com.android.dx.ssa

Class Dominators

java.lang.Object

com.android.dx.ssa.Dominators

public final class Dominators
extends java.lang.Object

This class computes dominator and post-dominator information using the Lengauer-Tarjan method. See A Fast Algorithm for Finding Dominators in a Flowgraph T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141. This implementation runs in time O(n log n). The time bound could be changed to O(n * ack(n)) with a small change to the link and eval, and an addition of a child field to the DFS info. In reality, the constant overheads are high enough that the current method is faster in all but the strangest artificially constructed examples. The basic idea behind this algorithm is to perform a DFS walk, keeping track of various info about parents. We then use this info to calculate the dominators, using union-find structures to link together the DFS info, then finally evaluate the union-find results to get the dominators. This implementation is m log n because it does not perform union by rank to keep the union-find tree balanced.

Method Summary

Modifier and Type	Method and Description
static Dominators	make(SsaMethod meth, DomFront.DomInfo[] domInfos, boolean postdom) Constructs a fully-initialized instance.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

make

public static Dominators make(SsaMethod meth,
                              DomFront.DomInfo[] domInfos,
                              boolean postdom)

Constructs a fully-initialized instance. (This method exists so as to avoid calling a large amount of code in the constructor.)

Parameters:

meth - non-null; method to process

domInfos - non-null; the raw dominator info

postdom - true for postdom information, false for normal dom info