[DebugInfo] Implement TAG_label entries for debug_names #71724
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The DWARF 5 specification says that: > The name index must contain an entry for each debugging information entry that > defines a named [...] label [...]. The verifier currently verifies this, but the AsmPrinter does not add entries for TAG_labels in debug_names. This patch addresses the issue by ensuring we add labels in the accelerator tables once we have a fully completed DIE for the TAG_label entry. We also respect the spec as follows: > DW_TAG_label debugging information entries without an address attribute > (DW_AT_low_pc, DW_AT_high_pc, DW_AT_ranges, or DW_AT_entry_pc) are excluded. The effect of this on the size of accelerator tables is minimal, as TAG_labels are usually created by C/C++ labels (see example in test), which are typically paired with "goto" statements.
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@llvm/pr-subscribers-debuginfo Author: Felipe de Azevedo Piovezan (felipepiovezan) ChangesThe DWARF 5 specification says that: > The name index must contain an entry for each debugging information entry that The verifier currently verifies this, but the AsmPrinter does not add entries for TAG_labels in debug_names. This patch addresses the issue by ensuring we add labels in the accelerator tables once we have a fully completed DIE for the TAG_label entry. We also respect the spec as follows: The effect of this on the size of accelerator tables is minimal, as TAG_labels are usually created by C/C++ labels (see example in test), which are typically paired with "goto" statements. Full diff: https://github.com/llvm/llvm-project/pull/71724.diff 2 Files Affected:
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 42bf755737506b4..feb5ab665a17d8c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -1422,9 +1422,18 @@ void DwarfCompileUnit::finishEntityDefinition(const DbgEntity *Entity) {
llvm_unreachable("DbgEntity must be DbgVariable or DbgLabel.");
}
- if (Label)
- if (const auto *Sym = Label->getSymbol())
- addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
+ if (!Label)
+ return;
+
+ const auto *Sym = Label->getSymbol();
+ if (!Sym)
+ return;
+
+ addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
+
+ // A TAG_label with a name and an AT_low_pc must be placed in debug_names.
+ if (StringRef Name = Label->getName(); !Name.empty())
+ getDwarfDebug().addAccelName(*CUNode, Name, *Die);
}
DbgEntity *DwarfCompileUnit::getExistingAbstractEntity(const DINode *Node) {
diff --git a/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll b/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll
index 8cd1f0c18292093..e5fd6be033ca767 100644
--- a/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll
+++ b/llvm/test/DebugInfo/X86/debug-names-dwarf64.ll
@@ -10,6 +10,10 @@
; CHECK-NEXT: DW_AT_name ("foo")
; CHECK: [[TYPEDIE:.+]]: DW_TAG_base_type
; CHECK-NEXT: DW_AT_name ("int")
+; CHECK: [[SPDIE:.+]]: DW_TAG_subprogram
+; CHECK: DW_AT_name ("func")
+; CHECK: [[LABELDIE:.+]]: DW_TAG_label
+; CHECK-NEXT: DW_AT_name ("MyLabel")
; CHECK: .debug_names contents:
; CHECK-NEXT: Name Index @ 0x0 {
@@ -19,8 +23,8 @@
; CHECK-NEXT: CU count: 1
; CHECK-NEXT: Local TU count: 0
; CHECK-NEXT: Foreign TU count: 0
-; CHECK-NEXT: Bucket count: 2
-; CHECK-NEXT: Name count: 2
+; CHECK-NEXT: Bucket count: 4
+; CHECK-NEXT: Name count: 4
; CHECK: }
; CHECK-NEXT: Compilation Unit offsets [
; CHECK-NEXT: CU[0]: 0x00000000
@@ -30,6 +34,14 @@
; CHECK-NEXT: Tag: DW_TAG_variable
; CHECK-NEXT: DW_IDX_die_offset: DW_FORM_ref4
; CHECK-NEXT: }
+; CHECK-NEXT: Abbreviation [[ABBREV_SP:0x[0-9a-f]*]] {
+; CHECK-NEXT: Tag: DW_TAG_subprogram
+; CHECK-NEXT: DW_IDX_die_offset: DW_FORM_ref4
+; CHECK-NEXT: }
+; CHECK-NEXT: Abbreviation [[ABBREV_LABEL:0x[0-9a-f]*]] {
+; CHECK-NEXT: Tag: DW_TAG_label
+; CHECK-NEXT: DW_IDX_die_offset: DW_FORM_ref4
+; CHECK-NEXT: }
; CHECK-NEXT: Abbreviation [[ABBREV:0x[0-9a-f]*]] {
; CHECK-NEXT: Tag: DW_TAG_base_type
; CHECK-NEXT: DW_IDX_die_offset: DW_FORM_ref4
@@ -56,6 +68,29 @@
; CHECK-NEXT: DW_IDX_die_offset: [[VARDIE]]
; CHECK-NEXT: }
; CHECK-NEXT: }
+; CHECK-NEXT: Name 3 {
+; CHECK-NEXT: Hash: 0x7C96FE71
+; CHECK-NEXT: String: {{.+}} "func"
+; CHECK-NEXT: Entry @ {{.+}} {
+; CHECK-NEXT: Abbrev: [[ABBREV_SP]]
+; CHECK-NEXT: Tag: DW_TAG_subprogram
+; CHECK-NEXT: DW_IDX_die_offset: [[SPDIE]]
+; CHECK-NEXT: }
+; CHECK-NEXT: }
+; CHECK-NEXT: ]
+; CHECK-NEXT: Bucket 2 [
+; CHECK-NEXT: EMPTY
+; CHECK-NEXT: ]
+; CHECK-NEXT: Bucket 3 [
+; CHECK-NEXT: Name 4 {
+; CHECK-NEXT: Hash: 0xEC64E52B
+; CHECK-NEXT: String: {{.+}} "MyLabel"
+; CHECK-NEXT: Entry @ {{.+}} {
+; CHECK-NEXT: Abbrev: [[ABBREV_LABEL]]
+; CHECK-NEXT: Tag: DW_TAG_label
+; CHECK-NEXT: DW_IDX_die_offset: [[LABELDIE]]
+; CHECK-NEXT: }
+; CHECK-NEXT: }
; CHECK-NEXT: ]
; CHECK-NEXT: }
@@ -64,12 +99,25 @@
; IR generated and reduced from:
; $ cat foo.c
; int foo;
+; void func() {
+; goto MyLabel;
+;
+; MyLabel:
+; return 1;
+; }
; $ clang -g -gpubnames -S -emit-llvm foo.c -o foo.ll
target triple = "x86_64-unknown-linux-gnu"
@foo = dso_local global i32 0, align 4, !dbg !0
+define void @func() !dbg !11 {
+ call void @llvm.dbg.label(metadata !15), !dbg !14
+ ret void, !dbg !14
+}
+
+declare void @llvm.dbg.label(metadata)
+
!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!7, !8, !9}
!llvm.ident = !{!10}
@@ -85,3 +133,8 @@ target triple = "x86_64-unknown-linux-gnu"
!8 = !{i32 2, !"Debug Info Version", i32 3}
!9 = !{i32 1, !"wchar_size", i32 4}
!10 = !{!"clang version 12.0.0"}
+!11 = distinct !DISubprogram(name: "func", linkageName: "func", scope: !3, file: !3, line: 2, type: !12, unit: !2)
+!12 = !DISubroutineType(types: !13)
+!13 = !{null}
+!14 = !DILocation(line: 2, column: 13, scope: !11)
+!15 = !DILabel(scope: !11, name: "MyLabel", file: !3, line: 5)
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adrian-prantl
approved these changes
Nov 13, 2023
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I will go ahead and merge this, since it seems fairly straightforward. |
felipepiovezan
added a commit
to felipepiovezan/llvm-project
that referenced
this pull request
Nov 13, 2023
The DWARF 5 specification says that: > The name index must contain an entry for each debugging information entry that > defines a named [...] label [...]. The verifier currently verifies this, but the AsmPrinter does not add entries for TAG_labels in debug_names. This patch addresses the issue by ensuring we add labels in the accelerator tables once we have a fully completed DIE for the TAG_label entry. We also respect the spec as follows: > DW_TAG_label debugging information entries without an address attribute > (DW_AT_low_pc, DW_AT_high_pc, DW_AT_ranges, or DW_AT_entry_pc) are excluded. The effect of this on the size of accelerator tables is minimal, as TAG_labels are usually created by C/C++ labels (see example in test), which are typically paired with "goto" statements. (cherry picked from commit a195d1f)
zahiraam
pushed a commit
to zahiraam/llvm-project
that referenced
this pull request
Nov 20, 2023
The DWARF 5 specification says that: > The name index must contain an entry for each debugging information entry that > defines a named [...] label [...]. The verifier currently verifies this, but the AsmPrinter does not add entries for TAG_labels in debug_names. This patch addresses the issue by ensuring we add labels in the accelerator tables once we have a fully completed DIE for the TAG_label entry. We also respect the spec as follows: > DW_TAG_label debugging information entries without an address attribute > (DW_AT_low_pc, DW_AT_high_pc, DW_AT_ranges, or DW_AT_entry_pc) are excluded. The effect of this on the size of accelerator tables is minimal, as TAG_labels are usually created by C/C++ labels (see example in test), which are typically paired with "goto" statements.
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The DWARF 5 specification says that:
The verifier currently verifies this, but the AsmPrinter does not add entries for TAG_labels in debug_names. This patch addresses the issue by ensuring we add labels in the accelerator tables once we have a fully completed DIE for the TAG_label entry.
We also respect the spec as follows:
The effect of this on the size of accelerator tables is minimal, as TAG_labels are usually created by C/C++ labels (see example in test), which are typically paired with "goto" statements.