/** Print the value numbers for each node in the value graph. */
void printValueNumbers() {
for (Enumeration<GraphNode> e = valueGraph.enumerateVertices(); e.hasMoreElements(); ) {
ValueGraphVertex v = (ValueGraphVertex) e.nextElement();
int valueNumber = v.getValueNumber();
GVCongruenceClass c = B.get(valueNumber);
System.out.println(v.getName() + " " + valueNumber + " " + c.getLabel());
}
}
/**
* Due to PI nodes and Moves, the initial label for a register may be another register. Fix up the
* value graph for cases where the initial register label was not removed.
*/
private void computeClosure() {
for (Enumeration<GraphNode> e = enumerateVertices(); e.hasMoreElements(); ) {
ValueGraphVertex v = (ValueGraphVertex) e.nextElement();
if (v.getName() instanceof Register) {
if (v.getLabel() instanceof Register) {
if (v.getName() != v.getLabel()) {
ValueGraphVertex v2 = getVertex(v.getLabel());
if (VM.VerifyAssertions) {
if (v2.getName() instanceof Register
&& v2.getLabel() instanceof Register
&& v2.getLabel() != v2.getName()) {
VM._assert(VM.NOT_REACHED);
}
}
v.copyVertex(v2);
}
}
}
}
}
/**
* Transform to eliminate redundant branches passed on GVNs and dominator information.
*
* @param ir The IR on which to apply the phase
*/
public void perform(IR ir) {
// (1) Remove redundant conditional branches and locally fix the PHIs
GlobalValueNumberState gvns = ir.HIRInfo.valueNumbers;
DominatorTree dt = ir.HIRInfo.dominatorTree;
for (BasicBlockEnumeration bbs = ir.getBasicBlocks(); bbs.hasMoreElements(); ) {
BasicBlock candBB = bbs.next();
Instruction candTest = candBB.firstBranchInstruction();
if (candTest == null) continue;
if (!(IfCmp.conforms(candTest) || InlineGuard.conforms(candTest))) continue;
GVCongruenceClass cc = gvns.congruenceClass(candTest);
if (cc.size() > 1) {
for (ValueGraphVertex vertex : cc) {
Instruction poss = (Instruction) vertex.getName();
if (poss != candTest) {
BasicBlock notTaken = getNotTakenBlock(poss);
BasicBlock taken = poss.getBranchTarget();
if (taken == notTaken) continue; // both go to same block, so we don't know anything!
if (notTaken.hasOneIn() && dt.dominates(notTaken, candBB)) {
if (DEBUG)
VM.sysWrite(candTest + " is dominated by not-taken branch of " + poss + "\n");
removeCondBranch(candBB, candTest, ir, poss);
cc.removeVertex(gvns.valueGraph.getVertex(candTest));
break;
}
if (taken.hasOneIn() && dt.dominates(taken, candBB)) {
if (DEBUG)
VM.sysWrite(candTest + " is dominated by taken branch of " + poss + "\n");
takeCondBranch(candBB, candTest, ir);
cc.removeVertex(gvns.valueGraph.getVertex(candTest));
break;
}
}
}
}
}
// (2) perform a Depth-first search of the control flow graph,
// and remove any nodes we have made unreachable
removeUnreachableCode(ir);
}
