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Unpin locals, attempt 2 #70655

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Jun 17, 2022
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Unpin locals, attempt 2 #70655

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6cc1125
Unpin locals (#70264)
aromaa Jun 11, 2022
73df659
Fix OSR
aromaa Jun 13, 2022
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2 changes: 2 additions & 0 deletions src/coreclr/jit/compiler.h
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Original file line number Diff line number Diff line change
Expand Up @@ -614,6 +614,8 @@ class LclVarDsc
unsigned char lvSingleDefDisqualifyReason = 'H';
#endif

unsigned char lvAllDefsAreNoGc : 1; // For pinned locals: true if all defs of this local are no-gc

#if FEATURE_MULTIREG_ARGS
regNumber lvRegNumForSlot(unsigned slotNum)
{
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5 changes: 5 additions & 0 deletions src/coreclr/jit/gentree.h
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Expand Up @@ -1109,6 +1109,11 @@ struct GenTree
return true;
}

bool IsNotGcDef() const
{
return IsIntegralConst(0) || IsLocalAddrExpr();
}

// LIR flags
// These helper methods, along with the flag values they manipulate, are defined in lir.h
//
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78 changes: 48 additions & 30 deletions src/coreclr/jit/lclvars.cpp
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Expand Up @@ -4181,49 +4181,57 @@ void Compiler::lvaMarkLclRefs(GenTree* tree, BasicBlock* block, Statement* stmt,

/* Is this an assignment to a local variable? */

if (op1->gtOper == GT_LCL_VAR && op2->gtType != TYP_BOOL)
if (op1->gtOper == GT_LCL_VAR)
{
/* Only simple assignments allowed for booleans */
LclVarDsc* varDsc = lvaGetDesc(op1->AsLclVarCommon());

if (tree->gtOper != GT_ASG)
if (varDsc->lvPinned && varDsc->lvAllDefsAreNoGc)
{
goto NOT_BOOL;
if (!op2->IsNotGcDef())
{
varDsc->lvAllDefsAreNoGc = false;
}
}

/* Is the RHS clearly a boolean value? */

switch (op2->gtOper)
if (op2->gtType != TYP_BOOL)
{
unsigned lclNum;
/* Only simple assignments allowed for booleans */

case GT_CNS_INT:
if (tree->gtOper != GT_ASG)
{
goto NOT_BOOL;
}

if (op2->AsIntCon()->gtIconVal == 0)
{
break;
}
if (op2->AsIntCon()->gtIconVal == 1)
{
break;
}
/* Is the RHS clearly a boolean value? */

// Not 0 or 1, fall through ....
FALLTHROUGH;
switch (op2->gtOper)
{
case GT_CNS_INT:

default:
if (op2->AsIntCon()->gtIconVal == 0)
{
break;
}
if (op2->AsIntCon()->gtIconVal == 1)
{
break;
}

if (op2->OperIsCompare())
{
break;
}
// Not 0 or 1, fall through ....
FALLTHROUGH;

NOT_BOOL:
default:

lclNum = op1->AsLclVarCommon()->GetLclNum();
noway_assert(lclNum < lvaCount);
if (op2->OperIsCompare())
{
break;
}

lvaTable[lclNum].lvIsBoolean = false;
break;
NOT_BOOL:

varDsc->lvIsBoolean = false;
break;
}
}
}
}
Expand Down Expand Up @@ -4278,7 +4286,8 @@ void Compiler::lvaMarkLclRefs(GenTree* tree, BasicBlock* block, Statement* stmt,
{
if (lvaVarAddrExposed(lclNum))
{
varDsc->lvIsBoolean = false;
varDsc->lvIsBoolean = false;
varDsc->lvAllDefsAreNoGc = false;
}

if (tree->gtOper == GT_LCL_FLD)
Expand Down Expand Up @@ -4750,6 +4759,8 @@ void Compiler::lvaComputeRefCounts(bool isRecompute, bool setSlotNumbers)
{
varDsc->lvSingleDef = varDsc->lvIsParam;
varDsc->lvSingleDefRegCandidate = varDsc->lvIsParam;

varDsc->lvAllDefsAreNoGc = (varDsc->lvImplicitlyReferenced == false);
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Suggested change
varDsc->lvAllDefsAreNoGc = (varDsc->lvImplicitlyReferenced == false);
// if there are implicit refs, assume they may be gc defs
varDsc->lvAllDefsAreNoGc = !varDsc->lvImplicitlyReferenced;

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This actually gives a compiler warning of "Using logical '!' when bitwise '~' was probably intended"

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Yeah, it's ok to leave this as is. For some reason all these bit fields are unsigned char and not bool.

}
}

Expand Down Expand Up @@ -4868,6 +4879,13 @@ void Compiler::lvaComputeRefCounts(bool isRecompute, bool setSlotNumbers)
varDsc->lvImplicitlyReferenced = 1;
}
}

if (varDsc->lvPinned && varDsc->lvAllDefsAreNoGc)
{
varDsc->lvPinned = 0;

JITDUMP("V%02u was unpinned as all def candidates were local.\n", lclNum);
}
}
}

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