llvmbot
commented
2 months ago @llvm/issue-subscribers-clang-codegen
Author: None (mgschossmann)
When compiling following source, clang creates a virtual destructor for `A` with an artificial `vtt` argument. The `DILocalVariable` for `vtt` correctly has `arg: 2`.
However, the field `types` of the `DISubroutineType` for this virtual destructor seems to miss the additional parameter, as it only has two members and thus represents a function with only one parameter.
Source:
``` C
struct B {
virtual ~B() {}
};
struct A : virtual B {
};
A a;
```
LLVM-IR:
``` llvm
[...]
!5 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "A", file: !3, line: 5, size: 64, flags: DIFlagTypePassByReference | DIFlagNonTrivial, elements: !6, vtableHolder: !8, identifier: "_ZTS1A")
[...]
!34 = !DISubroutineType(types: !35)
!35 = !{null, !36}
!36 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !5, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
[...]
!70 = distinct !DISubprogram(name: "~A", linkageName: "_ZN1AD2Ev", scope: !5, file: !3, line: 5, type: !34, scopeLine: 5, flags: DIFlagArtificial | DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !2, declaration: !44, retainedNodes: !38)
!71 = !DILocalVariable(name: "this", arg: 1, scope: !70, type: !40, flags: DIFlagArtificial | DIFlagObjectPointer)
!72 = !DILocation(line: 0, scope: !70)
!73 = !DILocalVariable(name: "vtt", arg: 2, scope: !70, type: !74, flags: DIFlagArtificial)
!74 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !75, size: 64)
!75 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
[...]
```
I generated the IR using clang 19.1.0-rc2 on `x86_64-unknown-linux-gnu`.
DWARF generated from this IR is not affected and includes all formal parameters.
The issue seems to be that in `ItaniumCXXABI::addImplicitStructorParams`, the parameter is added, but in `CGDebugInfo::getOrCreateMethodType` another type array is read to create the `DISubroutineType`.
https://github.com/llvm/llvm-project/blob/d033ae172d1c5a85fd09c36e23608a9241ea2990/clang/lib/CodeGen/ItaniumCXXABI.cpp#L1870-L1890
https://github.com/llvm/llvm-project/blob/d033ae172d1c5a85fd09c36e23608a9241ea2990/clang/lib/CodeGen/CGDebugInfo.cpp#L1938-L1946
When compiling following source, clang creates a virtual destructor for
Awith an artificialvttargument. TheDILocalVariableforvttcorrectly hasarg: 2. However, the fieldtypesof theDISubroutineTypefor this virtual destructor seems to miss the additional parameter, as it only has two members and thus represents a function with only one parameter.Source:
LLVM-IR:
I generated the IR using clang 19.1.0-rc2 on
x86_64-unknown-linux-gnu. DWARF generated from this IR is not affected and includes all formal parameters.The issue seems to be that in
ItaniumCXXABI::addImplicitStructorParams, the parameter is added, but inCGDebugInfo::getOrCreateMethodTypeanother type array is read to create theDISubroutineType.https://github.com/llvm/llvm-project/blob/d033ae172d1c5a85fd09c36e23608a9241ea2990/clang/lib/CodeGen/ItaniumCXXABI.cpp#L1870-L1890
https://github.com/llvm/llvm-project/blob/d033ae172d1c5a85fd09c36e23608a9241ea2990/clang/lib/CodeGen/CGDebugInfo.cpp#L1938-L1946