// A critical edge is an edge which is neither its successor's only predecessor
// nor its predecessor's only successor. Critical edges must be split to
// prevent copy-insertion and code motion from affecting other edges.
bool
ion::SplitCriticalEdges(MIRGraph &graph)
{
for (MBasicBlockIterator block(graph.begin()); block != graph.end(); block++) {
if (block->numSuccessors() < 2)
continue;
for (size_t i = 0; i < block->numSuccessors(); i++) {
MBasicBlock *target = block->getSuccessor(i);
if (target->numPredecessors() < 2)
continue;
// Create a new block inheriting from the predecessor.
MBasicBlock *split = MBasicBlock::NewSplitEdge(graph, block->info(), *block);
split->setLoopDepth(block->loopDepth());
graph.insertBlockAfter(*block, split);
split->end(MGoto::New(target));
block->replaceSuccessor(i, split);
target->replacePredecessor(*block, split);
}
}
return true;
}
