diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -2968,6 +2968,12 @@
     if (YConst && YConst->isNullValue())
       return SDValue();
 
+    // Bail out if Y is already equivalent to Zero.  Otherwise we will
+    // infinitely recurse as (X' & Y) == Y (where X' is ~X) still matches the
+    // pattern (X & Y) == Y, where X = X'.
+    if (Y == Zero)
+      return SDValue();
+
     // Transform this into: ~X & Y == 0.
     SDValue NotX = DAG.getNOT(SDLoc(X), X, OpVT);
     SDValue NewAnd = DAG.getNode(ISD::AND, SDLoc(N0), OpVT, NotX, Y);