llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Michael Buch (Michael137) <details> <summary>Changes</summary> Depends on https://github.com/llvm/llvm-project/pull/154137 This patch is motivated by https://github.com/llvm/llvm-project/pull/149827, where we plan on using mangled names on structor declarations to find the exact structor definition that LLDB's expression evaluator should call. Given a `DW_TAG_subprogram` for a function declaration, the most convenient way for a debugger to find the corresponding definition is to use the `DW_AT_linkage_name` (i.e., the mangled name). However, we currently can't do that for constructors/destructors because Clang doesn't attach linkage names to them. This is because, depending on ABI, there can be multiple definitions for a single constructor/destructor declaration. The way GCC works around this is by producing a `C4`/`D4` "unified" mangling for structor declarations. GDB uses this to locate the relevant definitions. This patch aligns Clang with GCC's DWARF output and allows us to implement the same lookup scheme in LLDB. --- Full diff: https://github.com/llvm/llvm-project/pull/154142.diff 9 Files Affected: - (modified) clang/include/clang/Basic/ABI.h (+6-4) - (modified) clang/lib/AST/ItaniumMangle.cpp (+10) - (modified) clang/lib/AST/MicrosoftMangle.cpp (+2) - (modified) clang/lib/CodeGen/CGDebugInfo.cpp (+26-6) - (modified) clang/lib/CodeGen/CGDebugInfo.h (+4) - (modified) clang/lib/CodeGen/MicrosoftCXXABI.cpp (+4) - (added) clang/test/CodeGenCXX/debug-info-structor-linkage-names.cpp (+72) - (modified) llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (+2-5) - (added) llvm/test/DebugInfo/Generic/structor-declaration-linkage-names.ll (+68) ``````````diff diff --git a/clang/include/clang/Basic/ABI.h b/clang/include/clang/Basic/ABI.h index 231bad799a42c..8279529c316cf 100644 --- a/clang/include/clang/Basic/ABI.h +++ b/clang/include/clang/Basic/ABI.h @@ -27,14 +27,16 @@ enum CXXCtorType { Ctor_Comdat, ///< The COMDAT used for ctors Ctor_CopyingClosure, ///< Copying closure variant of a ctor Ctor_DefaultClosure, ///< Default closure variant of a ctor + Ctor_Unified, ///< GCC-style unified dtor }; /// C++ destructor types. enum CXXDtorType { - Dtor_Deleting, ///< Deleting dtor - Dtor_Complete, ///< Complete object dtor - Dtor_Base, ///< Base object dtor - Dtor_Comdat ///< The COMDAT used for dtors + Dtor_Deleting, ///< Deleting dtor + Dtor_Complete, ///< Complete object dtor + Dtor_Base, ///< Base object dtor + Dtor_Comdat, ///< The COMDAT used for dtors + Dtor_Unified, ///< GCC-style unified dtor }; } // end namespace clang diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp index a7380a19e3607..484f1b12f3588 100644 --- a/clang/lib/AST/ItaniumMangle.cpp +++ b/clang/lib/AST/ItaniumMangle.cpp @@ -6014,6 +6014,8 @@ void CXXNameMangler::mangleCXXCtorType(CXXCtorType T, // ::= CI2 <type> # base inheriting constructor // // In addition, C5 is a comdat name with C1 and C2 in it. + // C4 represents a ctor declaration and is used by debuggers to look up + // the various ctor variants. Out << 'C'; if (InheritedFrom) Out << 'I'; @@ -6024,6 +6026,9 @@ void CXXNameMangler::mangleCXXCtorType(CXXCtorType T, case Ctor_Base: Out << '2'; break; + case Ctor_Unified: + Out << '4'; + break; case Ctor_Comdat: Out << '5'; break; @@ -6041,6 +6046,8 @@ void CXXNameMangler::mangleCXXDtorType(CXXDtorType T) { // ::= D2 # base object destructor // // In addition, D5 is a comdat name with D1, D2 and, if virtual, D0 in it. + // D4 represents a dtor declaration and is used by debuggers to look up + // the various dtor variants. switch (T) { case Dtor_Deleting: Out << "D0"; @@ -6051,6 +6058,9 @@ void CXXNameMangler::mangleCXXDtorType(CXXDtorType T) { case Dtor_Base: Out << "D2"; break; + case Dtor_Unified: + Out << "D4"; + break; case Dtor_Comdat: Out << "D5"; break; diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp index 241c7c35fcc83..fe188de81b20f 100644 --- a/clang/lib/AST/MicrosoftMangle.cpp +++ b/clang/lib/AST/MicrosoftMangle.cpp @@ -1496,6 +1496,8 @@ void MicrosoftCXXNameMangler::mangleCXXDtorType(CXXDtorType T) { // it. case Dtor_Comdat: llvm_unreachable("not expecting a COMDAT"); + case Dtor_Unified: + llvm_unreachable("not expecting a unified dtor type"); } llvm_unreachable("Unsupported dtor type?"); } diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp index 994bdbdae860f..f32e1e8185337 100644 --- a/clang/lib/CodeGen/CGDebugInfo.cpp +++ b/clang/lib/CodeGen/CGDebugInfo.cpp @@ -2177,24 +2177,44 @@ static bool isFunctionLocalClass(const CXXRecordDecl *RD) { return false; } -llvm::DISubprogram *CGDebugInfo::CreateCXXMemberFunction( - const CXXMethodDecl *Method, llvm::DIFile *Unit, llvm::DIType *RecordTy) { +llvm::StringRef +CGDebugInfo::GetMethodLinkageName(const CXXMethodDecl *Method) const { + assert(Method); + bool IsCtorOrDtor = isa<CXXConstructorDecl>(Method) || isa<CXXDestructorDecl>(Method); + // In some ABIs (particularly Itanium) a single ctor/dtor + // corresponds to multiple functions. Attach a "unified" + // linkage name for those (which is the convention GCC uses). + // Otherwise, attach no linkage name. + if (IsCtorOrDtor && !CGM.getTarget().getCXXABI().hasConstructorVariants()) + return {}; + + if (const auto *Ctor = llvm::dyn_cast<CXXConstructorDecl>(Method)) + return CGM.getMangledName(GlobalDecl(Ctor, CXXCtorType::Ctor_Unified)); + + if (const auto *Dtor = llvm::dyn_cast<CXXDestructorDecl>(Method)) + return CGM.getMangledName(GlobalDecl(Dtor, CXXDtorType::Dtor_Unified)); + + return CGM.getMangledName(Method); +} + +llvm::DISubprogram *CGDebugInfo::CreateCXXMemberFunction( + const CXXMethodDecl *Method, llvm::DIFile *Unit, llvm::DIType *RecordTy) { + assert(Method); + StringRef MethodName = getFunctionName(Method); llvm::DISubroutineType *MethodTy = getOrCreateMethodType(Method, Unit); - // Since a single ctor/dtor corresponds to multiple functions, it doesn't - // make sense to give a single ctor/dtor a linkage name. StringRef MethodLinkageName; // FIXME: 'isFunctionLocalClass' seems like an arbitrary/unintentional // property to use here. It may've been intended to model "is non-external // type" but misses cases of non-function-local but non-external classes such // as those in anonymous namespaces as well as the reverse - external types // that are function local, such as those in (non-local) inline functions. - if (!IsCtorOrDtor && !isFunctionLocalClass(Method->getParent())) - MethodLinkageName = CGM.getMangledName(Method); + if (!isFunctionLocalClass(Method->getParent())) + MethodLinkageName = GetMethodLinkageName(Method); // Get the location for the method. llvm::DIFile *MethodDefUnit = nullptr; diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h index 497d3a6ab17b1..55c528031368d 100644 --- a/clang/lib/CodeGen/CGDebugInfo.h +++ b/clang/lib/CodeGen/CGDebugInfo.h @@ -899,6 +899,10 @@ class CGDebugInfo { std::memcpy(Data + A.size(), B.data(), B.size()); return StringRef(Data, A.size() + B.size()); } + + /// If one exists, returns the linkage name of the specified \ + /// (non-null) \c Method. Returns empty string otherwise. + llvm::StringRef GetMethodLinkageName(const CXXMethodDecl *Method) const; }; /// A scoped helper to set the current debug location to the specified diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp index 88f0648660965..94190a149e859 100644 --- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp +++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp @@ -77,6 +77,8 @@ class MicrosoftCXXABI : public CGCXXABI { return false; case Dtor_Comdat: llvm_unreachable("emitting dtor comdat as function?"); + case Dtor_Unified: + llvm_unreachable("unexpected unified dtor type"); } llvm_unreachable("bad dtor kind"); } @@ -1417,6 +1419,8 @@ llvm::GlobalValue::LinkageTypes MicrosoftCXXABI::getCXXDestructorLinkage( // and are emitted everywhere they are used. They are internal if the class // is internal. return llvm::GlobalValue::LinkOnceODRLinkage; + case Dtor_Unified: + llvm_unreachable("MS C++ ABI does not support unified dtors"); case Dtor_Comdat: llvm_unreachable("MS C++ ABI does not support comdat dtors"); } diff --git a/clang/test/CodeGenCXX/debug-info-structor-linkage-names.cpp b/clang/test/CodeGenCXX/debug-info-structor-linkage-names.cpp new file mode 100644 index 0000000000000..88b4ee75d4565 --- /dev/null +++ b/clang/test/CodeGenCXX/debug-info-structor-linkage-names.cpp @@ -0,0 +1,72 @@ +// Tests that we emit unified constructor/destructor linkage names +// for ABIs that support it. + +// RUN: %clang_cc1 -triple aarch64-apple-macosx -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck %s --check-prefixes=CHECK,ITANIUM +// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck %s --check-prefixes=CHECK,MSABI + +struct Base { + Base(int x); + ~Base(); +}; + +Base::Base(int x) {} +Base::~Base() {} + +// Check that we emit unified ctor/dtor (C4/D4) on Itanium but not for MS-ABI. + +// CHECK: ![[BASE_CTOR_DECL:[0-9]+]] = !DISubprogram(name: "Base" +// MSABI-NOT: linkageName: +// ITANIUM-SAME: linkageName: "_ZN4BaseC4Ei" +// CHECK-SAME: spFlags: 0 + +// CHECK: ![[BASE_DTOR_DECL:[0-9]+]] = !DISubprogram(name: "~Base" +// MSABI-NOT: linkageName: +// ITANIUM-SAME: linkageName: "_ZN4BaseD4Ev" +// CHECK-SAME: spFlags: 0 + +// Check that the ctor/dtor definitions have linkage names that aren't +// the ones on the declaration. + +// CHECK: !DISubprogram(name: "Base" +// MSABI-SAME: linkageName: +// ITANIUM-SAME: linkageName: "_ZN4BaseC2Ei" +// CHECK-SAME: spFlags: DISPFlagDefinition +// CHECK-SAME: declaration: ![[BASE_CTOR_DECL]] + +// ITANIUM: !DISubprogram(name: "Base" +// ITANIUM-SAME: linkageName: "_ZN4BaseC1Ei" +// ITANIUM-SAME: spFlags: DISPFlagDefinition +// ITANIUM-SAME: declaration: ![[BASE_CTOR_DECL]] + +// CHECK: !DISubprogram(name: "~Base" +// MSABI-SAME: linkageName: +// ITANIUM-SAME: linkageName: "_ZN4BaseD2Ev" +// CHECK-SAME: spFlags: DISPFlagDefinition +// CHECK-SAME: declaration: ![[BASE_DTOR_DECL]] + +// ITANIUM: !DISubprogram(name: "~Base" +// ITANIUM-SAME: linkageName: "_ZN4BaseD1Ev" +// ITANIUM-SAME: spFlags: DISPFlagDefinition +// ITANIUM-SAME: declaration: ![[BASE_DTOR_DECL]] + +struct Derived : public Base { + using Base::Base; +} d(5); + +// CHECK: !DISubprogram(name: "Base" +// MSABI-SAME: linkageName: +// ITANIUM-SAME: linkageName: "_ZN7DerivedCI14BaseEi" +// CHECK-SAME: spFlags: {{.*}}DISPFlagDefinition +// CHECK-SAME: declaration: ![[BASE_INHERIT_CTOR_DECL:[0-9]+]] + +// CHECK: [[BASE_INHERIT_CTOR_DECL]] = !DISubprogram(name: "Base" +// MSABI-NOT: linkageName: +// ITANIUM-SAME: linkageName: "_ZN7DerivedCI44BaseEi" +// CHECK-SAME spFlags: 0 + +// ITANIUM: !DISubprogram(name: "Base" +// ITANIUM-SAME: linkageName: "_ZN7DerivedCI24BaseEi" +// ITANIUM-SAME: spFlags: DISPFlagDefinition +// ITANIUM-SAME: declaration: ![[BASE_INHERIT_CTOR_DECL:[0-9]+]] + +// MSABI: !DISubprogram(name: "~Derived" diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp index b03fac2d22a52..4904ad03199c7 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp @@ -1403,11 +1403,8 @@ bool DwarfUnit::applySubprogramDefinitionAttributes(const DISubprogram *SP, // Add the linkage name if we have one and it isn't in the Decl. StringRef LinkageName = SP->getLinkageName(); - assert(((LinkageName.empty() || DeclLinkageName.empty()) || - LinkageName == DeclLinkageName) && - "decl has a linkage name and it is different"); - if (DeclLinkageName.empty() && - // Always emit it for abstract subprograms. + // Always emit linkage name for abstract subprograms. + if (DeclLinkageName != LinkageName && (DD->useAllLinkageNames() || DU->getAbstractScopeDIEs().lookup(SP))) addLinkageName(SPDie, LinkageName); diff --git a/llvm/test/DebugInfo/Generic/structor-declaration-linkage-names.ll b/llvm/test/DebugInfo/Generic/structor-declaration-linkage-names.ll new file mode 100644 index 0000000000000..9b1f2a5b2a186 --- /dev/null +++ b/llvm/test/DebugInfo/Generic/structor-declaration-linkage-names.ll @@ -0,0 +1,68 @@ +; RUN: %llc_dwarf < %s -filetype=obj | llvm-dwarfdump -debug-info - | FileCheck %s + +; Make sure we attach DW_AT_linkage_name on function declarations but only +; attach it on definitions if the value is different than on the declaration. + +target triple = "arm64-apple-macosx" + +define void @_Z11SameLinkagev() !dbg !4 { +entry: + ret void +} + +; CHECK: DW_AT_linkage_name ("_Z11SameLinkagev") +; CHECK: DW_AT_declaration (true) +; CHECK-NOT: DW_AT_linkage_name ("_Z11SameLinkagev") + +define void @_Z11DiffLinkagev() !dbg !8 { +entry: + ret void +} + +; CHECK: DW_AT_linkage_name ("SomeName") +; CHECK: DW_AT_declaration (true) +; CHECK: DW_AT_linkage_name ("_Z11DiffLinkagev") + +define void @_Z15EmptyDefLinkagev() !dbg !10 { +entry: + ret void +} + +; CHECK: DW_AT_linkage_name ("_Z15EmptyDefLinkagev") +; CHECK: DW_AT_declaration (true) +; CHECK-NOT: DW_AT_linkage_name + +define void @_Z16EmptyDeclLinkagev() !dbg !12 { +entry: + ret void +} + +; CHECK: DW_AT_declaration (true) +; CHECK: DW_AT_linkage_name ("_Z16EmptyDeclLinkagev") + +define void @_Z13EmptyLinkagesv() !dbg !14 { +entry: + ret void +} + +; CHECK-NOT: DW_AT_linkage_name + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!2, !3} + +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: Apple, sysroot: "/") +!1 = !DIFile(filename: "foo.cpp", directory: "/tmp") +!2 = !{i32 7, !"Dwarf Version", i32 5} +!3 = !{i32 2, !"Debug Info Version", i32 3} +!4 = distinct !DISubprogram(name: "SameLinkage", linkageName: "_Z11SameLinkagev", scope: !1, file: !1, line: 3, type: !5, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, declaration: !7) +!5 = !DISubroutineType(types: !6) +!6 = !{null} +!7 = !DISubprogram(name: "SameLinkage", linkageName: "_Z11SameLinkagev", scope: !1, file: !1, line: 3, type: !5, scopeLine: 3, flags: DIFlagPrototyped, spFlags: 0) +!8 = distinct !DISubprogram(name: "DiffLinkage", linkageName: "_Z11DiffLinkagev", scope: !1, file: !1, line: 5, type: !5, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, declaration: !9) +!9 = !DISubprogram(name: "DiffLinkage", linkageName: "SomeName", scope: !1, file: !1, line: 3, type: !5, scopeLine: 3, flags: DIFlagPrototyped, spFlags: 0) +!10 = distinct !DISubprogram(name: "EmptyDefLinkage", linkageName: "", scope: !1, file: !1, line: 5, type: !5, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, declaration: !11) +!11 = !DISubprogram(name: "EmptyDefLinkage", linkageName: "_Z15EmptyDefLinkagev", scope: !1, file: !1, line: 3, type: !5, scopeLine: 3, flags: DIFlagPrototyped, spFlags: 0) +!12 = distinct !DISubprogram(name: "EmptyDeclLinkage", linkageName: "_Z16EmptyDeclLinkagev", scope: !1, file: !1, line: 5, type: !5, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, declaration: !13) +!13 = !DISubprogram(name: "EmptyDeclLinkage", linkageName: "", scope: !1, file: !1, line: 3, type: !5, scopeLine: 3, flags: DIFlagPrototyped, spFlags: 0) +!14 = distinct !DISubprogram(name: "EmptyLinkages", linkageName: "", scope: !1, file: !1, line: 5, type: !5, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, declaration: !15) +!15 = !DISubprogram(name: "EmptyLinkages", linkageName: "", scope: !1, file: !1, line: 3, type: !5, scopeLine: 3, flags: DIFlagPrototyped, spFlags: 0) `````````` </details> https://github.com/llvm/llvm-project/pull/154142 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
