Runtime: Implement wrapper function to call metadata access functions

stdlib/public/SwiftShims/CMakeLists.txt

@@ -7,6 +7,7 @@ set(sources
   KeyPath.h
   LibcOverlayShims.h
   LibcShims.h
+  Metadata.h
   Random.h
   RefCount.h
   RuntimeShims.h

stdlib/public/SwiftShims/Metadata.h

@@ -0,0 +1,46 @@
+//===--- Metadata.h -------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_STDLIB_SHIMS_METADATA_H
+#define SWIFT_STDLIB_SHIMS_METADATA_H
+
+#include "SwiftStddef.h"
+#include "Visibility.h"
+
+#ifndef __swift__
+
+#include "swift/ABI/Metadata.h"
+
+#else // ifndef __swift__
+
+typedef struct {
+  const void *type;
+  __swift_size_t state;
+} MetadataResponse;
+
+#endif
+
+#ifdef __cplusplus
+namespace swift { extern "C" {
+#endif
+
+// Shims to call a metadata accessor in Swift.
+SWIFT_RUNTIME_STDLIB_API
+MetadataResponse _swift_metadataAccessorCall(void *accessor,
+                                             __swift_size_t request,
+                                             const void * const *args,
+                                             __swift_size_t size);
+#ifdef __cplusplus
+}} // extern "C", namespace swift
+#endif
+
+#endif

stdlib/public/SwiftShims/module.modulemap

@@ -6,6 +6,7 @@ module SwiftShims {
   header "HeapObject.h"
   header "KeyPath.h"
   header "LibcShims.h"
+  header "Metadata.h"
   header "Random.h"
   header "RefCount.h"
   header "RuntimeShims.h"

stdlib/public/stubs/CMakeLists.txt

@@ -3,6 +3,7 @@ set(swift_stubs_sources
     CommandLine.cpp
     GlobalObjects.cpp
     LibcShims.cpp
+    Metadata.cpp
     Random.cpp
     Stubs.cpp
     ThreadLocalStorage.cpp

stdlib/public/stubs/Metadata.cpp

@@ -0,0 +1,27 @@
+//===--- Metadata.cpp -----------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "../SwiftShims/Metadata.h"
+#include "swift/ABI/Metadata.h"
+
+// Shims to call a metadata accessor in Swift.
+SWIFT_RUNTIME_STDLIB_API
+swift::MetadataResponse
+swift::_swift_metadataAccessorCall(void *accessor,
+                                   __swift_size_t request,
+                                   const void * const *args,
+                                   __swift_size_t size) {
+  using Fn = MetadataResponse (...);
+  auto func = reinterpret_cast<Fn *>(accessor);
+  auto array = llvm::ArrayRef<const void *>(args, size);
+  return MetadataAccessFunction(func)(MetadataRequest(request), array);
+}

test/Interpreter/metadata_access.swift

@@ -0,0 +1,54 @@
+// RUN: %target-run-simple-swift | %FileCheck %s
+// REQUIRES: executable_test
+
+import SwiftShims
+
+struct MetadataAccessFunction {
+  let ptr: UnsafeMutableRawPointer
+
+  func callAsFunction(request: Int, args: [Any.Type]) -> MetadataResponse {
+    args.withUnsafeBufferPointer {
+      $0.baseAddress!.withMemoryRebound(
+        to: UnsafeRawPointer?.self,
+        capacity: args.count
+      ) {
+        _swift_metadataAccessorCall(ptr, request, $0, args.count)
+      }
+    }
+  }
+}
+
+func callStructAccessor(
+  for type: Any.Type,
+  with generics: Any.Type...
+) -> MetadataResponse {
+  let metadata = unsafeBitCast(type, to: UnsafeRawPointer.self)
+  let descriptor = metadata.advanced(by: MemoryLayout<Int>.size)
+                           .load(as: UnsafeMutableRawPointer.self)
+  let accessorLoc = descriptor.advanced(by: MemoryLayout<Int32>.size * 3)
+  let accessor = accessorLoc.advanced(by: Int(accessorLoc.load(as: Int32.self)))
+
+  let accessFn = MetadataAccessFunction(ptr: accessor)
+  return accessFn(request: 0, args: generics)
+}
+
+let int = callStructAccessor(for: Int.self)
+// CHECK: Int
+print(unsafeBitCast(int.type!, to: Any.Type.self))
+// CHECK: 0
+print(int.state)
+
+let doubleArray = callStructAccessor(for: [Int].self, with: Double.self)
+// CHECK: Array<Double>
+print(unsafeBitCast(doubleArray.type!, to: Any.Type.self))
+// CHECK: 0
+print(doubleArray.state)
+
+let dictOfIntAndDoubleArray = callStructAccessor(
+  for: [String: [Int]].self,
+  with: Int.self, [Double].self
+)
+// CHECK: Dictionary<Int, Array<Double>>
+print(unsafeBitCast(dictOfIntAndDoubleArray.type!, to: Any.Type.self))
+// CHECK: 0
+print(dictOfIntAndDoubleArray.state)