Back-deploy creation of global-actor-qualified function type metadata.

When back-deploying, create global-actor-qualified function types via a
separate entrypoint
(`swift_getFunctionTypeMetadataGlobalActorBackDeploy`) in the
compatibility library, which checks whether it is running with a
new-enough runtime to use `swift_getFunctionTypeMetadataGlobalActor`.
Failing that, it calls into a separate copy of the implementation that
exists only in the back-deployed concurrency library.

Fixes rdar://79153988.

include/swift/Runtime/RuntimeFunctions.def

@@ -634,6 +634,24 @@ FUNCTION(GetFunctionMetadataGlobalActor,
               TypeMetadataPtrTy),
          ATTRS(NoUnwind, ReadOnly))
 
+// Metadata *
+// swift_getFunctionTypeMetadataGlobalActorBackDeploy(unsigned long flags,
+//                                                    unsigned long diffKind,
+//                                               const Metadata **parameters,
+//                                               const uint32_t *parameterFlags,
+//                                               const Metadata *result,
+//                                               const Metadata *globalActor);
+FUNCTION(GetFunctionMetadataGlobalActorBackDeploy,
+         swift_getFunctionTypeMetadataGlobalActorBackDeploy,
+         C_CC, OpaqueTypeAvailability,
+         RETURNS(TypeMetadataPtrTy),
+         ARGS(SizeTy,
+              SizeTy,
+              TypeMetadataPtrTy->getPointerTo(0),
+              Int32Ty->getPointerTo(0),
+              TypeMetadataPtrTy,
+              TypeMetadataPtrTy),
+         ATTRS(NoUnwind, ReadOnly))
 
 // Metadata *swift_getFunctionTypeMetadata0(unsigned long flags,
 //                                          const Metadata *resultMetadata);

lib/IRGen/MetadataRequest.cpp

@@ -1230,6 +1230,13 @@ static MetadataResponse emitTupleTypeMetadataRef(IRGenFunction &IGF,
   }
 }
 
+/// Determine whether concurrency support is available in the runtime.
+static bool isConcurrencyAvailable(ASTContext &ctx) {
+  auto deploymentAvailability =
+    AvailabilityContext::forDeploymentTarget(ctx);
+  return deploymentAvailability.isContainedIn(ctx.getConcurrencyAvailability());
+}
+
 namespace {
   /// A visitor class for emitting a reference to a metatype object.
   /// This implements a "raw" access, useful for implementing cache
@@ -1591,7 +1598,9 @@ namespace {
         }
 
         auto *getMetadataFn = type->getGlobalActor()
-            ? IGF.IGM.getGetFunctionMetadataGlobalActorFn()
+            ? (isConcurrencyAvailable(IGF.getSwiftModule()->getASTContext())
+               ? IGF.IGM.getGetFunctionMetadataGlobalActorFn()
+               : IGF.IGM.getGetFunctionMetadataGlobalActorBackDeployFn())
             : type->isDifferentiable()
               ? IGF.IGM.getGetFunctionMetadataDifferentiableFn()
               : IGF.IGM.getGetFunctionMetadataFn();

stdlib/public/BackDeployConcurrency/CMakeLists.txt

@@ -43,6 +43,8 @@ set(swift_concurrency_install_component back-deployment)
 set(swift_concurrency_options
   BACK_DEPLOYMENT_LIBRARY 5.5
   DARWIN_INSTALL_NAME_DIR "@rpath")
-set(swift_concurrency_extra_sources "../BackDeployConcurrency/Exclusivity.cpp")
+set(swift_concurrency_extra_sources
+  "../BackDeployConcurrency/Exclusivity.cpp"
+  "../BackDeployConcurrency/Metadata.cpp")
 
 add_subdirectory(../Concurrency stdlib/public/BackDeployConcurrency)

stdlib/public/BackDeployConcurrency/Metadata.cpp

@@ -0,0 +1,255 @@
+//===--- Metadata.cpp - Exclusivity tracking ------------------------------===//
+//
+// 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 implements the runtime support for metadata accessors that aren't
+// available in Swift runtimes prior to macOS 12/iOS 15 era.
+//
+//===----------------------------------------------------------------------===//
+#include <cinttypes>
+
+#include "swift/Runtime/Concurrent.h"
+#include "swift/Runtime/Metadata.h"
+
+using namespace swift;
+
+namespace swift {
+
+SWIFT_EXPORT_FROM(swift_Concurrency)
+const FunctionTypeMetadata *
+swift_getFunctionTypeMetadataGlobalActorStandalone(
+    FunctionTypeFlags flags, FunctionMetadataDifferentiabilityKind diffKind,
+    const Metadata *const *parameters, const uint32_t *parameterFlags,
+    const Metadata *result, const Metadata *globalActor);
+
+}
+
+namespace {
+
+constexpr size_t roundUpToAlignment(size_t offset, size_t alignment) {
+  return ((offset + alignment - 1) & ~(alignment - 1));
+}
+
+class MetadataAllocator : public llvm::AllocatorBase<MetadataAllocator> {
+private:
+  uint16_t Tag;
+
+public:
+  constexpr MetadataAllocator(uint16_t tag) : Tag(tag) {}
+  MetadataAllocator() = delete;
+
+  void Reset() {}
+
+  LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t size, size_t alignment) {
+    return malloc(size);
+  }
+  using AllocatorBase<MetadataAllocator>::Allocate;
+
+  void Deallocate(const void *Ptr, size_t size, size_t Alignment) {
+    free(const_cast<void *>(Ptr));
+  }
+  using AllocatorBase<MetadataAllocator>::Deallocate;
+
+  void PrintStats() const {}
+
+  MetadataAllocator withTag(uint16_t Tag) {
+    MetadataAllocator Allocator = *this;
+    Allocator.Tag = Tag;
+    return Allocator;
+  }
+};
+
+template <uint16_t StaticTag>
+class TaggedMetadataAllocator : public MetadataAllocator {
+public:
+  constexpr TaggedMetadataAllocator() : MetadataAllocator(StaticTag) {}
+};
+
+template <class EntryTy, uint16_t Tag>
+using SimpleGlobalCache =
+    StableAddressConcurrentReadableHashMap<EntryTy,
+                                           TaggedMetadataAllocator<Tag>>;
+
+class FunctionCacheEntry {
+public:
+  FullMetadata<FunctionTypeMetadata> Data;
+
+  struct Key {
+    const FunctionTypeFlags Flags;
+    const FunctionMetadataDifferentiabilityKind DifferentiabilityKind;
+    const Metadata *const *Parameters;
+    const uint32_t *ParameterFlags;
+    const Metadata *Result;
+    const Metadata *GlobalActor;
+
+    FunctionTypeFlags getFlags() const { return Flags; }
+
+    FunctionMetadataDifferentiabilityKind getDifferentiabilityKind() const {
+      return DifferentiabilityKind;
+    }
+
+    const Metadata *getParameter(unsigned index) const {
+      assert(index < Flags.getNumParameters());
+      return Parameters[index];
+    }
+    const Metadata *getResult() const { return Result; }
+
+    const uint32_t *getParameterFlags() const {
+      return ParameterFlags;
+    }
+
+    ::ParameterFlags getParameterFlags(unsigned index) const {
+      assert(index < Flags.getNumParameters());
+      auto flags = Flags.hasParameterFlags() ? ParameterFlags[index] : 0;
+      return ParameterFlags::fromIntValue(flags);
+    }
+
+    const Metadata *getGlobalActor() const { return GlobalActor; }
+
+    friend llvm::hash_code hash_value(const Key &key) {
+      auto hash = llvm::hash_combine(
+          key.Flags.getIntValue(),
+          key.DifferentiabilityKind.getIntValue(),
+          key.Result, key.GlobalActor);
+      for (unsigned i = 0, e = key.getFlags().getNumParameters(); i != e; ++i) {
+        hash = llvm::hash_combine(hash, key.getParameter(i));
+        hash = llvm::hash_combine(hash, key.getParameterFlags(i).getIntValue());
+      }
+      return hash;
+    }
+  };
+
+  FunctionCacheEntry(const Key &key);
+
+  intptr_t getKeyIntValueForDump() {
+    return 0; // No single meaningful value here.
+  }
+
+  bool matchesKey(const Key &key) const {
+    if (key.getFlags().getIntValue() != Data.Flags.getIntValue())
+      return false;
+    if (key.getDifferentiabilityKind().Value !=
+        Data.getDifferentiabilityKind().Value)
+      return false;
+    if (key.getResult() != Data.ResultType)
+      return false;
+    if (key.getGlobalActor() != Data.getGlobalActor())
+      return false;
+    for (unsigned i = 0, e = key.getFlags().getNumParameters(); i != e; ++i) {
+      if (key.getParameter(i) != Data.getParameter(i))
+        return false;
+      if (key.getParameterFlags(i).getIntValue() !=
+          Data.getParameterFlags(i).getIntValue())
+        return false;
+    }
+    return true;
+  }
+
+  friend llvm::hash_code hash_value(const FunctionCacheEntry &value) {
+    Key key = {value.Data.Flags, value.Data.getDifferentiabilityKind(),
+               value.Data.getParameters(), value.Data.getParameterFlags(),
+               value.Data.ResultType, value.Data.getGlobalActor()};
+    return hash_value(key);
+  }
+
+  static size_t getExtraAllocationSize(const Key &key) {
+    return getExtraAllocationSize(key.Flags);
+  }
+
+  size_t getExtraAllocationSize() const {
+    return getExtraAllocationSize(Data.Flags);
+  }
+
+  static size_t getExtraAllocationSize(const FunctionTypeFlags &flags) {
+    const auto numParams = flags.getNumParameters();
+    auto size = numParams * sizeof(FunctionTypeMetadata::Parameter);
+    if (flags.hasParameterFlags())
+      size += numParams * sizeof(uint32_t);
+    if (flags.isDifferentiable())
+      size = roundUpToAlignment(size, sizeof(void *)) +
+          sizeof(FunctionMetadataDifferentiabilityKind);
+    if (flags.hasGlobalActor())
+      size = roundUpToAlignment(size, sizeof(void *)) + sizeof(Metadata *);
+    return roundUpToAlignment(size, sizeof(void *));
+  }
+};
+
+} // end anonymous namespace
+
+FunctionCacheEntry::FunctionCacheEntry(const Key &key) {
+  auto flags = key.getFlags();
+
+  // Pick a value witness table appropriate to the function convention.
+  // All function types of a given convention have the same value semantics,
+  // so they share a value witness table.
+  switch (flags.getConvention()) {
+  case FunctionMetadataConvention::Swift:
+    if (!flags.isEscaping()) {
+      Data.ValueWitnesses = &VALUE_WITNESS_SYM(NOESCAPE_FUNCTION_MANGLING);
+    } else {
+      Data.ValueWitnesses = &VALUE_WITNESS_SYM(FUNCTION_MANGLING);
+    }
+    break;
+
+  case FunctionMetadataConvention::Thin:
+  case FunctionMetadataConvention::CFunctionPointer:
+    Data.ValueWitnesses = &VALUE_WITNESS_SYM(THIN_FUNCTION_MANGLING);
+    break;
+
+  case FunctionMetadataConvention::Block:
+#if SWIFT_OBJC_INTEROP
+    // Blocks are ObjC objects, so can share the AnyObject value
+    // witnesses (stored as "BO" rather than "yXl" for ABI compat).
+    Data.ValueWitnesses = &VALUE_WITNESS_SYM(BO);
+#else
+    assert(false && "objc block without objc interop?");
+#endif
+    break;
+  }
+
+  unsigned numParameters = flags.getNumParameters();
+
+  Data.setKind(MetadataKind::Function);
+  Data.Flags = flags;
+  Data.ResultType = key.getResult();
+  if (flags.hasGlobalActor())
+    *Data.getGlobalActorAddr() = key.getGlobalActor();
+  if (flags.isDifferentiable())
+    *Data.getDifferentiabilityKindAddress() = key.getDifferentiabilityKind();
+
+  for (unsigned i = 0; i < numParameters; ++i) {
+    Data.getParameters()[i] = key.getParameter(i);
+    if (flags.hasParameterFlags())
+      Data.getParameterFlags()[i] = key.getParameterFlags(i).getIntValue();
+  }
+}
+
+// Provide a definition and static initializer for the fixed seed. This
+// initializer should always be zero to ensure its value can never appear to be
+// non-zero, even during dynamic initialization.
+uint64_t llvm::hashing::detail::fixed_seed_override = 0;
+
+/// The uniquing structure for function type metadata with a global actor.
+static SimpleGlobalCache<FunctionCacheEntry, FunctionTypesTag> FunctionTypes;
+
+const FunctionTypeMetadata *
+swift::swift_getFunctionTypeMetadataGlobalActorStandalone(
+    FunctionTypeFlags flags, FunctionMetadataDifferentiabilityKind diffKind,
+    const Metadata *const *parameters, const uint32_t *parameterFlags,
+    const Metadata *result, const Metadata *globalActor) {
+  assert(flags.hasGlobalActor());
+    assert(flags.hasGlobalActor());
+  FunctionCacheEntry::Key key = {
+    flags, diffKind, parameters, parameterFlags, result, globalActor
+  };
+  return &FunctionTypes.getOrInsert(key).first->Data;
+
+}

stdlib/toolchain/CompatibilityConcurrency/CompatibilityConcurrency.cpp

@@ -9,7 +9,74 @@
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 //
 //===----------------------------------------------------------------------===//
+#include "swift/Runtime/Metadata.h"
+#include <dispatch/dispatch.h>
+#include <dlfcn.h>
 
 // Allow this library to get force-loaded by autolinking
 __attribute__((weak, visibility("hidden"))) extern "C" char
     _swift_FORCE_LOAD_$_swiftCompatibilityConcurrency = 0;
+using namespace swift;
+
+namespace swift {
+
+// Entrypoint provided by the runtime in the OS that first contains support for
+// concurrency. Explicitly redeclared as "weak" because this code will run on
+// systems where it is not present.
+const FunctionTypeMetadata *
+swift_getFunctionTypeMetadataGlobalActor(
+    FunctionTypeFlags flags, FunctionMetadataDifferentiabilityKind diffKind,
+    const Metadata *const *parameters, const uint32_t *parameterFlags,
+    const Metadata *result, const Metadata *globalActor
+) SWIFT_RUNTIME_WEAK_IMPORT;
+
+// Entrypoint provided only in the back-deployed concurrency library, which
+// has a separate allocation area for global-actor-qualified function types.
+extern "C"
+const FunctionTypeMetadata *
+swift_getFunctionTypeMetadataGlobalActorStandalone(
+    FunctionTypeFlags flags, FunctionMetadataDifferentiabilityKind diffKind,
+    const Metadata *const *parameters, const uint32_t *parameterFlags,
+    const Metadata *result, const Metadata *globalActor
+) SWIFT_RUNTIME_WEAK_IMPORT;
+
+// Entrypoint called by the compiler when back-deploying concurrency, which
+// switches between the real implementation of
+// swift_getFunctionTypeMetadataGlobalActor and
+// swift_getFunctionTypeMetadataGlobalActorStandalone depending on what system
+// it is running on.
+SWIFT_RUNTIME_STDLIB_INTERNAL
+const FunctionTypeMetadata *
+swift_getFunctionTypeMetadataGlobalActorBackDeploy(
+    FunctionTypeFlags flags, FunctionMetadataDifferentiabilityKind diffKind,
+    const Metadata *const *parameters, const uint32_t *parameterFlags,
+    const Metadata *result, const Metadata *globalActor);
+
+} // end namespace swift
+
+const FunctionTypeMetadata *
+swift::swift_getFunctionTypeMetadataGlobalActorBackDeploy(
+    FunctionTypeFlags flags, FunctionMetadataDifferentiabilityKind diffKind,
+    const Metadata *const *parameters, const uint32_t *parameterFlags,
+    const Metadata *result, const Metadata *globalActor) {
+  using BuilderFn = const FunctionTypeMetadata *(*)(
+      FunctionTypeFlags, FunctionMetadataDifferentiabilityKind,
+      const Metadata *const *, const uint32_t *,
+      const Metadata *, const Metadata *);
+  static BuilderFn builderFn;
+  static dispatch_once_t builderToken;
+  dispatch_once(&builderToken, ^{
+      if (swift_getFunctionTypeMetadataGlobalActor) {
+        builderFn = swift_getFunctionTypeMetadataGlobalActor;
+        return;
+      }
+
+      builderFn = reinterpret_cast<BuilderFn>(
+        dlsym(RTLD_DEFAULT,
+              "swift_getFunctionTypeMetadataGlobalActorStandalone"));
+    });
+
+  assert(builderFn && "No way to build global-actor-qualified function type");
+  return builderFn(
+      flags, diffKind, parameters, parameterFlags, result, globalActor);
+}

test/IRGen/global_actor_function_types.sil

@@ -12,7 +12,7 @@ func globalActorMetatype<T>(_: T.Type) -> Any.Type {
 // CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc %swift.type* @"$s4test19globalActorMetatypeyypXpxmlF"
 // CHECK: [[MAIN_ACTOR_RESPONSE:%[0-9]+]] = call swiftcc %swift.metadata_response @"$sScMMa"(i{{32|64}} 255)
 // CHECK-NEXT: [[MAIN_ACTOR_METADATA:%[0-9]+]] = extractvalue %swift.metadata_response [[MAIN_ACTOR_RESPONSE]], 0
-// CHECK: call %swift.type* @swift_getFunctionTypeMetadataGlobalActor(i{{32|64}} 335544320, i{{32|64}} 0, %swift.type** null, i32* null, %swift.type* %T, %swift.type* [[MAIN_ACTOR_METADATA]])
+// CHECK: call %swift.type* @swift_getFunctionTypeMetadataGlobalActor{{.*}}(i{{32|64}} 335544320, i{{32|64}} 0, %swift.type** null, i32* null, %swift.type* %T, %swift.type* [[MAIN_ACTOR_METADATA]])
 sil [ossa] @$s4test19globalActorMetatypeyypXpxmlF : $@convention(thin) <T> (@thick T.Type) -> @thick Any.Type {
 bb0(%0 : $@thick T.Type):
   %2 = metatype $@thin (@MainActor () -> T).Type

test/IRGen/global_actor_function_types_backdeploy.sil

@@ -0,0 +1,22 @@
+// RUN: %target-swift-frontend -target x86_64-apple-macos12 -emit-ir -o - -primary-file %s | %FileCheck %s --check-prefix CHECK-OS
+// RUN: %target-swift-frontend -target x86_64-apple-macos11 -emit-ir -o - -primary-file %s | %FileCheck %s --check-prefix CHECK-BACKDEPLOY
+// REQUIRES: concurrency
+// REQUIRES: OS=macosx
+
+import Swift
+import _Concurrency
+
+func globalActorMetatype<T>(_: T.Type) -> Any.Type {
+  typealias Fn = @MainActor () -> T
+  return Fn.self
+}
+
+// CHECK-OS: call %swift.type* @swift_getFunctionTypeMetadataGlobalActor{{.*}}(i{{32|64}} 335544320, i{{32|64}} 0, %swift.type** null, i32* null, %swift.type* %T, %swift.type* {{.*}})
+// CHECK-BACKDEPLOY: call %swift.type* @swift_getFunctionTypeMetadataGlobalActorBackDeploy{{.*}}(i{{32|64}} 335544320, i{{32|64}} 0, %swift.type** null, i32* null, %swift.type* %T, %swift.type* {{.*}})
+sil [ossa] @$s4test19globalActorMetatypeyypXpxmlF : $@convention(thin) <T> (@thick T.Type) -> @thick Any.Type {
+bb0(%0 : $@thick T.Type):
+  %2 = metatype $@thin (@MainActor () -> T).Type
+  %3 = metatype $@thick (@MainActor () -> T).Type
+  %4 = init_existential_metatype %3 : $@thick (@MainActor () -> T).Type, $@thick Any.Type
+  return %4 : $@thick Any.Type
+}