Add the ability for DWARFDie objects to get the parent DWARFDie.

In order for the llvm DWARF parser to be used in LLDB we will need to be able to get the parent of a DIE. This patch adds that functionality by changing the DWARFDebugInfoEntry class to store a depth field instead of a sibling index. Using a depth field allows us to easily calculate the sibling and the parent without increasing the size of DWARFDebugInfoEntry.

I tested llvm-dsymutil on a debug version of clang where this fully parses DWARF in over 1200 .o files to verify there was no serious regression in performance.

Added a full suite of unit tests to test this functionality.

Differential Revision: https://reviews.llvm.org/D27995

llvm-svn: 290274

7 files changed, 209 insertions, 82 deletions

diff --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h
index 57fb1f1da90..f36f470980b 100644
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h
@@ -31,13 +31,14 @@ class DWARFDebugInfoEntry {
   /// Offset within the .debug_info of the start of this entry.
   uint32_t Offset;
 
-  /// How many to add to "this" to get the sibling.
-  uint32_t SiblingIdx;
+  /// The integer depth of this DIE within the compile unit DIEs where the
+  /// compile/type unit DIE has a depth of zero.
+  uint32_t Depth;
 
   const DWARFAbbreviationDeclaration *AbbrevDecl;
 public:
   DWARFDebugInfoEntry()
-    : Offset(0), SiblingIdx(0), AbbrevDecl(nullptr) {}
+    : Offset(0), Depth(0), AbbrevDecl(nullptr) {}
 
   /// Extracts a debug info entry, which is a child of a given unit,
   /// starting at a given offset. If DIE can't be extracted, returns false and
@@ -45,33 +46,16 @@ public:
   bool extractFast(const DWARFUnit &U, uint32_t *OffsetPtr);
   /// High performance extraction should use this call.
   bool extractFast(const DWARFUnit &U, uint32_t *OffsetPtr,
-                   const DataExtractor &DebugInfoData, uint32_t UEndOffset);
+                   const DataExtractor &DebugInfoData,
+                   uint32_t UEndOffset,
+                   uint32_t Depth);
 
   uint32_t getOffset() const { return Offset; }
-  bool hasChildren() const { return AbbrevDecl && AbbrevDecl->hasChildren(); }
-
-  // We know we are kept in a vector of contiguous entries, so we know
-  // our sibling will be some index after "this".
-  const DWARFDebugInfoEntry *getSibling() const {
-    return SiblingIdx > 0 ? this + SiblingIdx : nullptr;
-  }
-
-  // We know we are kept in a vector of contiguous entries, so we know
-  // we don't need to store our child pointer, if we have a child it will
-  // be the next entry in the list...
-  const DWARFDebugInfoEntry *getFirstChild() const {
-    return hasChildren() ? this + 1 : nullptr;
+  uint32_t getDepth() const { return Depth; }
+  dwarf::Tag getTag() const {
+    return AbbrevDecl ? AbbrevDecl->getTag() : dwarf::DW_TAG_null;
   }
-
-  void setSibling(const DWARFDebugInfoEntry *Sibling) {
-    if (Sibling) {
-      // We know we are kept in a vector of contiguous entries, so we know
-      // our sibling will be some index after "this".
-      SiblingIdx = Sibling - this;
-    } else
-      SiblingIdx = 0;
-  }
-
+  bool hasChildren() const { return AbbrevDecl && AbbrevDecl->hasChildren(); }
   const DWARFAbbreviationDeclaration *getAbbreviationDeclarationPtr() const {
     return AbbrevDecl;
   }
diff --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFDie.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFDie.h
index 857cabab0df..f33758de6a5 100644
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFDie.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFDie.h
@@ -40,6 +40,9 @@ public:
   
   bool isValid() const { return U && Die; }
   explicit operator bool() const { return isValid(); }
+  bool operator ==(const DWARFDie &RHS) const {
+    return Die == RHS.Die && U == RHS.U;
+  }
   const DWARFDebugInfoEntry *getDebugInfoEntry() const { return Die; }
   DWARFUnit *getDwarfUnit() const { return U; }
 
@@ -82,23 +85,26 @@ public:
   /// Returns true if DIE represents a subprogram or an inlined subroutine.
   bool isSubroutineDIE() const;
 
-
-  /// Get the silbing of this DIE object.
+  /// Get the parent of this DIE object.
+  ///
+  /// \returns a valid DWARFDie instance if this object has a parent or an
+  /// invalid DWARFDie instance if it doesn't.
+  DWARFDie getParent() const;
+  
+  /// Get the sibling of this DIE object.
   ///
   /// \returns a valid DWARFDie instance if this object has a sibling or an
   /// invalid DWARFDie instance if it doesn't.
-  DWARFDie getSibling() const {
-    assert(isValid() && "must check validity prior to calling");
-    return DWARFDie(U, Die->getSibling());
-  }
+  DWARFDie getSibling() const;
   
   /// Get the first child of this DIE object.
   ///
   /// \returns a valid DWARFDie instance if this object has children or an
   /// invalid DWARFDie instance if it doesn't.
   DWARFDie getFirstChild() const {
-    assert(isValid() && "must check validity prior to calling");
-    return DWARFDie(U, Die->getFirstChild());
+    if (isValid() && Die->hasChildren())
+      return DWARFDie(U, Die + 1);
+    return DWARFDie();
   }
   
   /// Dump the DIE and all of its attributes to the supplied stream.
diff --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
index 0f4a6f0438d..78bbe098b2d 100644
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
@@ -140,6 +140,12 @@ class DWARFUnit {
 
   const DWARFUnitIndex::Entry *IndexEntry;
 
+  uint32_t getDIEIndex(const DWARFDebugInfoEntry *Die) {
+    auto First = DieArray.data();
+    assert(Die >= First && Die < First + DieArray.size());
+    return Die - First;
+  }
+
 protected:
   virtual bool extractImpl(DataExtractor debug_info, uint32_t *offset_ptr);
   /// Size in bytes of the unit header.
@@ -251,19 +257,18 @@ public:
   /// method on a DIE that isn't accessible by following
   /// children/sibling links starting from this unit's getUnitDIE().
   uint32_t getDIEIndex(const DWARFDie &D) {
-    auto DIE = D.getDebugInfoEntry();
-    assert(!DieArray.empty() && DIE >= &DieArray[0] &&
-           DIE < &DieArray[0] + DieArray.size());
-    return DIE - &DieArray[0];
+    return getDIEIndex(D.getDebugInfoEntry());
   }
 
   /// \brief Return the DIE object at the given index.
   DWARFDie getDIEAtIndex(unsigned Index) {
-    if (Index < DieArray.size())
-      return DWARFDie(this, &DieArray[Index]);
-    return DWARFDie();
+    assert(Index < DieArray.size());
+    return DWARFDie(this, &DieArray[Index]);
   }
 
+  DWARFDie getParent(const DWARFDebugInfoEntry *Die);
+  DWARFDie getSibling(const DWARFDebugInfoEntry *Die);
+
   /// \brief Return the DIE object for a given offset inside the
   /// unit's DIE vector.
   ///
@@ -298,10 +303,6 @@ private:
   /// extractDIEsToVector - Appends all parsed DIEs to a vector.
   void extractDIEsToVector(bool AppendCUDie, bool AppendNonCUDIEs,
                            std::vector<DWARFDebugInfoEntry> &DIEs) const;
-  /// setDIERelations - We read in all of the DIE entries into our flat list
-  /// of DIE entries and now we need to go back through all of them and set the
-  /// parent, sibling and child pointers for quick DIE navigation.
-  void setDIERelations();
   /// clearDIEs - Clear parsed DIEs to keep memory usage low.
   void clearDIEs(bool KeepCUDie);
 
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDebugInfoEntry.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDebugInfoEntry.cpp
index 8ea65ebfdd5..9f623e4954c 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDebugInfoEntry.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDebugInfoEntry.cpp
@@ -26,13 +26,13 @@ bool DWARFDebugInfoEntry::extractFast(const DWARFUnit &U,
                                              uint32_t *OffsetPtr) {
   DataExtractor DebugInfoData = U.getDebugInfoExtractor();
   const uint32_t UEndOffset = U.getNextUnitOffset();
-  return extractFast(U, OffsetPtr, DebugInfoData, UEndOffset);
+  return extractFast(U, OffsetPtr, DebugInfoData, UEndOffset, 0);
 }
-bool DWARFDebugInfoEntry::extractFast(const DWARFUnit &U,
-                                             uint32_t *OffsetPtr,
-                                             const DataExtractor &DebugInfoData,
-                                             uint32_t UEndOffset) {
+bool DWARFDebugInfoEntry::extractFast(const DWARFUnit &U, uint32_t *OffsetPtr,
+                                      const DataExtractor &DebugInfoData,
+                                      uint32_t UEndOffset, uint32_t D) {
   Offset = *OffsetPtr;
+  Depth = D;
   if (Offset >= UEndOffset || !DebugInfoData.isValidOffset(Offset))
     return false;
   uint64_t AbbrCode = DebugInfoData.getULEB128(OffsetPtr);
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index 94777109e44..deec1633022 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -428,3 +428,14 @@ void DWARFDie::getInlinedChainForAddress(
   std::reverse(InlinedChain.begin(), InlinedChain.end());
 }
 
+DWARFDie DWARFDie::getParent() const {
+  if (isValid())
+    return U->getParent(Die);
+  return DWARFDie();
+}
+
+DWARFDie DWARFDie::getSibling() const {
+  if (isValid())
+    return U->getSibling(Die);
+  return DWARFDie();
+}
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 2ddbc507ff6..63fb0d3bc36 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -158,35 +158,6 @@ Optional<uint64_t> DWARFUnit::getDWOId() {
   return getUnitDIE().getAttributeValueAsUnsignedConstant(DW_AT_GNU_dwo_id);
 }
 
-void DWARFUnit::setDIERelations() {
-  if (DieArray.size() <= 1)
-    return;
-
-  std::vector<DWARFDebugInfoEntry *> ParentChain;
-  DWARFDebugInfoEntry *SiblingChain = nullptr;
-  for (auto &DIE : DieArray) {
-    if (SiblingChain) {
-      SiblingChain->setSibling(&DIE);
-    }
-    if (const DWARFAbbreviationDeclaration *AbbrDecl =
-            DIE.getAbbreviationDeclarationPtr()) {
-      // Normal DIE.
-      if (AbbrDecl->hasChildren()) {
-        ParentChain.push_back(&DIE);
-        SiblingChain = nullptr;
-      } else {
-        SiblingChain = &DIE;
-      }
-    } else {
-      // NULL entry terminates the sibling chain.
-      SiblingChain = ParentChain.back();
-      ParentChain.pop_back();
-    }
-  }
-  assert(SiblingChain == nullptr || SiblingChain == &DieArray[0]);
-  assert(ParentChain.empty());
-}
-
 void DWARFUnit::extractDIEsToVector(
     bool AppendCUDie, bool AppendNonCUDies,
     std::vector<DWARFDebugInfoEntry> &Dies) const {
@@ -202,7 +173,8 @@ void DWARFUnit::extractDIEsToVector(
   uint32_t Depth = 0;
   bool IsCUDie = true;
 
-  while (DIE.extractFast(*this, &DIEOffset, DebugInfoData, NextCUOffset)) {
+  while (DIE.extractFast(*this, &DIEOffset, DebugInfoData, NextCUOffset,
+                         Depth)) {
     if (IsCUDie) {
       if (AppendCUDie)
         Dies.push_back(DIE);
@@ -266,7 +238,6 @@ size_t DWARFUnit::extractDIEsIfNeeded(bool CUDieOnly) {
     // skeleton CU DIE, so that DWARF users not aware of it are not broken.
   }
 
-  setDIERelations();
   return DieArray.size();
 }
 
@@ -409,4 +380,42 @@ const DWARFUnitIndex &getDWARFUnitIndex(DWARFContext &Context,
   return Context.getTUIndex();
 }
 
+DWARFDie DWARFUnit::getParent(const DWARFDebugInfoEntry *Die) {
+  if (!Die)
+    return DWARFDie();
+  const uint32_t Depth = Die->getDepth();
+  // Unit DIEs always have a depth of zero and never have parents.
+  if (Depth == 0)
+    return DWARFDie();
+  // Depth of 1 always means parent is the compile/type unit.
+  if (Depth == 1)
+    return getUnitDIE();
+  // Look for previous DIE with a depth that is one less than the Die's depth.
+  const uint32_t ParentDepth = Depth - 1;
+  for (uint32_t I = getDIEIndex(Die) - 1; I > 0; --I) {
+    if (DieArray[I].getDepth() == ParentDepth)
+      return DWARFDie(this, &DieArray[I]);
+  }
+  return DWARFDie();
+}
+
+DWARFDie DWARFUnit::getSibling(const DWARFDebugInfoEntry *Die) {
+  if (!Die)
+    return DWARFDie();
+  uint32_t Depth = Die->getDepth();
+  // Unit DIEs always have a depth of zero and never have siblings.
+  if (Depth == 0)
+    return DWARFDie();
+  // NULL DIEs don't have siblings.
+  if (Die->getAbbreviationDeclarationPtr() == nullptr)
+    return DWARFDie();
+  
+  // Find the next DIE whose depth is the same as the Die's depth.
+  for (size_t I=getDIEIndex(Die)+1, EndIdx = DieArray.size(); I<EndIdx; ++I) {
+    if (DieArray[I].getDepth() == Depth)
+      return DWARFDie(this, &DieArray[I]);
+  }
+  return DWARFDie();
+}
+
 } // end namespace llvm
diff --git a/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp b/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
index 6b9f435b2e7..e2f4bb788dd 100644
--- a/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
+++ b/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
@@ -967,5 +967,121 @@ TEST(DWARFDebugInfo, TestDWARF32Version4Addr8Addresses) {
   TestAddresses<4, AddrType>();
 }
 
+TEST(DWARFDebugInfo, TestRelations) {
+  // Test the DWARF APIs related to accessing the DW_AT_low_pc and
+  // DW_AT_high_pc.
+  uint16_t Version = 4;
+  
+  const uint8_t AddrSize = sizeof(void *);
+  initLLVMIfNeeded();
+  Triple Triple = getHostTripleForAddrSize(AddrSize);
+  auto ExpectedDG = dwarfgen::Generator::create(Triple, Version);
+  if (HandleExpectedError(ExpectedDG))
+    return;
+  dwarfgen::Generator *DG = ExpectedDG.get().get();
+  dwarfgen::CompileUnit &CU = DG->addCompileUnit();
+  
+  enum class Tag: uint16_t  {
+    A = dwarf::DW_TAG_lo_user,
+    B,
+    B1,
+    B2,
+    C,
+    C1
+  };
+
+  // Scope to allow us to re-use the same DIE names
+  {
+    // Create DWARF tree that looks like:
+    //
+    // CU
+    //   A
+    //   B
+    //     B1
+    //     B2
+    //   C
+    //     C1
+    dwarfgen::DIE CUDie = CU.getUnitDIE();
+    CUDie.addChild((dwarf::Tag)Tag::A);
+    dwarfgen::DIE B = CUDie.addChild((dwarf::Tag)Tag::B);
+    dwarfgen::DIE C = CUDie.addChild((dwarf::Tag)Tag::C);
+    B.addChild((dwarf::Tag)Tag::B1);
+    B.addChild((dwarf::Tag)Tag::B2);
+    C.addChild((dwarf::Tag)Tag::C1);
+  }
+
+  MemoryBufferRef FileBuffer(DG->generate(), "dwarf");
+  auto Obj = object::ObjectFile::createObjectFile(FileBuffer);
+  EXPECT_TRUE((bool)Obj);
+  DWARFContextInMemory DwarfContext(*Obj.get());
+  
+  // Verify the number of compile units is correct.
+  uint32_t NumCUs = DwarfContext.getNumCompileUnits();
+  EXPECT_EQ(NumCUs, 1u);
+  DWARFCompileUnit *U = DwarfContext.getCompileUnitAtIndex(0);
+  
+  // Get the compile unit DIE is valid.
+  auto CUDie = U->getUnitDIE(false);
+  EXPECT_TRUE(CUDie.isValid());
+  // DieDG.dump(llvm::outs(), U, UINT32_MAX);
+  
+  // The compile unit doesn't have a parent or a sibling.
+  auto ParentDie = CUDie.getParent();
+  EXPECT_FALSE(ParentDie.isValid());
+  auto SiblingDie = CUDie.getSibling();
+  EXPECT_FALSE(SiblingDie.isValid());
+  
+  // Get the children of the compile unit
+  auto A = CUDie.getFirstChild();
+  auto B = A.getSibling();
+  auto C = B.getSibling();
+  auto Null = C.getSibling();
+  
+  // Verify NULL Die is NULL and has no children or siblings
+  EXPECT_TRUE(Null.isNULL());
+  EXPECT_FALSE(Null.getSibling().isValid());
+  EXPECT_FALSE(Null.getFirstChild().isValid());
+  
+  // Verify all children of the compile unit DIE are correct.
+  EXPECT_EQ(A.getTag(), (dwarf::Tag)Tag::A);
+  EXPECT_EQ(B.getTag(), (dwarf::Tag)Tag::B);
+  EXPECT_EQ(C.getTag(), (dwarf::Tag)Tag::C);
+
+  // Verify who has children
+  EXPECT_FALSE(A.hasChildren());
+  EXPECT_TRUE(B.hasChildren());
+
+  // Make sure the parent of all the children of the compile unit are the
+  // compile unit.
+  EXPECT_EQ(A.getParent(), CUDie);
+  EXPECT_EQ(B.getParent(), CUDie);
+  EXPECT_EQ(Null.getParent(), CUDie);
+
+  EXPECT_FALSE(A.getFirstChild().isValid());
+
+  // Verify the children of the B DIE
+  auto B1 = B.getFirstChild();
+  auto B2 = B1.getSibling();
+  EXPECT_TRUE(B2.getSibling().isNULL());
+  
+  // Verify all children of the B DIE correctly valid or invalid.
+  EXPECT_EQ(B1.getTag(), (dwarf::Tag)Tag::B1);
+  EXPECT_EQ(B2.getTag(), (dwarf::Tag)Tag::B2);
+
+  // Make sure the parent of all the children of the B are the B.
+  EXPECT_EQ(B1.getParent(), B);
+  EXPECT_EQ(B2.getParent(), B);
+}
+
+TEST(DWARFDebugInfo, TestDWARFDie) {
+
+  // Make sure a default constructed DWARFDie doesn't have any parent, sibling
+  // or child;
+  DWARFDie DefaultDie;
+  EXPECT_FALSE(DefaultDie.getParent().isValid());
+  EXPECT_FALSE(DefaultDie.getFirstChild().isValid());
+  EXPECT_FALSE(DefaultDie.getSibling().isValid());
+}
+
 
 } // end anonymous namespace