[dart2wasm] Add simple way to test IR changes

In order to test generated code for a function one can

  * place a dart file in `pkg/dart2wasm/tets/ir_tests`
  * annotate functions that shouldn't be inlined
  * describe which functions we want to dump in the expectation file
  * generate an expectation file.

This will allow generating renatively small expectation files for only
functions we care about and types/globals/... those functions need.

Change-Id: Ic7b6b6dece16ab453202aa2c4f9412de2fc251ae
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/454840
Reviewed-by: Ömer Ağacan <omersa@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>

pkg/dart2wasm/lib/functions.dart

@@ -257,8 +257,20 @@ class FunctionCollector {
     if (target.isUncheckedEntryReference) {
       return "$memberName (unchecked entry)";
     }
+
+    final noInline =
+        translator.getPragma<bool>(member, "wasm:never-inline", true);
+
+    // We add "<noInline>" to the function name. When we invoke `wasm-opt` we
+    // then pass the `--no-inline=*<noInline>*` flag, which will prevent
+    // binaryen from inlining those functions.
+    //
+    // => Effectively we make `@pragma('wasm:never-inline')` work for binaryen
+    // as well.
+    final inlinePostfix = noInline == true ? ' <noInline>' : '';
+
     if (target.isBodyReference) {
-      return "$memberName (body)";
+      return "$memberName (body)$inlinePostfix";
     }
 
     if (memberName.endsWith('.')) {
@@ -283,11 +295,11 @@ class FunctionCollector {
     if (target.isInitializerReference) {
       return 'new $memberName (initializer)';
     } else if (target.isConstructorBodyReference) {
-      return 'new $memberName (constructor body)';
+      return 'new $memberName (constructor body)$inlinePostfix';
     } else if (member is Procedure && member.isFactory) {
       return 'new $memberName';
     } else {
-      return memberName;
+      return '$memberName$inlinePostfix';
     }
   }
 

pkg/dart2wasm/test/ir_test.dart

@@ -0,0 +1,139 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+import 'dart:io' as io;
+import 'dart:typed_data';
+
+import 'package:args/args.dart';
+import 'package:path/path.dart' as path;
+
+import 'package:wasm_builder/src/ir/ir.dart';
+import 'package:wasm_builder/src/serialize/deserializer.dart';
+import 'package:wasm_builder/src/serialize/printer.dart';
+
+import 'self_compile_test.dart' show withTempDir;
+
+void main(List<String> args) async {
+  final result = argParser.parse(args);
+  final help = result.flag('help');
+  final write = result.flag('write');
+  final runFromSource = result.flag('src');
+
+  if (help) {
+    print('Usage:\n${argParser.usage}');
+    io.exit(0);
+  }
+  if (result.rest.isNotEmpty) {
+    print('Unknown arguments: ${result.rest.join(' ')}');
+    print('Usage:\n${argParser.usage}');
+    io.exit(1);
+  }
+
+  await withTempDir((String tempDir) async {
+    for (final dartFilename in listIrTests()) {
+      void failTest() {
+        print('-> test "$dartFilename" failed\n');
+        io.exitCode = 254;
+      }
+
+      final dartCode = File(dartFilename).readAsStringSync();
+      final watFile = File(path.setExtension(dartFilename, '.wat'));
+      final wasmFile = File(path.join(
+          tempDir, path.setExtension(path.basename(dartFilename), '.wasm')));
+
+      print('Testing $dartFilename');
+
+      final result = await Process.run('/usr/bin/env', [
+        'bash',
+        'pkg/dart2wasm/tool/compile_benchmark',
+        if (runFromSource) '--src',
+        '--no-strip-wasm',
+        '-o',
+        wasmFile.path,
+        dartFilename
+      ]);
+      if (result.exitCode != 0) {
+        print('Compilation failed:');
+        print('stdout:\n${result.stdout}');
+        print('stderr:\n${result.stderr}\n');
+        failTest();
+        continue;
+      }
+
+      print('Compiled to ${wasmFile.path}');
+
+      final wasmBytes = wasmFile.readAsBytesSync();
+      final wat =
+          moduleToString(parseModule(wasmBytes), parseNameFilters(dartCode));
+      if (write) {
+        watFile.writeAsStringSync(wat);
+        continue;
+      }
+      if (!watFile.existsSync()) {
+        print('Expected "${watFile.path}" to exist.');
+        failTest();
+        continue;
+      }
+
+      final oldWat = watFile.readAsStringSync();
+      if (oldWat != wat) {
+        print(
+            '-> Expectation mismatch. Run with `-w` to update expectation file.');
+        failTest();
+        continue;
+      }
+    }
+  });
+}
+
+final argParser = ArgParser()
+  ..addFlag('help',
+      abbr: 'h', defaultsTo: false, help: 'Prints available options.')
+  ..addFlag('src', defaultsTo: false, help: 'Runs the compiler from source.')
+  ..addFlag('write',
+      abbr: 'w', defaultsTo: false, help: 'Writes new expectation files.');
+
+Iterable<String> listIrTests() {
+  return Directory('pkg/dart2wasm/test/ir_tests')
+      .listSync(recursive: true)
+      .whereType<File>()
+      .map((file) => file.path)
+      .where((path) => path.endsWith('.dart'));
+}
+
+Module parseModule(Uint8List wasmBytes) {
+  final deserializer = Deserializer(wasmBytes);
+  return Module.deserialize(deserializer);
+}
+
+String moduleToString(Module module, List<RegExp> functionNameFilters) {
+  bool printFunctionBody(BaseFunction function) {
+    final name = function.functionName;
+    if (name == null) return false;
+    return functionNameFilters.any((pattern) => name.contains(pattern));
+  }
+
+  final mp = ModulePrinter(module, printFunctionBody: printFunctionBody);
+  for (final function in module.functions.defined) {
+    if (printFunctionBody(function)) {
+      mp.enqueueFunction(function);
+    }
+  }
+  return mp.print();
+}
+
+List<RegExp> parseNameFilters(String dartCode) {
+  const functionFilter = '// functionFilter=';
+  final filters = <RegExp>[];
+  for (final line in dartCode.split('\n')) {
+    if (line.startsWith(functionFilter)) {
+      final filter = line.substring(functionFilter.length).trim();
+      if (filter.isNotEmpty) {
+        filters.add(RegExp(filter));
+      }
+    }
+  }
+  return filters;
+}

pkg/dart2wasm/test/ir_tests/hello.dart

@@ -0,0 +1,6 @@
+// functionFilter=main
+
+@pragma('wasm:never-inline')
+void main() {
+  print('hello world');
+}

pkg/dart2wasm/test/ir_tests/hello.wat

@@ -0,0 +1,11 @@
+(module $module0
+  (type $#Top (struct (field $field0 i32)))
+  (type $JSStringImpl (sub final $#Top (struct (field $field0 i32) (field $field1 externref))))
+  (global $"S.hello world" (import "S" "hello world") externref)
+  (global $"C327 \"hello world\"" (ref $JSStringImpl) (i32.const 4) (global.get $"S.hello world") (struct.new $JSStringImpl))
+  (func $"main <noInline>"
+    global.get $"C327 \"hello world\""
+    call $print
+  )
+  (func $print (param $var0 (ref $#Top)))
+)

pkg/dartdev/lib/src/commands/compile.dart

@@ -738,6 +738,8 @@ class CompileWasmCommand extends CompileSubcommandCommand {
       --enable-bulk-memory
       --enable-threads
 
+      --no-inline=*<noInline>*
+
       --closed-world
       --traps-never-happen
       --type-unfinalizing
@@ -761,6 +763,8 @@ class CompileWasmCommand extends CompileSubcommandCommand {
       --enable-bulk-memory
       --enable-threads
 
+      --no-inline=*<noInline>*
+
       -Os
     '''); // end of binaryenFlagsDeferredLoading
 

pkg/wasm_builder/lib/src/ir/function.dart

@@ -125,6 +125,14 @@ class DefinedFunction extends BaseFunction implements Serializable {
     p.write(')');
   }
 
+  void printDeclarationTo(IrPrinter p) {
+    p.write('(func \$$functionName ');
+    p.withLocalNames(localNames, () {
+      type.printSignatureWithNamesTo(p, oneLine: true);
+    });
+    p.writeln(')');
+  }
+
   @override
   String toString() => functionName ?? "#$finalizableIndex";
 }

pkg/wasm_builder/lib/src/serialize/printer.dart

@@ -26,7 +26,14 @@ class ModulePrinter {
   final _typeQueue = Queue<ir.DefType>();
   final _functionsQueue = Queue<ir.DefinedFunction>();
 
-  ModulePrinter(this._module);
+  /// Closure that tells us whether the body of a function should be printed or
+  /// not.
+  late final bool Function(ir.BaseFunction) _printFunctionBody;
+
+  ModulePrinter(this._module,
+      {bool Function(ir.BaseFunction)? printFunctionBody}) {
+    _printFunctionBody = printFunctionBody ?? (_) => true;
+  }
 
   IrPrinter newIrPrinter() => IrPrinter._(_module, _typeNamer, _globalNamer,
       _functionNamer, _tagNamer, _tableNamer);
@@ -74,7 +81,8 @@ class ModulePrinter {
     while (_functionsQueue.isNotEmpty || _typeQueue.isNotEmpty) {
       while (_functionsQueue.isNotEmpty) {
         final fun = _functionsQueue.removeFirst();
-        _generateFunction(fun);
+
+        _generateFunction(fun, includingBody: _printFunctionBody(fun));
       }
     }
 
@@ -172,10 +180,15 @@ class ModulePrinter {
     _functions[fun] = p.getText();
   }
 
-  void _generateFunction(ir.DefinedFunction fun) {
+  void _generateFunction(ir.DefinedFunction fun,
+      {required bool includingBody}) {
     final p = newIrPrinter();
-    fun.printTo(p);
-    _functions[fun] = p.getText();
+    if (includingBody) {
+      fun.printTo(p);
+    } else {
+      fun.printDeclarationTo(p);
+    }
+    _functions[fun] = p.getText().trimRight();
   }
 
   void _generateType(ir.DefType type) {