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//===--- AlwaysEmitConformanceMetadataPreservation.cpp -------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 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
//
//===----------------------------------------------------------------------===//
///
/// Some frameworks may rely on conformances to protocols they provide
/// to be present in binary product they are compiled into even if
/// such conformances are not otherwise referenced in user code.
/// Such conformances may then, for example, be queried and used by the
/// runtime.
///
/// The developer may not ever explicitly reference or instantiate this type in
/// their code, as it is effectively defining an XPC endpoint. However, when
/// optimizations are enabled, the type may be stripped from the binary as it is
/// never referenced. `@_alwaysEmitConformanceMetadata` can be used to mark
/// a protocol to ensure that its conformances are always marked as externally
/// visible even if not `public` to ensure they do not get optimized away.
/// This mandatory pass makes it so.
///
//===----------------------------------------------------------------------===//
#include "swift/AST/Attr.h"
#define DEBUG_TYPE "always-emit-conformance-metadata-preservation"
#include "swift/AST/ASTWalker.h"
#include "swift/AST/NameLookup.h"
#include "swift/AST/ProtocolConformance.h"
#include "swift/AST/SourceFile.h"
#include "swift/SIL/SILModule.h"
#include "swift/SILOptimizer/PassManager/Passes.h"
#include "swift/SILOptimizer/PassManager/Transforms.h"
using namespace swift;
namespace {
/// A helper class to collect all nominal type declarations that conform to
/// `@_alwaysEmitConformanceMetadata` protocols.
class AlwaysEmitMetadataConformanceCollector : public ASTWalker {
std::vector<NominalTypeDecl *> &AlwaysEmitMetadataConformanceDecls;
public:
AlwaysEmitMetadataConformanceCollector(
std::vector<NominalTypeDecl *> &AlwaysEmitMetadataConformanceDecls)
: AlwaysEmitMetadataConformanceDecls(AlwaysEmitMetadataConformanceDecls) {
}
PreWalkAction walkToDeclPre(Decl *D) override {
auto hasAlwaysEmitMetadataConformance =
[&](llvm::PointerUnion<const TypeDecl *, const ExtensionDecl *> Decl) {
bool anyObject = false;
InvertibleProtocolSet Inverses;
for (const auto &found :
getDirectlyInheritedNominalTypeDecls(Decl, Inverses, anyObject))
if (auto Protocol = dyn_cast<ProtocolDecl>(found.Item))
if (Protocol->getAttrs()
.hasAttribute<AlwaysEmitConformanceMetadataAttr>())
return true;
return false;
};
if (auto *NTD = dyn_cast<NominalTypeDecl>(D)) {
if (hasAlwaysEmitMetadataConformance(NTD))
AlwaysEmitMetadataConformanceDecls.push_back(NTD);
} else if (auto *ETD = dyn_cast<ExtensionDecl>(D)) {
if (hasAlwaysEmitMetadataConformance(ETD))
AlwaysEmitMetadataConformanceDecls.push_back(ETD->getExtendedNominal());
}
// Visit peers expanded from macros
D->visitAuxiliaryDecls([&](Decl *decl) { decl->walk(*this); },
/*visitFreestandingExpanded=*/false);
return Action::Continue();
}
};
class AlwaysEmitConformanceMetadataPreservation : public SILModuleTransform {
void run() override {
auto &M = *getModule();
std::vector<NominalTypeDecl *> AlwaysEmitMetadataConformanceDecls;
AlwaysEmitMetadataConformanceCollector Walker(
AlwaysEmitMetadataConformanceDecls);
SmallVector<Decl *> TopLevelDecls;
if (M.getSwiftModule()->isMainModule()) {
if (M.isWholeModule()) {
for (const auto File : M.getSwiftModule()->getFiles())
File->getTopLevelDecls(TopLevelDecls);
} else {
for (const auto Primary : M.getSwiftModule()->getPrimarySourceFiles()) {
Primary->getTopLevelDecls(TopLevelDecls);
// Visit macro expanded extensions
if (auto *synthesizedPrimary = Primary->getSynthesizedFile())
synthesizedPrimary->getTopLevelDecls(TopLevelDecls);
}
}
}
for (auto *TLD : TopLevelDecls)
TLD->walk(Walker);
for (auto &NTD : AlwaysEmitMetadataConformanceDecls)
M.addExternallyVisibleDecl(NTD);
}
};
} // end anonymous namespace
SILTransform *swift::createAlwaysEmitConformanceMetadataPreservation() {
return new AlwaysEmitConformanceMetadataPreservation();
}
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