[llvm] r207705 - Emit DW_AT_object_pointer once, on the declaration, for each function.
Eric Christopher
echristo at gmail.com
Wed Apr 30 14:40:26 PDT 2014
SGTM.
-eric
On Wed, Apr 30, 2014 at 2:29 PM, David Blaikie <dblaikie at gmail.com> wrote:
> Author: dblaikie
> Date: Wed Apr 30 16:29:41 2014
> New Revision: 207705
>
> URL: http://llvm.org/viewvc/llvm-project?rev=207705&view=rev
> Log:
> Emit DW_AT_object_pointer once, on the declaration, for each function.
>
> This effectively reverts r164326, but adds some comments and
> justification and ensures we /don't/ emit the DW_AT_object_pointer on
> the (abstract and concrete) definitions. (while still preserving it on
> standalone definitions involving ObjC Blocks)
>
> This does increase the size of member function declarations from 7 to 11
> bytes, unfortunately, but still seems like the Right Thing to do so that
> callers that see only the declaration still have the information about
> the object pointer. That said, I don't know what, if any, DWARF
> consumers don't have a heuristic to guess this in the case of normal
> C++ member functions - perhaps we can remove it entirely.
>
> Modified:
> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h
> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.h
> llvm/trunk/test/DebugInfo/X86/DW_AT_object_pointer.ll
> llvm/trunk/test/DebugInfo/X86/inline-member-function.ll
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=207705&r1=207704&r2=207705&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Wed Apr 30 16:29:41 2014
> @@ -548,11 +548,16 @@ DIE *DwarfDebug::createScopeChildrenDIE(
> }
>
> void DwarfDebug::createAndAddScopeChildren(DwarfCompileUnit &TheCU,
> - LexicalScope *Scope, DIE &ScopeDIE) {
> + LexicalScope *Scope,
> + DISubprogram Sub, DIE &ScopeDIE) {
> // We create children when the scope DIE is not null.
> SmallVector<std::unique_ptr<DIE>, 8> Children;
> if (DIE *ObjectPointer = createScopeChildrenDIE(TheCU, Scope, Children))
> - TheCU.addDIEEntry(ScopeDIE, dwarf::DW_AT_object_pointer, *ObjectPointer);
> + // The declaration will have the object_pointer, otherwise put it on the
> + // definition. This happens with ObjC blocks that have object_pointer on
> + // non-member functions.
> + if (!Sub.getFunctionDeclaration())
> + TheCU.addDIEEntry(ScopeDIE, dwarf::DW_AT_object_pointer, *ObjectPointer);
>
> // Add children
> for (auto &I : Children)
> @@ -571,7 +576,7 @@ void DwarfDebug::constructAbstractSubpro
>
> if (DIE *ScopeDIE = TheCU.getDIE(Sub)) {
> AbstractSPDies.insert(std::make_pair(Sub, ScopeDIE));
> - createAndAddScopeChildren(TheCU, Scope, *ScopeDIE);
> + createAndAddScopeChildren(TheCU, Scope, Sub, *ScopeDIE);
> }
> }
>
> @@ -588,7 +593,7 @@ DIE &DwarfDebug::constructSubprogramScop
>
> DIE &ScopeDIE = updateSubprogramScopeDIE(TheCU, Sub);
>
> - createAndAddScopeChildren(TheCU, Scope, ScopeDIE);
> + createAndAddScopeChildren(TheCU, Scope, Sub, ScopeDIE);
>
> return ScopeDIE;
> }
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h?rev=207705&r1=207704&r2=207705&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h Wed Apr 30 16:29:41 2014
> @@ -371,7 +371,7 @@ class DwarfDebug : public AsmPrinterHand
> std::unique_ptr<DIE> constructScopeDIE(DwarfCompileUnit &TheCU,
> LexicalScope *Scope);
> void createAndAddScopeChildren(DwarfCompileUnit &TheCU, LexicalScope *Scope,
> - DIE &ScopeDIE);
> + DISubprogram Sub, DIE &ScopeDIE);
> /// \brief Construct a DIE for this abstract scope.
> void constructAbstractSubprogramScopeDIE(DwarfCompileUnit &TheCU,
> LexicalScope *Scope);
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp?rev=207705&r1=207704&r2=207705&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp Wed Apr 30 16:29:41 2014
> @@ -1164,7 +1164,8 @@ void DwarfUnit::constructTypeDIE(DIE &Bu
> }
>
> /// constructSubprogramArguments - Construct function argument DIEs.
> -void DwarfUnit::constructSubprogramArguments(DIE &Buffer, DIArray Args) {
> +DIE *DwarfUnit::constructSubprogramArguments(DIE &Buffer, DIArray Args) {
> + DIE *ObjectPointer = nullptr;
> for (unsigned i = 1, N = Args.getNumElements(); i < N; ++i) {
> DIDescriptor Ty = Args.getElement(i);
> if (Ty.isUnspecifiedParameter()) {
> @@ -1175,8 +1176,11 @@ void DwarfUnit::constructSubprogramArgum
> addType(Arg, DIType(Ty));
> if (DIType(Ty).isArtificial())
> addFlag(Arg, dwarf::DW_AT_artificial);
> + if (DIType(Ty).isObjectPointer())
> + ObjectPointer = &Arg;
> }
> }
> + return ObjectPointer;
> }
>
> /// constructTypeDIE - Construct type DIE from DICompositeType.
> @@ -1497,7 +1501,8 @@ DIE *DwarfUnit::getOrCreateSubprogramDIE
>
> // Add arguments. Do not add arguments for subprogram definition. They will
> // be handled while processing variables.
> - constructSubprogramArguments(SPDie, Args);
> + if (DIE *ObjectPointer = constructSubprogramArguments(SPDie, Args))
> + addDIEEntry(SPDie, dwarf::DW_AT_object_pointer, *ObjectPointer);
> }
>
> if (SP.isArtificial())
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.h?rev=207705&r1=207704&r2=207705&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.h (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.h Wed Apr 30 16:29:41 2014
> @@ -416,7 +416,7 @@ public:
> bool isScopeAbstract);
>
> /// constructSubprogramArguments - Construct function argument DIEs.
> - void constructSubprogramArguments(DIE &Buffer, DIArray Args);
> + DIE *constructSubprogramArguments(DIE &Buffer, DIArray Args);
>
> /// Create a DIE with the given Tag, add the DIE to its parent, and
> /// call insertDIE if MD is not null.
>
> Modified: llvm/trunk/test/DebugInfo/X86/DW_AT_object_pointer.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/DW_AT_object_pointer.ll?rev=207705&r1=207704&r2=207705&view=diff
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/X86/DW_AT_object_pointer.ll (original)
> +++ llvm/trunk/test/DebugInfo/X86/DW_AT_object_pointer.ll Wed Apr 30 16:29:41 2014
> @@ -1,13 +1,28 @@
> ; RUN: llc -mtriple=x86_64-apple-darwin %s -o %t -filetype=obj
> ; RUN: llvm-dwarfdump -debug-dump=info %t | FileCheck %s
>
> -; CHECK: DW_TAG_formal_parameter [
> -; CHECK-NOT: ""
> +; Emit the DW_TAG_object_pointer on the declaration only, not the definition.
> +; This seems the most correct thing - the DW_TAG_object_pointer is inherited
> +; from the declaration to any (abstract or concrete) definitions and DWARF
> +; consumers can use this information for callers that can only see the
> +; declaration.
> +; That said, it isn't very space efficient - making member function
> +; declarations 11 bytes instead of 7 and I'm not sure which tools actually
> +; use this information here (ObjC Blocks are a different story & most likely
> +; require object_pointer) - perhaps we should omit it entirely for space.
> +; No overall space impact study has been performed.
> +
> +; CHECK: [[DEFINITION:0x[0-9a-f]*]]: DW_TAG_subprogram
> +; CHECK-NOT: DW_TAG
> +; CHECK-NOT: DW_TAG_object_pointer
> ; CHECK: DW_TAG
> +
> ; CHECK: DW_TAG_class_type
> +; CHECK-NOT: NULL
> +; CHECK: DW_TAG_subprogram
> +; CHECK-NEXT: DW_AT_name {{.*}} "A"
> ; CHECK: DW_AT_object_pointer [DW_FORM_ref4] (cu + 0x{{[0-9a-f]*}} => {[[PARAM:0x[0-9a-f]*]]})
> ; CHECK: [[PARAM]]: DW_TAG_formal_parameter
> -; CHECK-NEXT: DW_AT_name [DW_FORM_strp] ( .debug_str[0x{{[0-9a-f]*}}] = "this")
>
> %class.A = type { i32 }
>
>
> Modified: llvm/trunk/test/DebugInfo/X86/inline-member-function.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/inline-member-function.ll?rev=207705&r1=207704&r2=207705&view=diff
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/X86/inline-member-function.ll (original)
> +++ llvm/trunk/test/DebugInfo/X86/inline-member-function.ll Wed Apr 30 16:29:41 2014
> @@ -20,12 +20,21 @@
> ; CHECK-NOT: DW_AT_object_pointer
> ; CHECK: DW_TAG
>
> -; But make sure we emit DW_AT_object_pointer on the abstract definition.
> -; CHECK: [[ABSTRACT_ORIGIN]]: DW_TAG_subprogram
> +; But make sure we emit DW_AT_object_pointer on the declaration.
> +; CHECK: DW_TAG_structure_type
> +; CHECK-NEXT: DW_AT_name {{.*}} "foo"
> ; CHECK-NOT: NULL
> -; CHECK-NOT: TAG
> +; CHECK: [[DECLARATION:0x[0-9a-e]*]]: DW_TAG_subprogram
> +; CHECK-NOT: DW_TAG
> ; CHECK: DW_AT_object_pointer
>
> +; But don't put it on the abstract definition, either.
> +; CHECK: [[ABSTRACT_ORIGIN]]: DW_TAG_subprogram
> +; CHECK-NEXT: DW_AT_specification {{.*}}{[[DECLARATION]]}
> +; CHECK-NOT: NULL
> +; CHECK-NOT: DW_AT_object_pointer
> +; CHECK: DW_TAG_formal_parameter
> +
> %struct.foo = type { i8 }
>
> @i = global i32 0, align 4
>
>
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