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JIT: run local struct to field update in morph both pre and post order for returns #75304

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Merged
merged 2 commits into from
Sep 13, 2022
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JIT: run local struct to field update in morph both pre and post order for returns #75304

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4795c46
JIT: run local assertion prop before morphing return of local struct …
AndyAyersMS Sep 8, 2022
217140d
revise to try the update pre and post with ap in between
AndyAyersMS Sep 9, 2022
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1 change: 1 addition & 0 deletions src/coreclr/jit/compiler.h
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Original file line number Diff line number Diff line change
Expand Up @@ -5768,6 +5768,7 @@ class Compiler
GenTree* fgMorphStoreDynBlock(GenTreeStoreDynBlk* tree);
GenTree* fgMorphForRegisterFP(GenTree* tree);
GenTree* fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optAssertionPropDone = nullptr);
void fgTryReplaceStructLocalWithField(GenTree* tree);
GenTree* fgOptimizeCast(GenTreeCast* cast);
GenTree* fgOptimizeCastOnAssignment(GenTreeOp* asg);
GenTree* fgOptimizeEqualityComparisonWithConst(GenTreeOp* cmp);
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81 changes: 55 additions & 26 deletions src/coreclr/jit/morph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10243,32 +10243,8 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optA
{
op1 = fgMorphRetInd(tree->AsUnOp());
}
if (op1->OperIs(GT_LCL_VAR))
{
// With a `genReturnBB` this `RETURN(src)` tree will be replaced by a `ASG(genReturnLocal, src)`
// and `ASG` will be transformed into field by field copy without parent local referencing if
// possible.
GenTreeLclVar* lclVar = op1->AsLclVar();
unsigned lclNum = lclVar->GetLclNum();
if ((genReturnLocal == BAD_VAR_NUM) || (genReturnLocal == lclNum))
{
LclVarDsc* varDsc = lvaGetDesc(lclVar);
if (varDsc->CanBeReplacedWithItsField(this))
{
// We can replace the struct with its only field and allow copy propagation to replace
// return value that was written as a field.
unsigned fieldLclNum = varDsc->lvFieldLclStart;
LclVarDsc* fieldDsc = lvaGetDesc(fieldLclNum);

JITDUMP("Replacing an independently promoted local var V%02u with its only field "
"V%02u for "
"the return [%06u]\n",
lclVar->GetLclNum(), fieldLclNum, dspTreeID(tree));
lclVar->SetLclNum(fieldLclNum);
lclVar->ChangeType(fieldDsc->lvType);
}
}
}

fgTryReplaceStructLocalWithField(op1);
}

// normalize small integer return values
Expand Down Expand Up @@ -11681,6 +11657,17 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optA
}
break;

case GT_RETURN:

// Retry updating op1 to a field -- assertion
// prop done when morphing op1 changed the local.
//
if (op1 != nullptr)
{
fgTryReplaceStructLocalWithField(op1);
}
break;

default:
break;
}
Expand Down Expand Up @@ -11725,6 +11712,48 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optA
return tree;
}

//------------------------------------------------------------------------
// fgTryReplaceStructLocalWithField: see if a struct use can be replaced
// with an equivalent field use
//
// Arguments:
// tree - tree to examine and possibly modify
//
// Notes:
// Currently only called when the tree parent is a GT_RETURN.
//
void Compiler::fgTryReplaceStructLocalWithField(GenTree* tree)
{
if (!tree->OperIs(GT_LCL_VAR))
{
return;
}

// With a `genReturnBB` this `RETURN(src)` tree will be replaced by a `ASG(genReturnLocal, src)`
// and `ASG` will be transformed into field by field copy without parent local referencing if
// possible.
GenTreeLclVar* lclVar = tree->AsLclVar();
unsigned lclNum = lclVar->GetLclNum();
if ((genReturnLocal == BAD_VAR_NUM) || (genReturnLocal == lclNum))
{
LclVarDsc* const varDsc = lvaGetDesc(lclVar);
if (varDsc->CanBeReplacedWithItsField(this))
{
// We can replace the struct with its only field and allow copy propagation to replace
// return value that was written as a field.
unsigned const fieldLclNum = varDsc->lvFieldLclStart;
LclVarDsc* const fieldDsc = lvaGetDesc(fieldLclNum);

JITDUMP("Replacing an independently promoted local var V%02u with its only field "
"V%02u for "
"the return [%06u]\n",
lclVar->GetLclNum(), fieldLclNum, dspTreeID(tree));
lclVar->SetLclNum(fieldLclNum);
lclVar->ChangeType(fieldDsc->lvType);
}
}
}

//------------------------------------------------------------------------
// fgOptimizeCast: Optimizes the supplied GT_CAST tree.
//
Expand Down