Michael137 created this revision.
Michael137 added reviewers: dblaikie, aprantl.
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Michael137 requested review of this revision.
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**Summary**
After this patch, any `AbiTagAttr` attribute on a constructor/destructor
(like the ones for numerous types in libcxx) will be attached to the
declaration `DW_TAG_subprogram` as a `DW_TAG_LLVM_annotation`. E.g.,
DW_TAG_subprogram
DW_AT_name ("shared_ptr")
DW_AT_decl_file ("./bin/../include/c++/v1/__memory/shared_ptr.h")
DW_AT_decl_line (475)
DW_AT_declaration (true)
DW_AT_external (true)
DW_AT_accessibility (DW_ACCESS_public)
DW_TAG_LLVM_annotation
DW_AT_name ("abi_tag")
DW_AT_const_value ("v170000")
We only emit these annotations for constructors/destructors declarations
because those don't carry linkage names, which is where this information
is usually encoded.
**Motivation**
ABI tags affect a function's linkage name, which LLDB uses to resolve
function calls during expression evaluation. However,
constructors/destructors are emitted as declarations and can have
multiple definitions with different linkage names for a single
declaration DIE. LLDB relies on Clang to mangle the function AST node
into the correct linkage name. However, LLDB doesn't know about the
`AbiTagAttr` that was attached to a constructor/destructor in the
source, so there's no way to cleanly reconstruct the AST and resolve
the function symbol.
With this patch, LLDB can attach the ABI tag to the ctor/dtor decl
and let clang determine which linkage name to pick.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D144181
Files:
clang/lib/CodeGen/CGDebugInfo.cpp
clang/lib/CodeGen/CGDebugInfo.h
clang/test/CodeGen/attr-abi_tag-ctors-dtors.cpp
Index: clang/test/CodeGen/attr-abi_tag-ctors-dtors.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGen/attr-abi_tag-ctors-dtors.cpp
@@ -0,0 +1,25 @@
+// RUN: %clang -g -S -emit-llvm -o - %s | FileCheck %s
+
+struct Foo {
+ [[gnu::abi_tag("Ctor")]] Foo() {}
+ [[gnu::abi_tag("Dtor")]] ~Foo() {}
+};
+
+Foo f;
+
+// CHECK: ![[#]] = !DISubprogram(name: "Foo",
+// CHECK-SAME: flags: DIFlagPrototyped, spFlags: [[#]], annotations: ![[CTOR_ANNOTS:[0-9]+]])
+// CHECK: ![[CTOR_ANNOTS]] = !{![[CTOR:[0-9]+]]}
+// CHECK: ![[CTOR]] = !{!"abi_tag", !"Ctor"}
+// CHECK: ![[#]] = !DISubprogram(name: "~Foo",
+// CHECK-SAME: flags: DIFlagPrototyped, spFlags: [[#]], annotations: ![[DTOR_ANNOTS:[0-9]+]])
+// CHECK: ![[DTOR_ANNOTS]] = !{![[DTOR:[0-9]+]]}
+// CHECK: ![[DTOR]] = !{!"abi_tag", !"Dtor"}
+// CHECK: ![[#]] = distinct !DISubprogram(name: "Foo",
+// FCHECK-SAME: flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: ![[#]], declaration: ![[#]], retainedNodes: ![[#]], annotations: ![[CTOR_ANNOTS]])
+// FCHECK: ![[#]] = distinct !DISubprogram(name: "~Foo",
+// FCHECK-SAME: flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: ![[#]], declaration: ![[#]], retainedNodes: ![[#]], annotations: ![[DTOR_ANNOTS]])
+// FCHECK: ![[#]] = distinct !DISubprogram(name: "Foo",
+// FCHECK-SAME: flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: ![[#]], declaration: ![[#]], retainedNodes: ![[#]], annotations: ![[CTOR_ANNOTS]])
+// FCHECK: ![[#]] = distinct !DISubprogram(name: "~Foo",
+// FCHECK-SAME: flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: ![[#]], declaration: ![[#]], retainedNodes: ![[#]], annotations: ![[DTOR_ANNOTS]])
Index: clang/lib/CodeGen/CGDebugInfo.h
===================================================================
--- clang/lib/CodeGen/CGDebugInfo.h
+++ clang/lib/CodeGen/CGDebugInfo.h
@@ -303,6 +303,10 @@
/// A helper function to collect debug info for btf_decl_tag annotations.
llvm::DINodeArray CollectBTFDeclTagAnnotations(const Decl *D);
+ /// A helper function to collect debug info for abi_tag annotations.
+ /// Returns a null DINodeArray if 'D' doesn't have any 'clang::AbiTagAttr's.
+ llvm::DINodeArray CollectAbiTagAnnotations(const Decl *D);
+
llvm::DIType *createFieldType(StringRef name, QualType type,
SourceLocation loc, AccessSpecifier AS,
uint64_t offsetInBits, uint32_t AlignInBits,
Index: clang/lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- clang/lib/CodeGen/CGDebugInfo.cpp
+++ clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1350,6 +1350,8 @@
SourceLocation Loc = Ty->getDecl()->getLocation();
uint32_t Align = getDeclAlignIfRequired(Ty->getDecl(), CGM.getContext());
+ // TODO: need to account for tags on typedefs? Or would LLDB correctly
+ // call through typedefs of abi-tagged decls?
// Typedefs are derived from some other type.
llvm::DINodeArray Annotations = CollectBTFDeclTagAnnotations(Ty->getDecl());
@@ -1842,11 +1844,19 @@
SPFlags |= llvm::DISubprogram::SPFlagDeleted;
};
+ llvm::DINodeArray AbiTagAnnotations = nullptr;
+
switch (Method->getKind()) {
case Decl::CXXConstructor:
case Decl::CXXDestructor:
checkAttrDeleted(Method);
+
+ // Add annotations for abi_tag's for constructors/destructors
+ // because their declarations don't carry linkage names (which
+ // encodes the existance of abi-tags). LLDB uses these annotations
+ // to resolve calls to abi-tagged constructors/destructors.
+ AbiTagAnnotations = CollectAbiTagAnnotations(Method);
break;
case Decl::CXXMethod:
if (Method->isCopyAssignmentOperator() ||
@@ -1893,7 +1903,7 @@
llvm::DISubprogram *SP = DBuilder.createMethod(
RecordTy, MethodName, MethodLinkageName, MethodDefUnit, MethodLine,
MethodTy, VIndex, ThisAdjustment, ContainingType, Flags, SPFlags,
- TParamsArray.get());
+ TParamsArray.get(), nullptr, AbiTagAnnotations);
SPCache[Method->getCanonicalDecl()].reset(SP);
@@ -2195,6 +2205,21 @@
return DBuilder.getOrCreateArray(Annotations);
}
+llvm::DINodeArray CGDebugInfo::CollectAbiTagAnnotations(const Decl *D) {
+ if (!D->hasAttr<AbiTagAttr>())
+ return nullptr;
+
+ SmallVector<llvm::Metadata *, 4> Annotations;
+ auto const *Attr = D->getAttr<AbiTagAttr>();
+ for (const auto Tag : Attr->tags()) {
+ llvm::Metadata *Ops[2] = {
+ llvm::MDString::get(CGM.getLLVMContext(), StringRef("abi_tag")),
+ llvm::MDString::get(CGM.getLLVMContext(), Tag)};
+ Annotations.push_back(llvm::MDNode::get(CGM.getLLVMContext(), Ops));
+ }
+ return DBuilder.getOrCreateArray(Annotations);
+}
+
llvm::DIType *CGDebugInfo::getOrCreateVTablePtrType(llvm::DIFile *Unit) {
if (VTablePtrType)
return VTablePtrType;
@@ -4212,6 +4237,8 @@
if (CGM.getLangOpts().Optimize)
SPFlags |= llvm::DISubprogram::SPFlagOptimized;
+ // No need to collect ABI tags on formal parameters because they
+ // don't affect name mangling.
llvm::DINodeArray Annotations = CollectBTFDeclTagAnnotations(D);
llvm::DISubroutineType *STy = getOrCreateFunctionType(D, FnType, Unit);
llvm::DISubprogram *SP =
@@ -4564,6 +4591,7 @@
// Create the descriptor for the variable.
llvm::DILocalVariable *D = nullptr;
if (ArgNo) {
+ // TODO: need to collect ABI tags? probably not for parameters
llvm::DINodeArray Annotations = CollectBTFDeclTagAnnotations(VD);
D = DBuilder.createParameterVariable(Scope, Name, *ArgNo, Unit, Line, Ty,
CGM.getLangOpts().Optimize, Flags,
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