void DominatorTree::findDominanceFrontiers()
{
BasicBlock *bb;
for (IteratorRef dtIt = iteratorDFS(false); !dtIt->end(); dtIt->next()) {
EdgeIterator succIt, chldIt;
bb = BasicBlock::get(reinterpret_cast<Node *>(dtIt->get()));
bb->getDF().clear();
for (succIt = bb->cfg.outgoing(); !succIt.end(); succIt.next()) {
BasicBlock *dfLocal = BasicBlock::get(succIt.getNode());
if (dfLocal->idom() != bb)
bb->getDF().insert(dfLocal);
}
for (chldIt = bb->dom.outgoing(); !chldIt.end(); chldIt.next()) {
BasicBlock *cb = BasicBlock::get(chldIt.getNode());
DLList::Iterator dfIt = cb->getDF().iterator();
for (; !dfIt.end(); dfIt.next()) {
BasicBlock *dfUp = BasicBlock::get(dfIt);
if (dfUp->idom() != bb)
bb->getDF().insert(dfUp);
}
}
}
}
bool
PrintPass::visit(BasicBlock *bb)
{
#if 0
INFO("---\n");
for (Graph::EdgeIterator ei = bb->cfg.incident(); !ei.end(); ei.next())
INFO(" <- BB:%i (%s)\n",
BasicBlock::get(ei.getNode())->getId(),
ei.getEdge()->typeStr());
#endif
INFO("BB:%i (%u instructions) - ", bb->getId(), bb->getInsnCount());
if (bb->idom())
INFO("idom = BB:%i, ", bb->idom()->getId());
INFO("df = { ");
for (DLList::Iterator df = bb->getDF().iterator(); !df.end(); df.next())
INFO("BB:%i ", BasicBlock::get(df)->getId());
INFO("}\n");
for (Graph::EdgeIterator ei = bb->cfg.outgoing(); !ei.end(); ei.next())
INFO(" -> BB:%i (%s)\n",
BasicBlock::get(ei.getNode())->getId(),
ei.getEdge()->typeStr());
return true;
}
// 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();
}