r256962 - Module debugging: Defer emitting tag types until their definition
Adrian Prantl via cfe-commits
cfe-commits at lists.llvm.org
Fri Jan 8 17:15:42 PST 2016
> On Jan 8, 2016, at 2:18 PM, Adrian Prantl via cfe-commits <cfe-commits at lists.llvm.org> wrote:
>
>>
>> On Jan 8, 2016, at 1:59 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>
>>
>>
>> On Fri, Jan 8, 2016 at 1:34 PM, Adrian Prantl <aprantl at apple.com> wrote:
>>
>>> On Jan 8, 2016, at 1:31 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>>
>>>
>>>
>>> On Wed, Jan 6, 2016 at 11:22 AM, Adrian Prantl via cfe-commits <cfe-commits at lists.llvm.org> wrote:
>>> Author: adrian
>>> Date: Wed Jan 6 13:22:19 2016
>>> New Revision: 256962
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=256962&view=rev
>>> Log:
>>> Module debugging: Defer emitting tag types until their definition
>>> was visited and all decls have been merged.
>>>
>>> We only get a single chance to emit the types for virtual classes because
>>> CGDebugInfo::completeRequiredType() categorically doesn't complete them.
>>>
>>> Not sure I'm following this comment. Could you explain this in other words/detail?
>>>
>>> If we visit a declaration we shouldn't do anything, right? (no point putting declarations in the modules debug info, unless it's needed for something else?) & then when we see the definition we'd build the debug info for it?
>>
>> Yes. Your statement pretty much summarizes this commit :-)
>>
>> Then I'm still confused - were we emitting type declarations in modules prior to this change?
>
> Yes. Dsymutil used to expect every forward declaration in a skeleton CU to have a corresponding declaration in the module dwo. I just verified that dsymutil does no longer prune forward declarations from skeleton CUs that don’t have a definition in the DWO, so everything should be fine now.
>
>> Perhaps a test case for a lone declaration (with no follow up definition) would be in order, then?
>
> Yes, that would make sense. I’ll add one.
Done in r257241.
-- adrian
>
>>
>> -- adrian
>>
>>>
>>>
>>> Modified:
>>> cfe/trunk/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
>>> cfe/trunk/test/Modules/Inputs/DebugCXX.h
>>> cfe/trunk/test/Modules/ModuleDebugInfo.cpp
>>>
>>> Modified: cfe/trunk/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/ObjectFilePCHContainerOperations.cpp?rev=256962&r1=256961&r2=256962&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/lib/CodeGen/ObjectFilePCHContainerOperations.cpp (original)
>>> +++ cfe/trunk/lib/CodeGen/ObjectFilePCHContainerOperations.cpp Wed Jan 6 13:22:19 2016
>>> @@ -59,8 +59,10 @@ class PCHContainerGenerator : public AST
>>> struct DebugTypeVisitor : public RecursiveASTVisitor<DebugTypeVisitor> {
>>> clang::CodeGen::CGDebugInfo &DI;
>>> ASTContext &Ctx;
>>> - DebugTypeVisitor(clang::CodeGen::CGDebugInfo &DI, ASTContext &Ctx)
>>> - : DI(DI), Ctx(Ctx) {}
>>> + bool SkipTagDecls;
>>> + DebugTypeVisitor(clang::CodeGen::CGDebugInfo &DI, ASTContext &Ctx,
>>> + bool SkipTagDecls)
>>> + : DI(DI), Ctx(Ctx), SkipTagDecls(SkipTagDecls) {}
>>>
>>> /// Determine whether this type can be represented in DWARF.
>>> static bool CanRepresent(const Type *Ty) {
>>> @@ -75,6 +77,12 @@ class PCHContainerGenerator : public AST
>>> }
>>>
>>> bool VisitTypeDecl(TypeDecl *D) {
>>> + // TagDecls may be deferred until after all decls have been merged and we
>>> + // know the complete type. Pure forward declarations will be skipped, but
>>> + // they don't need to be emitted into the module anyway.
>>> + if (SkipTagDecls && isa<TagDecl>(D))
>>> + return true;
>>> +
>>> QualType QualTy = Ctx.getTypeDeclType(D);
>>> if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
>>> DI.getOrCreateStandaloneType(QualTy, D->getLocation());
>>> @@ -165,7 +173,7 @@ public:
>>> // Collect debug info for all decls in this group.
>>> for (auto *I : D)
>>> if (!I->isFromASTFile()) {
>>> - DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
>>> + DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx, true);
>>> DTV.TraverseDecl(I);
>>> }
>>> return true;
>>> @@ -179,6 +187,11 @@ public:
>>> if (Diags.hasErrorOccurred())
>>> return;
>>>
>>> + if (D->isFromASTFile())
>>> + return;
>>> +
>>> + DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx, false);
>>> + DTV.TraverseDecl(D);
>>> Builder->UpdateCompletedType(D);
>>> }
>>>
>>>
>>> Modified: cfe/trunk/test/Modules/Inputs/DebugCXX.h
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/Inputs/DebugCXX.h?rev=256962&r1=256961&r2=256962&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/test/Modules/Inputs/DebugCXX.h (original)
>>> +++ cfe/trunk/test/Modules/Inputs/DebugCXX.h Wed Jan 6 13:22:19 2016
>>> @@ -50,3 +50,9 @@ namespace DebugCXX {
>>> typedef A<void> B;
>>> void foo(B) {}
>>> }
>>> +
>>> +// Virtual class with a forward declaration.
>>> +class FwdVirtual;
>>> +class FwdVirtual {
>>> + virtual ~FwdVirtual() {}
>>> +};
>>>
>>> Modified: cfe/trunk/test/Modules/ModuleDebugInfo.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/ModuleDebugInfo.cpp?rev=256962&r1=256961&r2=256962&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/test/Modules/ModuleDebugInfo.cpp (original)
>>> +++ cfe/trunk/test/Modules/ModuleDebugInfo.cpp Wed Jan 6 13:22:19 2016
>>> @@ -7,13 +7,11 @@
>>> // RUN: rm -rf %t
>>> // RUN: %clang_cc1 -triple %itanium_abi_triple -x objective-c++ -std=c++11 -debug-info-kind=limited -fmodules -fmodule-format=obj -fimplicit-module-maps -DMODULES -fmodules-cache-path=%t %s -I %S/Inputs -I %t -emit-llvm -o %t.ll -mllvm -debug-only=pchcontainer &>%t-mod.ll
>>> // RUN: cat %t-mod.ll | FileCheck %s
>>> -// RUN: cat %t-mod.ll | FileCheck --check-prefix=CHECK-NEG %s
>>> // RUN: cat %t-mod.ll | FileCheck --check-prefix=CHECK-DWO %s
>>>
>>> // PCH:
>>> // RUN: %clang_cc1 -triple %itanium_abi_triple -x c++ -std=c++11 -emit-pch -fmodule-format=obj -I %S/Inputs -o %t.pch %S/Inputs/DebugCXX.h -mllvm -debug-only=pchcontainer &>%t-pch.ll
>>> // RUN: cat %t-pch.ll | FileCheck %s
>>> -// RUN: cat %t-pch.ll | FileCheck --check-prefix=CHECK-NEG %s
>>>
>>> #ifdef MODULES
>>> @import DebugCXX;
>>> @@ -23,22 +21,32 @@
>>> // CHECK-SAME: isOptimized: false,
>>> // CHECK-SAME-NOT: splitDebugFilename:
>>> // CHECK-DWO: dwoId:
>>> +
>>> // CHECK: !DICompositeType(tag: DW_TAG_enumeration_type, name: "Enum"
>>> // CHECK-SAME: identifier: "_ZTSN8DebugCXX4EnumE")
>>> // CHECK: !DINamespace(name: "DebugCXX"
>>> +
>>> // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "Struct"
>>> // CHECK-SAME: identifier: "_ZTSN8DebugCXX6StructE")
>>> +
>>> // CHECK: !DICompositeType(tag: DW_TAG_class_type,
>>> // CHECK-SAME: name: "Template<int, DebugCXX::traits<int> >"
>>> // CHECK-SAME: identifier: "_ZTSN8DebugCXX8TemplateIiNS_6traitsIiEEEE")
>>> +
>>> +// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "A<void>"
>>> +// CHECK-SAME: identifier: "_ZTSN8DebugCXX1AIJvEEE")
>>> +
>>> // CHECK: !DICompositeType(tag: DW_TAG_class_type,
>>> // CHECK-SAME: name: "Template<float, DebugCXX::traits<float> >"
>>> // CHECK-SAME: identifier: "_ZTSN8DebugCXX8TemplateIfNS_6traitsIfEEEE")
>>> -// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "A<void>"
>>> -// CHECK-SAME: identifier: "_ZTSN8DebugCXX1AIJvEEE")
>>> +
>>> +// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "FwdVirtual"
>>> +// CHECK-SAME: elements:
>>> +// CHECK-SAME: identifier: "_ZTS10FwdVirtual")
>>> +// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "_vptr$FwdVirtual"
>>> +
>>> // CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "FloatInstatiation"
>>> // no mangled name here yet.
>>> +
>>> // CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "B",
>>> // no mangled name here yet.
>>> -
>>> -// CHECK-NEG-NOT: "_ZTSN8DebugCXX8TemplateIlNS_6traitsIlEEEE"
>>>
>>>
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