Add fix for tryToReplaceShiftLandWithRotateInstruction

Optimization will not work if the current node is commoned.

Fixes GH-4298

Signed-off-by: Aidan Ha <[email protected]>

compiler/z/codegen/BinaryEvaluator.cpp

@@ -1816,7 +1816,6 @@ OMR::Z::TreeEvaluator::tryToReplaceShiftLandWithRotateInstruction(TR::Node * nod
          // RISBG instructions perform unsigned rotation, so if we are selecting the sign bit via the logical AND we cannot
          // perform a signed shift because we must preserve the sign bit. In general we cannot handle this case because we are
          // not certain our input will be non-negative, hence we must conservatively disallow the optimization in such a case.
-
          if (longConstValue >= 0x8000000000000000LL && shiftAmount != 0 && isSignedShift)
             {
             return NULL;
@@ -1826,6 +1825,13 @@ OMR::Z::TreeEvaluator::tryToReplaceShiftLandWithRotateInstruction(TR::Node * nod
             {
             return NULL;
             }
+         // If the node entered is a common node, then there is no guarantee that the child of the common node will still be alive.
+         // And when we try to access the value in that node, we might receive values from a node that might've been killed already.
+         // Thus, The optimization will not work.
+         if (node->getRegister() != NULL)
+            {
+            return NULL;
+            }
          int32_t tZeros = trailingZeroes(longConstValue);
          int32_t lZeros = leadingZeroes(longConstValue);
          int32_t tOnes  = trailingZeroes(~longConstValue);