r256962 - Module debugging: Defer emitting tag types until their definition
Adrian Prantl via cfe-commits
cfe-commits at lists.llvm.org
Fri Jan 8 14:18:20 PST 2016
> 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 <mailto:aprantl at apple.com>> wrote:
>
>> On Jan 8, 2016, at 1:31 PM, David Blaikie <dblaikie at gmail.com <mailto: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 <mailto: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 <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.
>
> -- 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 <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 <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 <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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