err) {
if (!Err)
return;
@@ -355,6 +372,7 @@ static DIDumpOptions getDumpOpts(DWARFContext &C) {
DumpOpts.ShowAddresses = !Diff;
DumpOpts.ShowChildren = ShowChildren;
DumpOpts.ShowParents = ShowParents;
+ DumpOpts.ChildTagsFilter = makeTagVector(ChildTags);
DumpOpts.ShowForm = ShowForm;
DumpOpts.SummarizeTypes = SummarizeTypes;
DumpOpts.Verbose = Verbose;
@@ -898,6 +916,12 @@ int main(int argc, char **argv) {
Find.empty() && !FindAllApple)
ShowChildren = true;
+ if (!ShowChildren && !ChildTags.empty()) {
+ WithColor::error()
+ << "incompatible arguments: --child-tags requires --show-children";
+ return 1;
+ }
+
// Defaults to a.out if no filenames specified.
if (InputFilenames.empty())
InputFilenames.push_back("a.out");
More information about the llvm-commits
mailing list