public Cost computeRefCost(LoopHeaderChord loop, SubscriptExpr se) {
Cost tripL = loop.getTripCount();
InductionVar ivar = loop.getPrimaryInductionVar();
if (ivar == null) return tripL;
// Compute
// tripL = (ubL - lbL + stepL) / stepL
int nsubs = se.numSubscripts(); // number of subscripts in the subscript
LoopHeaderChord tloop = loop.getTopLoop();
VariableDecl iv = ivar.getVar();
for (int i = 0; i < nsubs - 1; i++) { // for c code
// If the loop index variable of this loop appears in any of the
// subscripts other then the last, then return tripL.
Expr sI = se.getSubscript(i);
AffineExpr ae = tloop.isAffine(sI);
if (ae == null) return null;
if (ae.hasTerm(iv)) return tripL;
}
int fs = nsubs - 1;
Expr s0 = se.getSubscript(fs);
AffineExpr ae = tloop.isAffine(s0);
if (ae == null) return null;
int at = ae.getTermIndexOrig(iv);
long coeff = 0;
if (at >= 0) coeff = ae.getCoefficient(at);
if (coeff == 0) // Invariant Reuse.
return new Cost(1.0, 0);
long stepL = loop.getStepValue();
long stride = stepL * coeff;
if (stride < 0) stride = -stride;
// Unit Reuse.
Type et = se.getCoreType().getPointedTo();
int bs = et.memorySizeAsInt(Machine.currentMachine);
int cs = Machine.currentMachine.getCacheSize(bs);
if (stride <= cs) { // cache line or block size
tripL.multiply(stride);
tripL.divide(cs);
return tripL;
}
// No Reuse.
return tripL;
}
/**
* Compute the reference groups for this loop. Two array references are in the same group with
* respect to this loop if - there is a loop-independent dependence between them, or - the
* dependence distance(dependence vector entry dl) for this loop is less than some constant
* *dist*, and all other dependence vector entries are 0. - the two array refer to the same array
* and differ by at most *dist2* in the first subscript dimension, where d is less than or equal
* to the cache line size in terms of array elements. All other subscripts must be identical.
* Notes: Here we assume dist1 = dist2 = 2
*/
private void computeRefGroups(
int level,
int dist1,
int dist2,
Table<Declaration, SubscriptExpr> arrayRefs,
Vector<RefGroup> refGroups) {
if (arrayRefs == null) return;
Enumeration<Declaration> ek = arrayRefs.keys();
while (ek.hasMoreElements()) {
VariableDecl vd = (VariableDecl) ek.nextElement();
String s = vd.getName(); // array name
Object[] v = arrayRefs.getRowArray(vd); // vector of SubscriptExpr's
int vi = v.length;
for (int j = vi - 1; j >= 0; j--) {
SubscriptExpr sr = (SubscriptExpr) v[j];
Vector<LoopHeaderChord> allRelatedLoops =
sr.allRelatedLoops(); // ** Incorrect when something like a[(j+i][j]
int arls = allRelatedLoops.size();
int firstsub = arls - 1; // ** Making an invalid assumption here
// Process the list of references r' with which r has a data
// dependence, and r is the source(data flows from r to r').
RefGroup rg = new RefGroup(s, sr);
Object[] edges = graph.getEdges(sr);
int len = edges.length;
for (int i = 0; i < len; i++) {
DDEdge edge = (DDEdge) edges[i];
if (edge.isSpatial()) continue;
// Condition(1)-(a) in McKinley's paper
if (edge.isLoopIndependentDependency()) { // add rP to the RefGroup of r:
rg.add(edge);
continue;
}
// Condition(1)-(b) in McKinley's paper
computeEdgeRefs(edge, rg, level, dist1);
if (arls <= 0) continue;
// Condition(2) in McKinley's paper
// rlevel is the level of the loop related to the first subscript.
int rlevel = allRelatedLoops.elementAt(firstsub).getNestedLevel();
computeEdgeRefs(edge, rg, rlevel, dist2);
}
boolean isInExistingRefGroups = false;
int rgl = refGroups.size();
for (int i = 0; i < rgl; i++) {
RefGroup rg2 = refGroups.elementAt(i);
if (!rg2.getName().equals(s)) continue;
isInExistingRefGroups = rg2.contains(rg);
if (isInExistingRefGroups) {
rg2.add(rg);
break;
}
}
if (!isInExistingRefGroups) refGroups.addElement(rg);
}
}
}
