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morphblock.cpp
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morphblock.cpp
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
#include "jitpch.h"
class MorphInitBlockHelper
{
public:
static GenTree* MorphInitBlock(Compiler* comp, GenTree* tree);
protected:
MorphInitBlockHelper(Compiler* comp, GenTree* asg, bool initBlock);
GenTree* Morph();
void PrepareDst();
virtual void PrepareSrc();
virtual void TrySpecialCases();
virtual void MorphStructCases();
virtual const char* GetHelperName() const
{
return "MorphInitBlock";
}
static GenTree* MorphBlock(Compiler* comp, GenTree* tree, bool isDest);
static GenTree* MorphCommaBlock(Compiler* comp, GenTreeOp* firstComma);
static GenTreeBlk* MorphDynamicBlock(Compiler* comp, GenTreeDynBlk* dynBlock);
protected:
Compiler* m_comp;
bool m_initBlock;
GenTreeOp* m_asg = nullptr;
GenTree* m_dst = nullptr;
GenTree* m_src = nullptr;
unsigned m_blockSize = 0;
bool m_blockSizeIsConst = false;
unsigned m_dstLclNum = BAD_VAR_NUM;
GenTreeLclVarCommon* m_dstLclNode = nullptr;
LclVarDsc* m_dstVarDsc = nullptr;
FieldSeqNode* m_dstFldSeq = nullptr;
unsigned m_dstLclOffset = 0;
bool m_dstUseLclFld = false;
bool m_dstSingleLclVarAsg = false;
GenTree* m_dstAddr = nullptr;
ssize_t m_dstAddOff = 0;
#if defined(DEBUG)
bool m_isLateArg = false;
#endif // DEBUG
enum class BlockTransformation
{
Undefined,
FieldByField,
OneAsgBlock,
StructBlock,
SkipCallSrc,
Nop
};
BlockTransformation m_transformationDecision = BlockTransformation::Undefined;
GenTree* m_result = nullptr;
};
//------------------------------------------------------------------------
// MorphInitBlock: Morph a block initialization assignment tree.
//
// Arguments:
// comp - a compiler instance;
// tree - A GT_ASG tree that performs block initialization.
//
// Return Value:
// A possibly modified tree to perfom the initializetion.
//
// static
GenTree* MorphInitBlockHelper::MorphInitBlock(Compiler* comp, GenTree* tree)
{
const bool initBlock = true;
MorphInitBlockHelper helper(comp, tree, initBlock);
return helper.Morph();
}
//------------------------------------------------------------------------
// MorphInitBlockHelper: helper's constructor.
//
// Arguments:
// comp - a compiler instance;
// initBlock - true if this is init block op, false if it is a copy block;
// asg - GT_ASG node to morph.
//
// Notes:
// Most class members are initialized via in-class member initializers.
//
MorphInitBlockHelper::MorphInitBlockHelper(Compiler* comp, GenTree* asg, bool initBlock = true)
: m_comp(comp), m_initBlock(initBlock)
{
assert(asg->OperIs(GT_ASG));
#if defined(DEBUG)
if (m_initBlock)
{
assert(asg->OperIsInitBlkOp());
}
else
{
assert(asg->OperIsCopyBlkOp());
}
#endif // DEBUG
m_asg = asg->AsOp();
}
//------------------------------------------------------------------------
// Morph: transform the asg to a possible better form and changes its children
// to an appropriate form for later phases, for example, adds SIMD_INIT nodes
// or sets lvDoNotEnregister on locals.
//
// Return Value:
// A possibly modified tree to perfom the block operation.
//
// Notes:
// It is used for both init and copy block.
//
GenTree* MorphInitBlockHelper::Morph()
{
JITDUMP("%s:\n", GetHelperName());
PrepareDst();
PrepareSrc();
INDEBUG(m_isLateArg = (m_asg->gtFlags & GTF_LATE_ARG) != 0);
TrySpecialCases();
if (m_transformationDecision == BlockTransformation::Undefined)
{
GenTree* oneAsgTree = nullptr;
if (m_dst != m_dstLclNode)
{
oneAsgTree = m_comp->fgMorphOneAsgBlockOp(m_asg);
}
if (oneAsgTree != nullptr)
{
assert((m_asg == oneAsgTree) && "fgMorphOneAsgBlock must return the incoming tree.");
m_transformationDecision = BlockTransformation::OneAsgBlock;
m_result = oneAsgTree;
}
else
{
MorphStructCases();
}
}
assert(m_transformationDecision != BlockTransformation::Undefined);
assert(m_result != nullptr);
if (m_result != m_asg)
{
const bool isLateArg = ((m_asg->gtFlags & GTF_LATE_ARG) != 0);
assert(m_isLateArg == isLateArg);
if (isLateArg)
{
assert(!m_initBlock && "do not expect a block init as a late arg.");
m_result->gtFlags |= GTF_LATE_ARG;
}
}
#ifdef DEBUG
if (m_result != m_asg)
{
m_result->gtDebugFlags |= GTF_DEBUG_NODE_MORPHED;
}
if (m_comp->verbose)
{
printf("%s (after):\n", GetHelperName());
m_comp->gtDispTree(m_result);
}
#endif // DEBUG
return m_result;
}
//------------------------------------------------------------------------
// PrepareDst: Transform the asg destination to an appropriate form and initialize member fields
// with information about it.
//
// Notes:
// When assertion propagation is enabled this method kills assertions about the dst local,
// so the correctness depends on `IsLocalAddrExpr` recognizing all patterns.
//
void MorphInitBlockHelper::PrepareDst()
{
GenTree* origDst = m_asg->gtGetOp1();
m_dst = MorphBlock(m_comp, origDst, true);
if (m_dst != origDst)
{
m_asg->gtOp1 = m_dst;
}
if (m_asg->TypeGet() != m_dst->TypeGet())
{
assert(!m_initBlock && "the asg type should be final for an init block.");
JITDUMP("changing type of asignment from %-6s to %-6s\n", varTypeName(m_asg->TypeGet()),
varTypeName(m_dst->TypeGet()));
m_asg->ChangeType(m_dst->TypeGet());
}
if (m_dst->IsLocal())
{
m_dstLclNode = m_dst->AsLclVarCommon();
m_dstVarDsc = m_comp->lvaGetDesc(m_dstLclNode);
m_blockSizeIsConst = true;
if (m_dst->OperIs(GT_LCL_VAR))
{
if (m_dstVarDsc->TypeGet() == TYP_STRUCT)
{
#ifdef DEBUG
const bool isSizeMistmatch =
(m_dstVarDsc->lvExactSize != m_comp->info.compCompHnd->getClassSize(m_dstVarDsc->GetStructHnd()));
const bool isStackAllocCandidate =
m_comp->compObjectStackAllocation() && !m_dstVarDsc->GetLayout()->IsValueClass();
// There were cases where for temps lvExactSize did not correspond to the struct size
// so we were using `getClassSize` result here, however, now this cases are gone and the only
// scenario when `getClassSize` != `lvExactSize` it is a class object optimized to be on stack
assert(!isSizeMistmatch || isStackAllocCandidate);
#endif // DEBUG
m_blockSize = m_dstVarDsc->lvExactSize;
}
else
{
m_blockSize = genTypeSize(m_dstVarDsc);
}
}
else
{
assert(m_dst->OperIs(GT_LCL_FLD) && !m_dst->TypeIs(TYP_STRUCT));
GenTreeLclFld* destFld = m_dst->AsLclFld();
m_blockSize = genTypeSize(destFld->TypeGet());
m_dstFldSeq = destFld->GetFieldSeq();
}
}
else
{
assert(m_dst == m_dst->gtEffectiveVal() && "the commas were skipped in MorphBlock");
assert(m_dst->OperIs(GT_IND, GT_BLK, GT_OBJ, GT_DYN_BLK));
GenTree* dstAddr = m_dst->AsIndir()->Addr();
if (m_dst->OperGet() == GT_IND)
{
assert(m_dst->TypeGet() != TYP_STRUCT);
m_blockSize = genTypeSize(m_dst);
m_blockSizeIsConst = true;
}
else
{
assert(m_dst->OperIsBlk());
GenTreeBlk* blk = m_dst->AsBlk();
m_blockSize = blk->Size();
m_blockSizeIsConst = !blk->OperIs(GT_DYN_BLK);
}
noway_assert(dstAddr->TypeIs(TYP_BYREF, TYP_I_IMPL));
if (dstAddr->IsLocalAddrExpr(m_comp, &m_dstLclNode, &m_dstFldSeq, &m_dstAddOff))
{
// Don't expect `IsLocalAddrExpr` to pass `INDEX_ADDR`.
assert((m_dst->gtFlags & GTF_IND_ARR_INDEX) == 0);
// Note that lclNode can be a field, like `BLK<4> struct(ADD(ADDR(LCL_FLD int), CNST_INT))`.
m_dstVarDsc = m_comp->lvaGetDesc(m_dstLclNode);
}
}
if (m_dstLclNode != nullptr)
{
m_dstLclNum = m_dstLclNode->GetLclNum();
m_dstLclOffset = m_dstLclNode->GetLclOffs();
// Kill everything about m_dstLclNum (and its field locals)
if (m_comp->optLocalAssertionProp && (m_comp->optAssertionCount > 0))
{
m_comp->fgKillDependentAssertions(m_dstLclNum DEBUGARG(m_asg));
}
}
#if defined(DEBUG)
if (m_comp->verbose)
{
printf("PrepareDst for [%06u] ", m_comp->dspTreeID(origDst));
if (m_dstLclNode != nullptr)
{
printf("have found a local var V%02u.\n", m_dstLclNum);
}
else
{
printf("have not found a local var.\n");
}
}
#endif // DEBUG
}
//------------------------------------------------------------------------
// PrepareSrc: Transform the asg src to an appropriate form and initialize member fields
// with information about it.
//
void MorphInitBlockHelper::PrepareSrc()
{
m_src = m_asg->gtGetOp2();
}
//------------------------------------------------------------------------
// TrySpecialCases: check special cases that require special transformations.
// We don't have any for for init block.
//
void MorphInitBlockHelper::TrySpecialCases()
{
return;
}
//------------------------------------------------------------------------
// MorphStructCases: transforms the asg as field by field init or keeps it as a block init
// but sets appropriate flags for the involved lclVars.
//
// Assumptions:
// we have already checked that it is not a special case and can't be transformed as OneAsgBlock.
//
void MorphInitBlockHelper::MorphStructCases()
{
GenTree* initVal = m_src->OperIsInitVal() ? m_src->gtGetOp1() : m_src;
if (m_dstLclNum != BAD_VAR_NUM)
{
// If we have already determined that a promoted TYP_STRUCT lclVar will not be enregistered,
// we are better off doing a block init.
bool tryFieldByField = false;
if (m_dstVarDsc->lvPromoted)
{
assert(m_dstLclNode->OperIs(GT_LCL_VAR)); // Don't expect a promoted LCL_VAR with a field reference.
if (m_dstVarDsc->lvDoNotEnregister)
{
tryFieldByField = false;
}
else
{
tryFieldByField = true;
}
}
if (tryFieldByField)
{
GenTreeLclVar* dstLclVar = m_dstLclNode->AsLclVar();
GenTree* newTree = m_comp->fgMorphPromoteLocalInitBlock(dstLclVar, initVal, m_blockSize);
if (newTree != nullptr)
{
m_transformationDecision = BlockTransformation::FieldByField;
m_result = newTree;
}
}
}
if (m_transformationDecision == BlockTransformation::Undefined)
{
// For an InitBlock we always require a block operand.
m_dst = m_comp->fgMorphBlockOperand(m_dst, m_dst->TypeGet(), m_blockSize, true /*isBlkReqd*/);
m_transformationDecision = BlockTransformation::StructBlock;
m_dst->gtFlags |= GTF_DONT_CSE;
m_result = m_asg;
m_result->AsOp()->gtOp1 = m_dst;
m_result->gtFlags |= (m_dst->gtFlags & GTF_ALL_EFFECT);
#if FEATURE_SIMD
if (varTypeIsSIMD(m_asg) && (m_dst == m_dstLclNode))
{
// For a SIMD local init we need to call SIMDIntrinsic init.
// We need this block becuase morph does not create SIMD init for promoted lclVars.
assert(m_src->IsIntegralConst(0) || m_src->IsFPZero());
assert(m_dstVarDsc != nullptr);
const var_types asgType = m_asg->TypeGet();
CorInfoType simdBaseJitType = m_dstVarDsc->GetSimdBaseJitType();
m_src = m_comp->gtNewSIMDNode(asgType, m_src, SIMDIntrinsicInit, simdBaseJitType, m_blockSize);
m_result->AsOp()->gtOp2 = m_src;
}
#endif // FEATURE_SIMD
if (m_dstVarDsc != nullptr)
{
if (m_dst != m_dstLclNode)
{
// If we access the dst as a whole but not directly, for example, with OBJ(ADDR(LCL_VAR))
// then set doNotEnreg.
// TODO-1stClassStructs: remove it when we can represent narowing struct cast
// without taking address of the lcl.
m_comp->lvaSetVarDoNotEnregister(m_dstLclNum DEBUGARG(DoNotEnregisterReason::CastTakesAddr));
}
else if (m_dstVarDsc->lvPromoted)
{
m_comp->lvaSetVarDoNotEnregister(m_dstLclNum DEBUGARG(DoNotEnregisterReason::BlockOp));
}
}
}
}
//------------------------------------------------------------------------
// MorphBlock: Morph a block node preparatory to morphing a block assignment.
//
// Arguments:
// comp - a compiler instance;
// tree - a struct type node;
// isDest - true if this is the destination of an assignment;
//
// Return Value:
// Returns the possibly-morphed node. The caller is responsible for updating
// the parent of this node.
//
// static
GenTree* MorphInitBlockHelper::MorphBlock(Compiler* comp, GenTree* tree, bool isDest)
{
JITDUMP("MorphBlock for %s tree, before:\n", (isDest ? "dst" : "src"));
DISPTREE(tree);
// Src can be a primitive type.
assert(!isDest || varTypeIsStruct(tree));
GenTree* handleTree = nullptr;
GenTree* addr = nullptr;
if (tree->OperIs(GT_COMMA))
{
// TODO-Cleanup: this block is not needed for not struct nodes, but
// fgMorphOneAsgBlockOp works wrong without this transformation.
tree = MorphCommaBlock(comp, tree->AsOp());
}
if (!tree->OperIsBlk())
{
JITDUMP("MorphBlock after:\n");
DISPTREE(tree);
return tree;
}
GenTreeBlk* blkNode = tree->AsBlk();
if (blkNode->OperIs(GT_DYN_BLK))
{
blkNode = MorphDynamicBlock(comp, blkNode->AsDynBlk());
if (blkNode->OperIs(GT_DYN_BLK))
{
JITDUMP("MorphBlock after:\n");
DISPTREE(blkNode);
return blkNode;
}
}
GenTree* blkAddr = blkNode->Addr();
assert(blkAddr != nullptr);
assert(blkAddr->TypeIs(TYP_I_IMPL, TYP_BYREF, TYP_REF));
// GT_ADDR, GT_LCL_VAR/FLD, GT_ADD, GT_COMMA, GT_CALL, GT_CNST_INT, GT_LCL_VAR/FLD_ADDR
JITDUMP("MorphBlock after:\n");
DISPTREE(tree);
return tree;
}
//------------------------------------------------------------------------
// MorphCommaBlock: transform COMMA<struct>(X) as OBJ<STRUCT>(COMMA byref(ADDR(X)).
//
// Notes:
// In order to CSE and value number array index expressions and bounds checks,
// the commas in which they are contained need to match.
// The pattern is that the COMMA should be the address expression.
// Therefore, we insert a GT_ADDR just above the node, and wrap it in an obj or ind.
// TODO-1stClassStructs: Consider whether this can be improved.
// Example:
// before: [3] comma struct <- [2] comma struct <- [1] LCL_VAR struct
// after: [5] obj <- [3] comma byref <- [2] comma byref <- [4] addr byref <- [1] LCL_VAR struct
//
// static
GenTree* MorphInitBlockHelper::MorphCommaBlock(Compiler* comp, GenTreeOp* firstComma)
{
assert(firstComma->OperIs(GT_COMMA));
Compiler::GenTreePtrStack commas(comp->getAllocator(CMK_ArrayStack));
for (GenTree* currComma = firstComma; currComma != nullptr && currComma->OperIs(GT_COMMA);
currComma = currComma->gtGetOp2())
{
commas.Push(currComma);
}
GenTree* lastComma = commas.Top();
GenTree* effectiveVal = lastComma->gtGetOp2();
assert(effectiveVal == firstComma->gtEffectiveVal());
GenTree* effectiveValAddr = comp->gtNewOperNode(GT_ADDR, TYP_BYREF, effectiveVal);
INDEBUG(effectiveValAddr->gtDebugFlags |= GTF_DEBUG_NODE_MORPHED);
lastComma->AsOp()->gtOp2 = effectiveValAddr;
while (!commas.Empty())
{
GenTree* comma = commas.Pop();
comma->gtType = TYP_BYREF;
comp->gtUpdateNodeSideEffects(comma);
}
const var_types blockType = effectiveVal->TypeGet();
GenTree* addr = firstComma;
GenTree* res;
if (blockType == TYP_STRUCT)
{
CORINFO_CLASS_HANDLE structHnd = comp->gtGetStructHandleIfPresent(effectiveVal);
if (structHnd == NO_CLASS_HANDLE)
{
// TODO-1stClassStructs: get rid of all such cases.
res = comp->gtNewIndir(blockType, addr);
}
else
{
res = comp->gtNewObjNode(structHnd, addr);
comp->gtSetObjGcInfo(res->AsObj());
}
}
else
{
res = comp->gtNewIndir(blockType, addr);
}
comp->gtUpdateNodeSideEffects(res);
INDEBUG(res->gtDebugFlags |= GTF_DEBUG_NODE_MORPHED);
return res;
}
//------------------------------------------------------------------------
// MorphDynamicBlock: tries to transform a dynamic block as a const block.
//
// static
GenTreeBlk* MorphInitBlockHelper::MorphDynamicBlock(Compiler* comp, GenTreeDynBlk* dynBlock)
{
if (dynBlock->gtDynamicSize->IsCnsIntOrI())
{
GenTreeIntCon* dynSize = dynBlock->gtDynamicSize->AsIntCon();
assert(dynSize->FitsInI32());
unsigned size = static_cast<unsigned>(dynSize->IconValue());
// A GT_BLK with size of zero is not supported,
// so if we encounter such a thing we just leave it as a GT_DYN_BLK
if (size != 0)
{
dynBlock->gtDynamicSize = nullptr;
GenTreeBlk* blkNode = dynBlock;
blkNode->ChangeOper(GT_BLK);
blkNode->SetLayout(comp->typGetBlkLayout(size));
JITDUMP("MorphDynamicBlock: DYN_BLK was morphed into BLK:\n");
return blkNode;
}
else
{
JITDUMP("MorphDynamicBlock: DYN_BLK with zero size can't be morphed:\n");
return dynBlock;
}
}
else
{
JITDUMP("MorphDynamicBlock: DYN_BLK with non-const size can't be morphed:\n");
return dynBlock;
}
}
class MorphCopyBlockHelper : public MorphInitBlockHelper
{
public:
static GenTree* MorphCopyBlock(Compiler* comp, GenTree* tree);
protected:
MorphCopyBlockHelper(Compiler* comp, GenTree* asg);
void PrepareSrc() override;
void TrySpecialCases() override;
void MorphStructCases() override;
GenTree* CopyFieldByField();
const char* GetHelperName() const override
{
return "MorphCopyBlock";
}
protected:
unsigned m_srcLclNum = BAD_VAR_NUM;
LclVarDsc* m_srcVarDsc = nullptr;
GenTreeLclVarCommon* m_srcLclNode = nullptr;
FieldSeqNode* m_srcFldSeq = nullptr;
bool m_srcUseLclFld = false;
unsigned m_srcLclOffset = 0;
bool m_srcSingleLclVarAsg = false;
GenTree* m_srcAddr = nullptr;
ssize_t m_srcAddOff = 0;
bool m_dstDoFldAsg = false;
bool m_srcDoFldAsg = false;
};
//------------------------------------------------------------------------
// MorphCopyBlock: Morph a block copy assignment tree.
//
// Arguments:
// comp - a compiler instance;
// tree - A GT_ASG tree that performs block copy.
//
// Return Value:
// A possibly modified tree to perfom the copy.
//
// static
GenTree* MorphCopyBlockHelper::MorphCopyBlock(Compiler* comp, GenTree* tree)
{
MorphCopyBlockHelper helper(comp, tree);
return helper.Morph();
}
//------------------------------------------------------------------------
// MorphCopyBlockHelper: helper's constructor.
//
// Arguments:
// comp - a compiler instance;
// asg - GT_ASG node to morph.
//
// Notes:
// Most class members are initialized via in-class member initializers.
//
MorphCopyBlockHelper::MorphCopyBlockHelper(Compiler* comp, GenTree* asg) : MorphInitBlockHelper(comp, asg, false)
{
}
//------------------------------------------------------------------------
// PrepareSrc: Transform the asg src to an appropriate form and initialize member fields
// with information about it.
//
void MorphCopyBlockHelper::PrepareSrc()
{
GenTree* origSrc = m_asg->gtGetOp2();
m_src = MorphBlock(m_comp, origSrc, false);
if (m_src != origSrc)
{
m_asg->gtOp2 = m_src;
}
if (m_src->IsLocal())
{
m_srcLclNode = m_src->AsLclVarCommon();
m_srcLclNum = m_srcLclNode->GetLclNum();
if (m_src->OperGet() == GT_LCL_FLD)
{
m_srcFldSeq = m_src->AsLclFld()->GetFieldSeq();
}
}
else if (m_src->OperIsIndir())
{
if (m_src->AsOp()->gtOp1->IsLocalAddrExpr(m_comp, &m_srcLclNode, &m_srcFldSeq, &m_srcAddOff))
{
m_srcLclNum = m_srcLclNode->GetLclNum();
}
else
{
m_srcAddr = m_src->AsOp()->gtOp1;
}
}
if (m_srcLclNum != BAD_VAR_NUM)
{
m_srcLclOffset = m_srcLclNode->GetLclOffs();
m_srcVarDsc = m_comp->lvaGetDesc(m_srcLclNum);
}
}
// TrySpecialCases: check special cases that require special transformations.
// The current special cases include asignments with calls in RHS.
//
// Notes:
// It could change multiReg flags or change m_dst node.
//
void MorphCopyBlockHelper::TrySpecialCases()
{
#if FEATURE_MULTIREG_RET
// If this is a multi-reg return, we will not do any morphing of this node.
if (m_src->IsMultiRegCall())
{
assert(m_dst->OperGet() == GT_LCL_VAR);
JITDUMP("Not morphing a multireg call return\n");
m_transformationDecision = BlockTransformation::SkipCallSrc;
m_result = m_asg;
}
else if (m_dst->IsMultiRegLclVar() && !m_src->IsMultiRegNode())
{
m_dst->AsLclVar()->ClearMultiReg();
}
#endif // FEATURE_MULTIREG_RET
if (m_transformationDecision == BlockTransformation::Undefined)
{
if (m_src->IsCall())
{
if (m_dst->OperIs(GT_OBJ))
{
GenTreeLclVar* lclVar = m_comp->fgMorphTryFoldObjAsLclVar(m_dst->AsObj());
if (lclVar != nullptr)
{
m_dst = lclVar;
m_asg->gtOp1 = lclVar;
}
}
if (m_dst->OperIs(GT_LCL_VAR))
{
LclVarDsc* varDsc = m_comp->lvaGetDesc(m_dst->AsLclVar());
if (varTypeIsStruct(varDsc) && varDsc->CanBeReplacedWithItsField(m_comp))
{
m_dst->gtFlags |= GTF_DONT_CSE;
JITDUMP("Not morphing a single reg call return\n");
m_transformationDecision = BlockTransformation::SkipCallSrc;
m_result = m_asg;
}
}
}
}
}
//------------------------------------------------------------------------
// MorphStructCases: transforms the asg as field by field copy or keeps it as a block init
// but sets appropriate flags for the involved lclVars.
//
// Assumptions:
// we have already checked that it is not a special case and can't be transformed as OneAsgBlock.
//
void MorphCopyBlockHelper::MorphStructCases()
{
JITDUMP("block assignment to morph:\n");
DISPTREE(m_asg);
if (m_dstVarDsc != nullptr)
{
if (m_dstVarDsc->lvPromoted && m_blockSizeIsConst)
{
noway_assert(varTypeIsStruct(m_dstVarDsc));
noway_assert(!m_comp->opts.MinOpts());
if (m_blockSize == m_dstVarDsc->lvExactSize)
{
JITDUMP(" (m_dstDoFldAsg=true)");
// We may decide later that a copyblk is required when this struct has holes
m_dstDoFldAsg = true;
}
else
{
JITDUMP(" with mismatched dest size");
}
}
}
if (m_srcVarDsc != nullptr)
{
if (m_srcVarDsc->lvPromoted && m_blockSizeIsConst)
{
noway_assert(varTypeIsStruct(m_srcVarDsc));
noway_assert(!m_comp->opts.MinOpts());
if (m_blockSize == m_srcVarDsc->lvExactSize)
{
JITDUMP(" (m_srcDoFldAsg=true)");
// We may decide later that a copyblk is required when this struct has holes
m_srcDoFldAsg = true;
}
else
{
JITDUMP(" with mismatched src size");
}
}
}
// Check to see if we are doing a copy to/from the same local block.
// If so, morph it to a nop.
if ((m_dstVarDsc != nullptr) && (m_srcVarDsc == m_dstVarDsc) && (m_dstFldSeq == m_srcFldSeq) &&
m_dstFldSeq != FieldSeqStore::NotAField())
{
JITDUMP("Self-copy; replaced with a NOP.\n");
m_transformationDecision = BlockTransformation::Nop;
GenTree* nop = m_comp->gtNewNothingNode();
m_result = nop;
return;
}
// Check to see if we are required to do a copy block because the struct contains holes
// and either the src or dest is externally visible
//
bool requiresCopyBlock = false;
// If either src or dest is a reg-sized non-field-addressed struct, keep the copyBlock.
if ((m_dstVarDsc != nullptr && m_dstVarDsc->lvRegStruct) || (m_srcVarDsc != nullptr && m_srcVarDsc->lvRegStruct))
{
requiresCopyBlock = true;
}
// Can we use field by field assignment for the dest?
if (m_dstDoFldAsg && m_dstVarDsc->lvCustomLayout && m_dstVarDsc->lvContainsHoles)
{
JITDUMP(" dest contains custom layout and contains holes");
// C++ style CopyBlock with holes
requiresCopyBlock = true;
}
// Can we use field by field assignment for the src?
if (m_srcDoFldAsg && m_srcVarDsc->lvCustomLayout && m_srcVarDsc->lvContainsHoles)
{
JITDUMP(" src contains custom layout and contains holes");
// C++ style CopyBlock with holes
requiresCopyBlock = true;
}
#if defined(TARGET_ARM)
if ((m_src->OperIsIndir()) && (m_src->gtFlags & GTF_IND_UNALIGNED))
{
JITDUMP(" src is unaligned");
requiresCopyBlock = true;
}
if (m_asg->gtFlags & GTF_BLK_UNALIGNED)
{
JITDUMP(" m_asg is unaligned");
requiresCopyBlock = true;
}
#endif // TARGET_ARM
// Don't use field by field assignment if the src is a call,
// lowering will handle it without spilling the call result into memory
// to access the individual fields.
//
if (m_src->OperGet() == GT_CALL)
{
JITDUMP(" src is a call");
requiresCopyBlock = true;
}
// If we passed the above checks, then we will check these two
if (!requiresCopyBlock)
{
// It is not always profitable to do field by field init for structs that are allocated to memory.
// A struct with 8 bool fields will require 8 moves instead of one if we do this transformation.
// A simple heuristic when field by field copy is prefered:
// - if fields can be enregistered;
// - if the struct has GCPtrs (block copy would be done via helper that is expensive);
// - if the struct has only one field.
bool dstFldIsProfitable =
((m_dstVarDsc != nullptr) &&
(!m_dstVarDsc->lvDoNotEnregister || m_dstVarDsc->HasGCPtr() || (m_dstVarDsc->lvFieldCnt == 1)));
bool srcFldIsProfitable =
((m_srcVarDsc != nullptr) &&
(!m_srcVarDsc->lvDoNotEnregister || m_srcVarDsc->HasGCPtr() || (m_srcVarDsc->lvFieldCnt == 1)));
// Are both dest and src promoted structs?
if (m_dstDoFldAsg && m_srcDoFldAsg && (dstFldIsProfitable || srcFldIsProfitable))
{
// Both structs should be of the same type, or have the same number of fields of the same type.
// If not we will use a copy block.
bool misMatchedTypes = false;
if (m_dstVarDsc->GetStructHnd() != m_srcVarDsc->GetStructHnd())
{
if (m_dstVarDsc->lvFieldCnt != m_srcVarDsc->lvFieldCnt)
{
misMatchedTypes = true;
}
else
{
for (int i = 0; i < m_dstVarDsc->lvFieldCnt; i++)
{
LclVarDsc* destFieldVarDsc = m_comp->lvaGetDesc(m_dstVarDsc->lvFieldLclStart + i);
LclVarDsc* srcFieldVarDsc = m_comp->lvaGetDesc(m_srcVarDsc->lvFieldLclStart + i);
if ((destFieldVarDsc->lvType != srcFieldVarDsc->lvType) ||
(destFieldVarDsc->lvFldOffset != srcFieldVarDsc->lvFldOffset))
{
misMatchedTypes = true;
break;
}
}
}
if (misMatchedTypes)
{
requiresCopyBlock = true; // Mismatched types, leave as a CopyBlock
JITDUMP(" with mismatched types");
}
}
}
else if (m_dstDoFldAsg && dstFldIsProfitable)
{
// Match the following kinds of trees:
// fgMorphTree BB01, stmt 9 (before)
// [000052] ------------ const int 8
// [000053] -A--G------- copyBlk void
// [000051] ------------ addr byref
// [000050] ------------ lclVar long V07 loc5
// [000054] --------R--- <list> void
// [000049] ------------ addr byref
// [000048] ------------ lclVar struct(P) V06 loc4
// long V06.h (offs=0x00) -> V17 tmp9
// Yields this transformation
// fgMorphCopyBlock (after):
// [000050] ------------ lclVar long V07 loc5
// [000085] -A---------- = long
// [000083] D------N---- lclVar long V17 tmp9
//
if (m_blockSizeIsConst && (m_dstVarDsc->lvFieldCnt == 1) && (m_srcVarDsc != nullptr) &&
(m_blockSize == genTypeSize(m_srcVarDsc->TypeGet())))
{
// Reject the following tree:
// - seen on x86chk jit\jit64\hfa\main\hfa_sf3E_r.exe
//
// fgMorphTree BB01, stmt 6 (before)
// [000038] ------------- const int 4
// [000039] -A--G-------- copyBlk void
// [000037] ------------- addr byref
// [000036] ------------- lclVar int V05 loc3
// [000040] --------R---- <list> void
// [000035] ------------- addr byref
// [000034] ------------- lclVar struct(P) V04 loc2
// float V04.f1 (offs=0x00) -> V13 tmp6
// As this would framsform into
// float V13 = int V05
//
unsigned fieldLclNum = m_comp->lvaGetDesc(m_dstLclNum)->lvFieldLclStart;
var_types destType = m_comp->lvaGetDesc(fieldLclNum)->TypeGet();
if (m_srcVarDsc->TypeGet() == destType)
{
m_srcSingleLclVarAsg = true;
}
}
}
else if (m_srcDoFldAsg && srcFldIsProfitable)
{
// Check for the symmetric case (which happens for the _pointer field of promoted spans):
//
// [000240] -----+------ /--* lclVar struct(P) V18 tmp9
// /--* byref V18._value (offs=0x00) -> V30
// tmp21
// [000245] -A------R--- * = struct (copy)
// [000244] -----+------ \--* obj(8) struct
// [000243] -----+------ \--* addr byref
// [000242] D----+-N---- \--* lclVar byref V28 tmp19
//
if (m_blockSizeIsConst && (m_srcVarDsc->lvFieldCnt == 1) && (m_dstVarDsc != nullptr) &&
(m_blockSize == genTypeSize(m_dstVarDsc->TypeGet())))
{
// Check for type agreement
unsigned fieldLclNum = m_comp->lvaGetDesc(m_srcLclNum)->lvFieldLclStart;
var_types srcType = m_comp->lvaGetDesc(fieldLclNum)->TypeGet();
if (m_dstVarDsc->TypeGet() == srcType)
{
m_dstSingleLclVarAsg = true;
}
}
}
// Are neither dest or src promoted structs?
else
{
assert(!(m_dstDoFldAsg && dstFldIsProfitable) && !(m_srcDoFldAsg && srcFldIsProfitable));
requiresCopyBlock = true; // Leave as a CopyBlock
JITDUMP(" with no promoted structs");
}
}
// If we require a copy block the set both of the field assign bools to false
if (requiresCopyBlock)
{
// If a copy block is required then we won't do field by field assignments
m_dstDoFldAsg = false;
m_srcDoFldAsg = false;
}
JITDUMP(requiresCopyBlock ? " this requires a CopyBlock.\n" : " using field by field assignments.\n");
if (requiresCopyBlock)
{
const var_types asgType = m_dst->TypeGet();
bool isBlkReqd = (asgType == TYP_STRUCT);
m_dst = m_comp->fgMorphBlockOperand(m_dst, asgType, m_blockSize, isBlkReqd);
m_dst->gtFlags |= GTF_DONT_CSE;
m_asg->gtOp1 = m_dst;
m_asg->gtFlags |= (m_dst->gtFlags & GTF_ALL_EFFECT);
// Eliminate the "OBJ or BLK" node on the src.
m_src = m_comp->fgMorphBlockOperand(m_src, asgType, m_blockSize, false /*!isBlkReqd*/);
m_asg->gtOp2 = m_src;
m_result = m_asg;
m_transformationDecision = BlockTransformation::StructBlock;
}
else