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Fix ICF assert in pdcmpgt vector evaluator #3330

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Oct 18, 2018
Merged

Fix ICF assert in pdcmpgt vector evaluator #3330

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35 changes: 20 additions & 15 deletions runtime/compiler/z/codegen/J9BCDTreeEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2701,8 +2701,8 @@ J9::Z::TreeEvaluator::pdcmpVectorEvaluatorHelper(TR::Node *node, TR::CodeGenerat
generateRRInstruction(cg, TR::Compiler->target.is64Bit() ? TR::InstOpCode::XGR : TR::InstOpCode::XR, node, resultReg, resultReg);
generateLoad32BitConstant(cg, node, 1, resultReg, true);

TR::RegisterDependencyConditions* deps = new(cg->trHeapMemory()) TR::RegisterDependencyConditions(0, 1, cg);
TR::LabelSymbol* doneCompareLabel = TR::LabelSymbol::create(cg->trHeapMemory(), cg);
TR::RegisterDependencyConditions* deps = new(cg->trHeapMemory()) TR::RegisterDependencyConditions(0, 2, cg);
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Why 2 post dependencies? I only see one call of addPostCondition.

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Is it because generateLoad32BitConstant can potentially allocate another register?

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The implicit dependency changes in APIs like generateLoad32BitConstant() can be tricky.. How do we know the number of dependencies they are adding?

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Is it because generateLoad32BitConstant can potentially allocate another register?

Yes, this is precisely it.

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The implicit dependency changes in APIs like generateLoad32BitConstant() can be tricky.. How do we know the number of dependencies they are adding?

This is a problem today. I can't fix the issue at the moment but I opened one a long time ago that we need to have dynamically allocated register dependencies. It's absurd to expect developers do count them manually when it costs basically nothing to just allocate them dynamically.

deps->addPostConditionIfNotAlreadyInserted(resultReg, TR::RealRegister::AssignAny);

TR::Node* pd1Node = node->getFirstChild();
TR::Node* pd2Node = node->getSecondChild();
Expand All @@ -2713,40 +2713,45 @@ J9::Z::TreeEvaluator::pdcmpVectorEvaluatorHelper(TR::Node *node, TR::CodeGenerat
// TODO: should we correct bad sign before comparing them
TR::Instruction* cursor = generateVRRhInstruction(cg, TR::InstOpCode::VCP, node, pd1Value, pd2Value, 0);

TR::LabelSymbol* ifcStartLabel = generateLabelSymbol(cg);
cursor = generateS390LabelInstruction(cg, TR::InstOpCode::LABEL, node, ifcStartLabel);
cursor->setStartInternalControlFlow();
deps->addPostConditionIfNotAlreadyInserted(resultReg, TR::RealRegister::AssignAny);

TR::LabelSymbol* icfEndLabel = generateLabelSymbol(cg);

// Generate Branch Instructions
switch(node->getOpCodeValue())
{
case TR::pdcmpeq:
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC0, node, doneCompareLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC0, node, icfEndLabel);
break;
case TR::pdcmpne:
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC1, node, doneCompareLabel);
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC2, node, doneCompareLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC1, node, icfEndLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC2, node, icfEndLabel);
break;
case TR::pdcmplt:
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC1, node, doneCompareLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC1, node, icfEndLabel);
break;
case TR::pdcmple:
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC0, node, doneCompareLabel);
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC1, node, doneCompareLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC0, node, icfEndLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC1, node, icfEndLabel);
break;
case TR::pdcmpgt:
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC2, node, doneCompareLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC2, node, icfEndLabel);
break;
case TR::pdcmpge:
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC0, node, doneCompareLabel);
generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC2, node, doneCompareLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC0, node, icfEndLabel);
cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_CC2, node, icfEndLabel);
break;
default:
TR_ASSERT(0, "Unrecognized op code in pd cmp vector evaluator helper.");
}

cursor = generateLoad32BitConstant(cg, node, 0, resultReg, true);
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I actually think we should assert inside of these APIs that can take in dependencies for ICF. i.e. if you have ICF start already marked and you call this API and you don't pass in dependencies then assert because you're doing something wrong. This API can potentially allocate a register depending on the constant being loaded and that register has to be added to the dependencies. Food for thought.

cursor = generateS390LabelInstruction(cg, TR::InstOpCode::LABEL, node, doneCompareLabel);
cursor->setDependencyConditions(deps);
// TODO: The only reason we keep track of the cursor here is because `deps` has to be passed in after `cursor`. We
// don't really need this restriction however if we rearrange the parameters.
cursor = generateLoad32BitConstant(cg, node, 0, resultReg, true, cursor, deps);

cursor = generateS390LabelInstruction(cg, TR::InstOpCode::LABEL, node, icfEndLabel, deps);
cursor->setEndInternalControlFlow();

node->setRegister(resultReg);
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