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[gardening] Reduce indentation of SILGenLValue::visitRec by inverting an if condition. #11020

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Jul 17, 2017
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[gardening] Reduce indentation of SILGenLValue::visitRec by inverting an if condition. #11020

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129 changes: 66 additions & 63 deletions lib/SILGen/SILGenLValue.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1939,75 +1939,78 @@ LValue SILGenFunction::emitLValue(Expr *e, AccessKind accessKind) {

LValue SILGenLValue::visitRec(Expr *e, AccessKind accessKind,
AbstractionPattern orig) {
// Non-lvalue types (references, values, metatypes, etc) form the root of a
// logical l-value.
if (!e->getType()->is<LValueType>() && !e->getType()->is<InOutType>()) {
// Decide if we can evaluate this expression at +0 for the rest of the
// lvalue.
SGFContext Ctx;
ManagedValue rv;

// Calls through opaque protocols can be done with +0 rvalues. This allows
// us to avoid materializing copies of existentials.
if (SGF.SGM.Types.isIndirectPlusZeroSelfParameter(e->getType()))
Ctx = SGFContext::AllowGuaranteedPlusZero;
else if (auto *DRE = dyn_cast<DeclRefExpr>(e)) {
// Any reference to "self" can be done at +0 so long as it is a direct
// access, since we know it is guaranteed.
// TODO: it would be great to factor this even lower into SILGen to the
// point where we can see that the parameter is +0 guaranteed. Note that
// this handles the case in initializers where there is actually a stack
// allocation for it as well.
if (isa<ParamDecl>(DRE->getDecl()) &&
DRE->getDecl()->getFullName() == SGF.getASTContext().Id_self &&
DRE->getDecl()->isImplicit()) {
Ctx = SGFContext::AllowGuaranteedPlusZero;
if (SGF.SelfInitDelegationState != SILGenFunction::NormalSelf) {
// This needs to be inlined since there is a Formal Evaluation Scope
// in emitRValueForDecl that causing any borrow for this LValue to be
// popped too soon.
auto *vd = cast<ParamDecl>(DRE->getDecl());
ManagedValue selfLValue = SGF.emitLValueForDecl(
DRE, vd, DRE->getType()->getCanonicalType(), AccessKind::Read,
DRE->getAccessSemantics());
rv = SGF.emitRValueForSelfInDelegationInit(
e, DRE->getType()->getCanonicalType(),
selfLValue.getLValueAddress(), Ctx)
.getScalarValue();
}
} else if (auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
// All let values are guaranteed to be held alive across their lifetime,
// and won't change once initialized. Any loaded value is good for the
// duration of this expression evaluation.
if (VD->isLet())
Ctx = SGFContext::AllowGuaranteedPlusZero;
}
// First see if we have an lvalue type. If we do, then quickly handle that and
// return.
if (e->getType()->is<LValueType>() || e->getType()->is<InOutType>()) {
auto lv = visit(e, accessKind);
// If necessary, handle reabstraction with a SubstToOrigComponent that
// handles
// writeback in the original representation.
if (orig.isValid()) {
auto &origTL = SGF.getTypeLowering(orig, e->getType()->getRValueType());
if (lv.getTypeOfRValue() != origTL.getLoweredType().getObjectType())
lv.addSubstToOrigComponent(orig,
origTL.getLoweredType().getObjectType());
}
return lv;
}

if (!rv) {
// For an rvalue base, apply the reabstraction (if any) eagerly, since
// there's no need for writeback.
if (orig.isValid())
rv = SGF.emitRValueAsOrig(e, orig,
SGF.getTypeLowering(orig, e->getType()->getRValueType()));
else
rv = SGF.emitRValueAsSingleValue(e, Ctx);
// Otherwise we have a non-lvalue type (references, values, metatypes,
// etc). These act as the root of a logical lvalue.
SGFContext Ctx;
ManagedValue rv;

// Calls through opaque protocols can be done with +0 rvalues. This allows
// us to avoid materializing copies of existentials.
if (SGF.SGM.Types.isIndirectPlusZeroSelfParameter(e->getType()))
Ctx = SGFContext::AllowGuaranteedPlusZero;
else if (auto *DRE = dyn_cast<DeclRefExpr>(e)) {
// Any reference to "self" can be done at +0 so long as it is a direct
// access, since we know it is guaranteed.
// TODO: it would be great to factor this even lower into SILGen to the
// point where we can see that the parameter is +0 guaranteed. Note that
// this handles the case in initializers where there is actually a stack
// allocation for it as well.
if (isa<ParamDecl>(DRE->getDecl()) &&
DRE->getDecl()->getFullName() == SGF.getASTContext().Id_self &&
DRE->getDecl()->isImplicit()) {
Ctx = SGFContext::AllowGuaranteedPlusZero;
if (SGF.SelfInitDelegationState != SILGenFunction::NormalSelf) {
// This needs to be inlined since there is a Formal Evaluation Scope
// in emitRValueForDecl that causing any borrow for this LValue to be
// popped too soon.
auto *vd = cast<ParamDecl>(DRE->getDecl());
ManagedValue selfLValue =
SGF.emitLValueForDecl(DRE, vd, DRE->getType()->getCanonicalType(),
AccessKind::Read, DRE->getAccessSemantics());
rv = SGF.emitRValueForSelfInDelegationInit(
e, DRE->getType()->getCanonicalType(),
selfLValue.getLValueAddress(), Ctx)
.getScalarValue();
}
} else if (auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
// All let values are guaranteed to be held alive across their lifetime,
// and won't change once initialized. Any loaded value is good for the
// duration of this expression evaluation.
if (VD->isLet())
Ctx = SGFContext::AllowGuaranteedPlusZero;
}
CanType formalType = getSubstFormalRValueType(e);
auto typeData = getValueTypeData(formalType, rv.getValue());
LValue lv;
lv.add<ValueComponent>(rv, None, typeData, /*isRValue=*/true);
return lv;
}

auto lv = visit(e, accessKind);
// If necessary, handle reabstraction with a SubstToOrigComponent that handles
// writeback in the original representation.
if (orig.isValid()) {
auto &origTL = SGF.getTypeLowering(orig, e->getType()->getRValueType());
if (lv.getTypeOfRValue() != origTL.getLoweredType().getObjectType())
lv.addSubstToOrigComponent(orig, origTL.getLoweredType().getObjectType());
if (!rv) {
// For an rvalue base, apply the reabstraction (if any) eagerly, since
// there's no need for writeback.
if (orig.isValid())
rv = SGF.emitRValueAsOrig(
e, orig, SGF.getTypeLowering(orig, e->getType()->getRValueType()));
else
rv = SGF.emitRValueAsSingleValue(e, Ctx);
}

CanType formalType = getSubstFormalRValueType(e);
auto typeData = getValueTypeData(formalType, rv.getValue());
LValue lv;
lv.add<ValueComponent>(rv, None, typeData, /*isRValue=*/true);
return lv;
}

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