[llvm-dwarfdump] Fix split-dwarf bug in stats for inlined var loc cov

[djtodoro]

Summary

Initial (D96045) patch didn't handle split dwarf cases, so this fixes that bug.

In addition, before applying this patch, we had a slowdown that happened after the D96045. With this patch, the slowdown will be fixed.

[aprantl]

One comment inline.

llvm/tools/llvm-dwarfdump/Statistics.cpp

721

This comment is mostly repeats what's already in the name of the variable. It might more interesting to explain why these are being reset for each CU.

[dblaikie]

Generally good for me - but could you try to see if the test could be simplified any further (maybe "main" can be in test1 or test2 (replacing f1 or f2) and could call the other function in the other file) - and see if the auxiliary/input files could be represented as assembly instead of checked in object files?

[djtodoro]

• Reduce test
• Improve the comment

[djtodoro]

In D100951#2705718, @dblaikie wrote:

Generally good for me - but could you try to see if the test could be simplified any further (maybe "main" can be in test1 or test2 (replacing f1 or f2) and could call the other function in the other file) - and see if the auxiliary/input files could be represented as assembly instead of checked in object files?

I am not sure how to keep this as assembly code, since we'd need to create object files of it, and then to link it together...

[dblaikie]

In D100951#2707838, @djtodoro wrote:

In D100951#2705718, @dblaikie wrote:

Generally good for me - but could you try to see if the test could be simplified any further (maybe "main" can be in test1 or test2 (replacing f1 or f2) and could call the other function in the other file) - and see if the auxiliary/input files could be represented as assembly instead of checked in object files?

I am not sure how to keep this as assembly code, since we'd need to create object files of it, and then to link it together...

the dwo files should be able to be assembly without any particular restrictions/complications in authoring them, right? (taking the assembly of a split DWARF compilation and pulling out the .dwo parts should be adequate, I think)
The executable - it could probably actually be an object file that happens to have two skeleton units in it (like we generate under LTO, for instance - though without any of the LTO-specific cross-CU references) so that could be written in assembly relatively easily (to hand-craft it you could probably take the assembly of the two skeletons and copy/paste them into one file for instance)

[djtodoro]

In D100951#2708809, @dblaikie wrote:

In D100951#2707838, @djtodoro wrote:

In D100951#2705718, @dblaikie wrote:

Generally good for me - but could you try to see if the test could be simplified any further (maybe "main" can be in test1 or test2 (replacing f1 or f2) and could call the other function in the other file) - and see if the auxiliary/input files could be represented as assembly instead of checked in object files?

I am not sure how to keep this as assembly code, since we'd need to create object files of it, and then to link it together...

the dwo files should be able to be assembly without any particular restrictions/complications in authoring them, right? (taking the assembly of a split DWARF compilation and pulling out the .dwo parts should be adequate, I think)
The executable - it could probably actually be an object file that happens to have two skeleton units in it (like we generate under LTO, for instance - though without any of the LTO-specific cross-CU references) so that could be written in assembly relatively easily (to hand-craft it you could probably take the assembly of the two skeletons and copy/paste them into one file for instance)

I've accomplished to write these as asm files. Thanks!

[djtodoro]

• make the tests as assembly files

[dblaikie]

llvm/test/tools/llvm-dwarfdump/X86/inlined_variables_with_zero_cov.test

31

Output files should go in %t or a subdirectory of %t, so things like:

RUN: rm -r %t
RUN: mkdir %t
RUN: ... -o %t/test1.dwo
...

[dblaikie]

Other than the test file tweak, looks good to me!

llvm/test/tools/llvm-dwarfdump/X86/Inputs/split-dwarf-objfile1.s

+  .text
+  .file "test1.cpp"
+  .globl  _Z2f1v                          # -- Begin function _Z2f1v
+  .p2align  4, 0x90
+  .type _Z2f1v,@function
+_Z2f1v:                                 # @_Z2f1v
+.Lfunc_begin0:
+  .file 1 "./" "test1.cpp"
+  .loc  1 7 0                           # test1.cpp:7:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  pushq %rax
+  .cfi_def_cfa_offset 16
+.Ltmp0:
+  .loc  1 5 3 prologue_end              # test1.cpp:5:3
+  callq _ZL1xv
+.Ltmp1:
+  .loc  1 9 1                           # test1.cpp:9:1
+  popq  %rax
+  .cfi_def_cfa_offset 8
+  retq
+.Ltmp2:
+.Lfunc_end0:
+  .size _Z2f1v, .Lfunc_end0-_Z2f1v
+  .cfi_endproc
+                                        # -- End function
+  .p2align  4, 0x90                         # -- Begin function _ZL1xv
+  .type _ZL1xv,@function
+_ZL1xv:                                 # @_ZL1xv
+.Lfunc_begin1:
+  .loc  1 1 0                           # test1.cpp:1:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  .loc  1 2 1 prologue_end              # test1.cpp:2:1
+  retq
+.Ltmp3:
+.Lfunc_end1:
+  .size _ZL1xv, .Lfunc_end1-_ZL1xv
+  .cfi_endproc
+                                        # -- End function
+  .section  .debug_str.dwo,"eMS",@progbits,1
+.Linfo_string0:
+  .asciz  "_ZL1yv"                        # string offset=0
+.Linfo_string1:
+  .asciz  "y"                             # string offset=7
+.Linfo_string2:
+  .asciz  "var"                           # string offset=9
+.Linfo_string3:
+  .asciz  "int"                           # string offset=13
+.Linfo_string4:
+  .asciz  "_Z2f1v"                        # string offset=17
+.Linfo_string5:
+  .asciz  "f1"                            # string offset=24
+.Linfo_string6:
+  .asciz  "_ZL1xv"                        # string offset=27
+.Linfo_string7:
+  .asciz  "x"                             # string offset=34
+.Linfo_string8:
+  .asciz  "clang version 13.0.0" # string offset=36
+.Linfo_string9:
+  .asciz  "test1.cpp"                     # string offset=141
+.Linfo_string10:
+  .asciz  "test1.dwo"                     # string offset=151
+  .section  .debug_str_offsets.dwo,"e",@progbits
+  .long 0
+  .long 7
+  .long 9
+  .long 13
+  .long 17
+  .long 24
+  .long 27
+  .long 34
+  .long 36
+  .long 141
+  .long 151
+  .section  .debug_info.dwo,"e",@progbits
+  .long .Ldebug_info_dwo_end0-.Ldebug_info_dwo_start0 # Length of Unit
+.Ldebug_info_dwo_start0:
+  .short  4                               # DWARF version number
+  .long 0                               # Offset Into Abbrev. Section
+  .byte 8                               # Address Size (in bytes)
+  .byte 1                               # Abbrev [1] 0xb:0x4e DW_TAG_compile_unit
+  .byte 8                               # DW_AT_producer
+  .short  33                              # DW_AT_language
+  .byte 9                               # DW_AT_name
+  .byte 10                              # DW_AT_GNU_dwo_name
+  .quad -7114235821576765290            # DW_AT_GNU_dwo_id
+  .byte 2                               # Abbrev [2] 0x19:0xf DW_TAG_subprogram
+  .byte 0                               # DW_AT_linkage_name
+  .byte 1                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 3                               # DW_AT_decl_line
+  .byte 1                               # DW_AT_inline
+  .byte 3                               # Abbrev [3] 0x1f:0x8 DW_TAG_variable
+  .byte 2                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 4                               # DW_AT_decl_line
+  .long 40                              # DW_AT_type
+  .byte 0                               # End Of Children Mark
+  .byte 4                               # Abbrev [4] 0x28:0x4 DW_TAG_base_type
+  .byte 3                               # DW_AT_name
+  .byte 5                               # DW_AT_encoding
+  .byte 4                               # DW_AT_byte_size
+  .byte 5                               # Abbrev [5] 0x2c:0x20 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 87
+                                        # DW_AT_GNU_all_call_sites
+  .byte 4                               # DW_AT_linkage_name
+  .byte 5                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 7                               # DW_AT_decl_line
+                                        # DW_AT_external
+  .byte 6                               # Abbrev [6] 0x38:0xd DW_TAG_inlined_subroutine
+  .long 25                              # DW_AT_abstract_origin
+  .byte 1                               # DW_AT_low_pc
+  .long .Ltmp1-.Ltmp0                   # DW_AT_high_pc
+  .byte 1                               # DW_AT_call_file
+  .byte 8                               # DW_AT_call_line
+  .byte 3                               # DW_AT_call_column
+  .byte 7                               # Abbrev [7] 0x45:0x6 DW_TAG_GNU_call_site
+  .long 76                              # DW_AT_abstract_origin
+  .byte 2                               # DW_AT_low_pc
+  .byte 0                               # End Of Children Mark
+  .byte 8                               # Abbrev [8] 0x4c:0xc DW_TAG_subprogram
+  .byte 3                               # DW_AT_low_pc
+  .long .Lfunc_end1-.Lfunc_begin1       # DW_AT_high_pc
+  .byte 1                               # DW_AT_frame_base
+  .byte 87
+                                        # DW_AT_GNU_all_call_sites
+  .byte 6                               # DW_AT_linkage_name
+  .byte 7                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 1                               # DW_AT_decl_line
+  .byte 0                               # End Of Children Mark
+.Ldebug_info_dwo_end0:
+  .section  .debug_abbrev.dwo,"e",@progbits
+  .byte 1                               # Abbreviation Code
+  .byte 17                              # DW_TAG_compile_unit
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 37                              # DW_AT_producer
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 19                              # DW_AT_language
+  .byte 5                               # DW_FORM_data2
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .ascii  "\260B"                         # DW_AT_GNU_dwo_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .ascii  "\261B"                         # DW_AT_GNU_dwo_id
+  .byte 7                               # DW_FORM_data8
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 2                               # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 110                             # DW_AT_linkage_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 32                              # DW_AT_inline
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 3                               # Abbreviation Code
+  .byte 52                              # DW_TAG_variable
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .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 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 4                               # Abbreviation Code
+  .byte 36                              # DW_TAG_base_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .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 5                               # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 18                              # DW_AT_high_pc
+  .byte 6                               # DW_FORM_data4
+  .byte 64                              # DW_AT_frame_base
+  .byte 24                              # DW_FORM_exprloc
+  .ascii  "\227B"                         # DW_AT_GNU_all_call_sites
+  .byte 25                              # DW_FORM_flag_present
+  .byte 110                             # DW_AT_linkage_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 63                              # DW_AT_external
+  .byte 25                              # DW_FORM_flag_present
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 6                               # Abbreviation Code
+  .byte 29                              # DW_TAG_inlined_subroutine
+  .byte 0                               # DW_CHILDREN_no
+  .byte 49                              # DW_AT_abstract_origin
+  .byte 19                              # DW_FORM_ref4
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 18                              # DW_AT_high_pc
+  .byte 6                               # DW_FORM_data4
+  .byte 88                              # DW_AT_call_file
+  .byte 11                              # DW_FORM_data1
+  .byte 89                              # DW_AT_call_line
+  .byte 11                              # DW_FORM_data1
+  .byte 87                              # DW_AT_call_column
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 7                               # Abbreviation Code
+  .ascii  "\211\202\001"                  # DW_TAG_GNU_call_site
+  .byte 0                               # DW_CHILDREN_no
+  .byte 49                              # DW_AT_abstract_origin
+  .byte 19                              # DW_FORM_ref4
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 8                               # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 0                               # DW_CHILDREN_no
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 18                              # DW_AT_high_pc
+  .byte 6                               # DW_FORM_data4
+  .byte 64                              # DW_AT_frame_base
+  .byte 24                              # DW_FORM_exprloc
+  .ascii  "\227B"                         # DW_AT_GNU_all_call_sites
+  .byte 25                              # DW_FORM_flag_present
+  .byte 110                             # DW_AT_linkage_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 0                               # EOM(3)

llvm/test/tools/llvm-dwarfdump/X86/Inputs/split-dwarf-objfile2.s

+  .text
+  .file "test2.cpp"
+  .globl  main                            # -- Begin function main
+  .p2align  4, 0x90
+  .type main,@function
+main:                                   # @main
+.Lfunc_begin0:
+  .file 1 "/dir" "test2.cpp"
+  .loc  1 8 0                           # test2.cpp:8:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  pushq %rax
+  .cfi_def_cfa_offset 16
+.Ltmp0:
+  .loc  1 9 3 prologue_end              # test2.cpp:9:3
+  callq _Z2f1v
+.Ltmp1:
+  .loc  1 5 3                           # test2.cpp:5:3
+  callq _ZL1xv
+.Ltmp2:
+  .loc  1 11 1                          # test2.cpp:11:1
+  xorl  %eax, %eax
+  popq  %rcx
+  .cfi_def_cfa_offset 8
+  retq
+.Ltmp3:
+.Lfunc_end0:
+  .size main, .Lfunc_end0-main
+  .cfi_endproc
+                                        # -- End function
+  .p2align  4, 0x90                         # -- Begin function _ZL1xv
+  .type _ZL1xv,@function
+_ZL1xv:                                 # @_ZL1xv
+.Lfunc_begin1:
+  .loc  1 1 0                           # test2.cpp:1:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  .loc  1 2 1 prologue_end              # test2.cpp:2:1
+  retq
+.Ltmp4:
+.Lfunc_end1:
+  .size _ZL1xv, .Lfunc_end1-_ZL1xv
+  .cfi_endproc
+                                        # -- End function
+  .section  .debug_str.dwo,"eMS",@progbits,1
+.Linfo_string0:
+  .asciz  "_ZL1yv"                        # string offset=0
+.Linfo_string1:
+  .asciz  "y"                             # string offset=7
+.Linfo_string2:
+  .asciz  "var"                           # string offset=9
+.Linfo_string3:
+  .asciz  "int"                           # string offset=13
+.Linfo_string4:
+  .asciz  "_Z2f1v"                        # string offset=17
+.Linfo_string5:
+  .asciz  "f1"                            # string offset=24
+.Linfo_string6:
+  .asciz  "main"                          # string offset=27
+.Linfo_string7:
+  .asciz  "_ZL1xv"                        # string offset=32
+.Linfo_string8:
+  .asciz  "x"                             # string offset=39
+.Linfo_string9:
+  .asciz  "clang version 13.0.0" # string offset=41
+.Linfo_string10:
+  .asciz  "test2.cpp"                     # string offset=146
+.Linfo_string11:
+  .asciz  "test2.dwo"                     # string offset=156
+  .section  .debug_str_offsets.dwo,"e",@progbits
+  .long 0
+  .long 7
+  .long 9
+  .long 13
+  .long 17
+  .long 24
+  .long 27
+  .long 32
+  .long 39
+  .long 41
+  .long 146
+  .long 156
+  .section  .debug_info.dwo,"e",@progbits
+  .long .Ldebug_info_dwo_end0-.Ldebug_info_dwo_start0 # Length of Unit
+.Ldebug_info_dwo_start0:
+  .short  4                               # DWARF version number
+  .long 0                               # Offset Into Abbrev. Section
+  .byte 8                               # Address Size (in bytes)
+  .byte 1                               # Abbrev [1] 0xb:0x5c DW_TAG_compile_unit
+  .byte 9                               # DW_AT_producer
+  .short  33                              # DW_AT_language
+  .byte 10                              # DW_AT_name
+  .byte 11                              # DW_AT_GNU_dwo_name
+  .quad -6064033601213906696            # DW_AT_GNU_dwo_id
+  .byte 2                               # Abbrev [2] 0x19:0xf DW_TAG_subprogram
+  .byte 0                               # DW_AT_linkage_name
+  .byte 1                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 3                               # DW_AT_decl_line
+  .byte 1                               # DW_AT_inline
+  .byte 3                               # Abbrev [3] 0x1f:0x8 DW_TAG_variable
+  .byte 2                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 4                               # DW_AT_decl_line
+  .long 40                              # DW_AT_type
+  .byte 0                               # End Of Children Mark
+  .byte 4                               # Abbrev [4] 0x28:0x4 DW_TAG_base_type
+  .byte 3                               # DW_AT_name
+  .byte 5                               # DW_AT_encoding
+  .byte 4                               # DW_AT_byte_size
+  .byte 5                               # Abbrev [5] 0x2c:0x29 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 87
+                                        # DW_AT_GNU_all_call_sites
+  .byte 6                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 8                               # DW_AT_decl_line
+  .long 40                              # DW_AT_type
+                                        # DW_AT_external
+  .byte 6                               # Abbrev [6] 0x3b:0xd DW_TAG_inlined_subroutine
+  .long 25                              # DW_AT_abstract_origin
+  .byte 1                               # DW_AT_low_pc
+  .long .Ltmp2-.Ltmp1                   # DW_AT_high_pc
+  .byte 1                               # DW_AT_call_file
+  .byte 10                              # DW_AT_call_line
+  .byte 3                               # DW_AT_call_column
+  .byte 7                               # Abbrev [7] 0x48:0x6 DW_TAG_GNU_call_site
+  .long 85                              # DW_AT_abstract_origin
+  .byte 1                               # DW_AT_low_pc
+  .byte 7                               # Abbrev [7] 0x4e:0x6 DW_TAG_GNU_call_site
+  .long 90                              # DW_AT_abstract_origin
+  .byte 2                               # DW_AT_low_pc
+  .byte 0                               # End Of Children Mark
+  .byte 8                               # Abbrev [8] 0x55:0x5 DW_TAG_subprogram
+  .byte 4                               # DW_AT_linkage_name
+  .byte 5                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 7                               # DW_AT_decl_line
+                                        # DW_AT_declaration
+                                        # DW_AT_external
+  .byte 9                               # Abbrev [9] 0x5a:0xc DW_TAG_subprogram
+  .byte 3                               # DW_AT_low_pc
+  .long .Lfunc_end1-.Lfunc_begin1       # DW_AT_high_pc
+  .byte 1                               # DW_AT_frame_base
+  .byte 87
+                                        # DW_AT_GNU_all_call_sites
+  .byte 7                               # DW_AT_linkage_name
+  .byte 8                               # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 1                               # DW_AT_decl_line
+  .byte 0                               # End Of Children Mark
+.Ldebug_info_dwo_end0:
+  .section  .debug_abbrev.dwo,"e",@progbits
+  .byte 1                               # Abbreviation Code
+  .byte 17                              # DW_TAG_compile_unit
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 37                              # DW_AT_producer
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 19                              # DW_AT_language
+  .byte 5                               # DW_FORM_data2
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .ascii  "\260B"                         # DW_AT_GNU_dwo_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .ascii  "\261B"                         # DW_AT_GNU_dwo_id
+  .byte 7                               # DW_FORM_data8
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 2                               # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 110                             # DW_AT_linkage_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 32                              # DW_AT_inline
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 3                               # Abbreviation Code
+  .byte 52                              # DW_TAG_variable
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .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 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 4                               # Abbreviation Code
+  .byte 36                              # DW_TAG_base_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .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 5                               # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 18                              # DW_AT_high_pc
+  .byte 6                               # DW_FORM_data4
+  .byte 64                              # DW_AT_frame_base
+  .byte 24                              # DW_FORM_exprloc
+  .ascii  "\227B"                         # DW_AT_GNU_all_call_sites
+  .byte 25                              # DW_FORM_flag_present
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .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 6                               # Abbreviation Code
+  .byte 29                              # DW_TAG_inlined_subroutine
+  .byte 0                               # DW_CHILDREN_no
+  .byte 49                              # DW_AT_abstract_origin
+  .byte 19                              # DW_FORM_ref4
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 18                              # DW_AT_high_pc
+  .byte 6                               # DW_FORM_data4
+  .byte 88                              # DW_AT_call_file
+  .byte 11                              # DW_FORM_data1
+  .byte 89                              # DW_AT_call_line
+  .byte 11                              # DW_FORM_data1
+  .byte 87                              # DW_AT_call_column
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 7                               # Abbreviation Code
+  .ascii  "\211\202\001"                  # DW_TAG_GNU_call_site
+  .byte 0                               # DW_CHILDREN_no
+  .byte 49                              # DW_AT_abstract_origin
+  .byte 19                              # DW_FORM_ref4
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 8                               # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 0                               # DW_CHILDREN_no
+  .byte 110                             # DW_AT_linkage_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 60                              # DW_AT_declaration
+  .byte 25                              # DW_FORM_flag_present
+  .byte 63                              # DW_AT_external
+  .byte 25                              # DW_FORM_flag_present
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 9                               # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 0                               # DW_CHILDREN_no
+  .byte 17                              # DW_AT_low_pc
+  .ascii  "\201>"                         # DW_FORM_GNU_addr_index
+  .byte 18                              # DW_AT_high_pc
+  .byte 6                               # DW_FORM_data4
+  .byte 64                              # DW_AT_frame_base
+  .byte 24                              # DW_FORM_exprloc
+  .ascii  "\227B"                         # DW_AT_GNU_all_call_sites
+  .byte 25                              # DW_FORM_flag_present
+  .byte 110                             # DW_AT_linkage_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 3                               # DW_AT_name
+  .ascii  "\202>"                         # DW_FORM_GNU_str_index
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 0                               # EOM(3)

llvm/test/tools/llvm-dwarfdump/X86/Inputs/split-dwarf.s

+  .text
+  .file "main.cpp"
+  .globl  _Z2f1v                          # -- Begin function _Z2f1v
+  .p2align  4, 0x90
+  .type _Z2f1v,@function
+_Z2f1v:                                 # @_Z2f1v
+.Lfunc_begin0:
+  .file 1 "./" "main.cpp"
+  .loc  1 7 0                           # main.cpp:7:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  pushq %rax
+  .cfi_def_cfa_offset 16
+.Ltmp0:
+  .loc  1 5 3 prologue_end              # main.cpp:5:3
+  callq _ZL1xv
+.Ltmp1:
+  .loc  1 9 1                           # main.cpp:9:1
+  popq  %rax
+  .cfi_def_cfa_offset 8
+  retq
+.Ltmp2:
+.Lfunc_end0:
+  .size _Z2f1v, .Lfunc_end0-_Z2f1v
+  .cfi_endproc
+                                        # -- End function
+  .p2align  4, 0x90                         # -- Begin function _ZL1xv
+  .type _ZL1xv,@function
+_ZL1xv:                                 # @_ZL1xv
+.Lfunc_begin1:
+  .loc  1 1 0                           # main.cpp:1:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  .loc  1 2 1 prologue_end              # main.cpp:2:1
+  retq
+.Ltmp3:
+.Lfunc_end1:
+  .size _ZL1xv, .Lfunc_end1-_ZL1xv
+  .cfi_endproc
+                                        # -- End function
+  .section  .debug_abbrev,"",@progbits
+  .byte 1                               # Abbreviation Code
+  .byte 17                              # DW_TAG_compile_unit
+  .byte 0                               # DW_CHILDREN_no
+  .byte 16                              # DW_AT_stmt_list
+  .byte 23                              # DW_FORM_sec_offset
+  .byte 27                              # DW_AT_comp_dir
+  .byte 14                              # DW_FORM_strp
+  .ascii  "\264B"                         # DW_AT_GNU_pubnames
+  .byte 25                              # DW_FORM_flag_present
+  .ascii  "\260B"                         # DW_AT_GNU_dwo_name
+  .byte 14                              # DW_FORM_strp
+  .ascii  "\261B"                         # DW_AT_GNU_dwo_id
+  .byte 7                               # DW_FORM_data8
+  .byte 17                              # DW_AT_low_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 18                              # DW_AT_high_pc
+  .byte 6                               # DW_FORM_data4
+  .ascii  "\263B"                         # DW_AT_GNU_addr_base
+  .byte 23                              # DW_FORM_sec_offset
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 0                               # EOM(3)
+  .section  .debug_info,"",@progbits
+.Lcu_begin0:
+  .long .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+  .short  4                               # DWARF version number
+  .long .debug_abbrev                   # Offset Into Abbrev. Section
+  .byte 8                               # Address Size (in bytes)
+  .byte 1                               # Abbrev [1] 0xb:0x25 DW_TAG_compile_unit
+  .long .Lline_table_start0             # DW_AT_stmt_list
+  .long .Lskel_string0                  # DW_AT_comp_dir
+                                        # DW_AT_GNU_pubnames
+  .long .Lskel_string1                  # DW_AT_GNU_dwo_name
+  .quad -7114235821576765290            # DW_AT_GNU_dwo_id
+  .quad .Lfunc_begin0                   # DW_AT_low_pc
+  .long .Lfunc_end1-.Lfunc_begin0       # DW_AT_high_pc
+.Ldebug_info_end0:
+  .section  .debug_info,"",@progbits
+.Lcu_begin1:
+  .long .Ldebug_info_end1-.Ldebug_info_start1 # Length of Unit
+.Ldebug_info_start1:
+  .short  4                               # DWARF version number
+  .long .debug_abbrev                   # Offset Into Abbrev. Section
+  .byte 8                               # Address Size (in bytes)
+  .byte 1                               # Abbrev [1] 0xb:0x25 DW_TAG_compile_unit
+  .long .Lline_table_start0             # DW_AT_stmt_list
+  .long .Lskel_string0                  # DW_AT_comp_dir
+                                        # DW_AT_GNU_pubnames
+  .long .Lskel_string2                  # DW_AT_GNU_dwo_name
+  .quad -6064033601213906696            # DW_AT_GNU_dwo_id
+  .quad .Lfunc_begin0                   # DW_AT_low_pc
+  .long .Lfunc_end1-.Lfunc_begin0       # DW_AT_high_pc
+.Ldebug_info_end1:
+  .section  .debug_str,"MS",@progbits,1
+.Lskel_string0:
+  .asciz  "./" # string offset=0
+.Lskel_string1:
+  .asciz  "test1.dwo"                     # string offset=82
+.Lskel_string2:
+  .asciz  "test2.dwo"                     # string offset=82
+
+.Lline_table_start0:

llvm/test/tools/llvm-dwarfdump/X86/inlined_variables_with_zero_cov.test

+## This checks the number of inlined variables with 0% location
+## coverage in split dwarf cases.
+##  $ cat test1.cpp
+##  __attribute__((optnone)) static void x() {
+##  }
+##  __attribute__((always_inline)) static void y() {
+##    int var;
+##    x();
+##  }
+##  void f1() {
+##    y();
+##  }
+##
+##  $ cat test2.cpp
+##  __attribute__((optnone)) static void x() {
+##  }
+##  __attribute__((always_inline)) static void y() {
+##    int var;
+##    x();
+##  }
+##  void f1();
+##  int main() {
+##    f1();
+##    y();
+##  }
+##  $ clang++ -O1 -g -gsplit-dwarf test2.cpp test1.cpp -S
+##  The split-dwarf.s was handcrafted.
+
+REQUIRES: x86_64-linux
+RUN: rm -rf %t
+RUN: mkdir %t
+RUN: cd %t
+RUN: llvm-mc -triple x86_64-unknown-linux -filetype=obj %S/Inputs/split-dwarf-objfile1.s -o test1.dwo
+RUN: llvm-mc -triple x86_64-unknown-linux -filetype=obj %S/Inputs/split-dwarf-objfile2.s -o test2.dwo
+RUN: llvm-mc -triple x86_64-unknown-linux -filetype=obj %S/Inputs/split-dwarf.s -o split-dwarf.o
+RUN: llvm-dwarfdump --statistics split-dwarf.o | FileCheck %s
+
+CHECK: "#variables processed by location statistics": 2
+CHECK: "#variables with 0% of parent scope covered by DW_AT_location": 2
+CHECK: "#local vars processed by location statistics": 2
+CHECK: "#local vars with 0% of parent scope covered by DW_AT_location": 2

llvm/tools/llvm-dwarfdump/Statistics.cpp

 /// useful, only the delta between compiling the same program with different
 /// compilers is.
 bool dwarfdump::collectStatsForObjectFile(ObjectFile &Obj, DWARFContext &DICtx,
                                           const Twine &Filename,
                                           raw_ostream &OS) {
   StringRef FormatName = Obj.getFileFormatName();
   GlobalStats GlobalStats;
   LocationStats LocStats;
-  InlinedVarsTyMap GlobalInlinedFnInfo;
-  InlinedFnInstacesTy InlinedFnsToBeProcessed;
   StringMap<PerFunctionStats> Statistics;
   for (const auto &CU : static_cast<DWARFContext *>(&DICtx)->compile_units()) {
     if (DWARFDie CUDie = CU->getNonSkeletonUnitDIE(false)) {
+      // These variables are being reset for each CU, since there could be
+      // a situation where we have two subprogram DIEs with the same offsets
+      // in two diferent CUs, and we can end up using wrong variables info
+      // when trying to resolve abstract_orign attribute.
+      // TODO: Handle LTO cases where the abstract origin of
+      // the function is in a different CU than the one it's
+      // referenced from or inlined into.
+      InlinedVarsTyMap GlobalInlinedFnInfo;
+      InlinedFnInstacesTy InlinedFnsToBeProcessed;
+
       collectStatsRecursive(CUDie, "/", "g", 0, 0, Statistics, GlobalStats,
                             LocStats, GlobalInlinedFnInfo,
                             InlinedFnsToBeProcessed);
 
       collectZeroCovInlinedVars(CUDie.getDwarfUnit(), GlobalStats, LocStats,
                                 GlobalInlinedFnInfo, InlinedFnsToBeProcessed);
     }
   }