Index: lib/IR/ConstantFold.cpp
===================================================================
--- lib/IR/ConstantFold.cpp
+++ lib/IR/ConstantFold.cpp
@@ -1120,27 +1120,18 @@
         return ConstantInt::get(CI1->getContext(), C1V | C2V);
       case Instruction::Xor:
         return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
-      case Instruction::Shl: {
-        uint32_t shiftAmt = C2V.getZExtValue();
-        if (shiftAmt < C1V.getBitWidth())
-          return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt));
-        else
+      case Instruction::Shl:
+        if (C2V.getActiveBits() > 32 || C2V.getZExtValue() >= C1V.getBitWidth())
           return UndefValue::get(C1->getType()); // too big shift is undef
-      }
-      case Instruction::LShr: {
-        uint32_t shiftAmt = C2V.getZExtValue();
-        if (shiftAmt < C1V.getBitWidth())
-          return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt));
-        else
+        return ConstantInt::get(CI1->getContext(), C1V.shl(C2V.getZExtValue()));
+      case Instruction::LShr:
+        if (C2V.getActiveBits() > 32 || C2V.getZExtValue() >= C1V.getBitWidth())
           return UndefValue::get(C1->getType()); // too big shift is undef
-      }
-      case Instruction::AShr: {
-        uint32_t shiftAmt = C2V.getZExtValue();
-        if (shiftAmt < C1V.getBitWidth())
-          return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt));
-        else
+        return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V.getZExtValue()));
+      case Instruction::AShr:
+        if (C2V.getActiveBits() > 32 || C2V.getZExtValue() >= C1V.getBitWidth())
           return UndefValue::get(C1->getType()); // too big shift is undef
-      }
+        return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V.getZExtValue()));
       }
     }