Introduce DWARFContext.

LLVM's DWARF parsing library has a class called DWARFContext which holds
all of the various DWARF data sections and lots of other information.
LLDB's on the other hand stores all of this directly in SymbolFileDWARF
/ SymbolFileDWARFDwo and passes this interface around through the
parsing library. Obviously this is incompatible with a world where the
low level interface does not depend on the high level interface, so we
need to move towards a model similar to LLVM's - i.e. all of the context
needed for low level parsing should be in a single class, and that class
gets passed around.

This patch is a small incremental step towards achieving this. The
interface and internals deviate from LLVM's for technical reasons, but
the high level idea is the same. The goal is, eventually, to remove all
occurrences of SymbolFileDWARF from the low level parsing code.

For now I've chosen a very simple section - the .debug_aranges section
to move into DWARFContext while leaving everything else unchanged. In
the short term this is a bit confusing because now the information you
need might come from either of 2 different locations. But it's a huge
refactor to do this all at once and runs a much higher risk of breaking
things. So I think it would be wise to do this in very small pieces.

TL;DR - No functional change

Differential Revision: https://reviews.llvm.org/D59562

llvm-svn: 356612

8 files changed, 108 insertions, 54 deletions

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/CMakeLists.txt b/lldb/source/Plugins/SymbolFile/DWARF/CMakeLists.txt
index 2d614a64091..39efc9852af 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/CMakeLists.txt
+++ b/lldb/source/Plugins/SymbolFile/DWARF/CMakeLists.txt
@@ -7,6 +7,7 @@ add_lldb_library(lldbPluginSymbolFileDWARF PLUGIN
   DWARFAttribute.cpp
   DWARFBaseDIE.cpp
   DWARFCompileUnit.cpp
+  DWARFContext.cpp
   DWARFDataExtractor.cpp
   DWARFDebugAbbrev.cpp
   DWARFDebugAranges.cpp
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
new file mode 100644
index 00000000000..d8a44ccacb9
--- /dev/null
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.cpp
@@ -0,0 +1,43 @@
+//===-- DWARFContext.cpp ----------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "DWARFContext.h"
+
+#include "lldb/Core/Section.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+static const DWARFDataExtractor *
+LoadOrGetSection(Module &module, SectionType section_type,
+                 llvm::Optional<DWARFDataExtractor> &extractor) {
+  if (extractor.hasValue())
+    return extractor->GetByteSize() > 0 ? extractor.getPointer() : nullptr;
+
+  // Initialize to an empty extractor so that we always take the fast path going
+  // forward.
+  extractor.emplace();
+
+  const SectionList *section_list = module.GetSectionList();
+  if (!section_list)
+    return nullptr;
+
+  auto section_sp = section_list->FindSectionByType(section_type, true);
+  if (!section_sp)
+    return nullptr;
+
+  section_sp->GetSectionData(*extractor);
+  return extractor.getPointer();
+}
+
+DWARFContext::DWARFContext(Module &module) : m_module(module) {}
+
+const DWARFDataExtractor *DWARFContext::getOrLoadArangesData() {
+  return LoadOrGetSection(m_module, eSectionTypeDWARFDebugAranges,
+                          m_data_debug_aranges);
+}
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.h
new file mode 100644
index 00000000000..02887838705
--- /dev/null
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.h
@@ -0,0 +1,30 @@
+//===-- DWARFContext.h ------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_PLUGINS_SYMBOLFILE_DWARF_DWARFCONTEXT_H
+#define LLDB_PLUGINS_SYMBOLFILE_DWARF_DWARFCONTEXT_H
+
+#include "DWARFDataExtractor.h"
+#include "lldb/Core/Module.h"
+#include "llvm/ADT/Optional.h"
+#include <memory>
+
+namespace lldb_private {
+class DWARFContext {
+private:
+  Module &m_module;
+  llvm::Optional<DWARFDataExtractor> m_data_debug_aranges;
+
+public:
+  explicit DWARFContext(Module &module);
+
+  const DWARFDataExtractor *getOrLoadArangesData();
+};
+} // namespace lldb_private
+
+#endif
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
index 721d002d18e..9f235ffad6c 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -17,7 +17,7 @@
 #include "lldb/Utility/Stream.h"
 
 #include "DWARFCompileUnit.h"
-#include "DWARFDebugAranges.h"
+#include "DWARFContext.h"
 #include "DWARFDebugAranges.h"
 #include "DWARFDebugInfo.h"
 #include "DWARFDebugInfoEntry.h"
@@ -30,8 +30,9 @@ using namespace std;
 //----------------------------------------------------------------------
 // Constructor
 //----------------------------------------------------------------------
-DWARFDebugInfo::DWARFDebugInfo()
-    : m_dwarf2Data(NULL), m_compile_units(), m_cu_aranges_up() {}
+DWARFDebugInfo::DWARFDebugInfo(lldb_private::DWARFContext &context)
+    : m_dwarf2Data(NULL), m_context(context), m_compile_units(),
+      m_cu_aranges_up() {}
 
 //----------------------------------------------------------------------
 // SetDwarfData
@@ -48,10 +49,10 @@ llvm::Expected<DWARFDebugAranges &> DWARFDebugInfo::GetCompileUnitAranges() {
   assert(m_dwarf2Data);
 
   m_cu_aranges_up = llvm::make_unique<DWARFDebugAranges>();
-  const DWARFDataExtractor &debug_aranges_data =
-      m_dwarf2Data->get_debug_aranges_data();
-  if (debug_aranges_data.GetByteSize() > 0) {
-    llvm::Error error = m_cu_aranges_up->extract(debug_aranges_data);
+  const DWARFDataExtractor *debug_aranges_data =
+      m_context.getOrLoadArangesData();
+  if (debug_aranges_data) {
+    llvm::Error error = m_cu_aranges_up->extract(*debug_aranges_data);
     if (error)
       return std::move(error);
   }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
index 500e3627275..a29e3b17a75 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
@@ -19,6 +19,10 @@
 #include "lldb/lldb-private.h"
 #include "llvm/Support/Error.h"
 
+namespace lldb_private {
+class DWARFContext;
+}
+
 typedef std::multimap<const char *, dw_offset_t, CStringCompareFunctionObject>
     CStringToDIEMap;
 typedef CStringToDIEMap::iterator CStringToDIEMapIter;
@@ -32,7 +36,7 @@ public:
                                   const dw_offset_t next_offset,
                                   const uint32_t depth, void *userData);
 
-  DWARFDebugInfo();
+  explicit DWARFDebugInfo(lldb_private::DWARFContext &context);
   void SetDwarfData(SymbolFileDWARF *dwarf2Data);
 
   size_t GetNumCompileUnits();
@@ -62,6 +66,7 @@ protected:
   // Member variables
   //----------------------------------------------------------------------
   SymbolFileDWARF *m_dwarf2Data;
+  lldb_private::DWARFContext &m_context;
   CompileUnitColl m_compile_units;
   std::unique_ptr<DWARFDebugAranges>
       m_cu_aranges_up; // A quick address to compile unit table
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 339ec328a9d..3952a392911 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -355,12 +355,13 @@ SymbolFileDWARF::SymbolFileDWARF(ObjectFile *objfile)
                                   << 32), // Used by SymbolFileDWARFDebugMap to
                                           // when this class parses .o files to
                                           // contain the .o file index/ID
-      m_debug_map_module_wp(), m_debug_map_symfile(NULL), m_data_debug_abbrev(),
-      m_data_debug_aranges(), m_data_debug_frame(), m_data_debug_info(),
-      m_data_debug_line(), m_data_debug_macro(), m_data_debug_loc(),
-      m_data_debug_ranges(), m_data_debug_rnglists(), m_data_debug_str(),
-      m_data_apple_names(), m_data_apple_types(), m_data_apple_namespaces(),
-      m_abbr(), m_info(), m_line(), m_fetched_external_modules(false),
+      m_debug_map_module_wp(), m_debug_map_symfile(NULL),
+      m_context(*objfile->GetModule()), m_data_debug_abbrev(),
+      m_data_debug_frame(), m_data_debug_info(), m_data_debug_line(),
+      m_data_debug_macro(), m_data_debug_loc(), m_data_debug_ranges(),
+      m_data_debug_rnglists(), m_data_debug_str(), m_data_apple_names(),
+      m_data_apple_types(), m_data_apple_namespaces(), m_abbr(), m_info(),
+      m_line(), m_fetched_external_modules(false),
       m_supports_DW_AT_APPLE_objc_complete_type(eLazyBoolCalculate), m_ranges(),
       m_unique_ast_type_map() {}
 
@@ -394,15 +395,6 @@ TypeSystem *SymbolFileDWARF::GetTypeSystemForLanguage(LanguageType language) {
 
 void SymbolFileDWARF::InitializeObject() {
   Log *log = LogChannelDWARF::GetLogIfAll(DWARF_LOG_DEBUG_INFO);
-  ModuleSP module_sp(m_obj_file->GetModule());
-  if (module_sp) {
-    const SectionList *section_list = module_sp->GetSectionList();
-    Section *section =
-        section_list->FindSectionByName(GetDWARFMachOSegmentName()).get();
-
-    if (section)
-      m_obj_file->ReadSectionData(section, m_dwarf_data);
-  }
 
   if (!GetGlobalPluginProperties()->IgnoreFileIndexes()) {
     DWARFDataExtractor apple_names, apple_namespaces, apple_types, apple_objc;
@@ -549,19 +541,15 @@ void SymbolFileDWARF::LoadSectionData(lldb::SectionType sect_type,
                                       DWARFDataExtractor &data) {
   ModuleSP module_sp(m_obj_file->GetModule());
   const SectionList *section_list = module_sp->GetSectionList();
-  if (section_list) {
-    SectionSP section_sp(section_list->FindSectionByType(sect_type, true));
-    if (section_sp) {
-      // See if we memory mapped the DWARF segment?
-      if (m_dwarf_data.GetByteSize()) {
-        data.SetData(m_dwarf_data, section_sp->GetOffset(),
-                     section_sp->GetFileSize());
-      } else {
-        if (m_obj_file->ReadSectionData(section_sp.get(), data) == 0)
-          data.Clear();
-      }
-    }
-  }
+  if (!section_list)
+    return;
+
+  SectionSP section_sp(section_list->FindSectionByType(sect_type, true));
+  if (!section_sp)
+    return;
+
+  data.Clear();
+  m_obj_file->ReadSectionData(section_sp.get(), data);
 }
 
 const DWARFDataExtractor &SymbolFileDWARF::get_debug_abbrev_data() {
@@ -573,11 +561,6 @@ const DWARFDataExtractor &SymbolFileDWARF::get_debug_addr_data() {
   return GetCachedSectionData(eSectionTypeDWARFDebugAddr, m_data_debug_addr);
 }
 
-const DWARFDataExtractor &SymbolFileDWARF::get_debug_aranges_data() {
-  return GetCachedSectionData(eSectionTypeDWARFDebugAranges,
-                              m_data_debug_aranges);
-}
-
 const DWARFDataExtractor &SymbolFileDWARF::get_debug_frame_data() {
   return GetCachedSectionData(eSectionTypeDWARFDebugFrame, m_data_debug_frame);
 }
@@ -690,10 +673,8 @@ DWARFDebugInfo *SymbolFileDWARF::DebugInfo() {
     Timer scoped_timer(func_cat, "%s this = %p", LLVM_PRETTY_FUNCTION,
                        static_cast<void *>(this));
     if (get_debug_info_data().GetByteSize() > 0) {
-      m_info.reset(new DWARFDebugInfo());
-      if (m_info) {
-        m_info->SetDwarfData(this);
-      }
+      m_info = llvm::make_unique<DWARFDebugInfo>(m_context);
+      m_info->SetDwarfData(this);
     }
   }
   return m_info.get();
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
index 7d4b9e5128b..0328e5ff223 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -30,6 +30,7 @@
 #include "lldb/Utility/RangeMap.h"
 #include "lldb/lldb-private.h"
 
+#include "DWARFContext.h"
 #include "DWARFDataExtractor.h"
 #include "DWARFDefines.h"
 #include "DWARFIndex.h"
@@ -227,7 +228,6 @@ public:
 
   virtual const lldb_private::DWARFDataExtractor &get_debug_abbrev_data();
   virtual const lldb_private::DWARFDataExtractor &get_debug_addr_data();
-  const lldb_private::DWARFDataExtractor &get_debug_aranges_data();
   const lldb_private::DWARFDataExtractor &get_debug_frame_data();
   virtual const lldb_private::DWARFDataExtractor &get_debug_info_data();
   const lldb_private::DWARFDataExtractor &get_debug_line_data();
@@ -458,11 +458,10 @@ protected:
   llvm::once_flag m_dwp_symfile_once_flag;
   std::unique_ptr<SymbolFileDWARFDwp> m_dwp_symfile;
 
-  lldb_private::DWARFDataExtractor m_dwarf_data;
+  lldb_private::DWARFContext m_context;
 
   DWARFDataSegment m_data_debug_abbrev;
   DWARFDataSegment m_data_debug_addr;
-  DWARFDataSegment m_data_debug_aranges;
   DWARFDataSegment m_data_debug_frame;
   DWARFDataSegment m_data_debug_info;
   DWARFDataSegment m_data_debug_line;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
index 9d118d63dba..9542fde7e6a 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
@@ -33,12 +33,6 @@ void SymbolFileDWARFDwo::LoadSectionData(lldb::SectionType sect_type,
   if (section_list) {
     SectionSP section_sp(section_list->FindSectionByType(sect_type, true));
     if (section_sp) {
-      // See if we memory mapped the DWARF segment?
-      if (m_dwarf_data.GetByteSize()) {
-        data.SetData(m_dwarf_data, section_sp->GetOffset(),
-                     section_sp->GetFileSize());
-        return;
-      }
 
       if (m_obj_file->ReadSectionData(section_sp.get(), data) != 0)
         return;