This change removes the dependency on DwarfDebug that was used for DW_FORM_ref_addr by making a new DIEUnit class in DIE.cpp.

The DIEUnit class represents a compile or type unit and it owns the unit DIE as an instance variable. This allows anyone with a DIE, to get the unit DIE, and then get back to its DIEUnit without adding any new ivars to the DIE class. Why was this needed? The DIE class has an Offset that is always the CU relative DIE offset, not the "offset in debug info section" as was commented in the header file (the comment has been corrected). This is great for performance because most DIE references are compile unit relative and this means most code that accessed the DIE's offset didn't need to make it into a compile unit relative offset because it already was. When we needed to emit a DW_FORM_ref_addr though, we needed to find the absolute offset of the DIE by finding the DIE's compile/type unit. This class did have the absolute debug info/type offset and could be added to the CU relative offset to compute the absolute offset. With this change we can easily get back to a DIE's DIEUnit which will have this needed offset. Prior to this is required having a DwarfDebug and required calling:

DwarfCompileUnit *DwarfDebug::lookupUnit(const DIE *CU) const;
Now we can use the DIEUnit class to do so without needing DwarfDebug. All clients now use DIEUnit objects (the DwarfDebug stack and the DwarfLinker). A follow on patch for the DWARF generator will also take advantage of this.

Differential Revision: https://reviews.llvm.org/D27170

llvm-svn: 288399

9 files changed, 63 insertions, 85 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
index afb7e87d36a..6e9834a7cf0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -108,6 +108,10 @@ void DIEAbbrev::print(raw_ostream &O) {
 LLVM_DUMP_METHOD
 void DIEAbbrev::dump() { print(dbgs()); }
 
+DIE *DIE::getParent() const {
+  return Owner.dyn_cast<DIE*>();
+}
+
 DIEAbbrev DIE::generateAbbrev() const {
   DIEAbbrev Abbrev(Tag, hasChildren());
   for (const DIEValue &V : values())
@@ -115,17 +119,13 @@ DIEAbbrev DIE::generateAbbrev() const {
   return Abbrev;
 }
 
-/// Climb up the parent chain to get the unit DIE to which this DIE
-/// belongs.
-const DIE *DIE::getUnit() const {
-  const DIE *Cu = getUnitOrNull();
-  assert(Cu && "We should not have orphaned DIEs.");
-  return Cu;
+unsigned DIE::getDebugSectionOffset() const {
+  const DIEUnit *Unit = getUnit();
+  assert(Unit && "DIE must be owned by a DIEUnit to get its absolute offset");
+  return getUnit()->getDebugSectionOffset() + getOffset();
 }
 
-/// Climb up the parent chain to get the unit DIE this DIE belongs
-/// to. Return NULL if DIE is not added to an owner yet.
-const DIE *DIE::getUnitOrNull() const {
+const DIE *DIE::getUnitDie() const {
   const DIE *p = this;
   while (p) {
     if (p->getTag() == dwarf::DW_TAG_compile_unit ||
@@ -136,6 +136,13 @@ const DIE *DIE::getUnitOrNull() const {
   return nullptr;
 }
 
+const DIEUnit *DIE::getUnit() const {
+  const DIE *UnitDie = getUnitDie();
+  if (UnitDie)
+    return UnitDie->Owner.dyn_cast<DIEUnit*>();
+  return nullptr;
+}
+
 DIEValue DIE::findAttribute(dwarf::Attribute Attribute) const {
   // Iterate through all the attributes until we find the one we're
   // looking for, if we can't find it return NULL.
@@ -191,6 +198,16 @@ void DIE::dump() {
   print(dbgs());
 }
 
+DIEUnit::DIEUnit(uint16_t V, uint8_t A, dwarf::Tag UnitTag)
+    : Die(UnitTag), Section(nullptr), Offset(0), Length(0), Version(V),
+      AddrSize(A)
+{
+  Die.setUnit(this);
+  assert((UnitTag == dwarf::DW_TAG_compile_unit ||
+          UnitTag == dwarf::DW_TAG_type_unit ||
+          UnitTag == dwarf::DW_TAG_partial_unit) && "expected a unit TAG");
+}
+
 void DIEValue::EmitValue(const AsmPrinter *AP) const {
   switch (Ty) {
   case isNone:
@@ -443,19 +460,19 @@ void DIEString::print(raw_ostream &O) const {
 void DIEEntry::EmitValue(const AsmPrinter *AP, dwarf::Form Form) const {
 
   if (Form == dwarf::DW_FORM_ref_addr) {
-    const DwarfDebug *DD = AP->getDwarfDebug();
-    unsigned Addr = Entry->getOffset();
-    assert(!DD->useSplitDwarf() && "TODO: dwo files can't have relocations.");
-    // For DW_FORM_ref_addr, output the offset from beginning of debug info
-    // section. Entry->getOffset() returns the offset from start of the
-    // compile unit.
-    DwarfCompileUnit *CU = DD->lookupUnit(Entry->getUnit());
-    assert(CU && "CUDie should belong to a CU.");
-    Addr += CU->getDebugInfoOffset();
-    if (AP->MAI->doesDwarfUseRelocationsAcrossSections())
-      AP->EmitLabelPlusOffset(CU->getSectionSym(), Addr,
-                              DIEEntry::getRefAddrSize(AP));
-    else
+    // Get the absolute offset for this DIE within the debug info/types section.
+    unsigned Addr = Entry->getDebugSectionOffset();
+    if (AP->MAI->doesDwarfUseRelocationsAcrossSections()) {
+      const DwarfDebug *DD = AP->getDwarfDebug();
+      if (DD)
+        assert(!DD->useSplitDwarf() && "TODO: dwo files can't have relocations.");
+      const DIEUnit *Unit = Entry->getUnit();
+      assert(Unit && "CUDie should belong to a CU.");
+      MCSection *Section = Unit->getSection();
+      assert(Section && "Must have a section if we are doing relocations");
+      const MCSymbol *SectionSym = Section->getBeginSymbol();
+      AP->EmitLabelPlusOffset(SectionSym, Addr, DIEEntry::getRefAddrSize(AP));
+    } else
       AP->OutStreamer->EmitIntValue(Addr, DIEEntry::getRefAddrSize(AP));
   } else
     AP->EmitInt32(Entry->getOffset());
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfAccelTable.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfAccelTable.cpp
index 4ad3e186732..9c324ea26ac 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfAccelTable.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfAccelTable.cpp
@@ -221,9 +221,7 @@ void DwarfAccelTable::EmitData(AsmPrinter *Asm, DwarfDebug *D) {
       Asm->EmitInt32((*HI)->Data.Values.size());
       for (HashDataContents *HD : (*HI)->Data.Values) {
         // Emit the DIE offset
-        DwarfCompileUnit *CU = D->lookupUnit(HD->Die->getUnit());
-        assert(CU && "Accelerated DIE should belong to a CU.");
-        Asm->EmitInt32(HD->Die->getOffset() + CU->getDebugInfoOffset());
+        Asm->EmitInt32(HD->Die->getDebugSectionOffset());
         // If we have multiple Atoms emit that info too.
         // FIXME: A bit of a hack, we either emit only one atom or all info.
         if (HeaderData.Atoms.size() > 1) {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 1aabf69cb1a..84981ac16ac 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -242,7 +242,7 @@ void DwarfCompileUnit::initStmtList() {
   // is not okay to use line_table_start here.
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
   StmtListValue =
-      addSectionLabel(UnitDie, dwarf::DW_AT_stmt_list, LineTableStartSym,
+      addSectionLabel(getUnitDie(), dwarf::DW_AT_stmt_list, LineTableStartSym,
                       TLOF.getDwarfLineSection()->getBeginSymbol());
 }
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 766da4a3f7b..b1f818bfd67 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -32,9 +32,6 @@ class DwarfCompileUnit : public DwarfUnit {
   /// A numeric ID unique among all CUs in the module
   unsigned UniqueID;
 
-  /// Offset of the UnitDie from beginning of debug info section.
-  unsigned DebugInfoOffset = 0;
-
   /// The attribute index of DW_AT_stmt_list in the compile unit DIE, avoiding
   /// the need to search for it in applyStmtList.
   DIE::value_iterator StmtListValue;
@@ -84,8 +81,6 @@ public:
                    DwarfDebug *DW, DwarfFile *DWU);
 
   unsigned getUniqueID() const { return UniqueID; }
-  unsigned getDebugInfoOffset() const { return DebugInfoOffset; }
-  void setDebugInfoOffset(unsigned DbgInfoOff) { DebugInfoOffset = DbgInfoOff; }
 
   DwarfCompileUnit *getSkeleton() const {
     return Skeleton;
@@ -191,14 +186,9 @@ public:
   /// Set the skeleton unit associated with this unit.
   void setSkeleton(DwarfCompileUnit &Skel) { Skeleton = &Skel; }
 
-  const MCSymbol *getSectionSym() const {
-    assert(Section);
-    return Section->getBeginSymbol();
-  }
-
   unsigned getLength() {
     return sizeof(uint32_t) + // Length field
-        getHeaderSize() + UnitDie.getSize();
+        getHeaderSize() + getUnitDie().getSize();
   }
 
   void emitHeader(bool UseOffsets) override;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 1f662e58819..acb8ce0c73e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -437,9 +437,9 @@ DwarfDebug::constructDwarfCompileUnit(const DICompileUnit *DIUnit) {
   }
 
   if (useSplitDwarf())
-    NewCU.initSection(Asm->getObjFileLowering().getDwarfInfoDWOSection());
+    NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoDWOSection());
   else
-    NewCU.initSection(Asm->getObjFileLowering().getDwarfInfoSection());
+    NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoSection());
 
   if (DIUnit->getDWOId()) {
     // This CU is either a clang module DWO or a skeleton CU.
@@ -520,7 +520,7 @@ void DwarfDebug::finishVariableDefinitions() {
     // FIXME: Consider the time-space tradeoff of just storing the unit pointer
     // in the ConcreteVariables list, rather than looking it up again here.
     // DIE::getUnit isn't simple - it walks parent pointers, etc.
-    DwarfCompileUnit *Unit = lookupUnit(VariableDie->getUnit());
+    DwarfCompileUnit *Unit = CUDieMap.lookup(VariableDie->getUnitDie());
     assert(Unit);
     DbgVariable *AbsVar = getExistingAbstractVariable(
         InlinedVariable(Var->getVariable(), Var->getInlinedAt()));
@@ -1821,7 +1821,7 @@ DwarfCompileUnit &DwarfDebug::constructSkeletonCU(const DwarfCompileUnit &CU) {
   auto OwnedUnit = make_unique<DwarfCompileUnit>(
       CU.getUniqueID(), CU.getCUNode(), Asm, this, &SkeletonHolder);
   DwarfCompileUnit &NewCU = *OwnedUnit;
-  NewCU.initSection(Asm->getObjFileLowering().getDwarfInfoSection());
+  NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoSection());
 
   NewCU.initStmtList();
 
@@ -1913,11 +1913,10 @@ void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
   Ins.first->second = Signature;
 
   if (useSplitDwarf())
-    NewTU.initSection(Asm->getObjFileLowering().getDwarfTypesDWOSection());
+    NewTU.setSection(Asm->getObjFileLowering().getDwarfTypesDWOSection());
   else {
     CU.applyStmtList(UnitDie);
-    NewTU.initSection(
-        Asm->getObjFileLowering().getDwarfTypesSection(Signature));
+    NewTU.setSection(Asm->getObjFileLowering().getDwarfTypesSection(Signature));
   }
 
   NewTU.setType(NewTU.createTypeDIE(CTy));
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index b2d912b88cf..3a9fa8b9726 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -533,11 +533,6 @@ public:
     return Ref.resolve();
   }
 
-  /// Find the DwarfCompileUnit for the given CU Die.
-  DwarfCompileUnit *lookupUnit(const DIE *CU) const {
-    return CUDieMap.lookup(CU);
-  }
-
   void addSubprogramNames(const DISubprogram *SP, DIE &Die);
 
   AddressPool &getAddressPool() { return AddrPool; }
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp
index e9fe98ab3cf..3179ab15420 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp
@@ -80,7 +80,7 @@ void DwarfFile::computeSizeAndOffsets() {
   // Iterate over each compile unit and set the size and offsets for each
   // DIE within each compile unit. All offsets are CU relative.
   for (const auto &TheU : CUs) {
-    TheU->setDebugInfoOffset(SecOffset);
+    TheU->setDebugSectionOffset(SecOffset);
     SecOffset += computeSizeAndOffsetsForUnit(TheU.get());
   }
 }
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index ab4a7a334b7..1923d038f73 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -73,10 +73,8 @@ bool DIEDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI,
 
 DwarfUnit::DwarfUnit(dwarf::Tag UnitTag, const DICompileUnit *Node,
                      AsmPrinter *A, DwarfDebug *DW, DwarfFile *DWU)
-    : CUNode(Node), UnitDie(*DIE::get(DIEValueAllocator, UnitTag)), Asm(A),
-      DD(DW), DU(DWU), IndexTyDie(nullptr), Section(nullptr) {
-  assert(UnitTag == dwarf::DW_TAG_compile_unit ||
-         UnitTag == dwarf::DW_TAG_type_unit);
+    : DIEUnit(A->getDwarfVersion(), A->getPointerSize(), UnitTag), CUNode(Node),
+      Asm(A), DD(DW), DU(DWU), IndexTyDie(nullptr) {
 }
 
 DwarfTypeUnit::DwarfTypeUnit(DwarfCompileUnit &CU, AsmPrinter *A,
@@ -85,7 +83,7 @@ DwarfTypeUnit::DwarfTypeUnit(DwarfCompileUnit &CU, AsmPrinter *A,
     : DwarfUnit(dwarf::DW_TAG_type_unit, CU.getCUNode(), A, DW, DWU), CU(CU),
       SplitLineTable(SplitLineTable) {
   if (SplitLineTable)
-    addSectionOffset(UnitDie, dwarf::DW_AT_stmt_list, 0);
+    addSectionOffset(getUnitDie(), dwarf::DW_AT_stmt_list, 0);
 }
 
 DwarfUnit::~DwarfUnit() {
@@ -294,15 +292,15 @@ void DwarfUnit::addDIETypeSignature(DIE &Die, dwarf::Attribute Attribute,
 
 void DwarfUnit::addDIEEntry(DIE &Die, dwarf::Attribute Attribute,
                             DIEEntry Entry) {
-  const DIE *DieCU = Die.getUnitOrNull();
-  const DIE *EntryCU = Entry.getEntry().getUnitOrNull();
-  if (!DieCU)
+  const DIEUnit *CU = Die.getUnit();
+  const DIEUnit *EntryCU = Entry.getEntry().getUnit();
+  if (!CU)
     // We assume that Die belongs to this CU, if it is not linked to any CU yet.
-    DieCU = &getUnitDie();
+    CU = getUnitDie().getUnit();
   if (!EntryCU)
-    EntryCU = &getUnitDie();
+    EntryCU = getUnitDie().getUnit();
   Die.addValue(DIEValueAllocator, Attribute,
-               EntryCU == DieCU ? dwarf::DW_FORM_ref4 : dwarf::DW_FORM_ref_addr,
+               EntryCU == CU ? dwarf::DW_FORM_ref4 : dwarf::DW_FORM_ref_addr,
                Entry);
 }
 
@@ -1313,7 +1311,7 @@ DIE *DwarfUnit::getIndexTyDie() {
   if (IndexTyDie)
     return IndexTyDie;
   // Construct an integer type to use for indexes.
-  IndexTyDie = &createAndAddDIE(dwarf::DW_TAG_base_type, UnitDie);
+  IndexTyDie = &createAndAddDIE(dwarf::DW_TAG_base_type, getUnitDie());
   addString(*IndexTyDie, dwarf::DW_AT_name, "sizetype");
   addUInt(*IndexTyDie, dwarf::DW_AT_byte_size, None, sizeof(int64_t));
   addUInt(*IndexTyDie, dwarf::DW_AT_encoding, dwarf::DW_FORM_data1,
@@ -1535,7 +1533,7 @@ DIE *DwarfUnit::getOrCreateStaticMemberDIE(const DIDerivedType *DT) {
 void DwarfUnit::emitHeader(bool UseOffsets) {
   // Emit size of content not including length itself
   Asm->OutStreamer->AddComment("Length of Unit");
-  Asm->EmitInt32(getHeaderSize() + UnitDie.getSize());
+  Asm->EmitInt32(getHeaderSize() + getUnitDie().getSize());
 
   Asm->OutStreamer->AddComment("DWARF version number");
   Asm->EmitInt16(DD->getDwarfVersion());
@@ -1555,11 +1553,6 @@ void DwarfUnit::emitHeader(bool UseOffsets) {
   Asm->EmitInt8(Asm->getDataLayout().getPointerSize());
 }
 
-void DwarfUnit::initSection(MCSection *Section) {
-  assert(!this->Section);
-  this->Section = Section;
-}
-
 void DwarfTypeUnit::emitHeader(bool UseOffsets) {
   DwarfUnit::emitHeader(UseOffsets);
   Asm->OutStreamer->AddComment("Type Signature");
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
index e225f92116d..6d045eabe44 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
@@ -65,7 +65,7 @@ public:
 //===----------------------------------------------------------------------===//
 /// This dwarf writer support class manages information associated with a
 /// source file.
-class DwarfUnit {
+  class DwarfUnit : public DIEUnit {
 protected:
   /// MDNode for the compile unit.
   const DICompileUnit *CUNode;
@@ -73,9 +73,6 @@ protected:
   // All DIEValues are allocated through this allocator.
   BumpPtrAllocator DIEValueAllocator;
 
-  /// Unit debug information entry.
-  DIE &UnitDie;
-
   /// Target of Dwarf emission.
   AsmPrinter *Asm;
 
@@ -83,7 +80,7 @@ protected:
   DwarfDebug *DD;
   DwarfFile *DU;
 
-  /// An anonymous type for index type.  Owned by UnitDie.
+  /// An anonymous type for index type.  Owned by DIEUnit.
   DIE *IndexTyDie;
 
   /// Tracks the mapping of unit level debug information variables to debug
@@ -101,9 +98,6 @@ protected:
   /// corresponds to the MDNode mapped with the subprogram DIE.
   DenseMap<DIE *, const DINode *> ContainingTypeMap;
 
-  /// The section this unit will be emitted in.
-  MCSection *Section;
-
   DwarfUnit(dwarf::Tag, const DICompileUnit *CU, AsmPrinter *A, DwarfDebug *DW,
             DwarfFile *DWU);
 
@@ -112,21 +106,13 @@ protected:
 public:
   virtual ~DwarfUnit();
 
-  void initSection(MCSection *Section);
-
-  MCSection *getSection() const {
-    assert(Section);
-    return Section;
-  }
-
   // Accessors.
   AsmPrinter* getAsmPrinter() const { return Asm; }
   uint16_t getLanguage() const { return CUNode->getSourceLanguage(); }
   const DICompileUnit *getCUNode() const { return CUNode; }
-  DIE &getUnitDie() { return UnitDie; }
 
   /// Return true if this compile unit has something to write out.
-  bool hasContent() const { return UnitDie.hasChildren(); }
+  bool hasContent() const { return Die.hasChildren(); }
 
   /// Get string containing language specific context for a global name.
   ///