[llvm] [BOLT][DWARF] Slice .debug_str from the DWP for each CU (PR #159540)

Alexander Yermolovich via llvm-commits llvm-commits at lists.llvm.org
Sun Nov 2 16:49:14 PST 2025


================
@@ -0,0 +1,418 @@
+#--- main.s
+# clang++ -g2 -gdwarf-5 -gsplit-dwarf=split -S main.cpp
+# extern int getReturn();
+# int main() {
+#   return getReturn();
+# }
+	.file	"main.cpp"
+	.globl	main                            # -- Begin function main
+	.type	main, at function
+main:                                   # @main
+.Lfunc_begin0:
+	.file	0 "." "main.cpp" md5 0x9cdef858e26cf684ed9ef3b60e05bdad
+	.loc	0 2 0                           # main.cpp:2:0
+	.loc	0 3 10 prologue_end             # main.cpp:3:10
+	.loc	0 3 3 epilogue_begin is_stmt 0  # main.cpp:3:3
+	retq
+.Lfunc_end0:
+	.size	main, .Lfunc_end0-main
+	.section	.debug_abbrev,"", at progbits
+	.byte	1                               # Abbreviation Code
+	.byte	74                              # DW_TAG_skeleton_unit
+	.byte	0                               # DW_CHILDREN_no
+	.byte	16                              # DW_AT_stmt_list
+	.byte	23                              # DW_FORM_sec_offset
+	.byte	114                             # DW_AT_str_offsets_base
+	.byte	23                              # DW_FORM_sec_offset
+	.byte	27                              # DW_AT_comp_dir
+	.byte	37                              # DW_FORM_strx1
+	.ascii	"\264B"                         # DW_AT_GNU_pubnames
+	.byte	25                              # DW_FORM_flag_present
+	.byte	118                             # DW_AT_dwo_name
+	.byte	37                              # DW_FORM_strx1
+	.byte	17                              # DW_AT_low_pc
+	.byte	27                              # DW_FORM_addrx
+	.byte	18                              # DW_AT_high_pc
+	.byte	6                               # DW_FORM_data4
+	.byte	115                             # DW_AT_addr_base
+	.byte	23                              # DW_FORM_sec_offset
+	.byte	0                               # EOM(1)
+	.byte	0                               # EOM(2)
+	.byte	0                               # EOM(3)
+	.section	.debug_info,"", at progbits
+.Lcu_begin0:
+	.long	.Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+	.short	5                               # DWARF version number
+	.byte	4                               # DWARF Unit Type
+	.byte	8                               # Address Size (in bytes)
+	.long	.debug_abbrev                   # Offset Into Abbrev. Section
+	.quad	-9094791692727444213
+	.byte	1                               # Abbrev [1] 0x14:0x14 DW_TAG_skeleton_unit
+	.long	.Lline_table_start0             # DW_AT_stmt_list
+	.long	.Lstr_offsets_base0             # DW_AT_str_offsets_base
+	.byte	0                               # DW_AT_comp_dir
+                                        # DW_AT_GNU_pubnames
+	.byte	1                               # DW_AT_dwo_name
+	.byte	0                               # DW_AT_low_pc
+	.long	.Lfunc_end0-.Lfunc_begin0       # DW_AT_high_pc
+	.long	.Laddr_table_base0              # DW_AT_addr_base
+.Ldebug_info_end0:
+	.section	.debug_str_offsets,"", at progbits
+	.long	12                              # Length of String Offsets Set
+	.short	5
+	.short	0
+.Lstr_offsets_base0:
+	.section	.debug_str,"MS", at progbits,1
+.Lskel_string0:
+	.asciz	"." # string offset=0
+.Lskel_string1:
+	.asciz	"main.dwo"                      # string offset=2
+	.section	.debug_str_offsets,"", at progbits
+	.long	.Lskel_string0
+	.long	.Lskel_string1
+	.section	.debug_str_offsets.dwo,"e", at progbits
+	.long	24                              # Length of String Offsets Set
+	.short	5
+	.short	0
+	.section	.debug_str.dwo,"eMS", at progbits,1
+.Linfo_string0:
+	.asciz	"main"                          # string offset=0
+.Linfo_string1:
+	.asciz	"int"                           # string offset=5
+.Linfo_string2:
+	.asciz	"clang version 22.0.0" # string offset=9
+.Linfo_string3:
+	.asciz	"main.cpp"                      # string offset=30
+.Linfo_string4:
+	.asciz	"main.dwo"                      # string offset=39
+	.section	.debug_str_offsets.dwo,"e", at progbits
+	.long	0
+	.long	5
+	.long	9
+	.long	30
+	.long	39
+	.section	.debug_info.dwo,"e", at progbits
+	.long	.Ldebug_info_dwo_end0-.Ldebug_info_dwo_start0 # Length of Unit
+.Ldebug_info_dwo_start0:
+	.short	5                               # DWARF version number
+	.byte	5                               # DWARF Unit Type
+	.byte	8                               # Address Size (in bytes)
+	.long	0                               # Offset Into Abbrev. Section
+	.quad	-9094791692727444213
+	.byte	1                               # Abbrev [1] 0x14:0x1a DW_TAG_compile_unit
+	.byte	2                               # DW_AT_producer
+	.short	33                              # DW_AT_language
+	.byte	3                               # DW_AT_name
+	.byte	4                               # DW_AT_dwo_name
+	.byte	2                               # Abbrev [2] 0x1a:0xf DW_TAG_subprogram
+	.byte	0                               # DW_AT_low_pc
+	.long	.Lfunc_end0-.Lfunc_begin0       # DW_AT_high_pc
+	.byte	1                               # DW_AT_frame_base
+	.byte	86
+	.byte	0                               # DW_AT_name
+	.byte	0                               # DW_AT_decl_file
+	.byte	2                               # DW_AT_decl_line
+	.long	41                              # DW_AT_type
+                                        # DW_AT_external
+	.byte	3                               # Abbrev [3] 0x29:0x4 DW_TAG_base_type
+	.byte	1                               # DW_AT_name
+	.byte	5                               # DW_AT_encoding
+	.byte	4                               # DW_AT_byte_size
+	.byte	0                               # End Of Children Mark
+.Ldebug_info_dwo_end0:
+	.section	.debug_abbrev.dwo,"e", at progbits
+	.byte	1                               # Abbreviation Code
+	.byte	17                              # DW_TAG_compile_unit
+	.byte	1                               # DW_CHILDREN_yes
+	.byte	37                              # DW_AT_producer
+	.byte	37                              # DW_FORM_strx1
+	.byte	19                              # DW_AT_language
+	.byte	5                               # DW_FORM_data2
+	.byte	3                               # DW_AT_name
+	.byte	37                              # DW_FORM_strx1
+	.byte	118                             # DW_AT_dwo_name
+	.byte	37                              # DW_FORM_strx1
+	.byte	0                               # EOM(1)
+	.byte	0                               # EOM(2)
+	.byte	2                               # Abbreviation Code
+	.byte	46                              # DW_TAG_subprogram
+	.byte	0                               # DW_CHILDREN_no
+	.byte	17                              # DW_AT_low_pc
+	.byte	27                              # DW_FORM_addrx
+	.byte	18                              # DW_AT_high_pc
+	.byte	6                               # DW_FORM_data4
+	.byte	64                              # DW_AT_frame_base
+	.byte	24                              # DW_FORM_exprloc
+	.byte	3                               # DW_AT_name
+	.byte	37                              # DW_FORM_strx1
+	.byte	58                              # DW_AT_decl_file
+	.byte	11                              # DW_FORM_data1
+	.byte	59                              # DW_AT_decl_line
+	.byte	11                              # DW_FORM_data1
+	.byte	73                              # DW_AT_type
+	.byte	19                              # DW_FORM_ref4
+	.byte	63                              # DW_AT_external
+	.byte	25                              # DW_FORM_flag_present
+	.byte	0                               # EOM(1)
+	.byte	0                               # EOM(2)
+	.byte	3                               # Abbreviation Code
+	.byte	36                              # DW_TAG_base_type
+	.byte	0                               # DW_CHILDREN_no
+	.byte	3                               # DW_AT_name
+	.byte	37                              # DW_FORM_strx1
+	.byte	62                              # DW_AT_encoding
+	.byte	11                              # DW_FORM_data1
+	.byte	11                              # DW_AT_byte_size
+	.byte	11                              # DW_FORM_data1
+	.byte	0                               # EOM(1)
+	.byte	0                               # EOM(2)
+	.byte	0                               # EOM(3)
+	.section	.debug_addr,"", at progbits
+	.long	.Ldebug_addr_end0-.Ldebug_addr_start0 # Length of contribution
+.Ldebug_addr_start0:
+	.short	5                               # DWARF version number
+	.byte	8                               # Address size
+	.byte	0                               # Segment selector size
+.Laddr_table_base0:
+	.quad	.Lfunc_begin0
+.Ldebug_addr_end0:
+	.section	.debug_gnu_pubnames,"", at progbits
----------------
ayermolo wrote:

ditto

https://github.com/llvm/llvm-project/pull/159540


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