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 opcodes and set return register to NaN if either operands are NaN
- Pass float/double NaN values as immediate into GPR, to later load the NaN value into result FPR
- Enable the previously skipped S390 NaN test cases

Closes: #5157

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

compiler/z/codegen/ControlFlowEvaluator.cpp

@@ -338,21 +338,57 @@ xmaxxminHelper(TR::Node* node, TR::CodeGenerator* cg, TR::InstOpCode::Mnemonic c
  generateS390LabelInstruction(cg, TR::InstOpCode::label, node, cFlowRegionStart);
  cFlowRegionStart->setStartInternalControlFlow();
 
+ TR::RegisterDependencyConditions* deps = new (cg->trHeapMemory()) TR::RegisterDependencyConditions(0, 3, cg);
+ deps->addPostConditionIfNotAlreadyInserted(lhsReg, TR::RealRegister::AssignAny);
+ deps->addPostConditionIfNotAlreadyInserted(rhsReg, TR::RealRegister::AssignAny);
+
+ //Checking common Condition Code and branching to cFlowRegionEnd
  generateRREInstruction(cg, compareRROp, node, lhsReg, rhsReg);
  generateS390BranchInstruction(cg, TR::InstOpCode::BRC, branchCond, node, cFlowRegionEnd);
 
- generateRREInstruction(cg, moveRROp, node, lhsReg, rhsReg);
-
- TR::RegisterDependencyConditions* deps = new (cg->trHeapMemory()) TR::RegisterDependencyConditions(0, 2, cg);
+ //Label Symbols for handling possible NaN operand case for float/double
+ TR::LabelSymbol* nanLabel = NULL;
+ TR::LabelSymbol* notNaNLabel = generateLabelSymbol(cg);
+ //For Double & Float operands only, branching to nanLabel for Condition Code 3 when operands are unordered
+ if (node->getOpCode().isDouble() || node->getOpCode().isFloat())
+ {
+ nanLabel = generateLabelSymbol(cg);
+ generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC3, node, nanLabel);
+ //Branch to notNaNLabel as fallthrough
+ generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_BRC, node, notNaNLabel);
+
+ //Handle NaN case
+ generateS390LabelInstruction(cg, TR::InstOpCode::label, node, nanLabel);
+ //Allocate GPR for holding immediate NaN value for float/double
+ TR::Register * nanReg = cg->allocateRegister(TR_GPR);
+ //Handle NaN case for doubles
+ if (node->getOpCode().isDouble())
+ {
+ //Load immediate DOUBLE_NAN value into GPR, then move it to result FPR
+ genLoadLongConstant(cg, node, DOUBLE_NAN, nanReg, NULL, deps, NULL);
+ generateRRInstruction(cg, TR::InstOpCode::LDGR, node, lhsReg, nanReg);
+ }
+ else if (node->getOpCode().isFloat())
+ {
+ //Handle NaN case for floats by loading immediate FLOAT_NAN value into GPR
+ //Shift left the 32 least significant bits for preserving float representation before moving to FPR
+ generateRILInstruction(cg, TR::InstOpCode::LGFI, node, nanReg, FLOAT_NAN, NULL);
+ generateRSInstruction(cg, TR::InstOpCode::SLLG, node, nanReg, 32);
+ generateRRInstruction(cg, TR::InstOpCode::LDGR, node, lhsReg, nanReg);
+ }
+ deps->addPostConditionIfNotAlreadyInserted(nanReg, TR::RealRegister::AssignAny);
+ cg->stopUsingRegister(nanReg);
+ generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_BRC, node, cFlowRegionEnd);
+ }
 
- deps->addPostConditionIfNotAlreadyInserted(lhsReg, TR::RealRegister::AssignAny);
- deps->addPostConditionIfNotAlreadyInserted(rhsReg, TR::RealRegister::AssignAny);
+ generateS390LabelInstruction(cg, TR::InstOpCode::label, node, notNaNLabel);
+ //Move resulting operand to lhsReg as fallthrough for alternate Condition Code
+ generateRREInstruction(cg, moveRROp, node, lhsReg, rhsReg);
 
  generateS390LabelInstruction(cg, TR::InstOpCode::label, node, cFlowRegionEnd, deps);
  cFlowRegionEnd->setEndInternalControlFlow();
 
  node->setRegister(lhsReg);
-
  cg->decReferenceCount(lhsNode);
  cg->decReferenceCount(rhsNode);
 

fvtest/compilertriltest/MaxMinTest.cpp

@@ -202,11 +202,6 @@ TEST_P(FloatMaxMin, UsingConst) {
 
  auto param = TRTest::to_struct(GetParam());
 
- if (std::isnan(param.lhs) || std::isnan(param.rhs)) {
- SKIP_ON_S390(KnownBug) << "fmin / fmax returns wrong value for NaN on Z (see issue #5157)";
- SKIP_ON_S390X(KnownBug) << "fmin / fmax returns wrong value for NaN on Z (see issue #5157)";
- }
-
  char inputTrees[1024] = {0};
  std::snprintf(inputTrees, sizeof(inputTrees),
  "(method return=Float"
@@ -237,11 +232,6 @@ TEST_P(FloatMaxMin, UsingLoadParam) {
 
  auto param = TRTest::to_struct(GetParam());
 
- if (std::isnan(param.lhs) || std::isnan(param.rhs)) {
- SKIP_ON_S390(KnownBug) << "fmin / fmax returns wrong value for NaN on Z (see issue #5157)";
- SKIP_ON_S390X(KnownBug) << "fmin / fmax returns wrong value for NaN on Z (see issue #5157)";
- }
-
  char inputTrees[1024] = {0};
  std::snprintf(inputTrees, sizeof(inputTrees),
  "(method return=Float args=[Float, Float]"
@@ -280,11 +270,6 @@ TEST_P(DoubleMaxMin, UsingConst) {
 
  auto param = TRTest::to_struct(GetParam());
 
- if (std::isnan(param.lhs) || std::isnan(param.rhs)) {
- SKIP_ON_S390(KnownBug) << "dmin / dmax returns wrong value for NaN on Z (see issue #5157)";
- SKIP_ON_S390X(KnownBug) << "dmin / dmax returns wrong value for NaN on Z (see issue #5157)";
- }
-
  char inputTrees[1024] = {0};
  std::snprintf(inputTrees, sizeof(inputTrees),
  "(method return=Double"
@@ -315,12 +300,6 @@ TEST_P(DoubleMaxMin, UsingLoadParam) {
 
  auto param = TRTest::to_struct(GetParam());
 
- if (std::isnan(param.lhs) || std::isnan(param.rhs)) {
- SKIP_ON_S390(KnownBug) << "dmin / dmax returns wrong value for NaN on Z (see issue #5157)";
- SKIP_ON_S390X(KnownBug) << "dmin / dmax returns wrong value for NaN on Z (see issue #5157)";
-
- }
-
  char inputTrees[1024] = {0};
  std::snprintf(inputTrees, sizeof(inputTrees),
  "(method return=Double args=[Double, Double]"