void DominatorTree::build()
{
DLList *bucket = new DLList[count];
Node *nv, *nw;
int p, u, v, w;
buildDFS(cfg->getRoot());
for (w = count - 1; w >= 1; --w) {
nw = vert[w];
assert(nw->tag == w);
for (Graph::EdgeIterator ei = nw->incident(); !ei.end(); ei.next()) {
nv = ei.getNode();
v = nv->tag;
u = eval(v);
if (SEMI(u) < SEMI(w))
SEMI(w) = SEMI(u);
}
p = PARENT(w);
bucket[SEMI(w)].insert(nw);
link(p, w);
for (DLList::Iterator it = bucket[p].iterator(); !it.end(); it.erase()) {
v = reinterpret_cast<Node *>(it.get())->tag;
u = eval(v);
DOM(v) = (SEMI(u) < SEMI(v)) ? u : p;
}
}
for (w = 1; w < count; ++w) {
if (DOM(w) != SEMI(w))
DOM(w) = DOM(DOM(w));
}
DOM(0) = 0;
insert(&BasicBlock::get(cfg->getRoot())->dom);
do {
p = 0;
for (v = 1; v < count; ++v) {
nw = &BasicBlock::get(vert[DOM(v)])->dom;;
nv = &BasicBlock::get(vert[v])->dom;
if (nw->getGraph() && !nv->getGraph()) {
++p;
nw->attach(nv, Graph::Edge::TREE);
}
}
} while (p);
delete[] bucket;
}
// Efficiently Computing Static Single Assignment Form and
// the Control Dependence Graph,
// R. Cytron, J. Ferrante, B. K. Rosen, M. N. Wegman, F. K. Zadeck
bool
Function::convertToSSA()
{
// 0. calculate live in variables (for pruned SSA)
buildLiveSets();
// 1. create the dominator tree
domTree = new DominatorTree(&cfg);
reinterpret_cast<DominatorTree *>(domTree)->findDominanceFrontiers();
// 2. insert PHI functions
DLList workList;
LValue *lval;
BasicBlock *bb;
int var;
int iterCount = 0;
int *hasAlready = new int[allBBlocks.getSize() * 2];
int *work = &hasAlready[allBBlocks.getSize()];
memset(hasAlready, 0, allBBlocks.getSize() * 2 * sizeof(int));
// for each variable
for (var = 0; var < allLValues.getSize(); ++var) {
if (!allLValues.get(var))
continue;
lval = reinterpret_cast<Value *>(allLValues.get(var))->asLValue();
if (!lval || lval->defs.empty())
continue;
++iterCount;
// TODO: don't add phi functions for values that aren't used outside
// the BB they're defined in
// gather blocks with assignments to lval in workList
for (Value::DefIterator d = lval->defs.begin();
d != lval->defs.end(); ++d) {
bb = ((*d)->getInsn() ? (*d)->getInsn()->bb : NULL);
if (!bb)
continue; // instruction likely been removed but not XXX deleted
if (work[bb->getId()] == iterCount)
continue;
work[bb->getId()] = iterCount;
workList.insert(bb);
}
// for each block in workList, insert a phi for lval in the block's
// dominance frontier (if we haven't already done so)
for (DLList::Iterator wI = workList.iterator(); !wI.end(); wI.erase()) {
bb = BasicBlock::get(wI);
DLList::Iterator dfIter = bb->getDF().iterator();
for (; !dfIter.end(); dfIter.next()) {
Instruction *phi;
BasicBlock *dfBB = BasicBlock::get(dfIter);
if (hasAlready[dfBB->getId()] >= iterCount)
continue;
hasAlready[dfBB->getId()] = iterCount;
// pruned SSA: don't need a phi if the value is not live-in
if (!dfBB->liveSet.test(lval->id))
continue;
phi = new_Instruction(this, OP_PHI, typeOfSize(lval->reg.size));
dfBB->insertTail(phi);
phi->setDef(0, lval);
for (int s = 0; s < dfBB->cfg.incidentCount(); ++s)
phi->setSrc(s, lval);
if (work[dfBB->getId()] < iterCount) {
work[dfBB->getId()] = iterCount;
wI.insert(dfBB);
}
}
}
}
delete[] hasAlready;
RenamePass rename(this);
return rename.run();
}