Add internal pointer assert to Power select evaluator

The select evaluator in the Power codegen cannot handle select nodes
with children that are internal pointers, since information about the
pinning array pointer would be lost. An assert has been added to verify
that internal pointers are not passed to this evaluator.

Signed-off-by: Ben Thomas <ben@benthomas.ca>

compiler/p/codegen/ControlFlowEvaluator.cpp

@@ -1770,6 +1770,11 @@ TR::Register *OMR::Power::TreeEvaluator::iselectEvaluator(TR::Node *node, TR::Co
             generateTrg1Src3Instruction(cg, iselOp, node, trgReg, trueReg, falseReg, condReg);
          }
 
+      TR_ASSERT_FATAL_WITH_NODE(
+         node,
+         !trueReg->containsInternalPointer() && !falseReg->containsInternalPointer(),
+         "Select nodes cannot have children that are internal pointers"
+      );
       if (trueReg->containsCollectedReference() || falseReg->containsCollectedReference())
          trgReg->setContainsCollectedReference();
       }
@@ -1780,6 +1785,11 @@ TR::Register *OMR::Power::TreeEvaluator::iselectEvaluator(TR::Node *node, TR::Co
       trgReg = cg->gprClobberEvaluate(trueNode);
       TR::Register *falseReg = cg->evaluate(falseNode);
 
+      TR_ASSERT_FATAL_WITH_NODE(
+         node,
+         !trgReg->containsInternalPointer() && !falseReg->containsInternalPointer(),
+         "Select nodes cannot have children that are internal pointers"
+      );
       if (falseReg->containsCollectedReference())
          trgReg->setContainsCollectedReference();