Hi!
Hi Jochen,
I have seen that findNearestCommonDominator has been added
to class PostDominatorTree, maybe on my request.Now there is the following problem:
in class DominatorTreeBase there is an assert in findNearestCommonDominator
that asserts if the tree is not a PostDominator tree:assert (!this->isPostDominator()
&& "This is not implemented for post dominators");
assert (A->getParent() == B->getParent()
&& "Two blocks are not in same function");// If either A or B is a entry block then it is nearest common
dominator.
NodeT&Entry = A->getParent()->front();
if (A ==&Entry || B ==&Entry)
return&Entry;When commenting out the assert it seems to work. Perhaps it has to be
changed
that the check for entry block (which seems to be an optimization)
is only done for DominatorTree:if (!this->isPostDominator())
{
// If either A or B is a entry block then it is nearest common dominator.
NodeT&Entry = A->getParent()->front();
if (A ==&Entry || B ==&Entry)
return&Entry;
}
Yes, you are right.
I added it, as it looked like a trivial change. I should have verified this better, but did not take enough time as this code path was not used at the moment. I will do better next time! 
Your analysis seems to be correct. There is an optimization in findNearestCommonDominator() that does not work for PostDominatorTree.
I added a patch to not use it for the PostDominatorTree (as proposed by you). Can this patch be committed to trunk and the release branch to fix the bug I introduced?
It passes all LLVM tests on amd64.
0001-findNearestCommonDominator-works-for-PostDominator.patch (1.51 KB)