Fix recursive attribute fetching in DWARFDie

[clayborg]

Summary

The previous implementation would only look 1 DW_AT_specification or DW_AT_abstract_origin deep. This means DWARFDie::getName() would fail in certain cases. I ran into such a case while creating a tool that used the LLVM DWARF parser to generate a symbolication format so I have seen this in the wild.

[clayborg]

This change also stops extra calls to the Die.find() when a new Die wasn't fetched using Die.getAttributeValueAsReferencedDie as it was always calling Die.Find() even with the old Die...

[clayborg]

Ping

[probinson]

It looks like the test exercises a recursive DW_AT_abstract_origin but not a recursive DW_AT_specification? The code does both, so the test should verify both.

[clayborg]

I can add a test that does this if needed.

lib/DebugInfo/DWARF/DWARFDie.cpp

DWARFDie::find(ArrayRef<dwarf::Attribute> Attrs) const {
   }
   return None;
 }
 
 Optional<DWARFFormValue>
 DWARFDie::findRecursively(ArrayRef<dwarf::Attribute> Attrs) const {
   if (!isValid())
     return None;
-  auto Die = *this;
-  if (auto Value = Die.find(Attrs))
+  if (auto Value = find(Attrs))
     return Value;
-  if (auto D = Die.getAttributeValueAsReferencedDie(DW_AT_abstract_origin))
-    Die = D;
-  if (auto Value = Die.find(Attrs))
+  if (auto Die = getAttributeValueAsReferencedDie(DW_AT_abstract_origin)) {
+    if (auto Value = Die.findRecursively(Attrs))
       return Value;
-  if (auto D = Die.getAttributeValueAsReferencedDie(DW_AT_specification))
-    Die = D;
-  if (auto Value = Die.find(Attrs))
+  }
+  if (auto Die = getAttributeValueAsReferencedDie(DW_AT_specification)) {
+    if (auto Value = Die.findRecursively(Attrs))
       return Value;
+  }
   return None;
 }
 
 DWARFDie
 DWARFDie::getAttributeValueAsReferencedDie(dwarf::Attribute Attr) const {
   if (auto SpecRef = toReference(find(Attr))) {
     if (auto SpecUnit = U->getUnitSection().getUnitForOffset(*SpecRef))
       return SpecUnit->getDIEForOffset(*SpecRef);

unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

TEST(DWARFDebugInfo, TestFindRecurse) {
   StringRef SpecDieName = "spec";
   StringRef SpecLinkageName = "spec_linkage";
   StringRef AbsDieName = "abs";
   // Scope to allow us to re-use the same DIE names
   {
     auto CUDie = CU.getUnitDIE();
     auto FuncSpecDie = CUDie.addChild(DW_TAG_subprogram);
     auto FuncAbsDie = CUDie.addChild(DW_TAG_subprogram);
+    // Put the linkage name in a second abstract origin DIE to ensure we
+    // recurse through more than just one DIE when looking for attributes.
+    auto FuncAbsDie2 = CUDie.addChild(DW_TAG_subprogram);
     auto FuncDie = CUDie.addChild(DW_TAG_subprogram);
     auto VarAbsDie = CUDie.addChild(DW_TAG_variable);
     auto VarDie = CUDie.addChild(DW_TAG_variable);
     FuncSpecDie.addAttribute(DW_AT_name, DW_FORM_strp, SpecDieName);
-    FuncAbsDie.addAttribute(DW_AT_linkage_name, DW_FORM_strp, SpecLinkageName);
+    FuncAbsDie2.addAttribute(DW_AT_linkage_name, DW_FORM_strp, SpecLinkageName);
     FuncAbsDie.addAttribute(DW_AT_specification, DW_FORM_ref4, FuncSpecDie);
+    FuncAbsDie.addAttribute(DW_AT_abstract_origin, DW_FORM_ref4, FuncAbsDie2);
     FuncDie.addAttribute(DW_AT_abstract_origin, DW_FORM_ref4, FuncAbsDie);
     VarAbsDie.addAttribute(DW_AT_name, DW_FORM_strp, AbsDieName);
     VarDie.addAttribute(DW_AT_abstract_origin, DW_FORM_ref4, VarAbsDie);
   }
 
   MemoryBufferRef FileBuffer(DG->generate(), "dwarf");
   auto Obj = object::ObjectFile::createObjectFile(FileBuffer);
   EXPECT_TRUE((bool)Obj);
   std::unique_ptr<DWARFContext> DwarfContext = DWARFContext::create(**Obj);
 
   // Verify the number of compile units is correct.
   uint32_t NumCUs = DwarfContext->getNumCompileUnits();
   EXPECT_EQ(NumCUs, 1u);
   DWARFCompileUnit *U = DwarfContext->getCompileUnitAtIndex(0);
 
   // Get the compile unit DIE is valid.
   auto CUDie = U->getUnitDIE(false);
   EXPECT_TRUE(CUDie.isValid());
 
   auto FuncSpecDie = CUDie.getFirstChild();
   auto FuncAbsDie = FuncSpecDie.getSibling();
-  auto FuncDie = FuncAbsDie.getSibling();
+  auto FuncAbsDie2 = FuncAbsDie.getSibling();
+  auto FuncDie = FuncAbsDie2.getSibling();
   auto VarAbsDie = FuncDie.getSibling();
   auto VarDie = VarAbsDie.getSibling();
 
   // Make sure we can't extract the name from the specification die when using
   // DWARFDie::find() since it won't check the DW_AT_specification DIE.
   EXPECT_FALSE(FuncDie.find(DW_AT_name));
 
   // Make sure we can extract the name from the specification die when using