[llvm] r314801 - [Dominators] Add DFS number verification
Jakub (Kuba) Kuderski via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 3 13:32:51 PDT 2017
Hi Juergen,
It seems like the patch caught some invalid DominatorTrees :).
I'm now investigating a failure in LoopRotation happening in
test/Transforms/ArgumentPromotion/pr3085.ll
with expensive checks enabled, but I don't know if that's related.
I looked and the buildbot's output and it seems to fail on OSX -- do you
know if it's reproducible on x86_64 linux?
Best,
Jakub
On Tue, Oct 3, 2017 at 4:26 PM, Juergen Ributzka <juergen at ributzka.de>
wrote:
> Hi Jakub,
>
> I think this broke one of our jobs on Green Dragon:
> http://green.lab.llvm.org/green/job/clang-stage1-cmake-
> RA-expensive/8568/consoleFull
>
> Could you please take a look?
>
> Thanks
>
> Cheers,
> Juergen
>
> On Tue, Oct 3, 2017 at 7:33 AM, Jakub Kuderski via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> 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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>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>
>
--
Jakub Kuderski
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