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Merge pull request eclipse-omr#7089 from jdmpapin/x86-compressed-null
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Improve x86 code generation for constant null compression sequences
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@0xdaryl
0xdaryl authored Aug 24, 2023
2 parents d458e29 + dfd3c65 commit 2148df2
Showing 1 changed file with 44 additions and 63 deletions.
107 changes: 44 additions & 63 deletions compiler/x/codegen/OMRTreeEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -781,14 +781,15 @@ OMR::X86::TreeEvaluator::fwrtbariEvaluator(TR::Node *node, TR::CodeGenerator *cg
// also used for iistore, astore and iastore
TR::Register *OMR::X86::TreeEvaluator::integerStoreEvaluator(TR::Node *node, TR::CodeGenerator *cg)
{

TR::Node *valueChild;
TR::Node *valueChild = NULL;
TR::Register *valueReg = NULL;
bool genLockedOpOutOfline = true;
TR::Compilation *comp = cg->comp();

bool usingCompressedPointers = false;
bool usingLowMemHeap = false;
TR::Node *origRef = NULL; // input to compression sequence (when there is one)
bool isCompressedNullStore = false;
bool isCompressedWithoutShift = false;

node->getFirstChild()->oneParentSupportsLazyClobber(comp);
if (node->getOpCode().isIndirect())
Expand All @@ -798,38 +799,24 @@ TR::Register *OMR::X86::TreeEvaluator::integerStoreEvaluator(TR::Node *node, TR:
if (comp->useCompressedPointers() &&
(node->getSymbolReference()->getSymbol()->getDataType() == TR::Address))
{
// pattern match the sequence
// iistore f iistore f <- node
// aload O aload O
// value l2i
// lshr
// lsub <- translatedNode
// a2l
// value <- valueChild
// lconst HB
// iconst shftKonst
//
// -or- if the field is known to be null or usingLowMemHeap
// iistore f
// aload O
// l2i
// a2l
// value <- valueChild
//
TR::Node *translatedNode = valueChild;
bool isSequence = false;
if (translatedNode->getOpCodeValue() == TR::l2i)
if (valueChild->getOpCodeValue() == TR::l2i)
{
translatedNode = translatedNode->getFirstChild();
isSequence = true;
}
if (translatedNode->getOpCode().isRightShift())
translatedNode = translatedNode->getFirstChild(); //optional
TR::Node *inner = valueChild->getChild(0);
bool haveShift = inner->getOpCode().isRightShift();
if (haveShift)
inner = inner->getChild(0);

usingLowMemHeap = true;
if (inner->getOpCodeValue() == TR::a2l)
{
usingCompressedPointers = true;
origRef = inner->getChild(0);
isCompressedNullStore =
valueChild->isZero() || inner->isZero() || origRef->isNull();

if (isSequence)
usingCompressedPointers = true;
// Ignore the shift (if any) if the value is null anyway.
isCompressedWithoutShift = !haveShift || isCompressedNullStore;
}
}
}
}
else
Expand All @@ -842,24 +829,31 @@ TR::Register *OMR::X86::TreeEvaluator::integerStoreEvaluator(TR::Node *node, TR:
TR::Node *originalValueChild = valueChild;

bool childIsConstant = false;
int64_t childConstValue = TR::getMinSigned<TR::Int64>();

if (valueChild->getOpCode().isLoadConst() &&
valueChild->getRegister() == NULL &&
!usingCompressedPointers)
if (valueChild->getOpCode().isLoadConst() && valueChild->getRegister() == NULL)
{
childIsConstant = true;
childConstValue = valueChild->getConstValue();
}
else if (isCompressedNullStore && origRef->getRegister() == NULL)
{
childIsConstant = true;
childConstValue = 0;
}

if (childIsConstant && (size <= 4 || IS_32BIT_SIGNED(valueChild->getLongInt())))
if (childIsConstant && (size <= 4 || IS_32BIT_SIGNED(childConstValue)))
{
cg->recursivelyDecReferenceCount(valueChild); // skip evaluation of entire subtree

TR::LabelSymbol * dstStored = NULL;
TR::RegisterDependencyConditions *deps = NULL;
int32_t konst = valueChild->getInt();

// Note that we can use getInt() here for all sizes, since only the
// Note that we can truncate to 32-bit here for all sizes, since only the
// low order "size" bytes of the int will be used by the instruction,
// and longs only get here if the constant fits in 32 bits.
//
int32_t konst = (int32_t)childConstValue;
tempMR = generateX86MemoryReference(node, cg);

if (size == 1)
Expand Down Expand Up @@ -896,15 +890,21 @@ TR::Register *OMR::X86::TreeEvaluator::integerStoreEvaluator(TR::Node *node, TR:
}

TR::Register *translatedReg = valueReg;
bool valueRegNeededInFuture = true;
// try to avoid unnecessary sign-extension

// try to avoid unnecessary sign-extension (or reg-reg moves in the case
// of a compression sequence)
if (valueChild->getRegister() == 0 &&
valueChild->getReferenceCount() == 1 &&
(valueChild->getOpCodeValue() == TR::l2i ||
valueChild->getOpCodeValue() == TR::l2s ||
valueChild->getOpCodeValue() == TR::l2b))
{
valueChild = valueChild->getFirstChild();
valueChild = isCompressedWithoutShift ? origRef : valueChild->getChild(0);

// Skipping evaluation of originalValueChild, but not valueChild.
cg->incReferenceCount(valueChild);
cg->recursivelyDecReferenceCount(originalValueChild);

if (cg->comp()->target().is64Bit())
translatedReg = cg->evaluate(valueChild);
else
Expand All @@ -915,23 +915,7 @@ TR::Register *OMR::X86::TreeEvaluator::integerStoreEvaluator(TR::Node *node, TR:
translatedReg = cg->evaluate(valueChild);
}

if (usingCompressedPointers && !usingLowMemHeap)
{
// do the translation and handle stores of nulls
//
valueReg = cg->evaluate(node->getSecondChild());

// check for stored value being null
//
generateRegRegInstruction(TR::InstOpCode::TESTRegReg(), node, translatedReg, translatedReg, cg);
generateRegRegInstruction(TR::InstOpCode::CMOVERegReg(), node, valueReg, translatedReg, cg);
}
else
{
valueReg = translatedReg;
if (valueChild->getReferenceCount() == 0)
valueRegNeededInFuture = false;
}
valueReg = translatedReg;

// If the evaluation of the child resulted in a NULL register value, the
// store has already been done by the child
Expand Down Expand Up @@ -1018,9 +1002,9 @@ TR::Register *OMR::X86::TreeEvaluator::integerStoreEvaluator(TR::Node *node, TR:
{
TR_ASSERT(valueChild->isDirectMemoryUpdate(), "Null valueReg should only occur in direct memory upates");
}
}

cg->decReferenceCount(valueChild);
cg->decReferenceCount(valueChild);
}

if (tempMR)
tempMR->decNodeReferenceCounts(cg);
Expand Down Expand Up @@ -1051,9 +1035,6 @@ TR::Register *OMR::X86::TreeEvaluator::integerStoreEvaluator(TR::Node *node, TR:
if (instr && node->getOpCode().isIndirect())
cg->setImplicitExceptionPoint(instr);

if (usingCompressedPointers)
cg->decReferenceCount(node->getSecondChild());

if (comp->useAnchors() && node->getOpCode().isIndirect())
node->setStoreAlreadyEvaluated(true);

Expand Down

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