[llvm] [LLVM][DebugInfo]Allow ExtraData field to be a node reference (PR #165023)
Laxman Sole via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 24 10:58:00 PDT 2025
https://github.com/laxmansole created https://github.com/llvm/llvm-project/pull/165023
This change enhances debug info metadata handling to support node references in the `extraData` field for `DW_TAG_member`, `DW_TAG_variable`, and `DW_TAG_inheritance` tags.
The change enables LLVM to handle both direct constant values (e.g., extraData: i8 1) and node references (e.g., extraData: !18 where !18 = !{ i8 1 }).
>From 1c2088cb11e262eadbef42a28d555c6a46ecd088 Mon Sep 17 00:00:00 2001
From: Laxman Sole <lsole at nvidia.com>
Date: Wed, 22 Oct 2025 14:12:45 -0700
Subject: [PATCH] Allow ExtraData field to be a node reference when used with
DW_TAG_member/variable/inheritance
---
llvm/lib/IR/DebugInfoMetadata.cpp | 21 ++++-
.../DebugInfo/extradata-node-reference.ll | 91 +++++++++++++++++++
2 files changed, 108 insertions(+), 4 deletions(-)
create mode 100644 llvm/test/DebugInfo/extradata-node-reference.ll
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index e30df88e6b56b5..0113b02547c43a 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -959,16 +959,29 @@ DIType *DIDerivedType::getClassType() const {
assert(getTag() == dwarf::DW_TAG_ptr_to_member_type);
return cast_or_null<DIType>(getExtraData());
}
+
+// Helper function to extract ConstantAsMetadata from ExtraData,
+// handling extra data MDTuple unwrapping if needed.
+static ConstantAsMetadata *extractConstantMetadata(Metadata *ExtraData) {
+ Metadata *ED = ExtraData;
+ while (auto *Tuple = dyn_cast_or_null<MDTuple>(ED)) {
+ if (Tuple->getNumOperands() != 1)
+ return nullptr;
+ ED = Tuple->getOperand(0);
+ }
+ return cast_or_null<ConstantAsMetadata>(ED);
+}
+
uint32_t DIDerivedType::getVBPtrOffset() const {
assert(getTag() == dwarf::DW_TAG_inheritance);
- if (auto *CM = cast_or_null<ConstantAsMetadata>(getExtraData()))
+ if (auto *CM = extractConstantMetadata(getExtraData()))
if (auto *CI = dyn_cast_or_null<ConstantInt>(CM->getValue()))
return static_cast<uint32_t>(CI->getZExtValue());
return 0;
}
Constant *DIDerivedType::getStorageOffsetInBits() const {
assert(getTag() == dwarf::DW_TAG_member && isBitField());
- if (auto *C = cast_or_null<ConstantAsMetadata>(getExtraData()))
+ if (auto *C = extractConstantMetadata(getExtraData()))
return C->getValue();
return nullptr;
}
@@ -977,13 +990,13 @@ Constant *DIDerivedType::getConstant() const {
assert((getTag() == dwarf::DW_TAG_member ||
getTag() == dwarf::DW_TAG_variable) &&
isStaticMember());
- if (auto *C = cast_or_null<ConstantAsMetadata>(getExtraData()))
+ if (auto *C = extractConstantMetadata(getExtraData()))
return C->getValue();
return nullptr;
}
Constant *DIDerivedType::getDiscriminantValue() const {
assert(getTag() == dwarf::DW_TAG_member && !isStaticMember());
- if (auto *C = cast_or_null<ConstantAsMetadata>(getExtraData()))
+ if (auto *C = extractConstantMetadata(getExtraData()))
return C->getValue();
return nullptr;
}
diff --git a/llvm/test/DebugInfo/extradata-node-reference.ll b/llvm/test/DebugInfo/extradata-node-reference.ll
new file mode 100644
index 00000000000000..03240bf9920d54
--- /dev/null
+++ b/llvm/test/DebugInfo/extradata-node-reference.ll
@@ -0,0 +1,91 @@
+;; Test verifies that node reference in the extraData field are handled correctly
+;; when used with tags like DW_TAG_member, DW_TAG_inheritance etc.
+
+; REQUIRES: object-emission
+; RUN: %llc_dwarf %s -filetype=obj -o - | llvm-dwarfdump - | FileCheck %s
+
+; Example 1: BitField with storage offset (extraData: i64 0)
+%struct.BitField = type { i8 }
+ at bf = global %struct.BitField zeroinitializer, !dbg !9
+
+; Example 2: Static member with constant value (extraData: i32 42)
+%struct.Static = type { i32 }
+ at st = global %struct.Static zeroinitializer, !dbg !16
+
+; Example 3: Discriminant value for variant (extraData: i32 100)
+%union.Variant = type { [8 x i8] }
+ at var = global %union.Variant zeroinitializer, !dbg !24
+
+; Example 4: Inheritance VBPtr offset (extraData: i32 0)
+%class.Derived = type { i32 }
+ at der = global %class.Derived zeroinitializer, !dbg !35
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 11.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, globals: !8)
+!1 = !DIFile(filename: "test.cpp", directory: ".")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !{i32 1, !"wchar_size", i32 4}
+!4 = !{i32 2, !"Dwarf Version", i32 5}
+!8 = !{!9, !16, !24, !35}
+
+; extraData node definitions
+!15 = !{i64 0} ; BitField storage offset
+!22 = !{i32 42} ; Static member constant value
+!33 = !{!42}
+!41 = !{i32 0} ; VBPtr offset
+!42 = !{i32 100} ; Discriminant value
+
+; CHECK: {{.*}} DW_TAG_variable
+; CHECK: {{.*}} DW_AT_name ("bf")
+; CHECK: {{.*}} DW_TAG_member
+; CHECK: {{.*}} DW_AT_name ("field")
+; === BitField: extraData holds storage offset ===
+!9 = !DIGlobalVariableExpression(var: !10, expr: !DIExpression())
+!10 = distinct !DIGlobalVariable(name: "bf", scope: !0, file: !1, line: 5, type: !11, isLocal: false, isDefinition: true)
+!11 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "BitField", file: !1, line: 5, size: 8, elements: !12)
+!12 = !{!13}
+!13 = !DIDerivedType(tag: DW_TAG_member, name: "field", scope: !11, file: !1, line: 6, baseType: !14, size: 3, flags: DIFlagBitField, extraData: !15)
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+
+; CHECK: {{.*}} DW_TAG_variable
+; CHECK: {{.*}} DW_AT_name ("st")
+; CHECK: {{.*}} DW_TAG_member
+; CHECK: {{.*}} DW_AT_name ("const_val")
+; CHECK: {{.*}} DW_AT_const_value (42)
+; === Static Member: extraData holds constant value ===
+!16 = !DIGlobalVariableExpression(var: !17, expr: !DIExpression())
+!17 = distinct !DIGlobalVariable(name: "st", scope: !0, file: !1, line: 10, type: !18, isLocal: false, isDefinition: true)
+!18 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Static", file: !1, line: 10, size: 32, elements: !19)
+!19 = !{!20}
+!20 = !DIDerivedType(tag: DW_TAG_member, name: "const_val", scope: !18, file: !1, line: 11, baseType: !21, flags: DIFlagStaticMember, extraData: !22)
+!21 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !14)
+
+; CHECK: {{.*}} DW_TAG_variable
+; CHECK: {{.*}} DW_AT_name ("var")
+; CHECK: {{.*}} DW_TAG_member
+; CHECK: {{.*}} DW_AT_name ("variant_none")
+; CHECK: {{.*}} DW_AT_discr_value (0x64)
+; === Discriminant: extraData holds discriminant value ===
+!24 = !DIGlobalVariableExpression(var: !25, expr: !DIExpression())
+!25 = distinct !DIGlobalVariable(name: "var", scope: !0, file: !1, line: 15, type: !26, isLocal: false, isDefinition: true)
+!26 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Variant", file: !1, line: 15, size: 128, elements: !27)
+!27 = !{!28}
+!28 = !DICompositeType(tag: DW_TAG_variant_part, scope: !26, file: !1, size: 128, elements: !29, discriminator: !30)
+!29 = !{!31, !32}
+!30 = !DIDerivedType(tag: DW_TAG_member, scope: !28, file: !1, baseType: !14, size: 32, align: 32, flags: DIFlagArtificial)
+!31 = !DIDerivedType(tag: DW_TAG_member, name: "variant_none", scope: !28, file: !1, baseType: !14, size: 32)
+!32 = !DIDerivedType(tag: DW_TAG_member, name: "variant_some", scope: !28, file: !1, baseType: !14, size: 32, extraData: !33)
+
+; CHECK: {{.*}} DW_TAG_variable
+; CHECK: {{.*}} DW_AT_name ("der")
+; CHECK: {{.*}} DW_TAG_inheritance
+; CHECK: {{.*}} DW_AT_type ({{.*}} "Base")
+; === Inheritance: extraData holds VBPtr offset ===
+!35 = !DIGlobalVariableExpression(var: !36, expr: !DIExpression())
+!36 = distinct !DIGlobalVariable(name: "der", scope: !0, file: !1, line: 20, type: !37, isLocal: false, isDefinition: true)
+!37 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Derived", file: !1, line: 20, size: 32, elements: !38)
+!38 = !{!39}
+!39 = !DIDerivedType(tag: DW_TAG_inheritance, scope: !37, baseType: !40, extraData: !41)
+!40 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Base", file: !1, line: 19, size: 32)
More information about the llvm-commits
mailing list