[all-commits] [llvm/llvm-project] f8656e: [llvm][dwarfdump] Add --child-tags option to filte...

Tue Nov 4 03:38:17 PST 2025

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f8656ed4557500345ba29128d9ec85ef1a637240
      https://github.com/llvm/llvm-project/commit/f8656ed4557500345ba29128d9ec85ef1a637240
  Author: Michael Buch <michaelbuch12 at gmail.com>
  Date:   2025-11-04 (Tue, 04 Nov 2025)

  Changed paths:
    M llvm/docs/CommandGuide/llvm-dwarfdump.rst
    M llvm/include/llvm/DebugInfo/DIContext.h
    M llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
    A llvm/test/tools/llvm-dwarfdump/X86/filter-child-tag.yaml
    M llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp

  Log Message:
  -----------
  [llvm][dwarfdump] Add --child-tags option to filter by DWARF tags (#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)             
...                                       
```

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