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WIP: Clear array header padding field #20998

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WIP: Clear array header padding field #20998

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c44ee15
x: clear padding
VermaSh Jan 24, 2025
868a191
p: clear padding
VermaSh Jan 24, 2025
5660573
aarch64: clear padding
VermaSh Jan 24, 2025
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17 changes: 17 additions & 0 deletions runtime/compiler/aarch64/codegen/J9TreeEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3298,6 +3298,23 @@ genInitArrayHeader(TR::Node *node, TR::CodeGenerator *cg, TR_OpaqueClassBlock *c
tempReg1);
}
}

// Clear padding after the size field
if (!isTLHHasNotBeenCleared)
{
if (TR::Compiler->om.generateCompressedObjectHeaders())
{
generateMemSrc1Instruction(cg, TR::InstOpCode::strimmw, node,
TR::MemoryReference::createWithDisplacement(cg, objectReg, fej9->getOffsetOfDiscontiguousArraySizeField() + 4),
zeroReg);
}
else
{
generateMemSrc1Instruction(cg, TR::InstOpCode::strimmw, node,
TR::MemoryReference::createWithDisplacement(cg, objectReg, fej9->getOffsetOfContiguousArraySizeField() + 4),
zeroReg);
}
}
}

/**
Expand Down
20 changes: 20 additions & 0 deletions runtime/compiler/p/codegen/J9TreeEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6163,6 +6163,26 @@ static void genInitArrayHeader(TR::Node *node, TR::Instruction *&iCursor, bool i
TR::MemoryReference::createWithDisplacement(cg, resReg, fej9->getOffsetOfContiguousArraySizeField(), 4),
instanceSizeReg, iCursor);
}

// Clear padding after size field
if (needZeroInit)
{
TR_ASSERT_FATAL_WITH_NODE(node, zeroReg, "zeroReg is expected to be intialized but wasn't.\n");
if (TR::Compiler->om.compressObjectReferences())
{
// padding field starts at fej9->getOffsetOfDiscontiguousArraySizeField() + 4
iCursor = generateMemSrc1Instruction(cg, TR::InstOpCode::stw, node,
TR::MemoryReference::createWithDisplacement(cg, resReg, fej9->getOffsetOfDiscontiguousArraySizeField() + 4, 4),
zeroReg, iCursor);
}
else
{
// padding field starts at fej9->getOffsetOfDiscontiguousArraySizeField()
iCursor = generateMemSrc1Instruction(cg, TR::InstOpCode::stw, node,
TR::MemoryReference::createWithDisplacement(cg, resReg, fej9->getOffsetOfDiscontiguousArraySizeField(), 4),
zeroReg, iCursor);
}
}
}

static void genZeroInit(TR::CodeGenerator *cg, TR::Node *node, TR::Register *objectReg, int32_t headerSize, int32_t totalSize, bool useInitInfo)
Expand Down
27 changes: 27 additions & 0 deletions runtime/compiler/x/codegen/J9TreeEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1554,6 +1554,11 @@ static TR::Register * generateMultianewArrayWithInlineAllocators(TR::Node *node,
// Init size and mustBeZero ('0') fields to 0
generateMemImmInstruction(TR::InstOpCode::S4MemImm4, node, generateX86MemoryReference(targetReg, fej9->getOffsetOfContiguousArraySizeField(), cg), 0, cg);
generateMemImmInstruction(TR::InstOpCode::S4MemImm4, node, generateX86MemoryReference(targetReg, fej9->getOffsetOfDiscontiguousArraySizeField(), cg), 0, cg);
if (TR::Compiler->om.compressObjectReferences())
{
// Clear padding in contiguous array header layout. +4 because size field is 4 bytes wide.
generateMemImmInstruction(TR::InstOpCode::S4MemImm4, node, generateX86MemoryReference(targetReg, fej9->getOffsetOfDiscontiguousArraySizeField() + 4, cg), 0, cg);
}

#if defined(J9VM_GC_SPARSE_HEAP_ALLOCATION)
if (isOffHeapAllocationEnabled)
Expand Down Expand Up @@ -1633,6 +1638,10 @@ static TR::Register * generateMultianewArrayWithInlineAllocators(TR::Node *node,
generateMemRegInstruction(TR::InstOpCode::SMemReg(use64BitClasses), node, generateX86MemoryReference(targetReg, TR::Compiler->om.offsetOfObjectVftField(), cg), classReg, cg);
// Init 1st dim array size field
generateMemRegInstruction(TR::InstOpCode::S4MemReg, node, generateX86MemoryReference(targetReg, fej9->getOffsetOfContiguousArraySizeField(), cg), firstDimLenReg, cg);
if (!TR::Compiler->om.compressObjectReferences())
{ // Clear padding in contiguous array header layout. +4 because size field is 4 bytes wide.
generateMemImmInstruction(TR::InstOpCode::S4MemImm4, node, generateX86MemoryReference(targetReg, fej9->getOffsetOfContiguousArraySizeField() + 4, cg), 0, cg);
}

// temp2 point to end of 1st dim array i.e. start of 2nd dim
generateRegRegInstruction(TR::InstOpCode::MOVRegReg(), node, temp2Reg, targetReg, cg);
Expand All @@ -1647,6 +1656,10 @@ static TR::Register * generateMultianewArrayWithInlineAllocators(TR::Node *node,
// Init 2nd dim element's size and mustBeZero ('0') fields to 0
generateMemImmInstruction(TR::InstOpCode::S4MemImm4, node, generateX86MemoryReference(temp2Reg, fej9->getOffsetOfContiguousArraySizeField(), cg), 0, cg);
generateMemImmInstruction(TR::InstOpCode::S4MemImm4, node, generateX86MemoryReference(temp2Reg, fej9->getOffsetOfDiscontiguousArraySizeField(), cg), 0, cg);
if (TR::Compiler->om.compressObjectReferences())
{ // Clear padding in contiguous array header layout. +4 because size field is 4 bytes wide.
generateMemImmInstruction(TR::InstOpCode::S4MemImm4, node, generateX86MemoryReference(temp2Reg, fej9->getOffsetOfDiscontiguousArraySizeField() + 4, cg), 0, cg);
}

#if defined(J9VM_GC_SPARSE_HEAP_ALLOCATION)
if (isOffHeapAllocationEnabled)
Expand Down Expand Up @@ -6827,6 +6840,20 @@ static void genInitArrayHeader(
}
}

// Clear padding after size field in array header
int32_t paddingOffset = fej9->getOffsetOfDiscontiguousArraySizeField();
if (TR::Compiler->om.compressObjectReferences())
{
// In compressed refs, padding is after the size field in discontiguous
// header layout (for 0 length arrays)
paddingOffset+=4;
}
generateMemImmInstruction(TR::InstOpCode::S4MemImm4,
node,
generateX86MemoryReference(objectReg, paddingOffset, cg),
0,
cg);

bool generateArraylets = comp->generateArraylets();

if (generateArraylets)
Expand Down