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Read Barrier for CompareAndSwapObject #1965

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May 24, 2018
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Read Barrier for CompareAndSwapObject #1965

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aad7323
Read Barrier for CompareAndSwapObject
fjeremic May 22, 2018
c451080
Add NIAI for exclusive write before CAS read barrier
fjeremic May 23, 2018
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15 changes: 15 additions & 0 deletions runtime/compiler/trj9/z/codegen/J9TreeEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9747,6 +9747,21 @@ static TR::Register *VMinlineCompareAndSwap(
}
}

if (TR::Compiler->om.shouldGenerateReadBarriersForFieldLoads() && isObj)
{
TR::Register* tempReadBarrier = cg->allocateRegister();

auto guardedLoadMnemonic = usingCompressedPointers ? TR::InstOpCode::LLGFSG : TR::InstOpCode::LGG;

// Compare-And-Swap on object reference, while primarily is a store operation, it is also an implicit read (it
// reads the existing value to be compared with a provided compare value, before the store itself), hence needs
// a read barrier
generateS390IEInstruction(cg, TR::InstOpCode::NIAI, 1, 0, node);
generateRXYInstruction(cg, guardedLoadMnemonic, node, tempReadBarrier, generateS390MemoryReference(*casMemRef, 0, cg));

cg->stopUsingRegister(tempReadBarrier);
}

// Compare and swap
//
generateRSInstruction(cg, casOp, node, oldVReg, newVReg, casMemRef);
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