/** Perform the actual copy propagation. */
public void perform() {
Stack<Chord> wl = WorkArea.<Chord>getStack("perform CP");
Chord start = scribble.getBegin();
boolean doSubscripts = scribble.scalarReplacementPerformed();
// If subscript addresses are propagated before scalar replacement
// is performed, scalar replacement generates incorrect code.
wl.push(start);
Chord.nextVisit();
start.setVisited();
while (!wl.empty()) {
Chord s = wl.pop();
s.pushOutCfgEdges(wl);
if (s.isAssignChord()) {
visitExprChord((ExprChord) s, doSubscripts);
}
}
WorkArea.<Chord>returnStack(wl);
if (rChanged) {
scribble.recomputeRefs();
}
}
private int[][] getDDVec(Table<Declaration, SubscriptExpr> arrayRefs, int loopDepth) {
if (arrayRefs == null) return new int[0][0];
int numEdges = 0;
Stack<DDEdge> wl = WorkArea.<DDEdge>getStack("g<SubscriptExpr>etDDVec");
Enumeration<DDEdge> k = graph.getEdges();
while (k.hasMoreElements()) { // Check out every array variable in the loop nest.
DDEdge edge = k.nextElement();
if (edge.isSpatial()) continue;
if (edge.isLoopIndependentDependency()) continue;
if (edge.representsAllInput()) continue;
wl.push(edge);
numEdges++;
}
int[][] DDVector = new int[numEdges][loopDepth];
int i = 0;
while (!wl.empty()) {
DDEdge edge = wl.pop();
if (trace) System.out.println(" edge " + edge);
// Find dependence distance.
for (int level = 1; level <= loopDepth; level++)
DDVector[i][level - 1] = edge.getDistance(level);
if (trace) {
System.out.print(i);
System.out.print(" ");
System.out.println(edge);
}
i++;
}
WorkArea.<DDEdge>returnStack(wl);
return DDVector;
}
/** Remove all the predicates which are not defined in the hyperblock. */
private BitVect removePredicates(PredicateBlock start) {
BitVect predicates = new BitVect();
Stack<Node> wl = new Stack<Node>();
// Determine all the predicates defined outside this hyperblock.
start.nextVisit();
start.setVisited();
wl.add(start);
while (!wl.isEmpty()) {
PredicateBlock block = (PredicateBlock) wl.pop();
block.pushOutEdges(wl);
for (Instruction inst = block.getFirstInstruction(); inst != null; inst = inst.getNext()) {
if (inst.isMarker()) {
continue;
}
if (inst.isBranch()) {
continue;
}
if (((TripsInstruction) inst).definesPredicate()) {
predicates.set(inst.getDestRegister());
}
}
}
// Remove the predicates.
start.nextVisit();
start.setVisited();
wl.add(start);
while (!wl.isEmpty()) {
PredicateBlock block = (PredicateBlock) wl.pop();
block.pushOutEdges(wl);
if (!block.isPredicated()) {
continue;
}
int rp = block.getPredicate();
if (predicates.get(rp)) {
continue;
}
block.removePredicates();
for (Instruction inst = block.getFirstInstruction(); inst != null; inst = inst.getNext()) {
inst.removePredicates();
}
}
return predicates;
}
/** The main routine for block splitting. */
public final void split(Hyperblock hbStart) {
Stack<Node> wl = WorkArea.<Node>getStack("split");
DataflowAnalysis df = new DataflowAnalysis(hbStart, regs);
int trips = 0;
// Add all the hyperblocks to the working set.
hbStart.nextVisit();
hbStart.setVisited();
wl.push(hbStart);
while (!wl.isEmpty()) {
Hyperblock hb = (Hyperblock) wl.pop();
hb.pushOutEdges(wl);
workingSet.add(hb);
}
// Split the hyperblocks.
while (!workingSet.isEmpty()) {
df.computeLiveness3();
wl.addAll(workingSet);
while (!wl.isEmpty()) {
Hyperblock hb = (Hyperblock) wl.pop();
hb.enterSSA();
hb.analyzeLeaveSSA();
if (!hb.isLegalBlock(true)) {
splitHyperblock(hb);
} else {
workingSet.remove(hb);
}
}
if ((++trips % WARN_SPLIT_ATTEMPTS) == 0) {
System.err.println(
"** Warning: the block splitter has run "
+ trips
+ " times for "
+ gen.getCurrentRoutine().getName()
+ "().");
}
}
WorkArea.<Node>returnStack(wl);
}
/** Reverse if-convert the given predicate block from the hyperblock. */
private void reverseIfConvert(Hyperblock hb, PredicateBlock start) {
Stack<Node> wl = WorkArea.<Node>getStack("reverseIfConvert");
Stack<PredicateBlock> reverse = WorkArea.<PredicateBlock>getStack("reverseIfConvert");
Vector<PredicateBlock> blocks = new Vector<PredicateBlock>();
Vector<Hyperblock> hbs = new Vector<Hyperblock>();
// Find the blocks which need to be reverse if-converted.
start.nextVisit();
start.setVisited();
wl.add(start);
while (!wl.isEmpty()) {
PredicateBlock block = (PredicateBlock) wl.pop();
block.pushOutEdges(wl);
for (int i = 0; i < block.numInEdges(); i++) {
PredicateBlock pred = (PredicateBlock) block.getInEdge(i);
if (!pred.visited()) {
blocks.add(block);
break;
} else if (blocks.contains(pred) && block.numInEdges() > 1) {
blocks.add(block);
break;
}
}
}
// Order the blocks to reverse if-convert based on their depth from the root.
PredicateBlock head = hb.getFirstBlock();
Vector<PredicateBlock> wl2 = new Vector<PredicateBlock>();
head.nextVisit();
head.setVisited();
wl2.add(head);
while (!wl2.isEmpty()) {
int l = wl2.size();
for (int i = 0; i < l; i++) {
PredicateBlock block = wl2.get(i);
if (blocks.contains(block)) {
blocks.remove(block);
reverse.push(block);
}
}
wl2 = hb.getNextPFGLevel(wl2);
}
// Remove the special "dummy" last block from the PFG.
PredicateBlock last = hb.getLastBlock();
assert (last.numOutEdges() == 0 && !last.isPredicated());
if (last.getFirstInstruction() == null) {
for (int i = last.numInEdges() - 1; i > -1; i--) {
PredicateBlock pred = (PredicateBlock) last.getInEdge(i);
pred.deleteOutEdge(last);
last.deleteInEdge(pred);
}
reverse.remove(last);
}
// Reverse if-convert.
while (!reverse.isEmpty()) {
PredicateBlock block = reverse.pop();
Hyperblock hbn = reverseIfConvertBlock(block);
hbs.add(hbn);
workingSet.add(hbn);
}
// Update the PFG.
hb.updateLastBlock();
hb.invalidateDomination(); // The dominators are now invalid.
// Insert the new hyperblocks in the HFG.
HashMap<Instruction, Hyperblock> entries = computeEntries(hb, hbs);
hbs.add(hb);
Hyperblock.computeHyperblockFlowGraph(hbs, entries);
// Update the return block. Since 'hbs' is an ordered list, the
// first element in the list is the hyperblock with the return
// because this was the original tail of the PFG which was reverse
// if-converted.
if (hb == gen.getReturnBlock()) {
gen.setReturnBlock(hbs.firstElement());
}
WorkArea.<Node>returnStack(wl);
WorkArea.<PredicateBlock>returnStack(reverse);
}
/**
* Return true if this is a legal loop. A legal loop contains no function calls and has no scalar
* variable cycles. A cycle exists when the variable is referenced before it is defed. We go to
* some trouble to allow loops containing cycles such as
*
* <pre>
* s = s + a(i,j)
* </pre>
*
* to be permuted.
*/
private boolean legalLoop(LoopHeaderChord loop) {
Stack<Chord> wl = WorkArea.<Chord>getStack("legalLoop");
References refs = scribble.getRefs();
Chord.nextVisit();
wl.push(loop);
loop.setVisited();
int n = loop.numLoopExits();
for (int i = 0; i < n; i++) loop.getLoopExit(i).setVisited();
boolean legal = true;
outer:
while (!wl.empty()) {
Chord c = wl.pop();
if (c.getCall(true) != null) {
legal = false;
break;
}
if ((c instanceof DecisionChord) && (c != loop.getLoopTest())) {
legal = false;
break;
}
if (c.isAssignChord() && !c.isPhiExpr()) {
ExprChord ec = (ExprChord) c;
Expr lhs = ec.getLValue();
Expr rhs = ec.getRValue();
// The variable is both defed and used in the loop and
// we don't know how it is used. For example, it could be
// s = s + 1
// c(i,j) = s
// or
// c(i,j) = s
// s = s + 1
// We want to allow
// s = s + c(i,j)
// because we know that s is not used to specify the
// value of an array element. We want to allow
// s = ...
// = s
// since there is no cycle.
if (lhs instanceof LoadDeclAddressExpr) {
LoadDeclAddressExpr ldae = (LoadDeclAddressExpr) lhs;
VariableDecl vd = ldae.getDecl().returnVariableDecl();
if ((vd != null) && !loop.isLoopIndex(vd)) {
boolean cycle = false;
Iterator<Chord> it1 = refs.getUseChords(vd);
while (it1.hasNext()) {
Chord s = it1.next();
cycle |= (s == c);
}
Iterator<Chord> it2 = refs.getUseChords(vd);
while (it2.hasNext()) {
Chord s = it2.next();
if (c == s) continue;
if (s.getLoopHeader() != loop) continue;
if (cycle) {
// There was a cycle and another use.
// s = s + 1
// = s
legal = false;
break outer;
}
// Check for a use before the def.
while (true) {
s = s.getNextChord();
if (s == null) break;
if (s == c) {
legal = false;
break outer;
}
}
}
}
}
}
c.pushOutCfgEdges(wl);
}
WorkArea.<Chord>returnStack(wl);
return legal;
}