[clang] [llvm] [clang][DebugInfo] Emit DW_AT_object_pointer on function declarations with explicit `this` (PR #122928)

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Fri Jan 17 06:26:56 PST 2025


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-debuginfo

@llvm/pr-subscribers-clang

Author: Michael Buch (Michael137)

<details>
<summary>Changes</summary>

In https://github.com/llvm/llvm-project/pull/122897 we started attaching `DW_AT_object_pointer` to function definitions. This patch does the same but for function declarations (which we do for implicit object pointers already).

Fixes https://github.com/llvm/llvm-project/issues/120974

---
Full diff: https://github.com/llvm/llvm-project/pull/122928.diff


6 Files Affected:

- (modified) clang/lib/CodeGen/CGDebugInfo.cpp (+15-6) 
- (modified) clang/test/CodeGenCXX/debug-info-object-pointer.cpp (+3-4) 
- (modified) llvm/include/llvm-c/DebugInfo.h (+7-4) 
- (modified) llvm/include/llvm/IR/DIBuilder.h (+3-3) 
- (modified) llvm/lib/IR/DIBuilder.cpp (+6-2) 
- (modified) llvm/lib/IR/DebugInfo.cpp (+5-4) 


``````````diff
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

``````````

</details>


https://github.com/llvm/llvm-project/pull/122928


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