[DebugNames] Implement Entry::GetParentEntry query #78760
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This commit introduces a helper function to DWARFAcceleratorTable::Entry which follows DW_IDX_Parent attributes to returns the corresponding parent Entry in the table. It is tested by enhancing dwarfdump so that it now prints: 1. When data is corrupt. 2. When parent information is present, but the parent is not indexed. 3. The parent entry offset, when the parent is present and indexed. This is printed in terms a real entry offset (the same that gets printed at the start of each entry: "Entry @ 0x..."), instead of the encoded number in the table (which is an offset from the start off the Entry list). This makes it easy to visually inspect the dwarfdump and check what the parent is.
felipepiovezan
requested review from
JDevlieghere,
adrian-prantl and
clayborg
|
@llvm/pr-subscribers-backend-x86 @llvm/pr-subscribers-debuginfo Author: Felipe de Azevedo Piovezan (felipepiovezan) ChangesThis commit introduces a helper function to DWARFAcceleratorTable::Entry which follows DW_IDX_Parent attributes to returns the corresponding parent Entry in the table. It is tested by enhancing dwarfdump so that it now prints:
Full diff: https://github.com/llvm/llvm-project/pull/78760.diff 8 Files Affected:
diff --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
index b89536bc0c7230c..57f74d70cf9671c 100644
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
@@ -460,6 +460,16 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
/// Returns the Offset of the DIE within the containing CU or TU.
std::optional<uint64_t> getDIEUnitOffset() const;
+ /// Returns true if this Entry has information about its parent DIE (i.e. if
+ /// it has an IDX_parent attribute)
+ bool hasParentInformation() const;
+
+ /// Returns the Entry corresponding to the parent of the DIE represented by
+ /// `this` Entry. If the parent is not in the table, nullopt is returned.
+ /// Precondition: hasParentInformation() == true.
+ /// An error is returned for ill-formed tables.
+ Expected<std::optional<DWARFDebugNames::Entry>> getParentDIEEntry() const;
+
/// Return the Abbreviation that can be used to interpret the raw values of
/// this Accelerator Entry.
const Abbrev &getAbbrev() const { return *Abbr; }
@@ -469,6 +479,7 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
std::optional<DWARFFormValue> lookup(dwarf::Index Index) const;
void dump(ScopedPrinter &W) const;
+ void dumpParentIdx(ScopedPrinter &W, const DWARFFormValue &FormValue) const;
friend class NameIndex;
friend class ValueIterator;
@@ -609,6 +620,13 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
Expected<Entry> getEntry(uint64_t *Offset) const;
+ // Returns the Entry at the relative `Offset` from the start of the Entry
+ // pool.
+ Expected<Entry> getEntryAtRelativeOffset(uint64_t Offset) const {
+ auto OffsetFromSection = Offset + this->EntriesBase;
+ return getEntry(&OffsetFromSection);
+ }
+
/// Look up all entries in this Name Index matching \c Key.
iterator_range<ValueIterator> equal_range(StringRef Key) const;
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
index 0f9c8ef485d456e..03ad5d133caddf4 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
@@ -611,6 +611,10 @@ DWARFDebugNames::Entry::lookup(dwarf::Index Index) const {
return std::nullopt;
}
+bool DWARFDebugNames::Entry::hasParentInformation() const {
+ return lookup(dwarf::DW_IDX_parent).has_value();
+}
+
std::optional<uint64_t> DWARFDebugNames::Entry::getDIEUnitOffset() const {
if (std::optional<DWARFFormValue> Off = lookup(dwarf::DW_IDX_die_offset))
return Off->getAsReferenceUVal();
@@ -650,13 +654,48 @@ std::optional<uint64_t> DWARFDebugNames::Entry::getLocalTUIndex() const {
return std::nullopt;
}
+Expected<std::optional<DWARFDebugNames::Entry>>
+DWARFDebugNames::Entry::getParentDIEEntry() const {
+ // The offset of the accelerator table entry for the parent.
+ std::optional<DWARFFormValue> ParentEntryOff = lookup(dwarf::DW_IDX_parent);
+ assert(ParentEntryOff.has_value() && "hasParentInformation() must be called");
+
+ if (ParentEntryOff->getForm() == dwarf::Form::DW_FORM_flag_present)
+ return std::nullopt;
+ return NameIdx->getEntryAtRelativeOffset(ParentEntryOff->getRawUValue());
+}
+
+void DWARFDebugNames::Entry::dumpParentIdx(
+ ScopedPrinter &W, const DWARFFormValue &FormValue) const {
+ Expected<std::optional<Entry>> ParentEntry = getParentDIEEntry();
+ if (!ParentEntry) {
+ W.getOStream() << "<invalid offset data>";
+ consumeError(ParentEntry.takeError());
+ return;
+ }
+
+ if (!ParentEntry->has_value()) {
+ W.getOStream() << "<parent not indexed>";
+ return;
+ }
+
+ auto AbsoluteOffset = NameIdx->EntriesBase + FormValue.getRawUValue();
+ W.getOStream() << "Entry @ 0x" + Twine::utohexstr(AbsoluteOffset);
+}
+
void DWARFDebugNames::Entry::dump(ScopedPrinter &W) const {
W.startLine() << formatv("Abbrev: {0:x}\n", Abbr->Code);
W.startLine() << formatv("Tag: {0}\n", Abbr->Tag);
assert(Abbr->Attributes.size() == Values.size());
for (auto Tuple : zip_first(Abbr->Attributes, Values)) {
- W.startLine() << formatv("{0}: ", std::get<0>(Tuple).Index);
- std::get<1>(Tuple).dump(W.getOStream());
+ auto Index = std::get<0>(Tuple).Index;
+ W.startLine() << formatv("{0}: ", Index);
+
+ auto FormValue = std::get<1>(Tuple);
+ if (Index == dwarf::Index::DW_IDX_parent)
+ dumpParentIdx(W, FormValue);
+ else
+ FormValue.dump(W.getOStream());
W.getOStream() << '\n';
}
}
diff --git a/llvm/test/CodeGen/X86/dwarf-headers.o b/llvm/test/CodeGen/X86/dwarf-headers.o
new file mode 100644
index 000000000000000..e69de29bb2d1d64
diff --git a/llvm/test/DebugInfo/Generic/debug-names-one-cu.ll b/llvm/test/DebugInfo/Generic/debug-names-one-cu.ll
index 92212a24bd153ad..46b753e9e2def8d 100644
--- a/llvm/test/DebugInfo/Generic/debug-names-one-cu.ll
+++ b/llvm/test/DebugInfo/Generic/debug-names-one-cu.ll
@@ -35,7 +35,7 @@
; CHECK-NEXT: Abbrev: [[ABBREV]]
; CHECK-NEXT: Tag: DW_TAG_variable
; CHECK-NEXT: DW_IDX_die_offset: 0x{{[0-9a-f]*}}
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK: String: 0x{{[0-9a-f]*}} "foobar"
@@ -43,7 +43,7 @@
; CHECK-NEXT: Abbrev: [[ABBREV]]
; CHECK-NEXT: Tag: DW_TAG_variable
; CHECK-NEXT: DW_IDX_die_offset: 0x{{[0-9a-f]*}}
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; VERIFY: No errors.
diff --git a/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll b/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll
index a6855d77a34ac23..c15e2ad1d56b0c4 100644
--- a/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll
+++ b/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll
@@ -59,7 +59,7 @@
; CHECK-NEXT: Abbrev: [[ABBREV]]
; CHECK-NEXT: Tag: DW_TAG_base_type
; CHECK-NEXT: DW_IDX_die_offset: [[TYPEDIE]]
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
@@ -71,17 +71,17 @@
; CHECK-NEXT: Abbrev: [[ABBREV1]]
; CHECK-NEXT: Tag: DW_TAG_variable
; CHECK-NEXT: DW_IDX_die_offset: [[VARDIE]]
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: Name 3 {
; CHECK-NEXT: Hash: 0x7C96FE71
; CHECK-NEXT: String: {{.+}} "func"
-; CHECK-NEXT: Entry @ {{.+}} {
+; CHECK-NEXT: Entry @ [[FUNC_ENTRY:0x.+]] {
; CHECK-NEXT: Abbrev: [[ABBREV_SP]]
; CHECK-NEXT: Tag: DW_TAG_subprogram
; CHECK-NEXT: DW_IDX_die_offset: [[SPDIE]]
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
@@ -96,7 +96,7 @@
; CHECK-NEXT: Abbrev: [[ABBREV_LABEL]]
; CHECK-NEXT: Tag: DW_TAG_label
; CHECK-NEXT: DW_IDX_die_offset: [[LABELDIE]]
-; CHECK-NEXT: DW_IDX_parent: 0x{{.*}}
+; CHECK-NEXT: DW_IDX_parent: Entry @ [[FUNC_ENTRY]]
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
diff --git a/llvm/test/DebugInfo/X86/debug-names-parents-same-offset.ll b/llvm/test/DebugInfo/X86/debug-names-parents-same-offset.ll
index 9170cfc8508fa5e..95d85ab0ffe0fb3 100644
--- a/llvm/test/DebugInfo/X86/debug-names-parents-same-offset.ll
+++ b/llvm/test/DebugInfo/X86/debug-names-parents-same-offset.ll
@@ -21,16 +21,30 @@
; CHECK-NEXT: Abbrev: [[ABBREV:0x.*]]
; CHECK-NEXT: Tag: DW_TAG_structure_type
; CHECK-NEXT: DW_IDX_type_unit: 0x01
-; CHECK-NEXT: DW_IDX_die_offset: [[DieOffset:0x.*]]
-; CHECK-NEXT: DW_IDX_parent: [[Parent1:0x.*]]
+; CHECK-NEXT: DW_IDX_die_offset: [[DieOffsetStruct:0x.*]]
+; CHECK-NEXT: DW_IDX_parent: Entry @ [[Parent2:0x.*]]
+; CHECK: String: {{.*}} "MyNamespace"
+; CHECK-NEXT: Entry @ [[Parent1:0x.*]] {
+; CHECK-NEXT: Abbrev: {{.*}}
+; CHECK-NEXT: Tag: DW_TAG_namespace
+; CHECK-NEXT: DW_IDX_type_unit: 0x00
+; CHECK-NEXT: DW_IDX_die_offset: [[DieOffsetNamespace:0x.*]]
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
+; CHECK-NEXT: }
+; CHECK-NEXT: Entry @ [[Parent2]] {
+; CHECK-NEXT: Abbrev: {{.*}}
+; CHECK-NEXT: Tag: DW_TAG_namespace
+; CHECK-NEXT: DW_IDX_type_unit: 0x01
+; CHECK-NEXT: DW_IDX_die_offset: [[DieOffsetNamespace:0x.*]]
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
+; CHECK-NEXT: }
; CHECK: String: {{.*}} "MyStruct1"
; CHECK-NEXT: Entry @ {{.*}} {
; CHECK-NEXT: Abbrev: [[ABBREV]]
; CHECK-NEXT: Tag: DW_TAG_structure_type
; CHECK-NEXT: DW_IDX_type_unit: 0x00
-; CHECK-NEXT: DW_IDX_die_offset: [[DieOffset:0x.*]]
-; CHECK-NOT: DW_IDX_parent: [[Parent1]]
-; CHECK-NEXT: DW_IDX_parent: 0x{{.*}}
+; CHECK-NEXT: DW_IDX_die_offset: [[DieOffsetStruct:0x.*]]
+; CHECK-NEXT: DW_IDX_parent: Entry @ [[Parent1]]
%"struct.MyNamespace::MyStruct1" = type { i8 }
diff --git a/llvm/test/DebugInfo/X86/debug-names-types.ll b/llvm/test/DebugInfo/X86/debug-names-types.ll
index c44e82578f14a42..f41bb5524b9c33f 100644
--- a/llvm/test/DebugInfo/X86/debug-names-types.ll
+++ b/llvm/test/DebugInfo/X86/debug-names-types.ll
@@ -73,7 +73,7 @@
; CHECK-NEXT: Abbrev: [[ABBREV]]
; CHECK-NEXT: Tag: DW_TAG_base_type
; CHECK-NEXT: DW_IDX_die_offset: 0x0000003e
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
@@ -86,13 +86,13 @@
; CHECK-NEXT: Tag: DW_TAG_structure_type
; CHECK-NEXT: DW_IDX_type_unit: 0x00
; CHECK-NEXT: DW_IDX_die_offset: 0x00000023
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: Entry @ {{.+}} {
; CHECK-NEXT: Abbrev: [[ABBREV1]]
; CHECK-NEXT: Tag: DW_TAG_structure_type
; CHECK-NEXT: DW_IDX_die_offset: 0x00000042
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
@@ -104,7 +104,7 @@
; CHECK-NEXT: Abbrev: [[ABBREV2]]
; CHECK-NEXT: Tag: DW_TAG_subprogram
; CHECK-NEXT: DW_IDX_die_offset: 0x00000023
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
@@ -117,7 +117,7 @@
; CHECK-NEXT: Tag: DW_TAG_base_type
; CHECK-NEXT: DW_IDX_type_unit: 0x00
; CHECK-NEXT: DW_IDX_die_offset: 0x00000038
-; CHECK-NEXT: DW_IDX_parent: true
+; CHECK-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-NEXT: }
; CHECK-NEXT: }
; CHECK-NEXT: ]
@@ -176,7 +176,7 @@
; CHECK-SPLIT-NEXT: Abbrev: [[ABBREV2]]
; CHECK-SPLIT-NEXT: Tag: DW_TAG_base_type
; CHECK-SPLIT-NEXT: DW_IDX_die_offset: 0x00000035
-; CHECK-SPLIT-NEXT: DW_IDX_parent: true
+; CHECK-SPLIT-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: ]
@@ -189,13 +189,13 @@
; CHECK-SPLIT-NEXT: Tag: DW_TAG_structure_type
; CHECK-SPLIT-NEXT: DW_IDX_type_unit: 0x00
; CHECK-SPLIT-NEXT: DW_IDX_die_offset: 0x00000021
-; CHECK-SPLIT-NEXT: DW_IDX_parent: true
+; CHECK-SPLIT-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: Entry @ {{.*}} {
; CHECK-SPLIT-NEXT: Abbrev: [[ABBREV]]
; CHECK-SPLIT-NEXT: Tag: DW_TAG_structure_type
; CHECK-SPLIT-NEXT: DW_IDX_die_offset: 0x00000039
-; CHECK-SPLIT-NEXT: DW_IDX_parent: true
+; CHECK-SPLIT-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: ]
@@ -207,7 +207,7 @@
; CHECK-SPLIT-NEXT: Abbrev: [[ABBREV3]]
; CHECK-SPLIT-NEXT: Tag: DW_TAG_subprogram
; CHECK-SPLIT-NEXT: DW_IDX_die_offset: 0x0000001a
-; CHECK-SPLIT-NEXT: DW_IDX_parent: true
+; CHECK-SPLIT-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: ]
@@ -220,7 +220,7 @@
; CHECK-SPLIT-NEXT: Tag: DW_TAG_base_type
; CHECK-SPLIT-NEXT: DW_IDX_type_unit: 0x00
; CHECK-SPLIT-NEXT: DW_IDX_die_offset: 0x00000036
-; CHECK-SPLIT-NEXT: DW_IDX_parent: true
+; CHECK-SPLIT-NEXT: DW_IDX_parent: <parent not indexed>
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: }
; CHECK-SPLIT-NEXT: ]
diff --git a/llvm/test/tools/dsymutil/ARM/accel-imported-declarations.test b/llvm/test/tools/dsymutil/ARM/accel-imported-declarations.test
index a8bf191e036f75a..8afbe34dcdbfb1d 100644
--- a/llvm/test/tools/dsymutil/ARM/accel-imported-declarations.test
+++ b/llvm/test/tools/dsymutil/ARM/accel-imported-declarations.test
@@ -23,13 +23,13 @@ DWARF-NEXT: Entry {{.*}} {
DWARF-NEXT: Abbrev: {{.*}}
DWARF-NEXT: Tag: DW_TAG_namespace
DWARF: DW_IDX_die_offset: [[NAMESPACE]]
-DWARF-NEXT: DW_IDX_parent: 0x{{.*}}
+DWARF-NEXT: DW_IDX_parent: Entry @ 0x{{.*}}
DWARF-NEXT: }
DWARF-NEXT: Entry {{.*}} {
DWARF-NEXT: Abbrev: {{.*}}
DWARF: Tag: DW_TAG_imported_declaration
DWARF: DW_IDX_die_offset: 0x0000005c
-DWARF-NEXT: DW_IDX_parent: 0x{{.*}}
+DWARF-NEXT: DW_IDX_parent: Entry @ 0x{{.*}}
DWARF-NEXT: }
DWARF-NEXT: }
|
clayborg
reviewed
Jan 19, 2024
| /// `this` Entry. If the parent is not in the table, nullopt is returned. | ||
| /// Precondition: hasParentInformation() == true. | ||
| /// An error is returned for ill-formed tables. | ||
| Expected<std::optional<DWARFDebugNames::Entry>> getParentDIEEntry() const; |
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Do we want expected and optional? Seems a bit much to double unwrap each time we call this?
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Yeah, this is the bit about this patch that I really dislike. But we have two distinct things we need to account for here:
- Invalid data: a bad offset for some reason. This is what the
Expectedis handling. - When the parent is present but not indexed by the table (e.g. the end of the parent chain). This is what the
optionalis handling.
We could remove the error handling portion (the Expected) and treat case 1 as if it were case 2, but it would make debugging the invalid data case a bit difficult, if we ever have to do that.
What do you think?
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(Drive-by) can you return some kind of no-data error for the parent-not-present case?
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Mmmm let me look into that, but I am not aware of other instances in LLVM where we use run-time type checking on the Error class to make decisions 🤔
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Since we have the boolean that tell us if the entry has a parent index case, can we remove the need for an error if we get a std::nullopt back but Entry::hasParentInformation() == true? I do agree this is nice for llvm-dwarfdump to get an error back and display it. If we just use the error somewhere, then it is worth adding.
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Another idea would be to have this function return an expected pair, where there is a bool indicating if there is parent info + Entry. Something like:
Expected<std::pair<bool, DWARFDebugNames::Entry>> getParentDIEEntry() const;
I am not a fan of std::pair in general though, so maybe this isn't any better.
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I think you reinvented std::optional there ;-)
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(Drive-by) can you return some kind of no-data error for the parent-not-present case?
I like the clean separation of errors that need to be logged/reported and unsuccessful lookups the current interface provides, as clumsy as it looks.
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So, given this discussion, I would like to propose we move forward with the interface as is.
As much as it looks off, I did put a lot of thought into this and our brainstorm session did not yield a better API.
This interface catches the reader's attention -- as it should -- because there are nuances on the return value that are only explained by reading the docs.
adrian-prantl
approved these changes
Jan 19, 2024
felipepiovezan
commented
Jan 19, 2024
|
I am ok with this as it is. |
felipepiovezan
added a commit
to felipepiovezan/llvm-project
that referenced
this pull request
Feb 2, 2024
This commit introduces a helper function to DWARFAcceleratorTable::Entry which follows DW_IDX_Parent attributes to returns the corresponding parent Entry in the table. It is tested by enhancing dwarfdump so that it now prints: 1. When data is corrupt. 2. When parent information is present, but the parent is not indexed. 3. The parent entry offset, when the parent is present and indexed. This is printed in terms a real entry offset (the same that gets printed at the start of each entry: "Entry @ 0x..."), instead of the encoded number in the table (which is an offset from the start off the Entry list). This makes it easy to visually inspect the dwarfdump and check what the parent is. (cherry picked from commit 380ac53)
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This commit introduces a helper function to DWARFAcceleratorTable::Entry which follows DW_IDX_Parent attributes to returns the corresponding parent Entry in the table.
It is tested by enhancing dwarfdump so that it now prints: