* Returns all the basic blocks in the method body.
*/
public Block[] basicBlocks() {
- dominatorTree2();
return basicBlocks;
}
* of the tree.
*
* <p> The order of the elements is the same as that
- * of the elements in the array returned by the <code>basicBlocks</code>
- * method.
+ * of the elements in the <code>Block</code> array returned
+ * by the <code>basicBlocks</code>
+ * method. If a <code>Block</code> object is at the i-th position
+ * in the <code>Block</code> array, then
+ * the <code>Node</code> object referring to that
+ * <code>Block</code> object is at the i-th position in the
+ * array returned by this method.
* For every array element <code>node</code>, its index in the
- * array is obtained by <code>node.block().index()</code>.
+ * array is equivalent to <code>node.block().index()</code>.
*
* @return an array of the tree nodes, or null if the method is abstract.
* @see Node#block()
/**
* Constructs a post dominator tree. This method returns an array of
- * the tree nodes. The parent of the root node is null.
- *
- * <p>For every array element <code>node</code>, its index in the
- * array is obtained by <code>node.block().index()</code>.
+ * the tree nodes. Note that the tree has multiple roots.
+ * The parent of the root nodes is null.
+ *
+ * <p> The order of the elements is the same as that
+ * of the elements in the <code>Block</code> array returned
+ * by the <code>basicBlocks</code>
+ * method. If a <code>Block</code> object is at the i-th position
+ * in the <code>Block</code> array, then
+ * the <code>Node</code> object referring to that
+ * <code>Block</code> object is at the i-th position in the
+ * array returned by this method.
+ * For every array element <code>node</code>, its index in the
+ * array is equivalent to <code>node.block().index()</code>.
*
* @return an array of the tree nodes, or null if the method is abstract.
* @see Node#block()
return nodes;
}
- private Block dominatorTree2() {
- int size = basicBlocks.length;
- if (size == 0)
- return null;
-
- if (basicBlocks[0].parent == null) {
- // a dominator tree has not been constructed.
- boolean[] visited = new boolean[size];
- int[] distance = new int[size];
- for (int i = 0; i < size; i++)
- visited[i] = false;
-
- basicBlocks[0].makeDepth1stTree(null, visited, 0, distance);
- for (int i = 0; i < size; i++)
- visited[i] = false;
-
- while (basicBlocks[0].makeDominatorTree(visited, distance))
- ;
-
- setChildren(size);
- }
-
- return basicBlocks[0];
- }
-
- private void setChildren(int size) {
- int[] nchildren = new int[size];
- for (int i = 0; i < size; i++)
- nchildren[i] = 0;
-
- for (int i = 0; i < size; i++) {
- Block p = basicBlocks[i].parent;
- if (p != null)
- nchildren[p.index]++;
- }
-
- for (int i = 0; i < size; i++)
- basicBlocks[i].children = new Block[nchildren[i]];
-
- for (int i = 0; i < size; i++)
- nchildren[i] = 0;
-
- for (int i = 0; i < size; i++) {
- Block b = basicBlocks[i];
- Block p = b.parent;
- if (p != null)
- p.children[nchildren[p.index]++] = b;
- }
- }
-
/**
* Basic block.
* It is a sequence of contiguous instructions that do not contain
int index;
MethodInfo method;
Block[] entrances;
- Block parent; // for a dominator tree
- Block[] children; // for a dominator tree
Block(int pos, MethodInfo minfo) {
super(pos);
- parent = null;
method = minfo;
}
sbuf.append(entrances[i].position).append(", ");
sbuf.append("}");
-
- sbuf.append("{parent=");
- sbuf.append(parent == null ? "*" : parent.position());
- sbuf.append(", children{");
- for (int i = 0; i < children.length; i++)
- sbuf.append(children[i].position()).append(", ");
- sbuf.append("}}");
}
BasicBlock[] getExit() { return exit; }
*/
public Block exit(int n) { return (Block)exit[n]; }
- /**
- * Returns the parent of this block in the dominator
- * tree.
- */
- public Block parent() { return parent; }
-
- /**
- * Returns the number of the children of this block
- * in the dominator tree.
- */
- public int children() { return children.length; }
-
- /**
- * Returns the n-th child of this block in the
- * dominator tree.
- *
- * @param n an index in the array of children.
- */
- public Block child(int n) { return children[n]; }
-
/**
* Returns catch clauses that will catch an exception thrown
* in this block.
return (Catcher[])catchers.toArray(new Catcher[catchers.size()]);
}
-
- /*
- * After executing this method, distance[] represents the post order of the tree nodes.
- * It also represents distances from the root; a bigger number represents a shorter
- * distance. parent is set to its parent in the depth first spanning tree.
- */
- int makeDepth1stTree(Block caller, boolean[] visited, int counter, int[] distance) {
- if (visited[index])
- return counter;
-
- visited[index] = true;
- parent = caller;
- if (exit == null) {
- distance[index] = counter++;
- return counter;
- }
- else
- for (int i = 0; i < exit.length; i++) {
- Block b = (Block)exit[i];
- counter = b.makeDepth1stTree(this, visited, counter, distance);
- }
-
- distance[index] = counter++;
- return counter;
- }
-
- boolean makeDominatorTree(boolean[] visited, int[] distance) {
- if (visited[index])
- return false;
-
- visited[index] = true;
- boolean changed = false;
- if (exit != null)
- for (int i = 0; i < exit.length; i++) {
- Block b = (Block)exit[i];
- if (b.makeDominatorTree(visited, distance))
- changed = true;
- }
-
- for (int i = 0; i < entrances.length; i++) {
- if (parent != null) {
- Block a = getAncestor(parent, entrances[i], distance);
- if (a != parent) {
- parent = a;
- changed = true;
- }
- }
- }
-
- return changed;
- }
-
- private Block getAncestor(Block b1, Block b2, int[] distance) {
- while (b1 != b2)
- if (distance[b1.index] < distance[b2.index])
- b1 = b1.parent;
- else
- b2 = b2.parent;
-
- return b1;
- }
}
static abstract class Access {
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