Move tree navigation to a new Path class that doesn't have to be a template.

The path also holds a reference to the root node, and that allows important
iterator accessors like start() and stop() to have no conditional code. (When
the compiler is clever enough to remove it.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120165 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/IntervalMap.cpp

@@ -16,6 +16,107 @@
 namespace llvm {
 namespace IntervalMapImpl {
 
+void Path::replaceRoot(void *Root, unsigned Size, IdxPair Offsets) {
+  assert(!path.empty() && "Can't replace missing root");
+  path.front() = Entry(Root, Size, Offsets.first);
+  path.insert(path.begin() + 1, Entry(subtree(0), Offsets.second));
+}
+
+NodeRef Path::getLeftSibling(unsigned Level) const {
+  // The root has no siblings.
+  if (Level == 0)
+    return NodeRef();
+
+  // Go up the tree until we can go left.
+  unsigned l = Level - 1;
+  while (l && path[l].offset == 0)
+    --l;
+
+  // We can't go left.
+  if (path[l].offset == 0)
+    return NodeRef();
+
+  // NR is the subtree containing our left sibling.
+  NodeRef NR = path[l].subtree(path[l].offset - 1);
+
+  // Keep right all the way down.
+  for (++l; l != Level; ++l)
+    NR = NR.subtree(NR.size() - 1);
+  return NR;
+}
+
+void Path::moveLeft(unsigned Level) {
+  assert(Level != 0 && "Cannot move the root node");
+
+  // Go up the tree until we can go left.
+  unsigned l = 0;
+  if (valid()) {
+    l = Level - 1;
+    while (path[l].offset == 0) {
+      assert(l != 0 && "Cannot move beyond begin()");
+      --l;
+    }
+  } else if (height() < Level)
+    // end() may have created a height=0 path.
+    path.resize(Level + 1, Entry(0, 0, 0));
+
+  // NR is the subtree containing our left sibling.
+  --path[l].offset;
+  NodeRef NR = subtree(l);
+
+  // Get the rightmost node in the subtree.
+  for (++l; l != Level; ++l) {
+    path[l] = Entry(NR, NR.size() - 1);
+    NR = NR.subtree(NR.size() - 1);
+  }
+  path[l] = Entry(NR, NR.size() - 1);
+}
+
+NodeRef Path::getRightSibling(unsigned Level) const {
+  // The root has no siblings.
+  if (Level == 0)
+    return NodeRef();
+
+  // Go up the tree until we can go right.
+  unsigned l = Level - 1;
+  while (l && atLastBranch(l))
+    --l;
+
+  // We can't go right.
+  if (atLastBranch(l))
+    return NodeRef();
+
+  // NR is the subtree containing our right sibling.
+  NodeRef NR = path[l].subtree(path[l].offset + 1);
+
+  // Keep left all the way down.
+  for (++l; l != Level; ++l)
+    NR = NR.subtree(0);
+  return NR;
+}
+
+void Path::moveRight(unsigned Level) {
+  assert(Level != 0 && "Cannot move the root node");
+
+  // Go up the tree until we can go right.
+  unsigned l = Level - 1;
+  while (l && atLastBranch(l))
+    --l;
+
+  // NR is the subtree containing our right sibling. If we hit end(), we have
+  // offset(0) == node(0).size().
+  if (++path[l].offset == path[l].size)
+    return;
+  NodeRef NR = subtree(l);
+
+  for (++l; l != Level; ++l) {
+    path[l] = Entry(NR, 0);
+    NR = NR.subtree(0);
+  }
+  path[l] = Entry(NR, 0);
+}
+
+
 IdxPair distribute(unsigned Nodes, unsigned Elements, unsigned Capacity,
                    const unsigned *CurSize, unsigned NewSize[],
                    unsigned Position, bool Grow) {
@@ -56,5 +157,5 @@ IdxPair distribute(unsigned Nodes, unsigned Elements, unsigned Capacity,
 }
 
 } // namespace IntervalMapImpl
-} // namespace llvm 
+} // namespace llvm