DWARF: Provide accessors to DIERef fields

Summary:
Instead of accessing the fields directly, use accessor functions to
provide access to the DIERef components. This allows us to decouple the
external interface, from the internal representation. The external
interface can use llvm::Optional and similar goodies, while the data can
still be stored internally in a more compact representation.

I also document the purpose of the existing DIERef fields.

The main motivation for this change is a need to introduce an additional
field to the DIERef class, but I believe the change has its own merit.

Reviewers: JDevlieghere, aprantl, clayborg

Subscribers: arphaman, lldb-commits

Differential Revision: https://reviews.llvm.org/D63400

llvm-svn: 363910

9 files changed, 65 insertions, 24 deletions

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp b/lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
index 9e990ae1762..bc435bc54ae 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
@@ -160,7 +160,7 @@ void AppleDWARFIndex::ReportInvalidDIERef(const DIERef &ref,
   m_module.ReportErrorIfModifyDetected(
       "the DWARF debug information has been modified (accelerator table had "
       "bad die 0x%8.8x for '%s')\n",
-      ref.die_offset, name.str().c_str());
+      ref.die_offset(), name.str().c_str());
 }
 
 void AppleDWARFIndex::Dump(Stream &s) {
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DIERef.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DIERef.cpp
index c95188760d4..11dbe3c0a1f 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DIERef.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DIERef.cpp
@@ -7,3 +7,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "DIERef.h"
+#include "llvm/Support/Format.h"
+
+void llvm::format_provider<DIERef>::format(const DIERef &ref, raw_ostream &OS,
+                                           StringRef Style) {
+  OS << (ref.section() == DIERef::DebugInfo ? "INFO" : "TYPE");
+  if (ref.unit_offset())
+    OS << "/" << format_hex_no_prefix(*ref.unit_offset(), 8);
+  OS << "/" << format_hex_no_prefix(ref.die_offset(), 8);
+}
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DIERef.h b/lldb/source/Plugins/SymbolFile/DWARF/DIERef.h
index e7843da404a..476539bf840 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DIERef.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DIERef.h
@@ -10,19 +10,51 @@
 #define SymbolFileDWARF_DIERef_h_
 
 #include "lldb/Core/dwarf.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/Support/FormatProviders.h"
 #include <vector>
 
-struct DIERef {
+/// Identifies a DWARF debug info entry within a given Module. It contains three
+/// "coordinates":
+/// - section: identifies the section of the debug info entry: debug_info or
+///   debug_types
+/// - unit_offset: the offset of the unit containing the debug info entry. For
+///   regular (unsplit) units, this field is optional, as the die_offset is
+///   enough to uniquely identify the containing unit. For split units, this
+///   field must contain the offset of the skeleton unit in the main object
+///   file.
+/// - die_offset: The offset of te debug info entry as an absolute offset from
+///   the beginning of the section specified in the section field.
+class DIERef {
+public:
   enum Section : uint8_t { DebugInfo, DebugTypes };
 
-  DIERef(Section s, dw_offset_t c, dw_offset_t d)
-      : section(s), cu_offset(c), die_offset(d) {}
+  DIERef(Section s, llvm::Optional<dw_offset_t> u, dw_offset_t d)
+      : m_section(s), m_unit_offset(u.getValueOr(DW_INVALID_OFFSET)),
+        m_die_offset(d) {}
 
-  Section section;
-  dw_offset_t cu_offset;
-  dw_offset_t die_offset;
+  Section section() const { return static_cast<Section>(m_section); }
+
+  llvm::Optional<dw_offset_t> unit_offset() const {
+    if (m_unit_offset != DW_INVALID_OFFSET)
+      return m_unit_offset;
+    return llvm::None;
+  }
+
+  dw_offset_t die_offset() const { return m_die_offset; }
+
+private:
+  unsigned m_section : 1;
+  dw_offset_t m_unit_offset;
+  dw_offset_t m_die_offset;
 };
 
 typedef std::vector<DIERef> DIEArray;
 
+namespace llvm {
+template<> struct format_provider<DIERef> {
+  static void format(const DIERef &ref, raw_ostream &OS, StringRef Style);
+};
+} // namespace llvm
+
 #endif // SymbolFileDWARF_DIERef_h_
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
index fc04580da96..cd2dfbc39f0 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -149,10 +149,9 @@ DWARFUnit *DWARFDebugInfo::GetUnitAtOffset(DIERef::Section section,
 }
 
 DWARFUnit *DWARFDebugInfo::GetUnit(const DIERef &die_ref) {
-  if (die_ref.cu_offset == DW_INVALID_OFFSET)
-    return GetUnitContainingDIEOffset(die_ref.section, die_ref.die_offset);
-  else
-    return GetUnitAtOffset(die_ref.section, die_ref.cu_offset);
+  if (die_ref.unit_offset())
+    return GetUnitAtOffset(die_ref.section(), *die_ref.unit_offset());
+  return GetUnitContainingDIEOffset(die_ref.section(), die_ref.die_offset());
 }
 
 DWARFUnit *
@@ -194,7 +193,7 @@ DWARFDIE
 DWARFDebugInfo::GetDIE(const DIERef &die_ref) {
   DWARFUnit *cu = GetUnit(die_ref);
   if (cu)
-    return cu->GetDIE(die_ref.die_offset);
+    return cu->GetDIE(die_ref.die_offset());
   return DWARFDIE(); // Not found
 }
 
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp
index 5e1624a82d8..b7bbe41a7a8 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp
@@ -166,7 +166,7 @@ void DebugNamesDWARFIndex::GetCompleteObjCClass(ConstString class_name,
       continue;
 
     DWARFUnit *cu = m_debug_info.GetUnitAtOffset(DIERef::Section::DebugInfo,
-                                                 ref->cu_offset);
+                                                 *ref->unit_offset());
     if (!cu || !cu->Supports_DW_AT_APPLE_objc_complete_type()) {
       incomplete_types.push_back(*ref);
       continue;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/HashedNameToDIE.h b/lldb/source/Plugins/SymbolFile/DWARF/HashedNameToDIE.h
index 06e157ea5e6..ddb01de02a4 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/HashedNameToDIE.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/HashedNameToDIE.h
@@ -61,7 +61,7 @@ public:
     DIEInfo(dw_offset_t o, dw_tag_t t, uint32_t f, uint32_t h);
 
     explicit operator DIERef() const {
-      return DIERef(DIERef::Section::DebugInfo, DW_INVALID_OFFSET, die_offset);
+      return DIERef(DIERef::Section::DebugInfo, llvm::None, die_offset);
     }
   };
 
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/NameToDIE.cpp b/lldb/source/Plugins/SymbolFile/DWARF/NameToDIE.cpp
index 6710ae1f2c6..26b6dde781e 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/NameToDIE.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/NameToDIE.cpp
@@ -26,6 +26,7 @@ void NameToDIE::Finalize() {
 }
 
 void NameToDIE::Insert(ConstString name, const DIERef &die_ref) {
+  assert(die_ref.unit_offset().hasValue());
   m_map.Append(name, die_ref);
 }
 
@@ -44,7 +45,7 @@ size_t NameToDIE::FindAllEntriesForCompileUnit(dw_offset_t cu_offset,
   const uint32_t size = m_map.GetSize();
   for (uint32_t i = 0; i < size; ++i) {
     const DIERef &die_ref = m_map.GetValueAtIndexUnchecked(i);
-    if (cu_offset == die_ref.cu_offset)
+    if (cu_offset == *die_ref.unit_offset())
       info_array.push_back(die_ref);
   }
   return info_array.size() - initial_size;
@@ -53,10 +54,8 @@ size_t NameToDIE::FindAllEntriesForCompileUnit(dw_offset_t cu_offset,
 void NameToDIE::Dump(Stream *s) {
   const uint32_t size = m_map.GetSize();
   for (uint32_t i = 0; i < size; ++i) {
-    ConstString cstr = m_map.GetCStringAtIndex(i);
-    const DIERef &die_ref = m_map.GetValueAtIndexUnchecked(i);
-    s->Printf("%p: {0x%8.8x/0x%8.8x} \"%s\"\n", (const void *)cstr.GetCString(),
-              die_ref.cu_offset, die_ref.die_offset, cstr.GetCString());
+    s->Format("{0} \"{1}\"\n", m_map.GetValueAtIndexUnchecked(i),
+              m_map.GetCStringAtIndexUnchecked(i));
   }
 }
 
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
index 947cca13282..d5e2eb873ea 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -277,8 +277,9 @@ public:
   }
 
   lldb::user_id_t GetUID(const DIERef &ref) {
-    return GetID() | ref.die_offset |
-           (lldb::user_id_t(ref.section == DIERef::Section::DebugTypes) << 63);
+    return GetID() | ref.die_offset() |
+           (lldb::user_id_t(ref.section() == DIERef::Section::DebugTypes)
+            << 63);
   }
 
   virtual std::unique_ptr<SymbolFileDWARFDwo>
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
index e3c178c89d5..5ddbbd0c606 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
@@ -124,7 +124,8 @@ SymbolFileDWARFDwo::GetTypeSystemForLanguage(LanguageType language) {
 
 DWARFDIE
 SymbolFileDWARFDwo::GetDIE(const DIERef &die_ref) {
-  lldbassert(die_ref.cu_offset == m_base_dwarf_cu.GetOffset() ||
-             die_ref.cu_offset == DW_INVALID_OFFSET);
-  return DebugInfo()->GetDIEForDIEOffset(die_ref.section, die_ref.die_offset);
+  lldbassert(!die_ref.unit_offset() ||
+             *die_ref.unit_offset() == m_base_dwarf_cu.GetOffset());
+  return DebugInfo()->GetDIEForDIEOffset(die_ref.section(),
+                                         die_ref.die_offset());
 }