Debug Info: Support for DW_AT_export_symbols for anonymous structs

[shafik]

Summary

This implements the DWARF 5 feature described in:

http://dwarfstd.org/ShowIssue.php?issue=141212.1

To support recognizing anonymous structs:

struct A { 
  struct { // Anonymous struct 
      int y;
  };  
} a;

This patch adds support in CGDebugInfo::CreateLimitedType(...) for this new flag and an accompanying test to verify this feature.

[aprantl]

test/CodeGenCXX/debug-info-export_symbols.cpp

3 ↗

(On Diff #216900)

This should just be CHECK: if it stands by itself.

It would be better to match both composite types, establish which one is the inner one, and then verify that only that one has the attribute.

[shafik]

Updating test to be more specific

[aprantl]

test/CodeGenCXX/debug-info-export_symbols.cpp

4 ↗

(On Diff #217271)

FYI: This is equivalent to the slightly more readable:

// CHECK: !DICompositeType(tag: DW_TAG_structure_type, scope: [[SCOPE]]
// CHECK-SAME:                      flags: DIFlagExportSymbols | DIFlagTypePassByValue

[shafik]

Simplifying test.

clang/lib/CodeGen/CGDebugInfo.cpp

llvm::DICompositeType *CGDebugInfo::CreateLimitedType(const RecordType *Ty) {
   if (!D || !D->isCompleteDefinition())
     return getOrCreateRecordFwdDecl(Ty, RDContext);
 
   uint64_t Size = CGM.getContext().getTypeSize(Ty);
   auto Align = getDeclAlignIfRequired(D, CGM.getContext());
 
   SmallString<256> Identifier = getTypeIdentifier(Ty, CGM, TheCU);
 
-  // Explicitly record the calling convention for C++ records.
+  // Explicitly record the calling convention and export symbols for C++
+  // records.
   auto Flags = llvm::DINode::FlagZero;
   if (auto CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
     if (CGM.getCXXABI().getRecordArgABI(CXXRD) == CGCXXABI::RAA_Indirect)
       Flags |= llvm::DINode::FlagTypePassByReference;
     else
       Flags |= llvm::DINode::FlagTypePassByValue;
 
     // Record if a C++ record is non-trivial type.
     if (!CXXRD->isTrivial())
       Flags |= llvm::DINode::FlagNonTrivial;
+
+    // Record exports it symbols to the containing structure.
+    if (CXXRD->isAnonymousStructOrUnion())
+        Flags |= llvm::DINode::FlagExportSymbols;
   }
 
   llvm::DICompositeType *RealDecl = DBuilder.createReplaceableCompositeType(
       getTagForRecord(RD), RDName, RDContext, DefUnit, Line, 0, Size, Align,
       Flags, Identifier);
 
   // Elements of composite types usually have back to the type, creating
   // uniquing cycles.  Distinct nodes are more efficient.

clang/test/CodeGenCXX/debug-info-export_symbols.cpp

+// RUN: %clang_cc1 -emit-llvm -debug-info-kind=standalone -triple %itanium_abi_triple %s -o - | FileCheck %s
+
+// CHECK: [[SCOPE:![0-9]+]] = distinct !DICompositeType({{.*}}flags: DIFlagTypePassByValue
+// CHECK: !DICompositeType(tag: DW_TAG_structure_type, scope: [[SCOPE]]
+// CHECK-SAME:                              DIFlagExportSymbols | DIFlagTypePassByValue
+struct A {
+ // Anonymous class exports its symbols into A
+ struct {
+     int y;
+ };
+} a;