Reapply "[llvm/DWARF] Recursively resolve DW_AT_signature references"… (#99495)

… (#99444)

The previous version introduced a bug (caught by cross-project tests).
Explicit signature resolution is still necessary when one wants to
access the children (not attributes) of a given DIE.

The new version keeps just the findRecursively extension, and reverts
all the DWARFTypePrinter modifications.

Author: labath

llvm/lib/DebugInfo/DWARF/DWARFDie.cpp

@@ -291,13 +291,12 @@ DWARFDie::findRecursively(ArrayRef<dwarf::Attribute> Attrs) const {
     if (auto Value = Die.find(Attrs))
       return Value;
 
-    if (auto D = Die.getAttributeValueAsReferencedDie(DW_AT_abstract_origin))
-      if (Seen.insert(D).second)
-        Worklist.push_back(D);
-
-    if (auto D = Die.getAttributeValueAsReferencedDie(DW_AT_specification))
-      if (Seen.insert(D).second)
-        Worklist.push_back(D);
+    for (dwarf::Attribute Attr :
+         {DW_AT_abstract_origin, DW_AT_specification, DW_AT_signature}) {
+      if (auto D = Die.getAttributeValueAsReferencedDie(Attr))
+        if (Seen.insert(D).second)
+          Worklist.push_back(D);
+    }
   }
 
   return std::nullopt;

llvm/unittests/DebugInfo/DWARF/DWARFDieTest.cpp

@@ -643,4 +643,65 @@ TEST(DWARFDie, getDeclFileSpecificationAcrossCUBoundary) {
   EXPECT_EQ(DeclFile, Ref);
 }
 
+TEST(DWARFDie, getNameFromTypeUnit) {
+  const char *yamldata = R"(
+  debug_abbrev:
+    - ID:              0
+      Table:
+        - Code:            0x1
+          Tag:             DW_TAG_compile_unit
+          Children:        DW_CHILDREN_yes
+        - Code:            0x2
+          Tag:             DW_TAG_structure_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_signature
+              Form:            DW_FORM_ref_sig8
+        - Code:            0x3
+          Tag:             DW_TAG_type_unit
+          Children:        DW_CHILDREN_yes
+        - Code:            0x4
+          Tag:             DW_TAG_structure_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_string
+  debug_info:
+    - Version:         5
+      UnitType:        DW_UT_compile
+      AbbrevTableID:   0
+      Entries:
+        - AbbrCode:        0x1
+        - AbbrCode:        0x2
+          Values:
+            - Value:           0xdeadbeefbaadf00d
+        - AbbrCode:        0x0
+    - Version:         5
+      UnitType:        DW_UT_type
+      AbbrevTableID:   0
+      TypeSignature:   0xdeadbeefbaadf00d
+      TypeOffset:      25
+      Entries:
+        - AbbrCode:        0x3
+        - AbbrCode:        0x4
+          Values:
+            - CStr:        "STRUCT"
+        - AbbrCode:        0x0
+  )";
+
+  Expected<StringMap<std::unique_ptr<MemoryBuffer>>> Sections =
+      DWARFYAML::emitDebugSections(StringRef(yamldata),
+                                   /*IsLittleEndian=*/true,
+                                   /*Is64BitAddrSize=*/true);
+  ASSERT_THAT_EXPECTED(Sections, Succeeded());
+  std::unique_ptr<DWARFContext> Ctx =
+      DWARFContext::create(*Sections, 4, /*isLittleEndian=*/true);
+  DWARFCompileUnit *CU = Ctx->getCompileUnitForOffset(0);
+  ASSERT_NE(nullptr, CU);
+  DWARFDie Die = CU->getUnitDIE(/*ExtractUnitDIEOnly=*/false).getFirstChild();
+  ASSERT_TRUE(Die.isValid());
+
+  ASSERT_STREQ(Die.getName(DINameKind::ShortName), "STRUCT");
+}
+
 } // end anonymous namespace