[clang] [llvm] [clang][DebugInfo] Emit DW_AT_object_pointer on function declarations with explicit `this` (PR #122928)
Michael Buch via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 17 06:24:53 PST 2025
https://github.com/Michael137 updated https://github.com/llvm/llvm-project/pull/122928
>From 88125a0f3a28d49877cedfd4350ab6e0f37185ed Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Tue, 14 Jan 2025 11:33:33 +0000
Subject: [PATCH] [clang][DebugInfo] Emit DW_AT_object_pointer on function
definitions with explicit `this`
We currently don't emit `DW_AT_object_pointer` on function
declarations or definitions. The DWARFv5 spec doesn't mandate
this attribute be present *only* for implicit object parameters:
```
If the member function entry describes a non-static member function,
then that entry has a DW_AT_object_pointer attribute whose value is a reference to
the formal parameter entry that corresponds to the object for which the
function is called.
That parameter also has a DW_AT_artificial attribute whose value is true.
```
The part about `DW_AT_artificial` seems overly restrictive, and not true for
explicit object parameters. We probably should relax this part of the DWARF spec.
This will help LLDB identify static vs. non-static member functions (see
https://github.com/llvm/llvm-project/issues/120856).
GCC suffers from the same issue: https://godbolt.org/z/h4jeT54G5
Partially fixes https://github.com/llvm/llvm-project/issues/120974
---
clang/lib/CodeGen/CGDebugInfo.cpp | 21 +++++++++++++------
.../CodeGenCXX/debug-info-object-pointer.cpp | 7 +++----
llvm/include/llvm-c/DebugInfo.h | 11 ++++++----
llvm/include/llvm/IR/DIBuilder.h | 6 +++---
llvm/lib/IR/DIBuilder.cpp | 8 +++++--
llvm/lib/IR/DebugInfo.cpp | 9 ++++----
6 files changed, 39 insertions(+), 23 deletions(-)
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index f88f56c98186da..6cbcaf03844102 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2016,13 +2016,15 @@ llvm::DISubroutineType *CGDebugInfo::getOrCreateInstanceMethodType(
// First element is always return type. For 'void' functions it is NULL.
Elts.push_back(Args[0]);
- // "this" pointer is always first argument.
- // ThisPtr may be null if the member function has an explicit 'this'
- // parameter.
- if (!ThisPtr.isNull()) {
+ const bool HasExplicitObjectParameter = ThisPtr.isNull();
+
+ // "this" pointer is always first argument. For explicit "this"
+ // parameters, it will already be in Args[1].
+ if (!HasExplicitObjectParameter) {
llvm::DIType *ThisPtrType = getOrCreateType(ThisPtr, Unit);
TypeCache[ThisPtr.getAsOpaquePtr()].reset(ThisPtrType);
- ThisPtrType = DBuilder.createObjectPointerType(ThisPtrType);
+ ThisPtrType =
+ DBuilder.createObjectPointerType(ThisPtrType, /*Implicit=*/true);
Elts.push_back(ThisPtrType);
}
@@ -2030,6 +2032,13 @@ llvm::DISubroutineType *CGDebugInfo::getOrCreateInstanceMethodType(
for (unsigned i = 1, e = Args.size(); i != e; ++i)
Elts.push_back(Args[i]);
+ // Attach FlagObjectPointer to the explicit "this" parameter.
+ if (HasExplicitObjectParameter) {
+ assert(Elts.size() >= 2 && Args.size() >= 2 &&
+ "Expected at least return type and object parameter.");
+ Elts[1] = DBuilder.createObjectPointerType(Args[1], /*Implicit=*/false);
+ }
+
llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(Elts);
return DBuilder.createSubroutineType(EltTypeArray, OriginalFunc->getFlags(),
@@ -5118,7 +5127,7 @@ llvm::DIType *CGDebugInfo::CreateSelfType(const QualType &QualTy,
llvm::DIType *CachedTy = getTypeOrNull(QualTy);
if (CachedTy)
Ty = CachedTy;
- return DBuilder.createObjectPointerType(Ty);
+ return DBuilder.createObjectPointerType(Ty, /*Implicit=*/true);
}
void CGDebugInfo::EmitDeclareOfBlockDeclRefVariable(
diff --git a/clang/test/CodeGenCXX/debug-info-object-pointer.cpp b/clang/test/CodeGenCXX/debug-info-object-pointer.cpp
index 594d4da791ee84..49079f59909968 100644
--- a/clang/test/CodeGenCXX/debug-info-object-pointer.cpp
+++ b/clang/test/CodeGenCXX/debug-info-object-pointer.cpp
@@ -5,12 +5,11 @@
// CHECK: !DIDerivedType(tag: DW_TAG_pointer_type
// CHECK-SAME: flags: DIFlagArtificial | DIFlagObjectPointer
//
-// // FIXME: DIFlagObjectPointer not attached to the explicit object
-// // argument in the subprogram declaration.
// CHECK: !DISubprogram(name: "explicit_this",
// flags: DIFlagPrototyped
-// CHECK-NOT: DIFlagObjectPointer
-// CHECK-NOT: DIFlagArtificial
+//
+// CHECK: !DIDerivedType(tag: DW_TAG_rvalue_reference_type
+// CHECK-SAME: flags: DIFlagObjectPointer)
//
// CHECK: !DILocalVariable(name: "this", arg: 1
// CHECK-SAME: flags: DIFlagArtificial | DIFlagObjectPointer
diff --git a/llvm/include/llvm-c/DebugInfo.h b/llvm/include/llvm-c/DebugInfo.h
index 07f87d44088e7e..ac7ee5a7cc9a19 100644
--- a/llvm/include/llvm-c/DebugInfo.h
+++ b/llvm/include/llvm-c/DebugInfo.h
@@ -870,13 +870,16 @@ LLVMDIBuilderCreateObjCProperty(LLVMDIBuilderRef Builder,
LLVMMetadataRef Ty);
/**
- * Create a uniqued DIType* clone with FlagObjectPointer and FlagArtificial set.
+ * Create a uniqued DIType* clone with FlagObjectPointer. If \c Implicit
+ * is true, then also set FlagArtificial.
* \param Builder The DIBuilder.
* \param Type The underlying type to which this pointer points.
+ * \param Implicit Indicates whether this pointer was implicitly generated
+ * (i.e., not spelled out in source).
*/
-LLVMMetadataRef
-LLVMDIBuilderCreateObjectPointerType(LLVMDIBuilderRef Builder,
- LLVMMetadataRef Type);
+LLVMMetadataRef LLVMDIBuilderCreateObjectPointerType(LLVMDIBuilderRef Builder,
+ LLVMMetadataRef Type,
+ LLVMBool Implicit);
/**
* Create debugging information entry for a qualified
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
index cb1150c269a1da..6c479415b9ed27 100644
--- a/llvm/include/llvm/IR/DIBuilder.h
+++ b/llvm/include/llvm/IR/DIBuilder.h
@@ -662,9 +662,9 @@ namespace llvm {
/// Create a uniqued clone of \p Ty with FlagArtificial set.
static DIType *createArtificialType(DIType *Ty);
- /// Create a uniqued clone of \p Ty with FlagObjectPointer and
- /// FlagArtificial set.
- static DIType *createObjectPointerType(DIType *Ty);
+ /// Create a uniqued clone of \p Ty with FlagObjectPointer set.
+ /// If \p Implicit is true, also set FlagArtificial.
+ static DIType *createObjectPointerType(DIType *Ty, bool Implicit);
/// Create a permanent forward-declared type.
DICompositeType *createForwardDecl(unsigned Tag, StringRef Name,
diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index b240a2a39de362..d9bd4f11e89a39 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -644,11 +644,15 @@ DIType *DIBuilder::createArtificialType(DIType *Ty) {
return createTypeWithFlags(Ty, DINode::FlagArtificial);
}
-DIType *DIBuilder::createObjectPointerType(DIType *Ty) {
+DIType *DIBuilder::createObjectPointerType(DIType *Ty, bool Implicit) {
// FIXME: Restrict this to the nodes where it's valid.
if (Ty->isObjectPointer())
return Ty;
- DINode::DIFlags Flags = DINode::FlagObjectPointer | DINode::FlagArtificial;
+ DINode::DIFlags Flags = DINode::FlagObjectPointer;
+
+ if (Implicit)
+ Flags |= DINode::FlagArtificial;
+
return createTypeWithFlags(Ty, Flags);
}
diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index e5b45e0082a823..4ce518009bd3ea 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -1432,10 +1432,11 @@ LLVMDIBuilderCreateObjCProperty(LLVMDIBuilderRef Builder,
PropertyAttributes, unwrapDI<DIType>(Ty)));
}
-LLVMMetadataRef
-LLVMDIBuilderCreateObjectPointerType(LLVMDIBuilderRef Builder,
- LLVMMetadataRef Type) {
- return wrap(unwrap(Builder)->createObjectPointerType(unwrapDI<DIType>(Type)));
+LLVMMetadataRef LLVMDIBuilderCreateObjectPointerType(LLVMDIBuilderRef Builder,
+ LLVMMetadataRef Type,
+ LLVMBool Implicit) {
+ return wrap(unwrap(Builder)->createObjectPointerType(unwrapDI<DIType>(Type),
+ Implicit));
}
LLVMMetadataRef
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