r258251 - Module Debugging: Don't emit external type references to anonymous types.

[Adrian Prantl via cfe-commits]

> On Jan 19, 2016, at 3:52 PM, David Blaikie <dblaikie at gmail.com> wrote:
> 
> 
> 
> On Tue, Jan 19, 2016 at 3:42 PM, Adrian Prantl via cfe-commits <cfe-commits at lists.llvm.org <mailto:cfe-commits at lists.llvm.org>> wrote:
> Author: adrian
> Date: Tue Jan 19 17:42:53 2016
> New Revision: 258251
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=258251&view=rev <http://llvm.org/viewvc/llvm-project?rev=258251&view=rev>
> Log:
> Module Debugging: Don't emit external type references to anonymous types.
> Even if they exist in the module, they can't be matched with the forward
> declaration in the object file.
> 
> They can't be matched because they're matched by (non-mangled) name?

Yes, dsymutil and lldb use the (non-mangled) name + DeclContext (which includes the qualified module name).

> I thought at least they'd be matched by mangled name (& perhaps we need to emit DW_AT_linkage_name on them to make that possible)?

Emitting the DW_AT_linkage_name and matching/indexing types based on it is definitely  interesting for the future (bag of dwarf ...), but currently LLVM doesn’t do that.

>  
> <rdar://problem/24199640>
> 
> Modified:
>     cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
>     cfe/trunk/test/Modules/ExtDebugInfo.cpp
> 
> Modified: cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDebugInfo.cpp?rev=258251&r1=258250&r2=258251&view=diff <http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDebugInfo.cpp?rev=258251&r1=258250&r2=258251&view=diff>
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGDebugInfo.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp Tue Jan 19 17:42:53 2016
> @@ -1536,8 +1536,9 @@ static bool shouldOmitDefinition(CodeGen
>                                   const RecordDecl *RD,
>                                   const LangOptions &LangOpts) {
>    // Does the type exist in an imported clang module?
> -  if (DebugTypeExtRefs && RD->isFromASTFile() && RD->getDefinition())
> -      return true;
> +  if (DebugTypeExtRefs && RD->isFromASTFile() && RD->getDefinition() &&
> +      RD->isExternallyVisible())
> 
> Not sure if this is the right check. There might be named things that are static (so not externally visible) in headers?

I used isExternallyVisible() because it implies that the type won’t have a mangled name, (mostly thinking about the future where this would become more relevant), but at the moment we can relax this to RD->getName().isEmpty() and worry about nonexisting mangled names later.

-- adrian

>  
> +    return true;
> 
>    if (DebugKind > CodeGenOptions::LimitedDebugInfo)
>      return false;
> 
> Modified: cfe/trunk/test/Modules/ExtDebugInfo.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/ExtDebugInfo.cpp?rev=258251&r1=258250&r2=258251&view=diff <http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/ExtDebugInfo.cpp?rev=258251&r1=258250&r2=258251&view=diff>
> ==============================================================================
> --- cfe/trunk/test/Modules/ExtDebugInfo.cpp (original)
> +++ cfe/trunk/test/Modules/ExtDebugInfo.cpp Tue Jan 19 17:42:53 2016
> @@ -84,4 +84,13 @@ void foo() {
>  // CHECK: !DICompositeType(tag: DW_TAG_enumeration_type, scope: ![[NS]],
>  // CHECK-SAME:             line: 16
> 
> +// CHECK: !DIGlobalVariable(name: "GlobalUnion",
> +// CHECK-SAME:              type: ![[GLOBAL_UNION:[0-9]+]]
> +// CHECK: ![[GLOBAL_UNION]] = !DICompositeType(tag: DW_TAG_union_type,
> +// CHECK-SAME:                elements: !{{[0-9]+}})
> +// CHECK: !DIGlobalVariable(name: "GlobalStruct",
> +// CHECK-SAME:              type: ![[GLOBAL_STRUCT:[0-9]+]]
> +// CHECK: ![[GLOBAL_STRUCT]] = !DICompositeType(tag: DW_TAG_structure_type,
> +// CHECK-SAME:                elements: !{{[0-9]+}})
> +
>  // CHECK: !DIImportedEntity(tag: DW_TAG_imported_declaration, scope: !0, entity: !"_ZTSN8DebugCXX6StructE", line: 24)
> 
> 
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