[Runtime] Stubbed entry points for task de/alloc.

include/swift/AST/ASTContext.h

@@ -694,6 +694,9 @@ class ASTContext final {
   /// generic metadata.
   AvailabilityContext getIntermodulePrespecializedGenericMetadataAvailability();
 
+  /// Get the runtime availability of support for concurrency.
+  AvailabilityContext getConcurrencyAvailability();
+
   /// Get the runtime availability of features introduced in the Swift 5.2
   /// compiler for the target platform.
   AvailabilityContext getSwift52Availability();

include/swift/Runtime/RuntimeFunctions.def

@@ -1461,6 +1461,22 @@ FUNCTION(GetTypeByMangledNameInContextInMetadataState,
               Int8PtrPtrTy),
          ATTRS(NoUnwind, ArgMemOnly))
 
+// void *swift_taskAlloc(SwiftTask *task, size_t size);
+FUNCTION(TaskAlloc,
+         swift_taskAlloc, SwiftCC,
+         ConcurrencyAvailability,
+         RETURNS(Int8PtrTy),
+         ARGS(SwiftTaskPtrTy, SizeTy),
+         ATTRS(NoUnwind, ArgMemOnly))
+
+// void swift_taskDealloc(SwiftTask *task, void *ptr);
+FUNCTION(TaskDealloc,
+         swift_taskDealloc, SwiftCC,
+         ConcurrencyAvailability,
+         RETURNS(VoidTy),
+         ARGS(SwiftTaskPtrTy, Int8PtrTy),
+         ATTRS(NoUnwind, ArgMemOnly))
+
 #undef RETURNS
 #undef ARGS
 #undef ATTRS

lib/AST/Availability.cpp

@@ -323,6 +323,10 @@ ASTContext::getIntermodulePrespecializedGenericMetadataAvailability() {
   return getSwift54Availability();
 }
 
+AvailabilityContext ASTContext::getConcurrencyAvailability() {
+  return getSwiftFutureAvailability();
+}
+
 AvailabilityContext ASTContext::getSwift52Availability() {
   auto target = LangOpts.Target;
 

lib/IRGen/IRGenModule.cpp

@@ -587,6 +587,11 @@ IRGenModule::IRGenModule(IRGenerator &irgen,
   DynamicReplacementKeyTy = createStructType(*this, "swift.dyn_repl_key",
                                              {RelativeAddressTy, Int32Ty});
 
+  SwiftContextTy = createStructType(*this, "swift.context", {});
+  SwiftTaskTy = createStructType(*this, "swift.task", {});
+  SwiftContextPtrTy = SwiftContextTy->getPointerTo(DefaultAS);
+  SwiftTaskPtrTy = SwiftTaskTy->getPointerTo(DefaultAS);
+
   DifferentiabilityWitnessTy = createStructType(
       *this, "swift.differentiability_witness", {Int8PtrTy, Int8PtrTy});
 }
@@ -681,6 +686,14 @@ namespace RuntimeConstants {
     }
     return RuntimeAvailability::AlwaysAvailable;
   }
+
+  RuntimeAvailability ConcurrencyAvailability(ASTContext &context) {
+    auto featureAvailability = context.getConcurrencyAvailability();
+    if (!isDeploymentAvailabilityContainedIn(context, featureAvailability)) {
+      return RuntimeAvailability::ConditionallyAvailable;
+    }
+    return RuntimeAvailability::AlwaysAvailable;
+  }
 } // namespace RuntimeConstants
 
 // We don't use enough attributes to justify generalizing the

lib/IRGen/IRGenModule.h

@@ -723,6 +723,11 @@ class IRGenModule {
       *DynamicReplacementLinkEntryPtrTy; // %link_entry*
   llvm::StructType *DynamicReplacementKeyTy; // { i32, i32}
 
+  llvm::StructType *SwiftContextTy;
+  llvm::StructType *SwiftTaskTy;
+  llvm::PointerType *SwiftContextPtrTy;
+  llvm::PointerType *SwiftTaskPtrTy;
+
   llvm::StructType *DifferentiabilityWitnessTy; // { i8*, i8* }
 
   llvm::GlobalVariable *TheTrivialPropertyDescriptor = nullptr;

stdlib/public/runtime/CMakeLists.txt

@@ -31,6 +31,7 @@ set(swift_runtime_sources
     BackDeployment.cpp
     Casting.cpp
     CompatibilityOverride.cpp
+    Concurrency.cpp
     CygwinPort.cpp
     Demangle.cpp
     DynamicCast.cpp

stdlib/public/runtime/Concurrency.cpp

@@ -0,0 +1,37 @@
+//===------------ Concurrency.cpp - Swift Concurrency Support ------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2020 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Implementations of the concurrency runtime functions.
+//
+// void *swift_taskAlloc(SwiftTask *task, size_t size);
+// void swift_taskDealloc(SwiftTask *task, void *ptr);
+//
+//===----------------------------------------------------------------------===//
+
+#include "../SwiftShims/Visibility.h"
+#include "swift/Runtime/Config.h"
+#include <cstddef>
+#include <stdlib.h>
+
+struct SwiftTask;
+
+SWIFT_RUNTIME_EXPORT
+SWIFT_CC(swift)
+void *swift_taskAlloc(SwiftTask *task, size_t size) {
+  return malloc(size);
+}
+
+SWIFT_RUNTIME_EXPORT
+SWIFT_CC(swift)
+void swift_taskDealloc(SwiftTask *task, void *ptr) {
+  free(ptr);
+}