This patch looks fine to me.
2011/4/6 Hui Shi <kalin....@gmail.com>
> Could a gatekeeper please review this patch?
> https://bugs.open64.net/show_bug.cgi?id=748
>
> When turn on nystrom alias analyzer, SPEC2006 base 445.gobmk assertion in
> ConstraintGraph::buildCGipa, constraint_graph.cxx:444
> if (pNode->checkFlags(CG_NODE_FLAGS_COLLAPSED)) {
> FmtAssert(pNode != pNode->parent(), ("Expecting a distinct parent "
> "for COLLAPSED node: %d\n", pNode->id()));
> This assertion means Node is collapsed but its parent field still point to
> itself which means it's not collapsed yet.
> Because collapsed node means it’s merged into its collapse parent, it will
> not show in any other nodes’ points to set.
>
> This bug related with three constraint graph node.
> CGNodeId: 2 is <677377, 408>
> CGNodeId: 3 is <677377, 0>
> CGNodeId: 4 is <677377, 416>
>
> ConstraintGraph::buildCGipa construct each PU's local constraint graph and
> merge global constraint graph node into ConstraintGraph ::GlobalCG. So their
> maybe complicated cases when different PU's IPL constraint graph has
> inconsistent parent relationship between nodes.
>
> This assertion happens with following steps when processing each individual
> PU's local constraint graph.
> 1. Process first function Node<4>'s parent is Node<3> in local constraint
> graph.
> 2. Process second function Node<4>'s parent is Node<2> in local constraint
> graph. Current implmentation is mergeing original parent Node<3> to new
> parent Node<2>. Then Node<2> becomes Node<3>'s parent.
> 3. Porcess third function Node<2>'s parent is Node<3> in local constraint
> graph. Current handling doesn't change Node<2>'s parent to Node<3>, because
> there will be a cyclic repParent chain.
>
> This is like break the parent cycle by letting Node<2> be top level parent
> node, without consider if Node<2> is collapsed or not. This trigger the
> assertion, that Node<2> is collapsed while has no repParent.
>
> Fix is breaking the parent cycle in another way when find cgNode has
> collapsed flag.
> Put the collapsed node at bottom of repParent chain, merge its edges and
> points_to to its parent.
> This makes collapsed node keep align with its definition.
>
> Index: osprey/ipa/main/analyze/ipa_nystrom_alias_analyzer.cxx
> ===================================================================
> --- osprey/ipa/main/analyze/ipa_nystrom_alias_analyzer.cxx (revision
> 3534)
> +++ osprey/ipa/main/analyze/ipa_nystrom_alias_analyzer.cxx (working
> copy)
> @@ -370,8 +370,27 @@
> repPNodeParent->merge(cgNode);
> cgNode->repParent(repPNodeParent);
> }
> + else if (repPNode != cgNode &&
> cgNode->checkFlags(CG_NODE_FLAGS_COLLAPSED)) {
> + // summNode parent is not cgNode, and cgNode is summNode parent's
> + // parent. Here is a cyclic repParent chain.
> + // if cgNode is collapsed node(means it will not used in points
> to),
> + // break the chain and make cgNode not top repParent.
> + repPNodeParent = repPNode;
> + while (true) {
> + if (repPNodeParent->repParent() == cgNode) {
> + repPNodeParent->repParent(NULL);
> + break;
> + }
> + repPNodeParent = repPNodeParent->repParent();
> + }
> + repPNodeParent->clearFlags(CG_NODE_FLAGS_MERGED);
> + repPNodeParent->merge(cgNode);
> + cgNode->repParent(repPNode);
> + }
> + else {
> + // here it is break the chain, and let cgNode be top repParent.
> + }
> }
> -
> // Set the collapsed parent
> if (cgNode->checkFlags(CG_NODE_FLAGS_COLLAPSED)) {
> if (summNode.collapsedParent() != 0) {
>
>
>
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>
--
Regards,
Lai Jian-Xin
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