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SILGenType.cpp
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//===--- SILGenType.cpp - SILGen for types and their members --------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file contains code for emitting code associated with types:
// - methods
// - vtables and vtable thunks
// - witness tables and witness thunks
//
//===----------------------------------------------------------------------===//
#include "ManagedValue.h"
#include "SILGenFunction.h"
#include "SILGenFunctionBuilder.h"
#include "Scope.h"
#include "swift/AST/ASTMangler.h"
#include "swift/AST/GenericEnvironment.h"
#include "swift/AST/PrettyStackTrace.h"
#include "swift/AST/PropertyWrappers.h"
#include "swift/AST/ProtocolConformance.h"
#include "swift/AST/SourceFile.h"
#include "swift/AST/SubstitutionMap.h"
#include "swift/AST/TypeMemberVisitor.h"
#include "swift/SIL/FormalLinkage.h"
#include "swift/SIL/PrettyStackTrace.h"
#include "swift/SIL/SILArgument.h"
#include "swift/SIL/SILVTableVisitor.h"
#include "swift/SIL/SILWitnessVisitor.h"
#include "swift/SIL/TypeLowering.h"
using namespace swift;
using namespace Lowering;
std::optional<SILVTable::Entry>
SILGenModule::emitVTableMethod(ClassDecl *theClass, SILDeclRef derived,
SILDeclRef base) {
assert(base.kind == derived.kind);
auto *baseDecl = cast<AbstractFunctionDecl>(base.getDecl());
auto *derivedDecl = cast<AbstractFunctionDecl>(derived.getDecl());
if (shouldSkipDecl(baseDecl))
return std::nullopt;
// Note: We intentionally don't support extension members here.
//
// Once extensions can override or introduce new vtable entries, this will
// all likely change anyway.
auto *baseClass = cast<ClassDecl>(baseDecl->getDeclContext());
auto *derivedClass = cast<ClassDecl>(derivedDecl->getDeclContext());
// Figure out if the vtable entry comes from the superclass, in which
// case we won't emit it if building a resilient module.
SILVTable::Entry::Kind implKind;
if (baseClass == theClass) {
// This is a vtable entry for a method of the immediate class.
implKind = SILVTable::Entry::Kind::Normal;
} else if (derivedClass == theClass) {
// This is a vtable entry for a method of a base class, but it is being
// overridden in the immediate class.
implKind = SILVTable::Entry::Kind::Override;
} else {
// This vtable entry is copied from the superclass.
implKind = SILVTable::Entry::Kind::Inherited;
// If the override is defined in a class from a different resilience
// domain, don't emit the vtable entry.
if (derivedClass->isResilient(M.getSwiftModule(),
ResilienceExpansion::Maximal)) {
return std::nullopt;
}
}
SILFunction *implFn;
// If the member is dynamic, reference its dynamic dispatch thunk so that
// it will be redispatched, funneling the method call through the runtime
// hook point.
bool usesObjCDynamicDispatch =
(derivedDecl->shouldUseObjCDispatch() &&
derived.kind != SILDeclRef::Kind::Allocator);
if (usesObjCDynamicDispatch) {
implFn = getDynamicThunk(
derived, Types.getConstantInfo(TypeExpansionContext::minimal(), derived)
.SILFnType);
} else if (auto *derivativeId = derived.getDerivativeFunctionIdentifier()) {
// For JVP/VJP methods, create a vtable entry thunk. The thunk contains an
// `differentiable_function` instruction, which is later filled during the
// differentiation transform.
auto derivedFnType =
Types.getConstantInfo(TypeExpansionContext::minimal(), derived)
.SILFnType;
implFn = getOrCreateDerivativeVTableThunk(derived, derivedFnType);
} else {
implFn = getFunction(derived, NotForDefinition);
}
// As a fast path, if there is no override, definitely no thunk is necessary.
if (derived == base)
return SILVTable::Entry(base, implFn, implKind, false);
// If the base method is less visible than the derived method, we need
// a thunk.
bool baseLessVisibleThanDerived =
(!usesObjCDynamicDispatch &&
!derivedDecl->isFinal() &&
derivedDecl->isMoreVisibleThan(baseDecl));
// Determine the derived thunk type by lowering the derived type against the
// abstraction pattern of the base.
auto baseInfo = Types.getConstantInfo(TypeExpansionContext::minimal(), base);
auto derivedInfo =
Types.getConstantInfo(TypeExpansionContext::minimal(), derived);
auto basePattern = AbstractionPattern(baseInfo.LoweredType);
auto overrideInfo = M.Types.getConstantOverrideInfo(
TypeExpansionContext::minimal(), derived, base);
// If base method's generic requirements are not satisfied by the derived
// method then we need a thunk.
using Direction = ASTContext::OverrideGenericSignatureReqCheck;
auto doesNotHaveGenericRequirementDifference =
getASTContext().overrideGenericSignatureReqsSatisfied(
baseDecl, derivedDecl, Direction::BaseReqSatisfiedByDerived);
// The override member type is semantically a subtype of the base
// member type. If the override is ABI compatible, we do not need
// a thunk.
bool compatibleCallingConvention;
switch (M.Types.checkFunctionForABIDifferences(M,
derivedInfo.SILFnType,
overrideInfo.SILFnType)) {
case TypeConverter::ABIDifference::CompatibleCallingConvention:
case TypeConverter::ABIDifference::CompatibleRepresentation:
compatibleCallingConvention = true;
break;
case TypeConverter::ABIDifference::NeedsThunk:
compatibleCallingConvention = false;
break;
case TypeConverter::ABIDifference::CompatibleCallingConvention_ThinToThick:
case TypeConverter::ABIDifference::CompatibleRepresentation_ThinToThick:
llvm_unreachable("shouldn't be thick methods");
}
if (doesNotHaveGenericRequirementDifference
&& !baseLessVisibleThanDerived
&& compatibleCallingConvention)
return SILVTable::Entry(base, implFn, implKind, false);
// Generate the thunk name.
std::string name;
{
Mangle::ASTMangler mangler;
if (isa<FuncDecl>(baseDecl)) {
name = mangler.mangleVTableThunk(
cast<FuncDecl>(baseDecl),
cast<FuncDecl>(derivedDecl));
} else {
name = mangler.mangleConstructorVTableThunk(
cast<ConstructorDecl>(baseDecl),
cast<ConstructorDecl>(derivedDecl),
base.kind == SILDeclRef::Kind::Allocator);
}
// TODO(TF-685): Use proper autodiff thunk mangling.
if (auto *derivativeId = derived.getDerivativeFunctionIdentifier()) {
switch (derivativeId->getKind()) {
case AutoDiffDerivativeFunctionKind::JVP:
name += "_jvp";
break;
case AutoDiffDerivativeFunctionKind::VJP:
name += "_vjp";
break;
}
}
}
// If we already emitted this thunk, reuse it.
if (auto existingThunk = M.lookUpFunction(name))
return SILVTable::Entry(base, existingThunk, implKind, false);
auto *genericEnv = overrideInfo.FormalType.getOptGenericSignature().getGenericEnvironment();
// Emit the thunk.
SILLocation loc(derivedDecl);
SILGenFunctionBuilder builder(*this);
auto thunk = builder.createFunction(
SILLinkage::Private, name, overrideInfo.SILFnType,
genericEnv, loc,
IsBare, IsNotTransparent, IsNotSerialized, IsNotDynamic,
IsNotDistributed, IsNotRuntimeAccessible, ProfileCounter(), IsThunk);
thunk->setDebugScope(new (M) SILDebugScope(loc, thunk));
PrettyStackTraceSILFunction trace("generating vtable thunk", thunk);
SILGenFunction(*this, *thunk, theClass)
.emitVTableThunk(base, derived, implFn, basePattern,
overrideInfo.LoweredType,
derivedInfo.LoweredType,
baseLessVisibleThanDerived);
emitLazyConformancesForFunction(thunk);
return SILVTable::Entry(base, thunk, implKind, false);
}
bool SILGenModule::requiresObjCMethodEntryPoint(FuncDecl *method) {
// Property accessors should be generated alongside the property unless
// the @NSManaged attribute is present.
if (auto accessor = dyn_cast<AccessorDecl>(method)) {
if (accessor->isGetterOrSetter()) {
auto asd = accessor->getStorage();
return asd->isObjC() && !asd->getAttrs().hasAttribute<NSManagedAttr>() &&
!method->isNativeMethodReplacement();
}
}
if (method->getAttrs().hasAttribute<NSManagedAttr>())
return false;
if (!method->isObjC())
return false;
// Don't emit the objective c entry point of @_dynamicReplacement(for:)
// methods in generic classes. There is no way to call it.
return !method->isNativeMethodReplacement();
}
bool SILGenModule::requiresObjCMethodEntryPoint(ConstructorDecl *constructor) {
if (!constructor->isObjC())
return false;
// Don't emit the objective c entry point of @_dynamicReplacement(for:)
// methods in generic classes. There is no way to call it.
return !constructor->isNativeMethodReplacement();
}
namespace {
/// An ASTVisitor for populating SILVTable entries from ClassDecl members.
class SILGenVTable : public SILVTableVisitor<SILGenVTable> {
public:
SILGenModule &SGM;
ClassDecl *theClass;
bool isResilient;
// Map a base SILDeclRef to the corresponding element in vtableMethods.
llvm::DenseMap<SILDeclRef, unsigned> baseToIndexMap;
// For each base method, store the corresponding override.
SmallVector<std::pair<SILDeclRef, SILDeclRef>, 8> vtableMethods;
SILGenVTable(SILGenModule &SGM, ClassDecl *theClass)
: SGM(SGM), theClass(theClass) {
isResilient = theClass->isResilient();
}
void emitVTable() {
PrettyStackTraceDecl("silgen emitVTable", theClass);
// Populate our list of base methods and overrides.
visitAncestor(theClass);
SmallVector<SILVTable::Entry, 8> vtableEntries;
vtableEntries.reserve(vtableMethods.size() + 2);
// For each base method/override pair, emit a vtable thunk or direct
// reference to the method implementation.
for (auto method : vtableMethods) {
SILDeclRef baseRef, derivedRef;
std::tie(baseRef, derivedRef) = method;
auto entry = SGM.emitVTableMethod(theClass, derivedRef, baseRef);
// We might skip emitting entries if the base class is resilient.
if (entry)
vtableEntries.push_back(*entry);
}
// Add the deallocating destructor to the vtable just for the purpose
// that it is referenced and cannot be eliminated by dead function removal.
// In reality, the deallocating destructor is referenced directly from
// the HeapMetadata for the class.
{
auto *dtor = theClass->getDestructor();
SILDeclRef dtorRef(dtor, SILDeclRef::Kind::Deallocator);
auto *dtorFn = SGM.getFunction(dtorRef, NotForDefinition);
vtableEntries.emplace_back(dtorRef, dtorFn,
SILVTable::Entry::Kind::Normal,
false);
}
if (SGM.requiresIVarDestroyer(theClass)) {
SILDeclRef dtorRef(theClass, SILDeclRef::Kind::IVarDestroyer);
auto *dtorFn = SGM.getFunction(dtorRef, NotForDefinition);
vtableEntries.emplace_back(dtorRef, dtorFn,
SILVTable::Entry::Kind::Normal,
false);
}
SerializedKind_t serialized = IsNotSerialized;
auto classIsPublic = theClass->getEffectiveAccess() >= AccessLevel::Public;
// Only public, fixed-layout classes should have serialized vtables.
if (classIsPublic && !isResilient)
serialized = IsSerialized;
// Finally, create the vtable.
SILVTable::create(SGM.M, theClass, serialized, vtableEntries);
}
void visitAncestor(ClassDecl *ancestor) {
// Imported types don't have vtables right now.
if (ancestor->hasClangNode())
return;
auto *superDecl = ancestor->getSuperclassDecl();
if (superDecl)
visitAncestor(superDecl);
addVTableEntries(ancestor);
}
// Try to find an overridden entry.
void addMethodOverride(SILDeclRef baseRef, SILDeclRef declRef) {
auto found = baseToIndexMap.find(baseRef);
assert(found != baseToIndexMap.end());
auto &method = vtableMethods[found->second];
assert(method.first == baseRef);
method.second = declRef;
}
// Add an entry to the vtable.
void addMethod(SILDeclRef member) {
unsigned index = vtableMethods.size();
vtableMethods.push_back(std::make_pair(member, member));
auto result = baseToIndexMap.insert(std::make_pair(member, index));
assert(result.second);
(void) result;
}
void addPlaceholder(MissingMemberDecl *m) {
#ifndef NDEBUG
auto *classDecl = cast<ClassDecl>(m->getDeclContext());
bool isResilient =
classDecl->isResilient(SGM.M.getSwiftModule(),
ResilienceExpansion::Maximal);
assert(isResilient || m->getNumberOfVTableEntries() == 0 &&
"Should not be emitting fragile class with missing members");
#endif
}
};
} // end anonymous namespace
static void emitTypeMemberGlobalVariable(SILGenModule &SGM,
VarDecl *var) {
if (var->getDeclContext()->isGenericContext()) {
assert(var->getDeclContext()->getGenericSignatureOfContext()
->areAllParamsConcrete()
&& "generic static vars are not implemented yet");
}
if (var->getDeclContext()->getSelfClassDecl()) {
assert(var->isFinal() && "only 'static' ('class final') stored properties are implemented in classes");
}
SGM.addGlobalVariable(var);
}
namespace {
// Is this a free function witness satisfying a static method requirement?
static IsFreeFunctionWitness_t isFreeFunctionWitness(ValueDecl *requirement,
ValueDecl *witness) {
if (!witness->getDeclContext()->isTypeContext()) {
assert(!requirement->isInstanceMember()
&& "free function satisfying instance method requirement?!");
return IsFreeFunctionWitness;
}
return IsNotFreeFunctionWitness;
}
/// A CRTP class for emitting witness thunks for the requirements of a
/// protocol.
///
/// There are two subclasses:
///
/// - SILGenConformance: emits witness thunks for a conformance of a
/// a concrete type to a protocol
/// - SILGenDefaultWitnessTable: emits default witness thunks for
/// default implementations of protocol requirements
///
template<typename T> class SILGenWitnessTable : public SILWitnessVisitor<T> {
T &asDerived() { return *static_cast<T*>(this); }
public:
void addMethod(SILDeclRef requirementRef) {
// TODO: here the requirement is thunk_decl of the protocol; it is a FUNC
// detect here that it is a func dec + thunk.
// walk up to DC, and find storage.
// e requirementRef->getDecl()->dump()
//(func_decl implicit "distributedVariable()" interface type="<Self where Self : WorkerProtocol> (Self) -> () async throws -> String" access=internal nonisolated distributed_thunk
// (parameter "self")
// (parameter_list))
auto reqDecl = requirementRef.getDecl();
// Static functions can be witnessed by enum cases with payload
if (!(isa<AccessorDecl>(reqDecl) || isa<ConstructorDecl>(reqDecl))) {
auto FD = cast<FuncDecl>(reqDecl);
if (auto witness = asDerived().getWitness(FD)) {
if (auto EED = dyn_cast<EnumElementDecl>(witness.getDecl())) {
return addMethodImplementation(
requirementRef, SILDeclRef(EED, SILDeclRef::Kind::EnumElement),
witness);
}
}
}
auto reqAccessor = dyn_cast<AccessorDecl>(reqDecl);
/// If it is an accessor, or distributed_thunk that is witnessing an
/// accessor, we need to use the storage to get the witness.
ValueDecl *storage = nullptr;
// If it's not an accessor, just look for the witness.
if (!reqAccessor) {
if (!storage) {
if (auto witness = asDerived().getWitness(reqDecl)) {
auto newDecl = requirementRef.withDecl(witness.getDecl());
// Only import C++ methods as foreign. If the following
// Objective-C function is imported as foreign:
// () -> String
// It will be imported as the following type:
// () -> NSString
// But the first is correct, so make sure we don't mark this witness
// as foreign.
if (dyn_cast_or_null<clang::CXXMethodDecl>(
witness.getDecl()->getClangDecl()))
newDecl = newDecl.asForeign();
return addMethodImplementation(
requirementRef, getWitnessRef(newDecl, witness), witness);
}
return asDerived().addMissingMethod(requirementRef);
} // else, fallthrough to the usual accessor handling!
} else {
// Otherwise, we need to map the storage declaration and then get
// the appropriate accessor for it.
storage = reqAccessor->getStorage();
}
auto witness = asDerived().getWitness(storage);
if (!witness)
return asDerived().addMissingMethod(requirementRef);
// Static properties can be witnessed by enum cases without payload
if (auto EED = dyn_cast<EnumElementDecl>(witness.getDecl())) {
return addMethodImplementation(
requirementRef, SILDeclRef(EED, SILDeclRef::Kind::EnumElement),
witness);
}
auto witnessStorage = cast<AbstractStorageDecl>(witness.getDecl());
if (reqAccessor->isSetter() && !witnessStorage->supportsMutation()) {
return asDerived().addMissingMethod(requirementRef);
}
// Here we notice a `distributed var` thunk requirement,
// and witness it with the distributed thunk -- the "getter thunk".
if (requirementRef.isDistributedThunk()) {
return addMethodImplementation(
requirementRef, getWitnessRef(requirementRef, witnessStorage->getDistributedThunk()),
witness);
}
auto witnessAccessor =
witnessStorage->getSynthesizedAccessor(reqAccessor->getAccessorKind());
return addMethodImplementation(
requirementRef, getWitnessRef(requirementRef, witnessAccessor),
witness);
}
private:
void addMethodImplementation(SILDeclRef requirementRef,
SILDeclRef witnessRef,
Witness witness) {
// Free function witnesses have an implicit uncurry layer imposed on them by
// the inserted metatype argument.
auto isFree =
isFreeFunctionWitness(requirementRef.getDecl(), witnessRef.getDecl());
asDerived().addMethodImplementation(requirementRef, witnessRef,
isFree, witness);
}
SILDeclRef getWitnessRef(SILDeclRef requirementRef, Witness witness) {
auto witnessRef = requirementRef.withDecl(witness.getDecl());
// If the requirement/witness is a derivative function, we need to
// substitute the witness's derivative generic signature in its derivative
// function identifier.
if (requirementRef.isAutoDiffDerivativeFunction()) {
auto *reqrDerivativeId = requirementRef.getDerivativeFunctionIdentifier();
auto *witnessDerivativeId = AutoDiffDerivativeFunctionIdentifier::get(
reqrDerivativeId->getKind(), reqrDerivativeId->getParameterIndices(),
witness.getDerivativeGenericSignature(), witnessRef.getASTContext());
witnessRef = witnessRef.asAutoDiffDerivativeFunction(witnessDerivativeId);
}
return witnessRef;
}
};
static SerializedKind_t getConformanceSerializedKind(RootProtocolConformance *conf) {
return SILWitnessTable::conformanceSerializedKind(conf);
}
/// Emit a witness table for a protocol conformance.
class SILGenConformance : public SILGenWitnessTable<SILGenConformance> {
using super = SILGenWitnessTable<SILGenConformance>;
public:
SILGenModule &SGM;
NormalProtocolConformance *Conformance;
std::vector<SILWitnessTable::Entry> Entries;
std::vector<SILWitnessTable::ConditionalConformance> ConditionalConformances;
SILLinkage Linkage;
SerializedKind_t SerializedKind;
SILGenConformance(SILGenModule &SGM, NormalProtocolConformance *C)
: SGM(SGM), Conformance(C),
Linkage(getLinkageForProtocolConformance(Conformance,
ForDefinition)),
SerializedKind(getConformanceSerializedKind(Conformance))
{
auto *proto = Conformance->getProtocol();
// Not all protocols use witness tables; in this case we just skip
// all of emit() below completely.
if (!Lowering::TypeConverter::protocolRequiresWitnessTable(proto))
Conformance = nullptr;
}
SILWitnessTable *emit() {
// Nothing to do if this wasn't a normal conformance.
if (!Conformance)
return nullptr;
PrettyStackTraceConformance trace("generating SIL witness table",
Conformance);
Conformance->resolveValueWitnesses();
auto *proto = Conformance->getProtocol();
visitProtocolDecl(proto);
addConditionalRequirements();
// Check if we already have a declaration or definition for this witness
// table.
if (auto *wt = SGM.M.lookUpWitnessTable(Conformance)) {
// If we have a definition already, just return it.
//
// FIXME: I am not sure if this is possible, if it is not change this to an
// assert.
if (wt->isDefinition())
return wt;
// If we have a declaration, convert the witness table to a definition.
if (wt->isDeclaration()) {
wt->convertToDefinition(Entries, ConditionalConformances, SerializedKind);
// Since we had a declaration before, its linkage should be external,
// ensure that we have a compatible linkage for soundness. *NOTE* we are ok
// with both being shared since we do not have a shared_external
// linkage.
assert(stripExternalFromLinkage(wt->getLinkage()) == Linkage &&
"Witness table declaration has inconsistent linkage with"
" silgen definition.");
// And then override the linkage with the new linkage.
wt->setLinkage(Linkage);
return wt;
}
}
// Otherwise if we have no witness table yet, create it.
return SILWitnessTable::create(SGM.M, Linkage, SerializedKind, Conformance,
Entries, ConditionalConformances);
}
void addProtocolConformanceDescriptor() {
}
void addOutOfLineBaseProtocol(ProtocolDecl *baseProtocol) {
assert(Lowering::TypeConverter::protocolRequiresWitnessTable(baseProtocol));
auto conformance = Conformance->getInheritedConformance(baseProtocol);
Entries.push_back(SILWitnessTable::BaseProtocolWitness{
baseProtocol,
conformance,
});
// Emit the witness table for the base conformance if it is shared.
SGM.useConformance(ProtocolConformanceRef(conformance));
}
Witness getWitness(ValueDecl *decl) {
return Conformance->getWitness(decl);
}
// Treat placeholders and missing methods as no-ops. These may be encountered
// during lazy typechecking when SILGen triggers witness resolution and
// discovers and invalid conformance. The diagnostics emitted during witness
// resolution should cause compilation to fail.
void addPlaceholder(MissingMemberDecl *placeholder) {}
void addMissingMethod(SILDeclRef requirement) {}
void addMethodImplementation(SILDeclRef requirementRef,
SILDeclRef witnessRef,
IsFreeFunctionWitness_t isFree,
Witness witness) {
// Emit the witness thunk and add it to the table.
auto witnessLinkage = witnessRef.getLinkage(ForDefinition);
auto witnessSerializedKind = SerializedKind;
if (witnessSerializedKind != IsNotSerialized &&
// If package optimization is enabled, this is false;
// witness thunk should get a `shared` linkage in the
// else block below.
fixmeWitnessHasLinkageThatNeedsToBePublic(
witnessRef,
witnessRef.getASTContext().SILOpts.EnableSerializePackage)) {
witnessLinkage = SILLinkage::Public;
witnessSerializedKind = IsNotSerialized;
} else {
// This is the "real" rule; the above case should go away once we
// figure out what's going on.
// Normally witness thunks can be private.
witnessLinkage = SILLinkage::Private;
// Unless the witness table is going to be serialized.
if (witnessSerializedKind != IsNotSerialized)
witnessLinkage = SILLinkage::Shared;
// Or even if its not serialized, it might be for an imported
// conformance in which case it can be emitted multiple times.
if (Linkage == SILLinkage::Shared)
witnessLinkage = SILLinkage::Shared;
}
if (isa<EnumElementDecl>(witnessRef.getDecl())) {
assert(witnessRef.isEnumElement() && "Witness decl, but different kind?");
}
SILFunction *witnessFn = SGM.emitProtocolWitness(
ProtocolConformanceRef(Conformance), witnessLinkage, witnessSerializedKind,
requirementRef, witnessRef, isFree, witness);
Entries.push_back(
SILWitnessTable::MethodWitness{requirementRef, witnessFn});
}
void addAssociatedType(AssociatedType requirement) {
// Find the substitution info for the witness type.
auto td = requirement.getAssociation();
Type witness = Conformance->getTypeWitness(td);
// Emit the record for the type itself.
Entries.push_back(SILWitnessTable::AssociatedTypeWitness{td,
witness->getCanonicalType()});
}
void addAssociatedConformance(AssociatedConformance req) {
auto assocConformance =
Conformance->getAssociatedConformance(req.getAssociation(),
req.getAssociatedRequirement());
SGM.useConformance(assocConformance);
Entries.push_back(SILWitnessTable::AssociatedTypeProtocolWitness{
req.getAssociation(), req.getAssociatedRequirement(),
assocConformance});
}
void addConditionalRequirements() {
SILWitnessTable::enumerateWitnessTableConditionalConformances(
Conformance, [&](unsigned, CanType type, ProtocolDecl *protocol) {
auto conformance =
Conformance->getGenericSignature()->lookupConformance(type,
protocol);
assert(conformance &&
"unable to find conformance that should be known");
ConditionalConformances.push_back(
SILWitnessTable::ConditionalConformance{type, conformance});
return /*finished?*/ false;
});
}
};
} // end anonymous namespace
SILWitnessTable *
SILGenModule::getWitnessTable(NormalProtocolConformance *conformance) {
// If we've already emitted this witness table, return it.
auto found = emittedWitnessTables.find(conformance);
if (found != emittedWitnessTables.end())
return found->second;
SILWitnessTable *table = SILGenConformance(*this, conformance).emit();
emittedWitnessTables.insert({conformance, table});
return table;
}
SILFunction *SILGenModule::emitProtocolWitness(
ProtocolConformanceRef conformance, SILLinkage linkage,
SerializedKind_t serializedKind, SILDeclRef requirement,
SILDeclRef witnessRef, IsFreeFunctionWitness_t isFree, Witness witness) {
auto requirementInfo =
Types.getConstantInfo(TypeExpansionContext::minimal(), requirement);
auto shouldUseDistributedThunkWitness =
// always use a distributed thunk for distributed requirements:
requirement.isDistributedThunk() ||
// for non-distributed requirements, which are however async/throws,
// and have a proper witness (passed typechecking), we can still invoke
// them on the distributed actor; but must do so through the distributed
// thunk as the call "through an existential" we never statically know
// if the actor is local or not.
(requirement.hasDecl() && requirement.getFuncDecl() && requirement.hasAsync() &&
!requirement.getFuncDecl()->isDistributed() &&
witnessRef.hasDecl() && witnessRef.getFuncDecl() &&
witnessRef.getFuncDecl()->isDistributed());
if (shouldUseDistributedThunkWitness) {
// we may not have a thunk if we're in a protocol?
if (auto thunk = witnessRef.getFuncDecl()->getDistributedThunk()) {
auto thunkDeclRef = SILDeclRef(thunk, SILDeclRef::Kind::Func);
witnessRef = thunkDeclRef.asDistributed();
}
}
// Work out the lowered function type of the SIL witness thunk.
auto reqtOrigTy = cast<GenericFunctionType>(requirementInfo.LoweredType);
// Mapping from the requirement's generic signature to the witness
// thunk's generic signature.
auto reqtSubMap = witness.getRequirementToWitnessThunkSubs();
// The generic environment for the witness thunk.
auto *genericEnv = witness.getWitnessThunkSignature().getGenericEnvironment();
auto genericSig = witness.getWitnessThunkSignature().getCanonicalSignature();
// The type of the witness thunk.
auto reqtSubstTy = cast<AnyFunctionType>(
reqtOrigTy->substGenericArgs(reqtSubMap)
->getReducedType(genericSig));
// Generic signatures where all parameters are concrete are lowered away
// at the SILFunctionType level.
if (genericSig && genericSig->areAllParamsConcrete()) {
genericSig = nullptr;
genericEnv = nullptr;
}
// Rewrite the conformance in terms of the requirement environment's Self
// type, which might have a different generic signature than the type
// itself.
//
// For example, if the conforming type is a class and the witness is defined
// in a protocol extension, the generic signature will have an additional
// generic parameter representing Self, so the generic parameters of the
// class will all be shifted down by one.
if (reqtSubMap) {
auto requirement = conformance.getRequirement();
auto self = requirement->getSelfInterfaceType()->getCanonicalType();
conformance = reqtSubMap.lookupConformance(self, requirement);
}
reqtSubstTy =
CanAnyFunctionType::get(genericSig,
reqtSubstTy->getParams(),
reqtSubstTy.getResult(),
reqtSubstTy->getExtInfo());
// Coroutine lowering requires us to provide these substitutions
// in order to recreate the appropriate yield types for the accessor
// because they aren't reflected in the accessor's AST type.
// But this is expensive, so we only do it for coroutine lowering.
// When they're part of the AST function type, we can remove this
// parameter completely.
std::optional<SubstitutionMap> witnessSubsForTypeLowering;
if (auto accessor = dyn_cast<AccessorDecl>(requirement.getDecl())) {
if (accessor->isCoroutine()) {
witnessSubsForTypeLowering =
witness.getSubstitutions().mapReplacementTypesOutOfContext();
}
}
// Lower the witness thunk type with the requirement's abstraction level.
auto witnessSILFnType = getNativeSILFunctionType(
M.Types, TypeExpansionContext::minimal(), AbstractionPattern(reqtOrigTy),
reqtSubstTy, requirementInfo.SILFnType->getExtInfo(), requirement,
witnessRef, witnessSubsForTypeLowering, conformance);
// Mangle the name of the witness thunk.
Mangle::ASTMangler NewMangler;
auto manglingConformance =
conformance.isConcrete() ? conformance.getConcrete() : nullptr;
std::string nameBuffer =
NewMangler.mangleWitnessThunk(manglingConformance, requirement.getDecl());
// TODO(TF-685): Proper mangling for derivative witness thunks.
if (auto *derivativeId = requirement.getDerivativeFunctionIdentifier()) {
std::string kindString;
switch (derivativeId->getKind()) {
case AutoDiffDerivativeFunctionKind::JVP:
kindString = "jvp";
break;
case AutoDiffDerivativeFunctionKind::VJP:
kindString = "vjp";
break;
}
nameBuffer = "AD__" + nameBuffer + "_" + kindString + "_" +
derivativeId->getParameterIndices()->getString();
}
if (requirement.isDistributedThunk()) {
nameBuffer = nameBuffer + "TE";
}
// If the thunked-to function is set to be always inlined, do the
// same with the witness, on the theory that the user wants all
// calls removed if possible, e.g. when we're able to devirtualize
// the witness method call. Otherwise, use the default inlining
// setting on the theory that forcing inlining off should only
// effect the user's function, not otherwise invisible thunks.
Inline_t InlineStrategy = InlineDefault;
if (witnessRef.isAlwaysInline())
InlineStrategy = AlwaysInline;
SILGenFunctionBuilder builder(*this);
auto *f = builder.createFunction(
linkage, nameBuffer, witnessSILFnType, genericEnv,
SILLocation(witnessRef.getDecl()), IsNotBare, IsTransparent, serializedKind,
IsNotDynamic, IsNotDistributed, IsNotRuntimeAccessible, ProfileCounter(),
IsThunk, SubclassScope::NotApplicable, InlineStrategy);
f->setDebugScope(new (M)
SILDebugScope(RegularLocation(witnessRef.getDecl()), f));
PrettyStackTraceSILFunction trace("generating protocol witness thunk", f);
// Create the witness.
SILGenFunction SGF(*this, *f, SwiftModule);
// Substitutions mapping the generic parameters of the witness to
// archetypes of the witness thunk generic environment.
auto witnessSubs = witness.getSubstitutions();
// If the conformance is marked as `@preconcurrency` instead of
// emitting a hop to the executor (when needed) emit a dynamic check
// to make sure that witness has been unsed in the expected context.
bool isPreconcurrency = false;
if (conformance.isConcrete()) {
if (auto *C =
dyn_cast<NormalProtocolConformance>(conformance.getConcrete()))
isPreconcurrency = C->isPreconcurrency();
}
SGF.emitProtocolWitness(AbstractionPattern(reqtOrigTy), reqtSubstTy,
requirement, reqtSubMap, witnessRef,
witnessSubs, isFree,
/*isSelfConformance*/ false,
isPreconcurrency,
witness.getEnterIsolation());
emitLazyConformancesForFunction(f);
return f;
}
namespace {
static SILFunction *emitSelfConformanceWitness(SILGenModule &SGM,
SelfProtocolConformance *conformance,
SILLinkage linkage,
SILDeclRef requirement) {
auto requirementInfo =
SGM.Types.getConstantInfo(TypeExpansionContext::minimal(), requirement);
// Work out the lowered function type of the SIL witness thunk.
auto reqtOrigTy = cast<GenericFunctionType>(requirementInfo.LoweredType);
// The transformations we do here don't work for generic requirements.
GenericEnvironment *genericEnv = nullptr;
// A mapping from the requirement's generic signature to the type parameters
// of the witness thunk (which is non-generic).
auto protocol = conformance->getProtocol();
auto protocolType = protocol->getDeclaredInterfaceType();
auto reqtSubs = SubstitutionMap::getProtocolSubstitutions(protocol,
protocolType,
ProtocolConformanceRef(conformance));
// Open the protocol type.
auto openedType = OpenedArchetypeType::get(
protocol->getDeclaredExistentialType()->getCanonicalType(),
GenericSignature());
// Form the substitutions for calling the witness.
auto witnessSubs = SubstitutionMap::getProtocolSubstitutions(protocol,
openedType,
ProtocolConformanceRef(protocol));
// Substitute to get the formal substituted type of the thunk.
auto reqtSubstTy =
cast<AnyFunctionType>(reqtOrigTy.subst(reqtSubs)->getCanonicalType());
// Substitute into the requirement type to get the type of the thunk.
auto witnessSILFnType = requirementInfo.SILFnType->substGenericArgs(
SGM.M, reqtSubs, TypeExpansionContext::minimal());
// Mangle the name of the witness thunk.
std::string name = [&] {
Mangle::ASTMangler mangler;
return mangler.mangleWitnessThunk(conformance, requirement.getDecl());
}();
SILGenFunctionBuilder builder(SGM);
auto *f = builder.createFunction(
linkage, name, witnessSILFnType, genericEnv,
SILLocation(requirement.getDecl()), IsNotBare, IsTransparent,
IsSerialized, IsNotDynamic, IsNotDistributed, IsNotRuntimeAccessible,
ProfileCounter(), IsThunk, SubclassScope::NotApplicable, InlineDefault);
f->setDebugScope(new (SGM.M)
SILDebugScope(RegularLocation(requirement.getDecl()), f));
PrettyStackTraceSILFunction trace("generating protocol witness thunk", f);
// Create the witness.
SILGenFunction SGF(SGM, *f, SGM.SwiftModule);
auto isFree = isFreeFunctionWitness(requirement.getDecl(),
requirement.getDecl());
SGF.emitProtocolWitness(AbstractionPattern(reqtOrigTy), reqtSubstTy,
requirement, reqtSubs, requirement, witnessSubs,
isFree, /*isSelfConformance*/ true,
/*isPreconcurrency*/ false, std::nullopt);
SGM.emitLazyConformancesForFunction(f);
return f;
}
/// Emit a witness table for a self-conformance.
class SILGenSelfConformanceWitnessTable
: public SILWitnessVisitor<SILGenSelfConformanceWitnessTable> {
using super = SILWitnessVisitor<SILGenSelfConformanceWitnessTable>;
SILGenModule &SGM;
SelfProtocolConformance *conformance;
SILLinkage linkage;
SerializedKind_t serialized;
SmallVector<SILWitnessTable::Entry, 8> entries;
public:
SILGenSelfConformanceWitnessTable(SILGenModule &SGM,
SelfProtocolConformance *conformance)
: SGM(SGM), conformance(conformance),
linkage(getLinkageForProtocolConformance(conformance, ForDefinition)),
serialized(getConformanceSerializedKind(conformance)) {
}
void emit() {
PrettyStackTraceConformance trace("generating SIL witness table",
conformance);
// Add entries for all the requirements.
visitProtocolDecl(conformance->getProtocol());
// Create the witness table.
(void) SILWitnessTable::create(SGM.M, linkage, serialized, conformance,
entries, /*conditional*/ {});
}
void addProtocolConformanceDescriptor() {}
void addOutOfLineBaseProtocol(ProtocolDecl *protocol) {
// This is an unnecessary restriction that's just not necessary for Error.
llvm_unreachable("base protocols not supported in self-conformance");
}