[DebugInfo] Make children iterator bidirectional

Make the DIE iterator bidirectional so we can move to the previous
sibling of a DIE.

Differential revision: https://reviews.llvm.org/D49173

llvm-svn: 336823

2 files changed, 45 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index 0ef65c2b0b6..904ceab7b28 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -555,12 +555,24 @@ DWARFDie DWARFDie::getSibling() const {
   return DWARFDie();
 }
 
+DWARFDie DWARFDie::getPreviousSibling() const {
+  if (isValid())
+    return U->getPreviousSibling(Die);
+  return DWARFDie();
+}
+
 DWARFDie DWARFDie::getFirstChild() const {
   if (isValid())
     return U->getFirstChild(Die);
   return DWARFDie();
 }
 
+DWARFDie DWARFDie::getLastChild() const {
+  if (isValid())
+    return U->getLastChild(Die);
+  return DWARFDie();
+}
+
 iterator_range<DWARFDie::attribute_iterator> DWARFDie::attributes() const {
   return make_range(attribute_iterator(*this, false),
                     attribute_iterator(*this, true));
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 6b7970d426b..7581575e2a4 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -584,6 +584,24 @@ DWARFDie DWARFUnit::getSibling(const DWARFDebugInfoEntry *Die) {
   return DWARFDie();
 }
 
+DWARFDie DWARFUnit::getPreviousSibling(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();
+
+  // Find the previous DIE whose depth is the same as the Die's depth.
+  for (size_t I = getDIEIndex(Die) - 1; I >= 0; --I) {
+    if (DieArray[I].getDepth() == Depth - 1)
+      return DWARFDie();
+    if (DieArray[I].getDepth() == Depth)
+      return DWARFDie(this, &DieArray[I]);
+  }
+  return DWARFDie();
+}
+
 DWARFDie DWARFUnit::getFirstChild(const DWARFDebugInfoEntry *Die) {
   if (!Die->hasChildren())
     return DWARFDie();
@@ -595,6 +613,21 @@ DWARFDie DWARFUnit::getFirstChild(const DWARFDebugInfoEntry *Die) {
   return DWARFDie(this, &DieArray[I]);
 }
 
+DWARFDie DWARFUnit::getLastChild(const DWARFDebugInfoEntry *Die) {
+  if (!Die->hasChildren())
+    return DWARFDie();
+
+  uint32_t Depth = Die->getDepth();
+  for (size_t I = getDIEIndex(Die) + 1, EndIdx = DieArray.size(); I < EndIdx;
+       ++I) {
+    if (DieArray[I].getDepth() == Depth + 1 &&
+        DieArray[I].getTag() == dwarf::DW_TAG_null)
+      return DWARFDie(this, &DieArray[I]);
+    assert(DieArray[I].getDepth() > Depth && "Not processing children?");
+  }
+  return DWARFDie();
+}
+
 const DWARFAbbreviationDeclarationSet *DWARFUnit::getAbbreviations() const {
   if (!Abbrevs)
     Abbrevs = Abbrev->getAbbreviationDeclarationSet(Header.getAbbrOffset());