Revert r308025 due to uncovering a crash in SelectionDAG. This is filed

with a minimal test case in http://llvm.org/PR33833.

Original commit message:
  Improve Aliasing of operations to static alloca

llvm-svn: 308271

1 files changed, 6 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ab4578eeeb1..7e766fb2a74 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -11383,8 +11383,12 @@ SDValue DAGCombiner::visitLOAD(SDNode *N) {
       SDValue Token = DAG.getNode(ISD::TokenFactor, SDLoc(N),
                                   MVT::Other, Chain, ReplLoad.getValue(1));
 
-      // Replace uses with load result and token factor
-      return CombineTo(N, ReplLoad.getValue(0), Token);
+      // Make sure the new and old chains are cleaned up.
+      AddToWorklist(Token.getNode());
+
+      // Replace uses with load result and token factor. Don't add users
+      // to work list.
+      return CombineTo(N, ReplLoad.getValue(0), Token, false);
     }
   }
 
@@ -16709,20 +16713,6 @@ bool DAGCombiner::isAlias(LSBaseSDNode *Op0, LSBaseSDNode *Op1) const {
   if (BasePtr0.equalBaseIndex(BasePtr1, DAG, PtrDiff))
     return !((NumBytes0 <= PtrDiff) || (PtrDiff + NumBytes1 <= 0));
 
-  // If both BasePtr0 and BasePtr1 are FrameIndexes, we will not be
-  // able to calculate their relative offset if at least one arises
-  // from an alloca. However, these allocas cannot overlap and we
-  // can infer there is no alias.
-  if (auto *A = dyn_cast<FrameIndexSDNode>(BasePtr0.getBase()))
-    if (auto *B = dyn_cast<FrameIndexSDNode>(BasePtr1.getBase())) {
-      MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
-      // If the base are the same frame index but the we couldn't find a
-      // constant offset, (indices are different) be conservative.
-      if (A != B && (!MFI.isFixedObjectIndex(A->getIndex()) ||
-                     !MFI.isFixedObjectIndex(B->getIndex())))
-        return false;
-    }
-
   // FIXME: findBaseOffset and ConstantValue/GlobalValue/FrameIndex analysis
   // modified to use BaseIndexOffset.