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[SelectionDAG] Get rid of recursion in findNonImmUse 

The recursive implementation of findNonImmUse may overflow stack
on extremely long use chains. This patch replaces it with an equivalent
iterative implementation.

Reviewed By: bogner

Differential Revision: https://reviews.llvm.org/D33775

llvm-svn: 304522
This commit is contained in:
Max Kazantsev 2017-06-02 07:11:00 +00:00
parent 694e8a0d2f
commit 4d8748a987
1 changed files with 27 additions and 21 deletions
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48
llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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@ -2022,7 +2022,7 @@ static SDNode *findGlueUse(SDNode *N) {
}
/// findNonImmUse - Return true if "Use" is a non-immediate use of "Def".
/// This function recursively traverses up the operand chain, ignoring
/// This function iteratively traverses up the operand chain, ignoring
/// certain nodes.
static bool findNonImmUse(SDNode *Use, SDNode* Def, SDNode *ImmedUse,
SDNode *Root, SmallPtrSetImpl<SDNode*> &Visited,
@ -2035,30 +2035,36 @@ static bool findNonImmUse(SDNode *Use, SDNode* Def, SDNode *ImmedUse,
// The Use may be -1 (unassigned) if it is a newly allocated node. This can
// happen because we scan down to newly selected nodes in the case of glue
// uses.
if ((Use->getNodeId() < Def->getNodeId() && Use->getNodeId() != -1))
return false;
std::vector<SDNode *> WorkList;
WorkList.push_back(Use);
// Don't revisit nodes if we already scanned it and didn't fail, we know we
// won't fail if we scan it again.
if (!Visited.insert(Use).second)
return false;
for (const SDValue &Op : Use->op_values()) {
// Ignore chain uses, they are validated by HandleMergeInputChains.
if (Op.getValueType() == MVT::Other && IgnoreChains)
while (!WorkList.empty()) {
Use = WorkList.back();
WorkList.pop_back();
if (Use->getNodeId() < Def->getNodeId() && Use->getNodeId() != -1)
continue;
SDNode *N = Op.getNode();
if (N == Def) {
if (Use == ImmedUse || Use == Root)
continue; // We are not looking for immediate use.
assert(N != Root);
return true;
}
// Don't revisit nodes if we already scanned it and didn't fail, we know we
// won't fail if we scan it again.
if (!Visited.insert(Use).second)
continue;
// Traverse up the operand chain.
if (findNonImmUse(N, Def, ImmedUse, Root, Visited, IgnoreChains))
return true;
for (const SDValue &Op : Use->op_values()) {
// Ignore chain uses, they are validated by HandleMergeInputChains.
if (Op.getValueType() == MVT::Other && IgnoreChains)
continue;
SDNode *N = Op.getNode();
if (N == Def) {
if (Use == ImmedUse || Use == Root)
continue; // We are not looking for immediate use.
assert(N != Root);
return true;
}
// Traverse up the operand chain.
WorkList.push_back(N);
}
}
return false;
}