Fix ArrayPropertyOpt dominator update

Pass the DomTree into SILCloner so that edge splitting
properly creates new domtree nodes.

The confusing edge splitting code that was in ArrayPropertyOpt is no
longer needed.

We could cleanup ArrayPropertyOpt even more by moving fixDomTree
into SILCloner. But there's already too much going on in this patch.

Author: atrick

lib/SILOptimizer/LoopTransforms/ArrayPropertyOpt.cpp

@@ -430,37 +430,24 @@ namespace {
 /// in a set of basic blocks. Updates the dominator tree with the cloned blocks.
 /// However, the client needs to update the dominator of the exit blocks.
 ///
-/// FIXME: SILCloner is used to cloned CFG regions by multiple clients. All
-/// functionality for generating valid SIL (including the DomTree) should be
-/// handled by the common SILCloner.
+/// FIXME: All functionality for generating valid SIL (including the DomTree)
+/// should be handled by the common SILCloner. Currently, SILCloner only updates
+/// the DomTree for original (non-cloned) blocks when splitting edges. The
+/// cloned blocks won't be mapped to dominator nodes until fixDomTree()
+/// runs. However, since SILCloner always handles single-entry regions,
+/// fixDomTree() could be part of SILCloner itself.
 class RegionCloner : public SILCloner<RegionCloner> {
-  DominanceInfo &DomTree;
   SILBasicBlock *StartBB;
 
   friend class SILInstructionVisitor<RegionCloner>;
   friend class SILCloner<RegionCloner>;
 
 public:
   RegionCloner(SILBasicBlock *EntryBB, DominanceInfo &DT)
-      : SILCloner<RegionCloner>(*EntryBB->getParent()), DomTree(DT),
-        StartBB(EntryBB) {}
+      : SILCloner<RegionCloner>(*EntryBB->getParent(), &DT), StartBB(EntryBB) {}
 
   SILBasicBlock *cloneRegion(ArrayRef<SILBasicBlock *> exitBBs) {
-    assert (DomTree.getNode(StartBB) != nullptr && "Can't cloned dead code");
-
-    // We need to split any edge from a non cond_br basic block leading to a
-    // exit block. After cloning this edge will become critical if it came from
-    // inside the cloned region. The SSAUpdater can't handle critical non
-    // cond_br edges.
-    //
-    // FIXME: remove this in the next commit. The SILCloner will always do it.
-    for (auto *BB : exitBBs) {
-      SmallVector<SILBasicBlock *, 8> Preds(BB->getPredecessorBlocks());
-      for (auto *Pred : Preds)
-        if (!isa<CondBranchInst>(Pred->getTerminator()) &&
-            !isa<BranchInst>(Pred->getTerminator()))
-          splitEdgesFromTo(Pred, BB, &DomTree, nullptr);
-    }
+    assert(DomTree->getNode(StartBB) != nullptr && "Can't cloned dead code");
 
     cloneReachableBlocks(StartBB, exitBBs);
 
@@ -477,25 +464,25 @@ class RegionCloner : public SILCloner<RegionCloner> {
   void fixDomTree() {
     for (auto *BB : originalPreorderBlocks()) {
       auto *ClonedBB = getOpBasicBlock(BB);
-      auto *OrigDomBB = DomTree.getNode(BB)->getIDom()->getBlock();
+      auto *OrigDomBB = DomTree->getNode(BB)->getIDom()->getBlock();
       if (BB == StartBB) {
         // The cloned start node shares the same dominator as the original node.
-        auto *ClonedNode = DomTree.addNewBlock(ClonedBB, OrigDomBB);
+        auto *ClonedNode = DomTree->addNewBlock(ClonedBB, OrigDomBB);
         (void)ClonedNode;
         assert(ClonedNode);
         continue;
       }
       // Otherwise, map the dominator structure using the mapped block.
-      DomTree.addNewBlock(ClonedBB, getOpBasicBlock(OrigDomBB));
+      DomTree->addNewBlock(ClonedBB, getOpBasicBlock(OrigDomBB));
     }
   }
 
   SILValue getMappedValue(SILValue V) {
     if (auto *BB = V->getParentBlock()) {
-      if (!DomTree.dominates(StartBB, BB)) {
+      if (!DomTree->dominates(StartBB, BB)) {
         // Must be a value that dominates the start basic block.
-        assert(DomTree.dominates(BB, StartBB) &&
-               "Must dominated the start of the cloned region");
+        assert(DomTree->dominates(BB, StartBB)
+               && "Must dominated the start of the cloned region");
         return V;
       }
     }