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JIT: Disallow parameters passed in float regs from being enregistered in int regs #99286

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Merged
jakobbotsch merged 4 commits into from
Mar 8, 2024
Merged

JIT: Disallow parameters passed in float regs from being enregistered in int regs #99286

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17f8913
JIT: Validate some reg homing logic
jakobbotsch Mar 5, 2024
048f94c
Stop enregistering problematic case
jakobbotsch Mar 7, 2024
893f01f
Better fix
jakobbotsch Mar 7, 2024
33cdb8e
Clean up
jakobbotsch Mar 7, 2024
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Better fix
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@jakobbotsch
jakobbotsch committed Mar 7, 2024
commit 893f01f91cea0548310fb631ef3831d0401811ab
14 changes: 6 additions & 8 deletions src/coreclr/jit/lclvars.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3843,15 +3843,18 @@ var_types LclVarDsc::GetRegisterType(const GenTreeLclVarCommon* tree) const

if (targetType == TYP_STRUCT)
{
ClassLayout* layout;
if (tree->OperIs(GT_LCL_FLD, GT_STORE_LCL_FLD))
{
targetType = tree->AsLclFld()->GetLayout()->GetRegisterType();
layout = tree->AsLclFld()->GetLayout();
}
else
{
assert((TypeGet() == TYP_STRUCT) && tree->OperIs(GT_LCL_VAR, GT_STORE_LCL_VAR));
targetType = GetRegisterType();
layout = GetLayout();
}

targetType = layout->GetRegisterType();
}

#ifdef DEBUG
Expand Down Expand Up @@ -3885,12 +3888,7 @@ var_types LclVarDsc::GetRegisterType() const
return TypeGet();
}
assert(m_layout != nullptr);
var_types result = m_layout->GetRegisterType();
if ((result != TYP_UNDEF) && varTypeUsesIntReg(result) && lvIsRegArg && !lvPromoted && genIsValidFloatReg(GetArgReg()))
{
result = TYP_UNDEF;
}
return result;
return m_layout->GetRegisterType();
}

//------------------------------------------------------------------------
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14 changes: 14 additions & 0 deletions src/coreclr/jit/lsra.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1681,6 +1681,20 @@ bool LinearScan::isRegCandidate(LclVarDsc* varDsc)
return false;
}

// Avoid allocating parameters that are passed in float regs into integer
// registers. We currently home float registers before integer registers,
// so that kind of enregistration can trash integer registers containing
// other parameters.
// We assume that these cases will be homed to float registers if they are
// promoted.
// TODO-CQ: Combine integer and float register homing to handle these kinds
// of conflicts.
if (varTypeUsesIntReg(varDsc->GetRegisterType()) && varDsc->lvIsRegArg && !varDsc->lvPromoted && genIsValidFloatReg(varDsc->GetArgReg()))
{
compiler->lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::IsStructArg));
return false;
}

// Are we not optimizing and we have exception handlers?
// if so mark all args and locals as volatile, so that they
// won't ever get enregistered.
Expand Down