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Rewrite SelectionDAG::isPredecessorOf to be iterative instead of

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recursive to avoid consuming extraordinary amounts of stack space
when processing tall graphs.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85369 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-10-28 03:44:30 +00:00
parent 09d9ef4122
commit 6688d61797
1 changed files with 16 additions and 21 deletions
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37
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -5307,31 +5307,26 @@ bool SDValue::reachesChainWithoutSideEffects(SDValue Dest,
return false;
}
static void findPredecessor(SDNode *N, const SDNode *P, bool &found,
SmallPtrSet<SDNode *, 32> &Visited) {
if (found || !Visited.insert(N))
return;
for (unsigned i = 0, e = N->getNumOperands(); !found && i != e; ++i) {
SDNode *Op = N->getOperand(i).getNode();
if (Op == P) {
found = true;
return;
}
findPredecessor(Op, P, found, Visited);
}
}
/// isPredecessorOf - Return true if this node is a predecessor of N. This node
/// is either an operand of N or it can be reached by recursively traversing
/// up the operands.
/// is either an operand of N or it can be reached by traversing up the operands.
/// NOTE: this is an expensive method. Use it carefully.
bool SDNode::isPredecessorOf(SDNode *N) const {
SmallPtrSet<SDNode *, 32> Visited;
bool found = false;
findPredecessor(N, this, found, Visited);
return found;
SmallVector<SDNode *, 16> Worklist;
Worklist.push_back(N);
do {
N = Worklist.pop_back_val();
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
SDNode *Op = N->getOperand(i).getNode();
if (Op == this)
return true;
if (Visited.insert(Op))
Worklist.push_back(Op);
}
} while (!Worklist.empty());
return false;
}
uint64_t SDNode::getConstantOperandVal(unsigned Num) const {