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Address-expose locals under complex local addresses in block morphing #63100

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merged 2 commits into from
Jan 21, 2022
Merged

Address-expose locals under complex local addresses in block morphing #63100

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51fd539
Handle complex local addresses in block morphing
SingleAccretion Dec 23, 2021
772a91c
Add a TODO-CQ for LCL_FLD usage
SingleAccretion Jan 18, 2022
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53 changes: 17 additions & 36 deletions src/coreclr/jit/morphblock.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1048,9 +1048,9 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()
{
GenTreeOp* asgFields = nullptr;

GenTree* addrSpill = nullptr;
unsigned addrSpillTemp = BAD_VAR_NUM;
bool addrSpillIsStackDest = false; // true if 'addrSpill' represents the address in our local stack frame
GenTree* addrSpill = nullptr;
unsigned addrSpillSrcLclNum = BAD_VAR_NUM;
unsigned addrSpillTemp = BAD_VAR_NUM;

GenTree* addrSpillAsg = nullptr;

Expand Down Expand Up @@ -1095,7 +1095,8 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()
// We will spill m_srcAddr (i.e. assign to a temp "BlockOp address local")
// no need to clone a new copy as it is only used once
//
addrSpill = m_srcAddr; // addrSpill represents the 'm_srcAddr'
addrSpill = m_srcAddr; // addrSpill represents the 'm_srcAddr'
addrSpillSrcLclNum = m_srcLclNum;
}
}
}
Expand Down Expand Up @@ -1144,28 +1145,13 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()
// We will spill m_dstAddr (i.e. assign to a temp "BlockOp address local")
// no need to clone a new copy as it is only used once
//
addrSpill = m_dstAddr; // addrSpill represents the 'm_dstAddr'
addrSpill = m_dstAddr; // addrSpill represents the 'm_dstAddr'
addrSpillSrcLclNum = m_dstLclNum;
}
}
}
}

// TODO-CQ: this should be based on a more general
// "BaseAddress" method, that handles fields of structs, before or after
// morphing.
if ((addrSpill != nullptr) && addrSpill->OperIs(GT_ADDR))
{
GenTree* addrSpillOp = addrSpill->AsOp()->gtGetOp1();
if (addrSpillOp->IsLocal())
{
// We will *not* consider this to define the local, but rather have each individual field assign
// be a definition.
addrSpillOp->gtFlags &= ~(GTF_LIVENESS_MASK);
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This was deleted as it was redundant with the code above.

addrSpillIsStackDest = true; // addrSpill represents the address of LclVar[varNum] in our
// local stack frame
}
}

if (addrSpill != nullptr)
{
// 'addrSpill' is already morphed
Expand All @@ -1178,38 +1164,33 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()

addrSpillDsc->lvType = TYP_BYREF;

if (addrSpillIsStackDest)
if (addrSpillSrcLclNum != BAD_VAR_NUM)
{
// addrSpill represents the address of LclVar[varNum] in our local stack frame.
addrSpillDsc->lvStackByref = true;
}

GenTreeLclVar* addrSpillNode = m_comp->gtNewLclvNode(addrSpillTemp, TYP_BYREF);
addrSpillAsg = m_comp->gtNewAssignNode(addrSpillNode, addrSpill);

// If we are assigning the address of a LclVar here
// liveness does not account for this kind of address taken use.
// If we are assigning the address of a LclVar here liveness will not
// account for this kind of address taken use. Mark the local as
// address-exposed so that we don't do illegal optimizations with it.
//
// We have to mark this local as address exposed so
// that we don't delete the definition for this LclVar
// as a dead store later on.
// TODO-CQ: usage of "addrSpill" for local addresses is a workaround
// for cases where we fail to use LCL_FLD nodes instead. Fix them and
// delete this code.
//
if (addrSpill->OperGet() == GT_ADDR)
if (addrSpillSrcLclNum != BAD_VAR_NUM)
{
GenTree* addrOp = addrSpill->AsOp()->gtOp1;
if (addrOp->IsLocal())
{
unsigned lclVarNum = addrOp->AsLclVarCommon()->GetLclNum();
m_comp->lvaGetDesc(lclVarNum)->SetAddressExposed(true DEBUGARG(AddressExposedReason::COPY_FLD_BY_FLD));
m_comp->lvaSetVarDoNotEnregister(lclVarNum DEBUGARG(DoNotEnregisterReason::AddrExposed));
}
m_comp->lvaSetVarAddrExposed(addrSpillSrcLclNum DEBUGARG(AddressExposedReason::COPY_FLD_BY_FLD));
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@SingleAccretion SingleAccretion Dec 23, 2021 •
edited
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lvaSetVarAddrExposed calls lvaSetVarDoNotEnregister.

}
}

// We may have allocated a temp above, and that may have caused the lvaTable to be expanded.
// So, beyond this point we cannot rely on the old values of 'm_srcVarDsc' and 'm_dstVarDsc'.
for (unsigned i = 0; i < fieldCnt; ++i)
{

GenTree* dstFld;
if (m_dstDoFldAsg)
{
Expand Down