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make ComputeTopDownOrdering significantly faster and use less stack space

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by making it non-recursive


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37629 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-06-18 21:28:10 +00:00
parent f50cd749e1
commit e10e6f7a36
1 changed files with 37 additions and 32 deletions
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69
lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
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@ -302,24 +302,45 @@ SelectionDAGLegalize::SelectionDAGLegalize(SelectionDAG &dag)
"Too many value types for ValueTypeActions to hold!");
}
/// ComputeTopDownOrdering - Add the specified node to the Order list if it has
/// not been visited yet and if all of its operands have already been visited.
static void ComputeTopDownOrdering(SDNode *N, SmallVector<SDNode*, 64> &Order,
DenseMap<SDNode*, unsigned> &Visited) {
if (++Visited[N] != N->getNumOperands())
return; // Haven't visited all operands yet
/// ComputeTopDownOrdering - Compute a top-down ordering of the dag, where Order
/// contains all of a nodes operands before it contains the node.
static void ComputeTopDownOrdering(SelectionDAG &DAG,
SmallVector<SDNode*, 64> &Order) {
DenseMap<SDNode*, unsigned> Visited;
std::vector<SDNode*> Worklist;
Worklist.reserve(128);
Order.push_back(N);
if (N->hasOneUse()) { // Tail recurse in common case.
ComputeTopDownOrdering(*N->use_begin(), Order, Visited);
return;
// Compute ordering from all of the leaves in the graphs, those (like the
// entry node) that have no operands.
for (SelectionDAG::allnodes_iterator I = DAG.allnodes_begin(),
E = DAG.allnodes_end(); I != E; ++I) {
if (I->getNumOperands() == 0) {
Visited[I] = 0 - 1U;
Worklist.push_back(I);
}
}
// Now that we have N in, add anything that uses it if all of their operands
// are now done.
for (SDNode::use_iterator UI = N->use_begin(), E = N->use_end(); UI != E;++UI)
ComputeTopDownOrdering(*UI, Order, Visited);
while (!Worklist.empty()) {
SDNode *N = Worklist.back();
Worklist.pop_back();
if (++Visited[N] != N->getNumOperands())
continue; // Haven't visited all operands yet
Order.push_back(N);
// Now that we have N in, add anything that uses it if all of their operands
// are now done.
for (SDNode::use_iterator UI = N->use_begin(), E = N->use_end();
UI != E; ++UI)
Worklist.push_back(*UI);
}
assert(Order.size() == Visited.size() &&
Order.size() ==
(unsigned)std::distance(DAG.allnodes_begin(), DAG.allnodes_end()) &&
"Error: DAG is cyclic!");
}
@ -333,24 +354,8 @@ void SelectionDAGLegalize::LegalizeDAG() {
// practice however, this causes us to run out of stack space on large basic
// blocks. To avoid this problem, compute an ordering of the nodes where each
// node is only legalized after all of its operands are legalized.
DenseMap<SDNode*, unsigned> Visited;
SmallVector<SDNode*, 64> Order;
// Compute ordering from all of the leaves in the graphs, those (like the
// entry node) that have no operands.
for (SelectionDAG::allnodes_iterator I = DAG.allnodes_begin(),
E = DAG.allnodes_end(); I != E; ++I) {
if (I->getNumOperands() == 0) {
Visited[I] = 0 - 1U;
ComputeTopDownOrdering(I, Order, Visited);
}
}
assert(Order.size() == Visited.size() &&
Order.size() ==
(unsigned)std::distance(DAG.allnodes_begin(), DAG.allnodes_end()) &&
"Error: DAG is cyclic!");
Visited.clear();
ComputeTopDownOrdering(DAG, Order);
for (unsigned i = 0, e = Order.size(); i != e; ++i)
HandleOp(SDOperand(Order[i], 0));