[SymbolFile] Implement GetCompleteObjCClass for .debug_names

When running the test suite with .debug_names a bunch of tests were
failing because GetCompleteObjCClass was not yet implemented for
DebugNamesDWARFIndex. This patch adds the required logic.

We use the .debug_names to find the Objective-C class and then rely on
DW_AT_APPLE_objc_complete_type to find the complete type. If we can't
find it or the attribute is not supported, we return a list of potential
complete types.

Differential revision: https://reviews.llvm.org/D48596

llvm-svn: 335776

lldb/packages/Python/lldbsuite/test/lang/objc/forward-decl/TestForwardDecl.py

@@ -23,9 +23,8 @@ class ForwardDeclTestCase(TestBase):
         self.line = line_number(self.source, '// Set breakpoint 0 here.')
         self.shlib_names = ["Container"]
 
-    @skipUnlessDarwin
-    def test_expr(self):
-        self.build()
+    def do_test(self, dictionary=None):
+        self.build(dictionary=dictionary)
 
         # Create a target by the debugger.
         target = self.dbg.CreateTarget(self.getBuildArtifact("a.out"))
@@ -57,3 +56,17 @@ class ForwardDeclTestCase(TestBase):
         # This should display correctly.
         self.expect("expression [j getMember]", VARIABLES_DISPLAYED_CORRECTLY,
                     substrs=["= 0x"])
+
+    @skipUnlessDarwin
+    def test_expr(self):
+        self.do_test()
+
+    @no_debug_info_test
+    @skipUnlessDarwin
+    @skipIf(compiler=no_match("clang"))
+    @skipIf(compiler_version=["<", "7.0"])
+    def test_debug_names(self):
+        """Test that we are able to find complete types when using DWARF v5
+        accelerator tables"""
+        self.do_test(
+            dict(CFLAGS_EXTRAS="-dwarf-version=5 -mllvm -accel-tables=Dwarf"))

lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp

@@ -146,6 +146,49 @@ void DebugNamesDWARFIndex::GetGlobalVariables(const DWARFUnit &cu,
   }
 }
 
+void DebugNamesDWARFIndex::GetCompleteObjCClass(ConstString class_name,
+                                                bool must_be_implementation,
+                                                DIEArray &offsets) {
+  m_fallback.GetCompleteObjCClass(class_name, must_be_implementation, offsets);
+
+  // Keep a list of incomplete types as fallback for when we don't find the
+  // complete type.
+  DIEArray incomplete_types;
+
+  for (const DebugNames::Entry &entry :
+       m_debug_names_up->equal_range(class_name.GetStringRef())) {
+    if (entry.tag() != DW_TAG_structure_type &&
+        entry.tag() != DW_TAG_class_type)
+      continue;
+
+    DIERef ref = ToDIERef(entry);
+    if (!ref)
+      continue;
+
+    DWARFUnit *cu = m_debug_info.GetCompileUnit(ref.cu_offset);
+    if (!cu || !cu->Supports_DW_AT_APPLE_objc_complete_type()) {
+      incomplete_types.push_back(ref);
+      continue;
+    }
+
+    // FIXME: We should return DWARFDIEs so we don't have to resolve it twice.
+    DWARFDIE die = m_debug_info.GetDIE(ref);
+    if (!die)
+      continue;
+
+    if (die.GetAttributeValueAsUnsigned(DW_AT_APPLE_objc_complete_type, 0)) {
+      // If we find the complete version we're done.
+      offsets.push_back(ref);
+      return;
+    } else {
+      incomplete_types.push_back(ref);
+    }
+  }
+
+  offsets.insert(offsets.end(), incomplete_types.begin(),
+                 incomplete_types.end());
+}
+
 void DebugNamesDWARFIndex::GetTypes(ConstString name, DIEArray &offsets) {
   m_fallback.GetTypes(name, offsets);
 

lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.h

@@ -31,7 +31,7 @@ public:
   void GetGlobalVariables(const DWARFUnit &cu, DIEArray &offsets) override;
   void GetObjCMethods(ConstString class_name, DIEArray &offsets) override {}
   void GetCompleteObjCClass(ConstString class_name, bool must_be_implementation,
-                            DIEArray &offsets) override {}
+                            DIEArray &offsets) override;
   void GetTypes(ConstString name, DIEArray &offsets) override;
   void GetTypes(const DWARFDeclContext &context, DIEArray &offsets) override;
   void GetNamespaces(ConstString name, DIEArray &offsets) override;