[Debug-Info] [llvm-dwarfdump] Don't treat DW_FORM_data4/8 to be section offsets in DWARF3.

[Esme]

Summary

We found a similar error as the description in D58698 when dumping the debug info of the SPEC xalancbmk_r with llvm-dwarfdump under DWARF3, ie. the location list overflows the debug_loc section.

Although in DWARF3 DW_FORM_data4 and DW_FORM_data8 served also as a section offset, but they may actually be size values instead of offsets in some scenarios. The overflow-error occurred when we try to dump the location list for such scenarios.

After narrowing down the cases, we found the error occurs for three attributes, DW_AT_data_member_location, DW_AT_count and DW_AT_byte_size.

DW_FORM_data4 and DW_FORM_data8 are obviously not offsets in DWARF3+, but it’s hard to tell whether they are offsets in DWARF3. In this patch, we are dropping the support of dumping location for DW_AT_data_member_location, DW_AT_count and DW_AT_byte_size if the form is DW_FORM_data4 and DW_FORM_data8.

[probinson]

In DWARF2, there isn't a specific form-class for pointing to location lists.
DW_AT_byte_size is always a constant, so DW_FORM_data4/8 are not location-list pointers.
DW_AT_count is either a constant or a reference (to a DIE describing how to compute the count), so DW_FORM_data4/8 are not location-list pointers.
DW_AT_data_member_location is always a location description (either embedded in a block, or referring to .debug_loc), so DW_FORM_data4/8 are actually location-list pointers.

In DWARF3, the forms DW_FORM_data4 and DW_FORM_data8 can be class constant or class loclistptr, depending on the attribute, and if a given attribute allows both, loclistptr is assumed.
DW_AT_byte_size is either a block, constant, or reference, so DW_FORM_data4/8 are not location-list pointers.
DW_AT_count is either a block, constant, or reference, so DW_FORM_data4/8 are not location-list pointers.
DW_AT_data_member_location is either a block, constant, or loclistptr, so DW_FORM_data4/8 must be considered pointers to a location list.

Starting in DWARF4, attributes pointing to a location list would use DW_FORM_sec_offset, and forms data4/data8 are always class constant, never location-list pointers.

This means that DW_AT_byte_size can never point to a location list, and it was a bug to have it say it could (similarly for at least DW_AT_bit_size, and we probably should re-review the entire list). I suppose as an extension it could point to a location list, which would allow different size values based on the current execution address, although the only case I'm familiar with would derive the size from a variable, and so not have to have an actual location list.

Similarly, DW_AT_count can never point to a location list, with the same caveat as for DW_AT_byte_size.

DW_AT_data_member_location is another story; FORM_data4/data8 are supposed to be interpreted as location-list pointers in DWARF 2 and 3. I think the post-commit comments in D58698 suggest that we could always have a version, and I doubt we'll get this completely sorted out until DWARFFormValue requires it.

[shchenz]

This means that DW_AT_byte_size can never point to a location list, and it was a bug to have it say it could (similarly for at least DW_AT_bit_size, and we probably should re-review the entire list). I suppose as an extension it could point to a location list, which would allow different size values based on the current execution address, although the only case I'm familiar with would derive the size from a variable, and so not have to have an actual location list.

DW_AT_byte_size can not be a pointer to a location list, but it could be a exprloc/block kind location, so I guess it is ok to return true for DW_AT_byte_size in function mayHaveLocationDescription(). That function seems check for location descriptions for both exprloc/block kind location and also a location in .debug_loc section. See the function dumpLocation() when mayHaveLocationDescription() returns true.

Maybe a more clear way is to add a new function to check loclistptr related attributes and a new function to dump locations related to loclistptr?

DW_AT_data_member_location is another story; FORM_data4/data8 are supposed to be interpreted as location-list pointers in DWARF 2 and 3. I think the post-commit comments in D58698 suggest that we could always have a version, and I doubt we'll get this completely sorted out until DWARFFormValue requires it.

For DW_AT_data_member_location at DWARF3(default DWARF version for XCOFF), seems now we can not tell if the FORM_data4/data8 are for loclistptr or for constant. for the test case formclass3-atmemloc.s, it is a constant, so making it as location offset to the .debug_loc causes llvm-dwarfdump emit error message, I think we need to fix this. But if we always treat it as constant, it will also cause issue if the value is indeed an offset to .debug_loc. Maybe we have to find a way to differentiate FORM_data4/data8 for loclistptr and FORM_data4/data8 for constant.

[probinson]

In D105469#2861423, @shchenz wrote:

This means that DW_AT_byte_size can never point to a location list, and it was a bug to have it say it could (similarly for at least DW_AT_bit_size, and we probably should re-review the entire list). I suppose as an extension it could point to a location list, which would allow different size values based on the current execution address, although the only case I'm familiar with would derive the size from a variable, and so not have to have an actual location list.

DW_AT_byte_size can not be a pointer to a location list, but it could be a exprloc/block kind location, so I guess it is ok to return true for DW_AT_byte_size in function mayHaveLocationDescription(). That function seems check for location descriptions for both exprloc/block kind location and also a location in .debug_loc section. See the function dumpLocation() when mayHaveLocationDescription() returns true.

Hmmm in that case the value is an expression that computes the value, not a location description. There may be some looseness in the terminology in the code that could be tidied up.

For DW_AT_data_member_location at DWARF3(default DWARF version for XCOFF), seems now we can not tell if the FORM_data4/data8 are for loclistptr or for constant. for the test case formclass3-atmemloc.s, it is a constant, so making it as location offset to the .debug_loc causes llvm-dwarfdump emit error message, I think we need to fix this. But if we always treat it as constant, it will also cause issue if the value is indeed an offset to .debug_loc. Maybe we have to find a way to differentiate FORM_data4/data8 for loclistptr and FORM_data4/data8 for constant.

The standard specifies that if an attribute allows one of the '*ptr' classes, then data4/data8 must be interpreted that way. The interpretation is fixed for each attribute. DWARF 3, section 7.5.4 "Attribute Encodings" third paragraph. If the test is using data4 to encode a constant, the test is incorrect. (I haven't really looked at the tests in this patch, except to see that they could probably be reduced quite a bit.)

[Esme]

In D105469#2860046, @probinson wrote:

This means that DW_AT_byte_size can never point to a location list, and it was a bug to have it say it could (similarly for at least DW_AT_bit_size, and we probably should re-review the entire list). I suppose as an extension it could point to a location list, which would allow different size values based on the current execution address, although the only case I'm familiar with would derive the size from a variable, and so not have to have an actual location list.

Similarly, DW_AT_count can never point to a location list, with the same caveat as for DW_AT_byte_size.

I am trying to split this patch into 2 patches.
I have posted the first one D105613 to handle the bug that we try to dump the location list for those attributes that don't have the localist class.

The standard specifies that if an attribute allows one of the '*ptr' classes, then data4/data8 must be interpreted that way. The interpretation is fixed for each attribute. DWARF 3, section 7.5.4 "Attribute Encodings" third paragraph. If the test is using data4 to encode a constant, the test is incorrect. (I haven't really looked at the tests in this patch, except to see that they could probably be reduced quite a bit.)

The test was compiled from a c++ source code, and the overflow error does exist for DW_AT_data_member_location in DWARF3.
Do you mean that we should use other forms to encode a constant in DW_AT_data_member_location?
I will have a look into the issue and post another patch for it.

[probinson]

In D105469#2863965, @Esme wrote:

In D105469#2860046, @probinson wrote:

The standard specifies that if an attribute allows one of the '*ptr' classes, then data4/data8 must be interpreted that way. The interpretation is fixed for each attribute. DWARF 3, section 7.5.4 "Attribute Encodings" third paragraph. If the test is using data4 to encode a constant, the test is incorrect. (I haven't really looked at the tests in this patch, except to see that they could probably be reduced quite a bit.)

The test was compiled from a c++ source code, and the overflow error does exist for DW_AT_data_member_location in DWARF3.
Do you mean that we should use other forms to encode a constant in DW_AT_data_member_location?
I will have a look into the issue and post another patch for it.

Yes, that would be a compiler bug. I agree it's annoying because it means we can't just always use data4, for some attributes.
Note that fixed-size FORMs are preferable to using a LEB, because it helps debugger parsing when DIEs have a fixed size.

[Esme]

@probinson @shchenz Thanks for your review.
This patch has been split into D105613 and D105687.
Looking forward to your more comments on new patches.

llvm/include/llvm/DebugInfo/DWARF/DWARFAttribute.h

struct DWARFAttribute {
   }
 
   explicit operator bool() const {
     return isValid();
   }
 
   /// Identifies DWARF attributes that may contain a reference to a
   /// DWARF expression.
-  static bool mayHaveLocationDescription(dwarf::Attribute Attr);
+  static bool mayHaveLocationDescription(dwarf::Attribute Attr,
+                                         dwarf::Form Form);
 };
 
 } // end namespace llvm
 
 #endif // LLVM_DEBUGINFO_DWARF_DWARFATTRIBUTE_H

llvm/lib/DWARFLinker/DWARFLinker.cpp

unsigned DWARFLinker::DIECloner::cloneBlockAttribute(
   else
     Value = DIEValue(dwarf::Attribute(AttrSpec.Attr),
                      dwarf::Form(AttrSpec.Form), Block);
 
   // If the block is a DWARF Expression, clone it into the temporary
   // buffer using cloneExpression(), otherwise copy the data directly.
   SmallVector<uint8_t, 32> Buffer;
   ArrayRef<uint8_t> Bytes = *Val.getAsBlock();
-  if (DWARFAttribute::mayHaveLocationDescription(AttrSpec.Attr) &&
+  if (DWARFAttribute::mayHaveLocationDescription(AttrSpec.Attr,
+                                                 AttrSpec.Form) &&
       (Val.isFormClass(DWARFFormValue::FC_Block) ||
        Val.isFormClass(DWARFFormValue::FC_Exprloc))) {
     DWARFUnit &OrigUnit = Unit.getOrigUnit();
     DataExtractor Data(StringRef((const char *)Bytes.data(), Bytes.size()),
                        IsLittleEndian, OrigUnit.getAddressByteSize());
     DWARFExpression Expr(Data, OrigUnit.getAddressByteSize(),
                          OrigUnit.getFormParams().Format);
     cloneExpression(Data, Expr, File, Unit, Buffer);

llvm/lib/DebugInfo/DWARF/DWARFDie.cpp

if (DumpOpts.ShowAddresses) {
       // Print the actual address rather than the offset.
       uint64_t LowPC, HighPC, Index;
       if (Die.getLowAndHighPC(LowPC, HighPC, Index))
         DWARFFormValue::dumpAddress(OS, U->getAddressByteSize(), HighPC);
       else
         FormValue.dump(OS, DumpOpts);
     }
   } else if (Form == dwarf::Form::DW_FORM_exprloc ||
-             DWARFAttribute::mayHaveLocationDescription(Attr))
+             DWARFAttribute::mayHaveLocationDescription(Attr, Form))
     dumpLocation(OS, FormValue, U, sizeof(BaseIndent) + Indent + 4, DumpOpts);
   else
     FormValue.dump(OS, DumpOpts);
 
   std::string Space = DumpOpts.ShowAddresses ? " " : "";
 
   // We have dumped the attribute raw value. For some attributes
   // having both the raw value and the pretty-printed value is

 }
 
 DWARFDie::attribute_iterator &DWARFDie::attribute_iterator::operator++() {
   if (auto AbbrDecl = Die.getAbbreviationDeclarationPtr())
     updateForIndex(*AbbrDecl, Index + 1);
   return *this;
 }
 
-bool DWARFAttribute::mayHaveLocationDescription(dwarf::Attribute Attr) {
+bool DWARFAttribute::mayHaveLocationDescription(dwarf::Attribute Attr,
+                                                dwarf::Form Form) {
   switch (Attr) {
   // From the DWARF v5 specification.
   case DW_AT_location:
-  case DW_AT_byte_size:
   case DW_AT_bit_size:
   case DW_AT_string_length:
   case DW_AT_lower_bound:
   case DW_AT_return_addr:
   case DW_AT_bit_stride:
   case DW_AT_upper_bound:
-  case DW_AT_count:
-  case DW_AT_data_member_location:
   case DW_AT_frame_base:
   case DW_AT_segment:
   case DW_AT_static_link:
   case DW_AT_use_location:
   case DW_AT_vtable_elem_location:
   case DW_AT_allocated:
   case DW_AT_associated:
   case DW_AT_byte_stride:
   case DW_AT_rank:
   case DW_AT_call_value:
   case DW_AT_call_origin:
   case DW_AT_call_target:
   case DW_AT_call_target_clobbered:
   case DW_AT_call_data_location:
   case DW_AT_call_data_value:
   // Extensions.
   case DW_AT_GNU_call_site_value:
   case DW_AT_GNU_call_site_target:
     return true;
+  case DW_AT_byte_size:
+  case DW_AT_count:
+  case DW_AT_data_member_location: {
+    // FIXME: Return true if DW_FORM_data4/DW_FORM_data8 is served as a section
+    // offset here.
+    if (Form == dwarf::Form::DW_FORM_data4 ||
+        Form == dwarf::Form::DW_FORM_data8)
+      return false;
+    return true;
+  }
   default:
     return false;
   }
 }

llvm/test/tools/llvm-dwarfdump/ELF/formclass3-atcount.s

+# Source:
+#   typedef unsigned char XMLByte;
+#   static XMLByte arr[0x100000];
+#   
+#   int main()
+#   {
+#     arr[0] = 100;
+#     arr[10000] = 50;
+#     return arr[0] + arr[50];
+#   }
+# Compile with:
+#   clang -O2 -gdwarf-3 -S b.cpp -o b3.s
+
+# RUN: llvm-mc %s -filetype obj -triple powerpc64le-unknown-unknown -o %t.o
+# RUN: llvm-dwarfdump -debug-info %t.o | FileCheck %s -check-prefix=AT-COUNT
+
+# AT-COUNT: DW_TAG_subrange_type
+# AT-COUNT: DW_AT_count (0x00010400)
+
+  .text
+  .abiversion 2
+  .file "b.cpp"
+  .file 1 "/llvm-project" "b.cpp"
+  .globl  main                            # -- Begin function main
+  .p2align  4
+  .type main,@function
+main:                                   # @main
+.Lfunc_begin0:
+  .loc  1 8 0                           # b.cpp:8:0
+  .cfi_startproc
+.Lfunc_gep0:
+  addis 2, 12, .TOC.-.Lfunc_gep0@ha
+  addi 2, 2, .TOC.-.Lfunc_gep0@l
+.Lfunc_lep0:
+  .localentry main, .Lfunc_lep0-.Lfunc_gep0
+# %bb.0:                                # %entry
+  .loc  1 9 14 prologue_end             # b.cpp:9:14
+  addis 4, 2, a@toc@ha
+  li 5, 100
+  .loc  1 10 2                          # b.cpp:10:2
+  li 3, 100
+  .loc  1 9 14                          # b.cpp:9:14
+  stb 5, a@toc@l(4)
+  .loc  1 10 2                          # b.cpp:10:2
+  blr
+.Ltmp0:
+  .long 0
+  .quad 0
+.Lfunc_end0:
+  .size main, .Lfunc_end0-.Lfunc_begin0
+  .cfi_endproc
+                                        # -- End function
+  .type a,@object                       # @a
+  .section  .bss,"aw",@nobits
+  .globl  a
+a:
+  .space  66560
+  .size a, 66560
+
+  .section  .debug_abbrev,"",@progbits
+  .byte 1                               # Abbreviation Code
+  .byte 17                              # DW_TAG_compile_unit
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 37                              # DW_AT_producer
+  .byte 14                              # DW_FORM_strp
+  .byte 19                              # DW_AT_language
+  .byte 5                               # DW_FORM_data2
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 16                              # DW_AT_stmt_list
+  .byte 6                               # DW_FORM_data4
+  .byte 27                              # DW_AT_comp_dir
+  .byte 14                              # DW_FORM_strp
+  .byte 17                              # DW_AT_low_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 18                              # DW_AT_high_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 2                               # Abbreviation Code
+  .byte 52                              # DW_TAG_variable
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 63                              # DW_AT_external
+  .byte 12                              # DW_FORM_flag
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 2                               # DW_AT_location
+  .byte 10                              # DW_FORM_block1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 3                               # Abbreviation Code
+  .byte 2                               # DW_TAG_class_type
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 54                              # DW_AT_calling_convention
+  .byte 11                              # DW_FORM_data1
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 11                              # DW_AT_byte_size
+  .byte 6                               # DW_FORM_data4
+  .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 4                               # Abbreviation Code
+  .byte 13                              # DW_TAG_member
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 56                              # DW_AT_data_member_location
+  .byte 11                              # DW_FORM_data1
+  .byte 50                              # DW_AT_accessibility
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 5                               # Abbreviation Code
+  .byte 1                               # DW_TAG_array_type
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 6                               # Abbreviation Code
+  .byte 33                              # DW_TAG_subrange_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 55                              # DW_AT_count
+  .byte 6                               # DW_FORM_data4
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 7                               # Abbreviation Code
+  .byte 36                              # DW_TAG_base_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .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 8                               # Abbreviation Code
+  .byte 36                              # DW_TAG_base_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 11                              # DW_AT_byte_size
+  .byte 11                              # DW_FORM_data1
+  .byte 62                              # DW_AT_encoding
+  .byte 11                              # DW_FORM_data1
+  .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
+  .byte 1                               # DW_FORM_addr
+  .byte 18                              # DW_AT_high_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 64                              # DW_AT_frame_base
+  .byte 10                              # DW_FORM_block1
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .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 12                              # DW_FORM_flag
+  .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  3                               # DWARF version number
+  .long .debug_abbrev                   # Offset Into Abbrev. Section
+  .byte 8                               # Address Size (in bytes)
+  .byte 1                               # Abbrev [1] 0xb:0x96 DW_TAG_compile_unit
+  .long .Linfo_string0                  # DW_AT_producer
+  .short  33                              # DW_AT_language
+  .long .Linfo_string1                  # DW_AT_name
+  .long .Lline_table_start0             # DW_AT_stmt_list
+  .long .Linfo_string2                  # DW_AT_comp_dir
+  .quad .Lfunc_begin0                   # DW_AT_low_pc
+  .quad .Lfunc_end0                     # DW_AT_high_pc
+  .byte 2                               # Abbrev [2] 0x2e:0x16 DW_TAG_variable
+  .long .Linfo_string3                  # DW_AT_name
+  .long 68                              # DW_AT_type
+  .byte 1                               # DW_AT_external
+  .byte 1                               # DW_AT_decl_file
+  .byte 6                               # DW_AT_decl_line
+  .byte 9                               # DW_AT_location
+  .byte 3
+  .quad a
+  .byte 3                               # Abbrev [3] 0x44:0x1a DW_TAG_class_type
+  .byte 5                               # DW_AT_calling_convention
+  .long .Linfo_string7                  # DW_AT_name
+  .long 66560                           # DW_AT_byte_size
+  .byte 1                               # DW_AT_decl_file
+  .byte 1                               # DW_AT_decl_line
+  .byte 4                               # Abbrev [4] 0x50:0xd DW_TAG_member
+  .long .Linfo_string4                  # DW_AT_name
+  .long 94                              # DW_AT_type
+  .byte 1                               # DW_AT_decl_file
+  .byte 3                               # DW_AT_decl_line
+  .byte 0                               # DW_AT_data_member_location
+  .byte 1                               # DW_AT_accessibility
+                                        # DW_ACCESS_public
+  .byte 0                               # End Of Children Mark
+  .byte 5                               # Abbrev [5] 0x5e:0xf DW_TAG_array_type
+  .long 109                             # DW_AT_type
+  .byte 6                               # Abbrev [6] 0x63:0x9 DW_TAG_subrange_type
+  .long 116                             # DW_AT_type
+  .long 66560                           # DW_AT_count
+  .byte 0                               # End Of Children Mark
+  .byte 7                               # Abbrev [7] 0x6d:0x7 DW_TAG_base_type
+  .long .Linfo_string5                  # DW_AT_name
+  .byte 8                               # DW_AT_encoding
+  .byte 1                               # DW_AT_byte_size
+  .byte 8                               # Abbrev [8] 0x74:0x7 DW_TAG_base_type
+  .long .Linfo_string6                  # DW_AT_name
+  .byte 8                               # DW_AT_byte_size
+  .byte 7                               # DW_AT_encoding
+  .byte 9                               # Abbrev [9] 0x7b:0x1e DW_TAG_subprogram
+  .quad .Lfunc_begin0                   # DW_AT_low_pc
+  .quad .Lfunc_end0                     # DW_AT_high_pc
+  .byte 1                               # DW_AT_frame_base
+  .byte 81
+  .long .Linfo_string8                  # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 8                               # DW_AT_decl_line
+  .long 153                             # DW_AT_type
+  .byte 1                               # DW_AT_external
+  .byte 7                               # Abbrev [7] 0x99:0x7 DW_TAG_base_type
+  .long .Linfo_string9                  # DW_AT_name
+  .byte 5                               # DW_AT_encoding
+  .byte 4                               # DW_AT_byte_size
+  .byte 0                               # End Of Children Mark
+.Ldebug_info_end0:
+  .section  .debug_str,"MS",@progbits,1
+.Linfo_string0:
+  .asciz  "XL C/C++ for Linux on Power, (IBM Internal Development Branch), clang version 13.0.0" # string offset=0
+.Linfo_string1:
+  .asciz  "b.cpp"                         # string offset=85
+.Linfo_string2:
+  .asciz  "/llvm-project"                 # string offset=91
+.Linfo_string3:
+  .asciz  "a"                             # string offset=125
+.Linfo_string4:
+  .asciz  "bigarr"                        # string offset=127
+.Linfo_string5:
+  .asciz  "unsigned char"                 # string offset=134
+.Linfo_string6:
+  .asciz  "__ARRAY_SIZE_TYPE__"           # string offset=148
+.Linfo_string7:
+  .asciz  "A"                             # string offset=168
+.Linfo_string8:
+  .asciz  "main"                          # string offset=170
+.Linfo_string9:
+  .asciz  "int"                           # string offset=175
+  .ident  "XL C/C++ for Linux on Power, (IBM Internal Development Branch), clang version 13.0.0"
+  .section  ".note.GNU-stack","",@progbits
+  .addrsig
+  .section  .debug_line,"",@progbits
+.Lline_table_start0:

llvm/test/tools/llvm-dwarfdump/ELF/formclass3-atmemloc.s

+# Source:
+#   struct e {
+#     char f[16384];
+#     char g;
+#   };
+#   e foo() {
+#     auto E = new e;
+#     return *E;
+#   }
+# Compile with:
+#   clang -O2 -gdwarf-3 -S a.cpp -o a3.s
+
+# RUN: llvm-mc %s -filetype obj -triple powerpc64le-unknown-unknown -o %t.o
+# RUN: llvm-dwarfdump -debug-info -name g %t.o | FileCheck %s -check-prefix=AT-MEMLOC
+# RUN: llvm-dwarfdump -debug-info -name e %t.o | FileCheck %s -check-prefix=AT-BSIZE
+
+# AT-MEMLOC: DW_TAG_member
+# AT-MEMLOC: DW_AT_name ("g")
+# AT-MEMLOC: DW_AT_data_member_location (0x00010000)
+
+# AT-BSIZE: DW_TAG_structure_type
+# AT-BSIZE: DW_AT_name  ("e")
+# AT-BSIZE: DW_AT_byte_size (0x00010004)
+
+  .text
+  .abiversion 2
+  .file "a.cpp"
+  .file 1 "/llvm-project" "a.cpp"
+  .globl  _Z3foov                         # -- Begin function _Z3foov
+  .p2align  4
+  .type _Z3foov,@function
+_Z3foov:                                # @_Z3foov
+.Lfunc_begin0:
+  .loc  1 5 0                           # a.cpp:5:0
+  .cfi_startproc
+.Lfunc_gep0:
+  addis 2, 12, .TOC.-.Lfunc_gep0@ha
+  addi 2, 2, .TOC.-.Lfunc_gep0@l
+.Lfunc_lep0:
+  .localentry _Z3foov, .Lfunc_lep0-.Lfunc_gep0
+# %bb.0:                                # %entry
+  mflr 0
+  .cfi_def_cfa_offset 64
+  .cfi_offset lr, 16
+  .cfi_offset r29, -24
+  .cfi_offset r30, -16
+  std 29, -24(1)                          # 8-byte Folded Spill
+  std 30, -16(1)                          # 8-byte Folded Spill
+  std 0, 16(1)
+  stdu 1, -64(1)
+  mr  30, 3
+  lis 3, 1
+  ori 29, 3, 4
+.Ltmp0:
+  .loc  1 6 12 prologue_end             # a.cpp:6:12
+  mr  3, 29
+  bl _Znwm
+  nop
+  mr  4, 3
+.Ltmp1:
+  #DEBUG_VALUE: foo:E <- $x4
+  .loc  1 7 10                          # a.cpp:7:10
+  mr  3, 30
+  mr  5, 29
+  bl memcpy
+  nop
+.Ltmp2:
+  .loc  1 8 1                           # a.cpp:8:1
+  addi 1, 1, 64
+  ld 0, 16(1)
+  ld 30, -16(1)                           # 8-byte Folded Reload
+  ld 29, -24(1)                           # 8-byte Folded Reload
+  mtlr 0
+  blr
+.Ltmp3:
+  .long 0
+  .quad 0
+.Lfunc_end0:
+  .size _Z3foov, .Lfunc_end0-.Lfunc_begin0
+  .cfi_endproc
+                                        # -- End function
+  .section  .debug_loc,"",@progbits
+.Ldebug_loc0:
+  .quad .Ltmp1-.Lfunc_begin0
+  .quad .Ltmp2-.Lfunc_begin0
+  .short  1                               # Loc expr size
+  .byte 84                              # DW_OP_reg4
+  .quad 0
+  .quad 0
+  .section  .debug_abbrev,"",@progbits
+  .byte 1                               # Abbreviation Code
+  .byte 17                              # DW_TAG_compile_unit
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 37                              # DW_AT_producer
+  .byte 14                              # DW_FORM_strp
+  .byte 19                              # DW_AT_language
+  .byte 5                               # DW_FORM_data2
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 16                              # DW_AT_stmt_list
+  .byte 6                               # DW_FORM_data4
+  .byte 27                              # DW_AT_comp_dir
+  .byte 14                              # DW_FORM_strp
+  .byte 17                              # DW_AT_low_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 18                              # DW_AT_high_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 2                               # Abbreviation Code
+  .byte 19                              # DW_TAG_structure_type
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 54                              # DW_AT_calling_convention
+  .byte 11                              # DW_FORM_data1
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 11                              # DW_AT_byte_size
+  .byte 6                               # DW_FORM_data4
+  .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 3                               # Abbreviation Code
+  .byte 13                              # DW_TAG_member
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 56                              # DW_AT_data_member_location
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 4                               # Abbreviation Code
+  .byte 4                               # DW_TAG_enumeration_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 11                              # DW_AT_byte_size
+  .byte 11                              # DW_FORM_data1
+  .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 5                               # Abbreviation Code
+  .byte 13                              # DW_TAG_member
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 58                              # DW_AT_decl_file
+  .byte 11                              # DW_FORM_data1
+  .byte 59                              # DW_AT_decl_line
+  .byte 11                              # DW_FORM_data1
+  .byte 56                              # DW_AT_data_member_location
+  .byte 6                               # DW_FORM_data4
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 6                               # Abbreviation Code
+  .byte 1                               # DW_TAG_array_type
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 7                               # Abbreviation Code
+  .byte 33                              # DW_TAG_subrange_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .byte 55                              # DW_AT_count
+  .byte 5                               # DW_FORM_data2
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 8                               # Abbreviation Code
+  .byte 36                              # DW_TAG_base_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .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 9                               # Abbreviation Code
+  .byte 36                              # DW_TAG_base_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .byte 11                              # DW_AT_byte_size
+  .byte 11                              # DW_FORM_data1
+  .byte 62                              # DW_AT_encoding
+  .byte 11                              # DW_FORM_data1
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 10                              # Abbreviation Code
+  .byte 46                              # DW_TAG_subprogram
+  .byte 1                               # DW_CHILDREN_yes
+  .byte 17                              # DW_AT_low_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 18                              # DW_AT_high_pc
+  .byte 1                               # DW_FORM_addr
+  .byte 64                              # DW_AT_frame_base
+  .byte 10                              # DW_FORM_block1
+  .ascii  "\207@"                         # DW_AT_MIPS_linkage_name
+  .byte 14                              # DW_FORM_strp
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .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 12                              # DW_FORM_flag
+  .byte 0                               # EOM(1)
+  .byte 0                               # EOM(2)
+  .byte 11                              # Abbreviation Code
+  .byte 52                              # DW_TAG_variable
+  .byte 0                               # DW_CHILDREN_no
+  .byte 2                               # DW_AT_location
+  .byte 6                               # DW_FORM_data4
+  .byte 3                               # DW_AT_name
+  .byte 14                              # DW_FORM_strp
+  .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 12                              # Abbreviation Code
+  .byte 15                              # DW_TAG_pointer_type
+  .byte 0                               # DW_CHILDREN_no
+  .byte 73                              # DW_AT_type
+  .byte 19                              # DW_FORM_ref4
+  .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  3                               # DWARF version number
+  .long .debug_abbrev                   # Offset Into Abbrev. Section
+  .byte 8                               # Address Size (in bytes)
+  .byte 1                               # Abbrev [1] 0xb:0xad DW_TAG_compile_unit
+  .long .Linfo_string0                  # DW_AT_producer
+  .short  33                              # DW_AT_language
+  .long .Linfo_string1                  # DW_AT_name
+  .long .Lline_table_start0             # DW_AT_stmt_list
+  .long .Linfo_string2                  # DW_AT_comp_dir
+  .quad .Lfunc_begin0                   # DW_AT_low_pc
+  .quad .Lfunc_end0                     # DW_AT_high_pc
+  .byte 2                               # Abbrev [2] 0x2e:0x30 DW_TAG_structure_type
+  .byte 5                               # DW_AT_calling_convention
+  .long .Linfo_string8                  # DW_AT_name
+  .long 65540                           # DW_AT_byte_size
+  .byte 1                               # DW_AT_decl_file
+  .byte 1                               # DW_AT_decl_line
+  .byte 3                               # Abbrev [3] 0x3a:0xc DW_TAG_member
+  .long .Linfo_string3                  # DW_AT_name
+  .long 94                              # DW_AT_type
+  .byte 1                               # DW_AT_decl_file
+  .byte 2                               # DW_AT_decl_line
+  .byte 0                               # DW_AT_data_member_location
+  .byte 4                               # Abbrev [4] 0x46:0x8 DW_TAG_enumeration_type
+  .long 107                             # DW_AT_type
+  .byte 4                               # DW_AT_byte_size
+  .byte 1                               # DW_AT_decl_file
+  .byte 2                               # DW_AT_decl_line
+  .byte 5                               # Abbrev [5] 0x4e:0xf DW_TAG_member
+  .long .Linfo_string6                  # DW_AT_name
+  .long 121                             # DW_AT_type
+  .byte 1                               # DW_AT_decl_file
+  .byte 3                               # DW_AT_decl_line
+  .long 65536                           # DW_AT_data_member_location
+  .byte 0                               # End Of Children Mark
+  .byte 6                               # Abbrev [6] 0x5e:0xd DW_TAG_array_type
+  .long 70                              # DW_AT_type
+  .byte 7                               # Abbrev [7] 0x63:0x7 DW_TAG_subrange_type
+  .long 114                             # DW_AT_type
+  .short  16384                           # DW_AT_count
+  .byte 0                               # End Of Children Mark
+  .byte 8                               # Abbrev [8] 0x6b:0x7 DW_TAG_base_type
+  .long .Linfo_string4                  # DW_AT_name
+  .byte 7                               # DW_AT_encoding
+  .byte 4                               # DW_AT_byte_size
+  .byte 9                               # Abbrev [9] 0x72:0x7 DW_TAG_base_type
+  .long .Linfo_string5                  # DW_AT_name
+  .byte 8                               # DW_AT_byte_size
+  .byte 7                               # DW_AT_encoding
+  .byte 8                               # Abbrev [8] 0x79:0x7 DW_TAG_base_type
+  .long .Linfo_string7                  # DW_AT_name
+  .byte 5                               # DW_AT_encoding
+  .byte 2                               # DW_AT_byte_size
+  .byte 10                              # Abbrev [10] 0x80:0x32 DW_TAG_subprogram
+  .quad .Lfunc_begin0                   # DW_AT_low_pc
+  .quad .Lfunc_end0                     # DW_AT_high_pc
+  .byte 1                               # DW_AT_frame_base
+  .byte 81
+  .long .Linfo_string9                  # DW_AT_MIPS_linkage_name
+  .long .Linfo_string10                 # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 5                               # DW_AT_decl_line
+  .long 46                              # DW_AT_type
+  .byte 1                               # DW_AT_external
+  .byte 11                              # Abbrev [11] 0xa2:0xf DW_TAG_variable
+  .long .Ldebug_loc0                    # DW_AT_location
+  .long .Linfo_string11                 # DW_AT_name
+  .byte 1                               # DW_AT_decl_file
+  .byte 6                               # DW_AT_decl_line
+  .long 178                             # DW_AT_type
+  .byte 0                               # End Of Children Mark
+  .byte 12                              # Abbrev [12] 0xb2:0x5 DW_TAG_pointer_type
+  .long 46                              # DW_AT_type
+  .byte 0                               # End Of Children Mark
+.Ldebug_info_end0:
+  .section  .debug_str,"MS",@progbits,1
+.Linfo_string0:
+  .asciz  "XL C/C++ for Linux on Power, (IBM Internal Development Branch), clang version 13.0.0" # string offset=0
+.Linfo_string1:
+  .asciz  "a.cpp"                         # string offset=85
+.Linfo_string2:
+  .asciz  "/llvm-project"                 #string offset=91
+.Linfo_string3:
+  .asciz  "f"                             # string offset=125
+.Linfo_string4:
+  .asciz  "unsigned int"                  # string offset=127
+.Linfo_string5:
+  .asciz  "__ARRAY_SIZE_TYPE__"           # string offset=140
+.Linfo_string6:
+  .asciz  "g"                             # string offset=160
+.Linfo_string7:
+  .asciz  "short"                         # string offset=162
+.Linfo_string8:
+  .asciz  "e"                             # string offset=168
+.Linfo_string9:
+  .asciz  "_Z3foov"                       # string offset=170
+.Linfo_string10:
+  .asciz  "foo"                           # string offset=178
+.Linfo_string11:
+  .asciz  "E"                             # string offset=182
+  .ident  "XL C/C++ for Linux on Power, (IBM Internal Development Branch), clang version 13.0.0"
+  .section  ".note.GNU-stack","",@progbits
+  .addrsig
+  .section  .debug_line,"",@progbits
+.Lline_table_start0: