Index: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
@@ -25033,8 +25033,11 @@
   APInt APIntShiftAmt;
   if (!isConstantSplat(Amt, APIntShiftAmt))
     return SDValue();
-  assert(APIntShiftAmt.ult(VT.getScalarSizeInBits()) &&
-         "Out of range shift amount");
+
+  // If the shift amount is out of range, return undef.
+  if (APIntShiftAmt.uge(VT.getScalarSizeInBits()))
+    return DAG.getUNDEF(VT);
+
   uint64_t ShiftAmt = APIntShiftAmt.getZExtValue();
 
   if (SupportedVectorShiftWithImm(VT, Subtarget, Op.getOpcode()))