[GVNHoist] Fix: PR35222 gvn-hoist incorrectly erases load

w.r.t. the paper
"A Practical Improvement to the Partial Redundancy Elimination in SSA Form"
(https://sites.google.com/site/jongsoopark/home/ssapre.pdf)

Proper dominance check was missing here, so having a loopinfo should not be required.
Committing this diff as this fixes the bug, if there are
further concerns, I'll be happy to work on them.

Differential Revision: https://reviews.llvm.org/D39781

llvm-svn: 320607

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVNHoist.cpp b/llvm/lib/Transforms/Scalar/GVNHoist.cpp
index 3b551844dc2..c0cd1ea74a7 100644
--- a/llvm/lib/Transforms/Scalar/GVNHoist.cpp
+++ b/llvm/lib/Transforms/Scalar/GVNHoist.cpp
@@ -795,8 +795,8 @@ private:
       for (auto IDFB : IDFBlocks) { // TODO: Prune out useless CHI insertions.
         for (unsigned i = 0; i < V.size(); ++i) {
           CHIArg C = {VN, nullptr, nullptr};
-          if (DT->dominates(IDFB, V[i]->getParent())) { // Ignore spurious PDFs.
-            // InValue[V[i]->getParent()].push_back(std::make_pair(VN, V[i]));
+           // Ignore spurious PDFs.
+          if (DT->properlyDominates(IDFB, V[i]->getParent())) {
             OutValue[IDFB].push_back(C);
             DEBUG(dbgs() << "\nInsertion a CHI for BB: " << IDFB->getName()
                          << ", for Insn: " << *V[i]);