Add support for importing shared memory as per wasm threading proposal.

Change-Id: I077b8d3a60f543c3e54cd3e6d024260adcb8ed83
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/241420
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Commit-Queue: Jackson Gardner <jacksongardner@google.com>

pkg/dart2wasm/bin/dart2wasm.dart

@@ -13,6 +13,7 @@ import 'package:dart2wasm/translator.dart';
 
 final Map<String, void Function(TranslatorOptions, bool)> boolOptionMap = {
   "export-all": (o, value) => o.exportAll = value,
+  "import-shared-memory": (o, value) => o.importSharedMemory = value,
   "inlining": (o, value) => o.inlining = value,
   "lazy-constants": (o, value) => o.lazyConstants = value,
   "local-nullability": (o, value) => o.localNullability = value,
@@ -27,6 +28,7 @@ final Map<String, void Function(TranslatorOptions, bool)> boolOptionMap = {
   "string-data-segments": (o, value) => o.stringDataSegments = value,
 };
 final Map<String, void Function(TranslatorOptions, int)> intOptionMap = {
+  "shared-memory-max-pages": (o, value) => o.sharedMemoryMaxPages = value,
   "watch": (o, value) => (o.watchPoints ??= []).add(value),
 };
 
@@ -83,6 +85,11 @@ Future<int> main(List<String> args) async {
     usage("Missing argument to ${args.last}");
   }
 
+  if (options.importSharedMemory && options.sharedMemoryMaxPages == null) {
+    usage("--shared-memory-max-pages must be "
+        "specified if --import-shared-memory is used.");
+  }
+
   if (nonOptions.length != 2) usage("Requires two file arguments");
   String input = nonOptions[0];
   String output = nonOptions[1];

pkg/dart2wasm/dart2wasm.md

@@ -12,6 +12,7 @@ where *options* include:
 | --------------------------------------- | ------- | ----------- |
 | `--dart-sdk=`*path*                     | relative to script | The location of the `sdk` directory inside the Dart SDK, containing the core library sources.
 | `--`[`no-`]`export-all`                 | no      | Export all functions; otherwise, just export `main`.
+| `--`[`no-`]`import-shared-memory`       | no      | Import a shared memory buffer. If this is on, `--shared-memory-max-pages` must also be specified.
 | `--`[`no-`]`inlining`                   | no      | Inline small functions.
 | `--`[`no-`]`lazy-constants`             | no      | Instantiate constants lazily.
 | `--`[`no-`]`local-nullability`          | no      | Use non-nullable types for non-nullable locals and temporaries.
@@ -22,6 +23,7 @@ where *options* include:
 | `--`[`no-`]`print-kernel`               | no      | Print IR for each function before compiling it.
 | `--`[`no-`]`print-wasm`                 | no      | Print Wasm instructions of each compiled function.
 | `--`[`no-`]`runtime-types`              | no      | Use RTTs for allocations and casts.
+| `--shared-memory-max-pages` *pagecount* |         | Max size of the imported memory buffer. If `--shared-import-memory` is specified, this must also be specified.
 | `--`[`no-`]`string-data-segments`       | no      | Use experimental array init from data segment for string constants.
 | `--watch` *offset*                      |         | Print stack trace leading to the byte at offset *offset* in the `.wasm` output file. Can be specified multiple times.
 

pkg/dart2wasm/lib/constants.dart

@@ -175,7 +175,7 @@ class Constants {
         .toBytes();
 
     w.Memory stringMemory =
-        m.addMemory(stringsAsBytes.length, stringsAsBytes.length);
+        m.addMemory(false, stringsAsBytes.length, stringsAsBytes.length);
     m.addDataSegment(stringsAsBytes, stringMemory, 0);
     makeStringFunctionBody(translator.oneByteStringClass, oneByteStringFunction,
         (b) {

pkg/dart2wasm/lib/translator.dart

@@ -27,6 +27,7 @@ import 'package:wasm_builder/wasm_builder.dart' as w;
 /// Options controlling the translation.
 class TranslatorOptions {
   bool exportAll = false;
+  bool importSharedMemory = false;
   bool inlining = false;
   int inliningLimit = 3;
   bool lazyConstants = false;
@@ -38,6 +39,7 @@ class TranslatorOptions {
   bool printKernel = false;
   bool printWasm = false;
   bool runtimeTypes = false;
+  int? sharedMemoryMaxPages;
   bool stringDataSegments = false;
   List<int>? watchPoints = null;
 
@@ -127,7 +129,8 @@ class Translator {
   // Lazily create exception tag if used.
   late final w.Tag exceptionTag = createExceptionTag();
   // Lazily import FFI memory if used.
-  late final w.Memory ffiMemory = m.importMemory("ffi", "memory", 0);
+  late final w.Memory ffiMemory = m.importMemory("ffi", "memory",
+      options.importSharedMemory, 0, options.sharedMemoryMaxPages);
 
   // Caches for when identical source constructs need a common representation.
   final Map<w.StorageType, w.ArrayType> arrayTypeCache = {};

pkg/wasm_builder/lib/src/module.dart

@@ -130,9 +130,9 @@ class Module with SerializerMixin {
   }
 
   /// Add a new memory to the module.
-  DefinedMemory addMemory(int minSize, [int? maxSize]) {
+  DefinedMemory addMemory(bool shared, int minSize, [int? maxSize]) {
     anyMemoriesDefined = true;
-    final memory = DefinedMemory(memories.length, minSize, maxSize);
+    final memory = DefinedMemory(memories.length, shared, minSize, maxSize);
     memories.add(memory);
     return memory;
   }
@@ -195,13 +195,14 @@ class Module with SerializerMixin {
   ///
   /// All imported memories must be specified before any memories are declared
   /// using [Module.addMemory].
-  ImportedMemory importMemory(String module, String name, int minSize,
+  ImportedMemory importMemory(
+      String module, String name, bool shared, int minSize,
       [int? maxSize]) {
     if (anyMemoriesDefined) {
       throw "All memory imports must be specified before any definitions.";
     }
     final memory =
-        ImportedMemory(module, name, memories.length, minSize, maxSize);
+        ImportedMemory(module, name, memories.length, shared, minSize, maxSize);
     memories.add(memory);
     return memory;
   }
@@ -410,13 +411,23 @@ class Table implements Serializable {
 /// A memory in a module.
 class Memory {
   final int index;
+  final bool shared;
   final int minSize;
   final int? maxSize;
 
-  Memory(this.index, this.minSize, [this.maxSize]);
+  Memory(this.index, this.shared, this.minSize, [this.maxSize]) {
+    if (shared && maxSize == null) {
+      throw "Shared memory must specify a maximum size.";
+    }
+  }
 
   void _serializeLimits(Serializer s) {
-    if (maxSize == null) {
+    if (shared) {
+      assert(maxSize != null);
+      s.writeByte(0x03);
+      s.writeUnsigned(minSize);
+      s.writeUnsigned(maxSize!);
+    } else if (maxSize == null) {
       s.writeByte(0x00);
       s.writeUnsigned(minSize);
     } else {
@@ -428,8 +439,8 @@ class Memory {
 }
 
 class DefinedMemory extends Memory implements Serializable {
-  DefinedMemory(int index, int minSize, int? maxSize)
-      : super(index, minSize, maxSize);
+  DefinedMemory(int index, bool shared, int minSize, int? maxSize)
+      : super(index, shared, minSize, maxSize);
 
   @override
   void serialize(Serializer s) => _serializeLimits(s);
@@ -556,8 +567,9 @@ class ImportedMemory extends Memory implements Import {
   final String module;
   final String name;
 
-  ImportedMemory(this.module, this.name, int index, int minSize, int? maxSize)
-      : super(index, minSize, maxSize);
+  ImportedMemory(
+      this.module, this.name, int index, bool shared, int minSize, int? maxSize)
+      : super(index, shared, minSize, maxSize);
 
   @override
   void serialize(Serializer s) {

tests/lib/wasm/fn_import_error_test.dart

@@ -38,7 +38,7 @@ void main() {
 
   // Wrong kind of import.
   Expect.throws(
-      () => mod.instantiate().addMemory("env", "someFn", mod.createMemory(10)),
+      () => mod.instantiate().addMemory(false, "env", "someFn", mod.createMemory(10)),
       (Exception e) => "$e".contains("Import is not a memory"));
 
   // Wrong namespace.

tests/lib_2/wasm/fn_import_error_test.dart

@@ -40,7 +40,7 @@ void main() {
 
   // Wrong kind of import.
   Expect.throws(
-      () => mod.instantiate().addMemory("env", "someFn", mod.createMemory(10)),
+      () => mod.instantiate().addMemory(false, "env", "someFn", mod.createMemory(10)),
       (Exception e) => "$e".contains("Import is not a memory"));
 
   // Wrong namespace.