[llvm] r314801 - [Dominators] Add DFS number verification
Jakub Kuderski via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 3 07:33:41 PDT 2017
Author: kuhar
Date: Tue Oct 3 07:33:41 2017
New Revision: 314801
URL: http://llvm.org/viewvc/llvm-project?rev=314801&view=rev
Log:
[Dominators] Add DFS number verification
Summary:
This patch teaches the DominatorTree verifier to check DFS In/Out numbers which are used to answer dominance queries.
DFS number verification is done in O(nlogn), so it shouldn't add much overhead on top of the O(n^3) sibling property verification.
This check should detect errors like the one spotted in PR34466 and related bug reports.
The patch also cleans up the DFS calculation a bit, as all constructed trees should have a single root now.
I see 2 new test failures when running check-all after this change:
```
Failing Tests (2):
Polly :: Isl/CodeGen/OpenMP/reference-argument-from-non-affine-region.ll
Polly :: Isl/CodeGen/OpenMP/two-parallel-loops-reference-outer-indvar.ll
```
which seem to happen just after `Create LLVM-IR from SCoPs` -- I XFAILed them in r314800.
Reviewers: dberlin, grosser, davide, zhendongsu, bollu
Reviewed By: dberlin
Subscribers: nandini12396, bollu, Meinersbur, brzycki, llvm-commits
Differential Revision: https://reviews.llvm.org/D38331
Modified:
llvm/trunk/include/llvm/Support/GenericDomTree.h
llvm/trunk/include/llvm/Support/GenericDomTreeConstruction.h
Modified: llvm/trunk/include/llvm/Support/GenericDomTree.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/GenericDomTree.h?rev=314801&r1=314800&r2=314801&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/GenericDomTree.h (original)
+++ llvm/trunk/include/llvm/Support/GenericDomTree.h Tue Oct 3 07:33:41 2017
@@ -702,28 +702,25 @@ public:
return;
}
- unsigned DFSNum = 0;
-
SmallVector<std::pair<const DomTreeNodeBase<NodeT> *,
typename DomTreeNodeBase<NodeT>::const_iterator>,
32> WorkStack;
const DomTreeNodeBase<NodeT> *ThisRoot = getRootNode();
-
+ assert((!Parent || ThisRoot) && "Empty constructed DomTree");
if (!ThisRoot)
return;
- // Even in the case of multiple exits that form the post dominator root
- // nodes, do not iterate over all exits, but start from the virtual root
- // node. Otherwise bbs, that are not post dominated by any exit but by the
- // virtual root node, will never be assigned a DFS number.
- WorkStack.push_back(std::make_pair(ThisRoot, ThisRoot->begin()));
+ // Both dominators and postdominators have a single root node. In the case
+ // case of PostDominatorTree, this node is a virtual root.
+ WorkStack.push_back({ThisRoot, ThisRoot->begin()});
+
+ unsigned DFSNum = 0;
ThisRoot->DFSNumIn = DFSNum++;
while (!WorkStack.empty()) {
const DomTreeNodeBase<NodeT> *Node = WorkStack.back().first;
- typename DomTreeNodeBase<NodeT>::const_iterator ChildIt =
- WorkStack.back().second;
+ const auto ChildIt = WorkStack.back().second;
// If we visited all of the children of this node, "recurse" back up the
// stack setting the DFOutNum.
@@ -735,7 +732,7 @@ public:
const DomTreeNodeBase<NodeT> *Child = *ChildIt;
++WorkStack.back().second;
- WorkStack.push_back(std::make_pair(Child, Child->begin()));
+ WorkStack.push_back({Child, Child->begin()});
Child->DFSNumIn = DFSNum++;
}
}
Modified: llvm/trunk/include/llvm/Support/GenericDomTreeConstruction.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/GenericDomTreeConstruction.h?rev=314801&r1=314800&r2=314801&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/GenericDomTreeConstruction.h (original)
+++ llvm/trunk/include/llvm/Support/GenericDomTreeConstruction.h Tue Oct 3 07:33:41 2017
@@ -1349,6 +1349,102 @@ struct SemiNCAInfo {
return true;
}
+ // Check if the computed DFS numbers are correct. Note that DFS info may not
+ // be valid, and when that is the case, we don't verify the numbers.
+ static bool VerifyDFSNumbers(const DomTreeT &DT) {
+ if (!DT.DFSInfoValid || !DT.Parent)
+ return true;
+
+ const NodePtr RootBB = IsPostDom ? nullptr : DT.getRoots()[0];
+ const TreeNodePtr Root = DT.getNode(RootBB);
+
+ auto PrintNodeAndDFSNums = [](const TreeNodePtr TN) {
+ errs() << BlockNamePrinter(TN) << " {" << TN->getDFSNumIn() << ", "
+ << TN->getDFSNumOut() << '}';
+ };
+
+ // Verify the root's DFS In number. Although DFS numbering would also work
+ // if we started from some other value, we assume 0-based numbering.
+ if (Root->getDFSNumIn() != 0) {
+ errs() << "DFSIn number for the tree root is not:\n\t";
+ PrintNodeAndDFSNums(Root);
+ errs() << '\n';
+ errs().flush();
+ return false;
+ }
+
+ // For each tree node verify if children's DFS numbers cover their parent's
+ // DFS numbers with no gaps.
+ for (const auto &NodeToTN : DT.DomTreeNodes) {
+ const TreeNodePtr Node = NodeToTN.second.get();
+
+ // Handle tree leaves.
+ if (Node->getChildren().empty()) {
+ if (Node->getDFSNumIn() + 1 != Node->getDFSNumOut()) {
+ errs() << "Tree leaf should have DFSOut = DFSIn + 1:\n\t";
+ PrintNodeAndDFSNums(Node);
+ errs() << '\n';
+ errs().flush();
+ return false;
+ }
+
+ continue;
+ }
+
+ // Make a copy and sort it such that it is possible to check if there are
+ // no gaps between DFS numbers of adjacent children.
+ SmallVector<TreeNodePtr, 8> Children(Node->begin(), Node->end());
+ std::sort(Children.begin(), Children.end(),
+ [](const TreeNodePtr Ch1, const TreeNodePtr Ch2) {
+ return Ch1->getDFSNumIn() < Ch2->getDFSNumIn();
+ });
+
+ auto PrintChildrenError = [Node, &Children, PrintNodeAndDFSNums](
+ const TreeNodePtr FirstCh, const TreeNodePtr SecondCh = nullptr) {
+ assert(FirstCh);
+
+ errs() << "Incorrect DFS numbers for:\n\tParent ";
+ PrintNodeAndDFSNums(Node);
+
+ errs() << "\n\tChild ";
+ PrintNodeAndDFSNums(FirstCh);
+
+ if (SecondCh) {
+ errs() << "\n\tSecond child ";
+ PrintNodeAndDFSNums(SecondCh);
+ }
+
+ errs() << "\nAll children: ";
+ for (const TreeNodePtr Ch : Children) {
+ PrintNodeAndDFSNums(Ch);
+ errs() << ", ";
+ }
+
+ errs() << '\n';
+ errs().flush();
+ };
+
+ if (Children.front()->getDFSNumIn() != Node->getDFSNumIn() + 1) {
+ PrintChildrenError(Children.front());
+ return false;
+ }
+
+ if (Children.back()->getDFSNumOut() + 1 != Node->getDFSNumOut()) {
+ PrintChildrenError(Children.back());
+ return false;
+ }
+
+ for (size_t i = 0, e = Children.size() - 1; i != e; ++i) {
+ if (Children[i]->getDFSNumOut() + 1 != Children[i + 1]->getDFSNumIn()) {
+ PrintChildrenError(Children[i], Children[i + 1]);
+ return false;
+ }
+ }
+ }
+
+ return true;
+ }
+
// Checks if for every edge From -> To in the graph
// NCD(From, To) == IDom(To) or To.
bool verifyNCD(const DomTreeT &DT) {
@@ -1521,7 +1617,8 @@ bool Verify(const DomTreeT &DT) {
SemiNCAInfo<DomTreeT> SNCA(nullptr);
return SNCA.verifyRoots(DT) && SNCA.verifyReachability(DT) &&
SNCA.VerifyLevels(DT) && SNCA.verifyNCD(DT) &&
- SNCA.verifyParentProperty(DT) && SNCA.verifySiblingProperty(DT);
+ SNCA.verifyParentProperty(DT) && SNCA.verifySiblingProperty(DT) &&
+ SNCA.VerifyDFSNumbers(DT);
}
} // namespace DomTreeBuilder
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