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Do not even attempt to compute dominator information for unreachable blocks
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7963 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -48,7 +48,7 @@ void DominatorSet::calculateDominatorsFromBlock(BasicBlock *RootBB) {
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BasicBlock *BB = *It;
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pred_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
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if (PI != PEnd) { // Is there SOME predecessor?
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// Loop until we get to a predecessor that has had it's dom set filled
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// Loop until we get to a predecessor that has had its dom set filled
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// in at least once. We are guaranteed to have this because we are
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// traversing the graph in DFO and have handled start nodes specially,
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// except when there are unreachable blocks.
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@ -63,29 +63,15 @@ void DominatorSet::calculateDominatorsFromBlock(BasicBlock *RootBB) {
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if (PredSet.size())
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set_intersect(WorkingSet, PredSet);
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}
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} else {
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// Otherwise this block is unreachable. it doesn't really matter what
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// we use for the dominator set for the node...
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//
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WorkingSet = Doms[Root];
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}
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} else if (BB != Root) {
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// If this isn't the root basic block and it has no predecessors, it
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// must be an unreachable block. Fib a bit by saying that the root node
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// dominates this unreachable node. This isn't exactly true, because
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// there is no path from the entry node to this node, but it is sorta
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// true because any paths to this node would have to go through the
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// entry node.
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//
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// This allows for dominator properties to be built for unreachable code
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// in a reasonable manner.
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//
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WorkingSet = Doms[Root];
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} else {
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assert(BB == Root && "We got into unreachable code somehow!");
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}
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WorkingSet.insert(BB); // A block always dominates itself
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DomSetType &BBSet = Doms[BB];
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if (BBSet != WorkingSet) {
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//assert(WorkingSet.size() > BBSet.size() && "Must only grow sets!");
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BBSet.swap(WorkingSet); // Constant time operation!
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Changed = true; // The sets changed.
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}
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@ -113,16 +99,12 @@ void DominatorSet::recalculate() {
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// Calculate dominator sets for the reachable basic blocks...
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calculateDominatorsFromBlock(Root);
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// Every basic block in the function should at least dominate themselves, and
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// thus every basic block should have an entry in Doms. The one case where we
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// miss this is when a basic block is unreachable. To get these we now do an
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// extra pass over the function, calculating dominator information for
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// Loop through the function, ensuring that every basic block has at least an
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// empty set of nodes. This is important for the case when there is
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// unreachable blocks.
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//
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Function *F = Root->getParent();
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for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
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if (Doms[I].count(I) == 0)
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calculateDominatorsFromBlock(I);
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for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) Doms[I];
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}
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