Support NaN values w.r.t fmax/fmin/dmax/dmin opcodes on S390

This commit adds support to the S390 MaxMin evaluator to handle NaN operands for [fd]min/max opcodes.

- Add NaN checks for f/d operands and set return register to NaN if either operands are NaN

Closes: #5157

Signed-off-by: Sarwat Shaheen [email protected]

compiler/z/codegen/ControlFlowEvaluator.cpp

@@ -338,21 +338,38 @@ xmaxxminHelper(TR::Node* node, TR::CodeGenerator* cg, TR::InstOpCode::Mnemonic c
  generateS390LabelInstruction(cg, TR::InstOpCode::label, node, cFlowRegionStart);
  cFlowRegionStart->setStartInternalControlFlow();
 
+ //Checking common Condition Code and branching to cFlowRegionEnd
  generateRREInstruction(cg, compareRROp, node, lhsReg, rhsReg);
  generateS390BranchInstruction(cg, TR::InstOpCode::BRC, branchCond, node, cFlowRegionEnd);
 
+ //Check for NaN operands for float and double
+ if (node->getOpCode().isDouble() || node->getOpCode().isFloat())
+ {
+ if (node->getOpCode().isDouble())
+ {
+ // If first operand is NaN, then we are done, otherwise fallthrough to move second operand as result
+ generateRREInstruction(cg, TR::InstOpCode::LTDBR, node, lhsReg, lhsReg);
+ generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC3, node, cFlowRegionEnd);
+ }
+ else if (node->getOpCode().isFloat())
+ {
+ // If first operand is NaN, then we are done, otherwise fallthrough to move second operand as result
+ generateRREInstruction(cg, TR::InstOpCode::LTEBR, node, lhsReg, lhsReg);
+ generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC3, node, cFlowRegionEnd);
+ }
+ }
+
+ //Move resulting operand to lhsReg as fallthrough for alternate Condition Code
  generateRREInstruction(cg, moveRROp, node, lhsReg, rhsReg);
 
  TR::RegisterDependencyConditions* deps = new (cg->trHeapMemory()) TR::RegisterDependencyConditions(0, 2, cg);
-
  deps->addPostConditionIfNotAlreadyInserted(lhsReg, TR::RealRegister::AssignAny);
  deps->addPostConditionIfNotAlreadyInserted(rhsReg, TR::RealRegister::AssignAny);
 
  generateS390LabelInstruction(cg, TR::InstOpCode::label, node, cFlowRegionEnd, deps);
  cFlowRegionEnd->setEndInternalControlFlow();
 
  node->setRegister(lhsReg);
-
  cg->decReferenceCount(lhsNode);
  cg->decReferenceCount(rhsNode);