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Generate LCL_FLDs early
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@mikedn
mikedn committed Jun 11, 2019
1 parent d5906ec commit 40c2ba1
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Showing 2 changed files with 109 additions and 17 deletions.
23 changes: 23 additions & 0 deletions src/jit/gentree.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2770,6 +2770,29 @@ struct GenTreeLclFld : public GenTreeLclVarCommon
{
assert(sizeof(*this) <= s_gtNodeSizes[GT_LCL_FLD]);
}

unsigned GetLclOfsset() const
{
return gtLclOffs;
}

void SetLclOffset(unsigned offset)
{
assert(offset < 65536);
gtLclOffs = offset;
}

FieldSeqNode* GetFieldSeq() const
{
return gtFieldSeq;
}

void SetFieldSeq(FieldSeqNode* fieldSeq)
{
assert(fieldSeq != nullptr);
gtFieldSeq = fieldSeq;
}

#if DEBUGGABLE_GENTREE
GenTreeLclFld() : GenTreeLclVarCommon()
{
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103 changes: 86 additions & 17 deletions src/jit/morph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -17993,16 +17993,18 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
//
class Value
{
GenTree* m_node;
unsigned m_lclNum;
unsigned m_offset;
bool m_address;
GenTree* m_node;
FieldSeqNode* m_fieldSeq;
unsigned m_lclNum;
unsigned m_offset;
bool m_address;
INDEBUG(bool m_consumed;)

public:
// Produce an unknown value associated with the specified node.
Value(GenTree* node)
: m_node(node)
, m_fieldSeq(nullptr)
, m_lclNum(BAD_VAR_NUM)
, m_offset(0)
, m_address(false)
Expand Down Expand Up @@ -18048,6 +18050,12 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
return m_offset;
}

// Get the location's field sequence.
FieldSeqNode* FieldSeq() const
{
return m_fieldSeq;
}

//------------------------------------------------------------------------
// Location: Produce a location value.
//
Expand All @@ -18058,12 +18066,24 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
// Notes:
// - (lclnum, offset) => LOCATION(lclNum, offset)
//
void Location(unsigned lclNum, unsigned offset = 0)
void Location(GenTreeLclVar* lclVar)
{
assert(!IsLocation() && !IsAddress());

m_lclNum = lclNum;
m_offset = offset;
m_lclNum = lclVar->GetLclNum();
assert(m_offset == 0);
assert(m_fieldSeq == nullptr);
}

void Location(GenTreeLclFld* lclFld)
{
assert(!IsLocation() && !IsAddress());

m_lclNum = lclFld->GetLclNum();
m_offset = lclFld->GetLclOfsset();
m_fieldSeq = lclFld->GetFieldSeq();

assert(m_fieldSeq != nullptr);
}

//------------------------------------------------------------------------
Expand All @@ -18084,9 +18104,10 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>

if (val.IsLocation())
{
m_address = true;
m_lclNum = val.m_lclNum;
m_offset = val.m_offset;
m_address = true;
m_lclNum = val.m_lclNum;
m_offset = val.m_offset;
m_fieldSeq = val.m_fieldSeq;
}

INDEBUG(val.Consume();)
Expand All @@ -18111,7 +18132,7 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
// if the offset overflows then location is not representable, must escape
// - UNKNOWN => UNKNOWN
//
bool Field(Value& val, unsigned offset)
bool Field(Value& val, GenTreeField* field, FieldSeqStore* fieldSeqStore)
{
assert(!IsLocation() && !IsAddress());

Expand All @@ -18122,7 +18143,8 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>

if (val.IsAddress())
{
ClrSafeInt<unsigned> newOffset = ClrSafeInt<unsigned>(val.m_offset) + ClrSafeInt<unsigned>(offset);
ClrSafeInt<unsigned> newOffset =
ClrSafeInt<unsigned>(val.m_offset) + ClrSafeInt<unsigned>(field->gtFldOffset);

if (newOffset.IsOverflow())
{
Expand All @@ -18133,6 +18155,15 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
m_offset = newOffset.Value();
}

if (field->gtFldMayOverlap || (val.m_fieldSeq == FieldSeqStore::NotAField()))
{
m_fieldSeq = FieldSeqStore::NotAField();
}
else
{
m_fieldSeq = fieldSeqStore->Append(val.m_fieldSeq, fieldSeqStore->CreateSingleton(field->gtFldHnd));
}

INDEBUG(val.Consume();)
return true;
}
Expand Down Expand Up @@ -18164,8 +18195,9 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>

if (val.IsAddress())
{
m_lclNum = val.m_lclNum;
m_offset = val.m_offset;
m_lclNum = val.m_lclNum;
m_offset = val.m_offset;
m_fieldSeq = val.m_fieldSeq;
}

INDEBUG(val.Consume();)
Expand Down Expand Up @@ -18304,13 +18336,13 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
case GT_LCL_VAR:
assert(TopValue(0).Node() == node);

TopValue(0).Location(node->AsLclVar()->GetLclNum());
TopValue(0).Location(node->AsLclVar());
break;

case GT_LCL_FLD:
assert(TopValue(0).Node() == node);

TopValue(0).Location(node->AsLclFld()->GetLclNum(), node->AsLclFld()->gtLclOffs);
TopValue(0).Location(node->AsLclFld());
break;

case GT_ADDR:
Expand All @@ -18327,7 +18359,7 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
assert(TopValue(1).Node() == node);
assert(TopValue(0).Node() == node->AsField()->gtFldObj);

if (!TopValue(1).Field(TopValue(0), node->AsField()->gtFldOffset))
if (!TopValue(1).Field(TopValue(0), node->AsField(), m_compiler->GetFieldSeqStore()))
{
// Either the address comes from a location value (e.g. FIELD(IND(...)))
// or the field offset has overflowed.
Expand Down Expand Up @@ -18564,6 +18596,43 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
{
m_compiler->lvaSetVarAddrExposed(varDsc->lvIsStructField ? varDsc->lvParentLcl : val.LclNum());
}
else
{
if ((val.FieldSeq() != nullptr) && (val.Offset() < 65536) &&
// LCL_FLDs can be used for non-struct variables as well. However, in that case we don't have
// a real field access but rather we're reinterpreting the variable as a different type, as in
// *((float*)&intVar). Ideally, such cases should be handled in a different manner (GT_BITCAST,
// bit shifting and masking) so as not to make the variable not enregistrable. Leave such cases
// to morph for now.
(varDsc->TypeGet() == TYP_STRUCT) &&
// Dealing with implicit byref parameters is problematic now.
!varDsc->lvIsImplicitByRef &&
// For now just generate LCL_FLDs early. We could do promotion as well in the future.
!varDsc->lvPromoted && !varDsc->lvIsStructField)
{
if (node->OperIs(GT_OBJ, GT_BLK))
{
GenTree* addr = node->AsBlk()->Addr();
// The address should always be a GT_ADDR node (applied to a GT_FIELD or GT_LCL_VAR).
// Currently we don't track field sequences through pointer operations, that can be
// added in the future.
assert(addr->OperIs(GT_ADDR));
node = addr->AsUnOp()->gtGetOp1();
}

JITDUMP("Changing local indirection tree to GT_LCL_FLD\n");

m_compiler->lvaSetVarDoNotEnregister(val.LclNum() DEBUGARG(Compiler::DNER_LocalField));

node->ChangeOper(GT_LCL_FLD);
node->gtFlags &= ~GTF_ALL_EFFECT;
node->AsLclFld()->SetLclNum(val.LclNum());
node->AsLclFld()->SetLclOffset(val.Offset());
node->AsLclFld()->SetFieldSeq(val.FieldSeq());

INDEBUG(m_stmtModified = true);
}
}
}

INDEBUG(val.Consume();)
Expand Down

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