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Fix debug info metadata for string types #156379

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@demoitem demoitem commented Sep 2, 2025

ExtractMDNode in Core.cpp was asserting if the value input was string metadata.
This change fixes that and allows getting "llvm.ident" into the IR
Fixes issue #142367

@demoitem demoitem requested a review from nikic as a code owner September 2, 2025 00:41
@llvmbot llvmbot added the llvm:ir label Sep 2, 2025
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llvmbot commented Sep 2, 2025

@llvm/pr-subscribers-llvm-ir

Author: peter mckinna (demoitem)

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ExtractMDNode in Core.cpp was asserting if the value input was string metadata.
This change fixes that and allows getting "llvm.ident" into the IR
Fixes issue #142367

Full diff: https://github.com/llvm/llvm-project/pull/156379.diff

3 Files Affected:

  • (modified) llvm/lib/IR/Core.cpp (+3-2)
  • (modified) llvm/test/Bindings/llvm-c/debug_info_new_format.ll (+45-43)
  • (modified) llvm/tools/llvm-c-test/debuginfo.c (+6)
diff --git a/llvm/lib/IR/Core.cpp b/llvm/lib/IR/Core.cpp
index 8b5965ba45a6d..26352ef2106db 100644
--- a/llvm/lib/IR/Core.cpp
+++ b/llvm/lib/IR/Core.cpp
@@ -1090,8 +1090,9 @@ LLVMValueRef LLVMGetMetadata(LLVMValueRef Inst, unsigned KindID) {
 // This undoes this canonicalization, reconstructing the MDNode.
 static MDNode *extractMDNode(MetadataAsValue *MAV) {
   Metadata *MD = MAV->getMetadata();
-  assert((isa<MDNode>(MD) || isa<ConstantAsMetadata>(MD)) &&
-      "Expected a metadata node or a canonicalized constant");
+  assert(
+      (isa<MDNode>(MD) || isa<ConstantAsMetadata>(MD) || isa<MDString>(MD)) &&
+      "Expected a metadata node, a canonicalized constant or a string");
 
   if (MDNode *N = dyn_cast<MDNode>(MD))
     return N;
diff --git a/llvm/test/Bindings/llvm-c/debug_info_new_format.ll b/llvm/test/Bindings/llvm-c/debug_info_new_format.ll
index 83b37da759b5c..5972b4af02c8e 100644
--- a/llvm/test/Bindings/llvm-c/debug_info_new_format.ll
+++ b/llvm/test/Bindings/llvm-c/debug_info_new_format.ll
@@ -4,34 +4,35 @@
 ; CHECK: ; ModuleID = 'debuginfo.c'
 ; CHECK-NEXT: source_filename = "debuginfo.c"
  
-; CHECK:      define i64 @foo(i64 %0, i64 %1, <10 x i64> %2) !dbg !44 {
+; CHECK:      define i64 @foo(i64 %0, i64 %1, <10 x i64> %2) !dbg !45 {
 ; CHECK-NEXT: entry:
-; CHECK-NEXT:     #dbg_declare(i64 0, !49, !DIExpression(), !58)
-; CHECK-NEXT:     #dbg_declare(i64 0, !50, !DIExpression(), !58)
-; CHECK-NEXT:     #dbg_declare(i64 0, !51, !DIExpression(), !58)
-; CHECK-NEXT:     #dbg_label(!59, !58)
+; CHECK-NEXT:     #dbg_declare(i64 0, !50, !DIExpression(), !59)
+; CHECK-NEXT:     #dbg_declare(i64 0, !51, !DIExpression(), !59)
+; CHECK-NEXT:     #dbg_declare(i64 0, !52, !DIExpression(), !59)
+; CHECK-NEXT:     #dbg_label(!60, !59)
 ; CHECK-NEXT:   br label %vars
-; CHECK-NEXT:     #dbg_label(!60, !58)
+; CHECK-NEXT:     #dbg_label(!61, !59)
 ; CHECK-NEXT:   br label %vars
  
 ; CHECK:      vars:                                             ; preds = %entry, %entry
 ; CHECK-NEXT:   %p1 = phi i64 [ 0, %entry ]
 ; CHECK-NEXT:   %p2 = phi i64 [ 0, %entry ]
-; CHECK-NEXT:     #dbg_value(i64 0, !42, !DIExpression(DW_OP_constu, 0, DW_OP_stack_value), !61)
-; CHECK-NEXT:     #dbg_value(i64 1, !52, !DIExpression(DW_OP_constu, 1, DW_OP_stack_value), !61)
+; CHECK-NEXT:     #dbg_value(i64 0, !43, !DIExpression(DW_OP_constu, 0, DW_OP_stack_value), !62)
+; CHECK-NEXT:     #dbg_value(i64 1, !53, !DIExpression(DW_OP_constu, 1, DW_OP_stack_value), !62)
 ; CHECK-NEXT:   %a = add i64 %p1, %p2
 ; CHECK-NEXT:   ret i64 0
 ; CHECK-NEXT: }
  
 ; CHECK:      !llvm.dbg.cu = !{!0}
-; CHECK-NEXT: !FooType = !{!33}
+; CHECK-NEXT: !llvm.ident = !{!33}
+; CHECK-NEXT: !FooType = !{!34}
 ; CHECK-NEXT: !EnumTest = !{!3}
 ; CHECK-NEXT: !LargeEnumTest = !{!11}
-; CHECK-NEXT: !SubrangeType = !{!36}
-; CHECK-NEXT: !SetType1 = !{!37}
-; CHECK-NEXT: !SetType2 = !{!38}
-; CHECK-NEXT: !DynType = !{!39}
-; CHECK-NEXT: !ClassType = !{!54}
+; CHECK-NEXT: !SubrangeType = !{!37}
+; CHECK-NEXT: !SetType1 = !{!38}
+; CHECK-NEXT: !SetType2 = !{!39}
+; CHECK-NEXT: !DynType = !{!40}
+; CHECK-NEXT: !ClassType = !{!55}
  
 ; CHECK:      !0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "llvm-c-test", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !16, imports: !24, macros: !28, splitDebugInlining: false, sysroot: "/")
 ; CHECK-NEXT: !1 = !DIFile(filename: "debuginfo.c", directory: ".")
@@ -66,32 +67,33 @@
 ; CHECK-NEXT: !30 = !{!31, !32}
 ; CHECK-NEXT: !31 = !DIMacro(type: DW_MACINFO_define, name: "SIMPLE_DEFINE")
 ; CHECK-NEXT: !32 = !DIMacro(type: DW_MACINFO_define, name: "VALUE_DEFINE", value: "1")
-; CHECK-NEXT: !33 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !34, size: 192, dwarfAddressSpace: 0)
-; CHECK-NEXT: !34 = !DICompositeType(tag: DW_TAG_structure_type, name: "MyStruct", scope: !4, file: !1, size: 192, elements: !35, runtimeLang: DW_LANG_C89, identifier: "MyStruct")
-; CHECK-NEXT: !35 = !{!6, !6, !6}
-; CHECK-NEXT: !36 = !DISubrangeType(name: "foo", scope: !1, file: !1, line: 42, size: 64, baseType: !6, lowerBound: i64 0, upperBound: i64 1, stride: i64 8, bias: i64 4)
-; CHECK-NEXT: !37 = !DIDerivedType(tag: DW_TAG_set_type, name: "enumset", scope: !1, file: !1, line: 42, baseType: !3, size: 64)
-; CHECK-NEXT: !38 = !DIDerivedType(tag: DW_TAG_set_type, name: "subrangeset", scope: !1, file: !1, line: 42, baseType: !36, size: 64)
-; CHECK-NEXT: !39 = !DICompositeType(tag: DW_TAG_array_type, name: "foo", scope: !1, file: !1, line: 42, baseType: !6, size: 640, elements: !40, dataLocation: !DIExpression(), associated: !42, rank: !DIExpression())
-; CHECK-NEXT: !40 = !{!41}
-; CHECK-NEXT: !41 = !DISubrange(count: 10, lowerBound: 0)
-; CHECK-NEXT: !42 = !DILocalVariable(name: "d", scope: !43, file: !1, line: 43, type: !6)
-; CHECK-NEXT: !43 = distinct !DILexicalBlock(scope: !44, file: !1, line: 42)
-; CHECK-NEXT: !44 = distinct !DISubprogram(name: "foo", linkageName: "foo", scope: !1, file: !1, line: 42, type: !45, scopeLine: 42, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0, retainedNodes: !48)
-; CHECK-NEXT: !45 = !DISubroutineType(types: !46)
-; CHECK-NEXT: !46 = !{!6, !6, !47}
-; CHECK-NEXT: !47 = !DICompositeType(tag: DW_TAG_array_type, baseType: !6, size: 640, flags: DIFlagVector, elements: !40)
-; CHECK-NEXT: !48 = !{!49, !50, !51, !42, !52, !53}
-; CHECK-NEXT: !49 = !DILocalVariable(name: "a", arg: 1, scope: !44, file: !1, line: 42, type: !6)
-; CHECK-NEXT: !50 = !DILocalVariable(name: "b", arg: 2, scope: !44, file: !1, line: 42, type: !6)
-; CHECK-NEXT: !51 = !DILocalVariable(name: "c", arg: 3, scope: !44, file: !1, line: 42, type: !47)
-; CHECK-NEXT: !52 = !DILocalVariable(name: "e", scope: !43, file: !1, line: 44, type: !6)
-; CHECK-NEXT: !53 = !DILabel(scope: !44, name: "label3", file: !1, line: 42)
-; CHECK-NEXT: !54 = !DICompositeType(tag: DW_TAG_class_type, name: "Class", scope: !4, file: !1, size: 192, flags: DIFlagFwdDecl, elements: !55, identifier: "FooClass")
-; CHECK-NEXT: !55 = !{!56}
-; CHECK-NEXT: !56 = !{!6, !6, !57}
-; CHECK-NEXT: !57 = !DIBasicType(name: "Int32", size: 32)
-; CHECK-NEXT: !58 = !DILocation(line: 42, scope: !44)
-; CHECK-NEXT: !59 = !DILabel(scope: !44, name: "label1", file: !1, line: 42)
-; CHECK-NEXT: !60 = !DILabel(scope: !44, name: "label2", file: !1, line: 42)
-; CHECK-NEXT: !61 = !DILocation(line: 43, scope: !44)
+; CHECK-NEXT: !33 = !{!"Version 1.0"}
+; CHECK-NEXT: !34 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !35, size: 192, dwarfAddressSpace: 0)
+; CHECK-NEXT: !35 = !DICompositeType(tag: DW_TAG_structure_type, name: "MyStruct", scope: !4, file: !1, size: 192, elements: !36, runtimeLang: DW_LANG_C89, identifier: "MyStruct")
+; CHECK-NEXT: !36 = !{!6, !6, !6}
+; CHECK-NEXT: !37 = !DISubrangeType(name: "foo", scope: !1, file: !1, line: 42, size: 64, baseType: !6, lowerBound: i64 0, upperBound: i64 1, stride: i64 8, bias: i64 4)
+; CHECK-NEXT: !38 = !DIDerivedType(tag: DW_TAG_set_type, name: "enumset", scope: !1, file: !1, line: 42, baseType: !3, size: 64)
+; CHECK-NEXT: !39 = !DIDerivedType(tag: DW_TAG_set_type, name: "subrangeset", scope: !1, file: !1, line: 42, baseType: !37, size: 64)
+; CHECK-NEXT: !40 = !DICompositeType(tag: DW_TAG_array_type, name: "foo", scope: !1, file: !1, line: 42, baseType: !6, size: 640, elements: !41, dataLocation: !DIExpression(), associated: !43, rank: !DIExpression())
+; CHECK-NEXT: !41 = !{!42}
+; CHECK-NEXT: !42 = !DISubrange(count: 10, lowerBound: 0)
+; CHECK-NEXT: !43 = !DILocalVariable(name: "d", scope: !44, file: !1, line: 43, type: !6)
+; CHECK-NEXT: !44 = distinct !DILexicalBlock(scope: !45, file: !1, line: 42)
+; CHECK-NEXT: !45 = distinct !DISubprogram(name: "foo", linkageName: "foo", scope: !1, file: !1, line: 42, type: !46, scopeLine: 42, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0, retainedNodes: !49)
+; CHECK-NEXT: !46 = !DISubroutineType(types: !47)
+; CHECK-NEXT: !47 = !{!6, !6, !48}
+; CHECK-NEXT: !48 = !DICompositeType(tag: DW_TAG_array_type, baseType: !6, size: 640, flags: DIFlagVector, elements: !41)
+; CHECK-NEXT: !49 = !{!50, !51, !52, !43, !53, !54}
+; CHECK-NEXT: !50 = !DILocalVariable(name: "a", arg: 1, scope: !45, file: !1, line: 42, type: !6)
+; CHECK-NEXT: !51 = !DILocalVariable(name: "b", arg: 2, scope: !45, file: !1, line: 42, type: !6)
+; CHECK-NEXT: !52 = !DILocalVariable(name: "c", arg: 3, scope: !45, file: !1, line: 42, type: !48)
+; CHECK-NEXT: !53 = !DILocalVariable(name: "e", scope: !44, file: !1, line: 44, type: !6)
+; CHECK-NEXT: !54 = !DILabel(scope: !45, name: "label3", file: !1, line: 42)
+; CHECK-NEXT: !55 = !DICompositeType(tag: DW_TAG_class_type, name: "Class", scope: !4, file: !1, size: 192, flags: DIFlagFwdDecl, elements: !56, identifier: "FooClass")
+; CHECK-NEXT: !56 = !{!57}
+; CHECK-NEXT: !57 = !{!6, !6, !58}
+; CHECK-NEXT: !58 = !DIBasicType(name: "Int32", size: 32)
+; CHECK-NEXT: !59 = !DILocation(line: 42, scope: !45)
+; CHECK-NEXT: !60 = !DILabel(scope: !45, name: "label1", file: !1, line: 42)
+; CHECK-NEXT: !61 = !DILabel(scope: !45, name: "label2", file: !1, line: 42)
+; CHECK-NEXT: !62 = !DILocation(line: 43, scope: !45)
diff --git a/llvm/tools/llvm-c-test/debuginfo.c b/llvm/tools/llvm-c-test/debuginfo.c
index 0f09c74a476bb..476e14e8e05e3 100644
--- a/llvm/tools/llvm-c-test/debuginfo.c
+++ b/llvm/tools/llvm-c-test/debuginfo.c
@@ -54,6 +54,12 @@ int llvm_test_dibuilder(void) {
                               "/test/include/llvm-c-test.h", 27,
                               "", 0);
 
+  const char VerStr[] = "Version 1.0";
+  LLVMMetadataRef VerMD =
+      LLVMMDStringInContext2(LLVMGetModuleContext(M), VerStr, strlen(VerStr));
+  LLVMValueRef StrMD = LLVMMetadataAsValue(LLVMGetModuleContext(M), VerMD);
+  LLVMAddNamedMetadataOperand(M, "llvm.ident", StrMD);
+
   LLVMMetadataRef OtherModule =
     LLVMDIBuilderCreateModule(DIB, CompileUnit,
                               "llvm-c-test-import", 18,

nikic
nikic reviewed Sep 2, 2025
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Not sure this is right. My understanding is that extractMDNode is supposed to undo canonicalizeMetadataForValue(), which doesn't do anything for MDString.

Isn't the problem here just that you're missing one level of MDNode wrapper in your construction logic? After all, the value is not !"Version 1.0", it's !{!"Version 1.0"}.

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demoitem commented Sep 4, 2025

I am not sure what you mean. I have to admit I am not metadata expert. If you can suggest a simpler way for me
to get a string as metadata value into LLVMAddNamedMetadataOperand, or some way to get llvm.ident into the IR,
I will implement that.
The thing is this change works and (maybe unintentionally) produces the tag !{!"Version 1.0"} as can be seen
in the running the test case and checking the IR. In my own testing I can see the ident tag in the assembly after
running through llc.

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