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[Devirtualizer] Handle default witnesses for generic requirements. #5571

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Merged
merged 1 commit into from
Nov 1, 2016
Merged

[Devirtualizer] Handle default witnesses for generic requirements. #5571

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48 changes: 28 additions & 20 deletions lib/SILOptimizer/Utils/Devirtualize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -791,6 +791,7 @@ static void getWitnessMethodSubstitutions(
GenericSignature *requirementSig,
GenericSignature *witnessThunkSig,
ArrayRef<Substitution> origSubs,
bool isDefaultWitness,
SmallVectorImpl<Substitution> &newSubs) {

if (witnessThunkSig == nullptr)
Expand All @@ -806,19 +807,28 @@ static void getWitnessMethodSubstitutions(
SubstitutionMap subMap;

// Take apart substitutions from the conforming type.
//
// If `Self` maps to a bound generic type, this gives us the
// substitutions for the concrete type's generic parameters.
auto witnessSubs = getSubstitutionsForProtocolConformance(conformanceRef);

ArrayRef<Substitution> witnessSubs;
auto *rootConformance = conformance->getRootNormalConformance();
auto *witnessSig = rootConformance->getGenericSignature();
unsigned depth = 0;
if (!witnessSubs.empty()) {
auto *rootConformance = conformance->getRootNormalConformance();
depth = rootConformance->getGenericSignature()->getGenericParams().back()
->getDepth() + 1;
auto *witnessSig = rootConformance->getGenericSignature();
if (isDefaultWitness) {
// For default witnesses, we substitute all of Self.
auto gp = witnessThunkSig->getGenericParams().front()->getCanonicalType();
subMap.addSubstitution(gp, origSubs.front().getReplacement());
subMap.addConformances(gp, origSubs.front().getConformances());

// For default witnesses, innermost generic parameters are always at
// depth 1.
depth = 1;
} else {
// If `Self` maps to a bound generic type, this gives us the
// substitutions for the concrete type's generic parameters.
witnessSubs = getSubstitutionsForProtocolConformance(conformanceRef);

witnessSig->getSubstitutionMap(witnessSubs, subMap);
if (!witnessSubs.empty()) {
witnessSig->getSubstitutionMap(witnessSubs, subMap);
depth = witnessSig->getGenericParams().back()->getDepth() + 1;
}
}

// Next, take apart caller-side substitutions.
Expand Down Expand Up @@ -890,17 +900,15 @@ static void getWitnessMethodSubstitutions(ApplySite AI, SILFunction *F,

ArrayRef<Substitution> origSubs = AI.getSubstitutions();

if (F->getLoweredFunctionType()->getRepresentation()
== SILFunctionTypeRepresentation::WitnessMethod &&
F->getLoweredFunctionType()->getDefaultWitnessMethodProtocol(
*Module.getSwiftModule())) {
// Default witness thunks use the generic signature of the requirement.
NewSubs.append(origSubs.begin(), origSubs.end());
return;
}
bool isDefaultWitness =
F->getLoweredFunctionType()->getRepresentation()
== SILFunctionTypeRepresentation::WitnessMethod &&
F->getLoweredFunctionType()->getDefaultWitnessMethodProtocol(
*Module.getSwiftModule())
== CRef.getRequirement();

getWitnessMethodSubstitutions(Module, CRef, requirementSig, witnessThunkSig,
origSubs, NewSubs);
origSubs, isDefaultWitness, NewSubs);
}

/// Check if an upcast is legal.
Expand Down
39 changes: 39 additions & 0 deletions test/SILOptimizer/devirt_default_witness_method.sil
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,10 @@ import Builtin
import Swift
import SwiftShims

public protocol P { }
public protocol Q : P { }
extension Int : P, Q { }

public protocol ResilientProtocol {
func defaultA()
}
Expand Down Expand Up @@ -35,6 +39,28 @@ sil_witness_table <T> ConformingGenericStruct<T> : ResilientProtocol module prot
method #ResilientProtocol.defaultA!1: @defaultA
}

public protocol ResilientProtocolWithGeneric {
func defaultB<T: Q>(_: T)
}

sil @defaultB : $@convention(witness_method) <Self where Self : ResilientProtocolWithGeneric><T where T : P> (@in T, @in_guaranteed Self) -> () {
bb0(%0 : $*T, %1 : $*Self):
%result = tuple ()
return %result : $()
}

sil_default_witness_table ResilientProtocolWithGeneric {
method #ResilientProtocolWithGeneric.defaultB!1: @defaultB
}

extension ConformingGenericStruct : ResilientProtocolWithGeneric {
func defaultB<T>(_: T)
}

sil_witness_table <T> ConformingGenericStruct<T> : ResilientProtocolWithGeneric module protocol_resilience {
method #ResilientProtocolWithGeneric.defaultB!1: @defaultB
}

// CHECK-LABEL: sil hidden @test_devirt_of_default_witness_method : $@convention(thin) (@in_guaranteed ConformingStruct) -> ()
// CHECK: bb0(%0 : $*ConformingStruct):
// CHECK: [[FN:%.*]] = function_ref @defaultA : $@convention(witness_method) <τ_0_0 where τ_0_0 : ResilientProtocol> (@in_guaranteed τ_0_0) -> ()
Expand All @@ -60,3 +86,16 @@ bb0(%0 : $*ConformingGenericStruct<Int>):
%result = apply %fn<ConformingGenericStruct<Int>>(%0) : $@convention(witness_method) <T where T : ResilientProtocol> (@in_guaranteed T) -> ()
return %result : $()
}

// CHECK-LABEL: test_devirt_of_inner_generic_default_witness_method
// CHECK: bb0(%0 : $*ConformingGenericStruct<Int>, %1 : $*Int):
// CHECK: [[FN:%[0-9]+]] = function_ref @defaultB : $@convention(witness_method) <τ_0_0 where τ_0_0 : ResilientProtocolWithGeneric><τ_1_0 where τ_1_0 : P> (@in τ_1_0, @in_guaranteed τ_0_0) -> ()
// CHECK: [[RESULT:%[0-9]+]] = apply [[FN]]<ConformingGenericStruct<Int>, Int>(%1, %0) : $@convention(witness_method) <τ_0_0 where τ_0_0 : ResilientProtocolWithGeneric><τ_1_0 where τ_1_0 : P> (@in τ_1_0, @in_guaranteed τ_0_0) -> ()
// CHECK: return [[RESULT]] : $()
// CHECK: }
sil hidden @test_devirt_of_inner_generic_default_witness_method : $@convention(thin) (@in_guaranteed ConformingGenericStruct<Int>, @in Int) -> () {
bb0(%0 : $*ConformingGenericStruct<Int>, %1 : $*Int):
%fn = witness_method $ConformingGenericStruct<Int>, #ResilientProtocolWithGeneric.defaultB!1 : $@convention(witness_method) <T where T : ResilientProtocolWithGeneric><U where U : Q> (@in U, @in_guaranteed T) -> ()
%result = apply %fn<ConformingGenericStruct<Int>, Int>(%1, %0) : $@convention(witness_method) <T where T : ResilientProtocolWithGeneric><U where U : Q> (@in U, @in_guaranteed T) -> ()
return %result : $()
}