[vm/ffi] Exercise unaligned reads/writes

This CL validates the hypothesis that the only misaligned reads/writes
which are not supported are double and float, and only on arm32.

Running these on the CI and Golem will validate this hypothesis.

Bug: https://github.com/dart-lang/sdk/issues/45009

Change-Id: I0a77fd1f47a388d1f454c1ded50cd7ecaeadb0f0
Cq-Include-Trybots: luci.dart.try:dart-sdk-linux-try,dart-sdk-mac-try,dart-sdk-win-try,vm-ffi-android-debug-arm-try,vm-ffi-android-debug-arm64-try,vm-kernel-asan-linux-release-x64-try,vm-kernel-mac-debug-x64-try,vm-kernel-linux-debug-ia32-try,vm-kernel-linux-debug-x64-try,vm-kernel-nnbd-linux-debug-x64-try,vm-kernel-nnbd-linux-debug-ia32-try,vm-kernel-nnbd-mac-release-x64-try,vm-kernel-nnbd-win-debug-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-linux-debug-simarm_x64-try,vm-kernel-precomp-nnbd-linux-debug-x64-try,vm-kernel-precomp-win-release-x64-try,vm-kernel-reload-linux-debug-x64-try,vm-kernel-reload-rollback-linux-debug-x64-try,vm-kernel-win-debug-x64-try,vm-kernel-win-debug-ia32-try,vm-precomp-ffi-qemu-linux-release-arm-try,vm-kernel-precomp-obfuscate-linux-release-x64-try,vm-kernel-msan-linux-release-x64-try,vm-kernel-precomp-msan-linux-release-x64-try,vm-kernel-precomp-android-release-arm_x64-try,analyzer-analysis-server-linux-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/190523
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Aske Simon Christensen <askesc@google.com>

benchmarks/FfiMemory/dart/FfiMemory.dart

@@ -390,6 +390,30 @@ class PointerUint32 extends BenchmarkBase {
   }
 }
 
+class PointerUint32Unaligned extends BenchmarkBase {
+  Pointer<Uint32> pointer = nullptr;
+  Pointer<Uint32> unalignedPointer = nullptr;
+  PointerUint32Unaligned() : super('FfiMemory.PointerUint32Unaligned');
+
+  @override
+  void setup() {
+    pointer = calloc(N + 1);
+    unalignedPointer = Pointer.fromAddress(pointer.address + 1);
+  }
+
+  @override
+  void teardown() => calloc.free(pointer);
+
+  @override
+  void run() {
+    doStoreUint32(unalignedPointer, N);
+    final int x = doLoadUint32(unalignedPointer, N);
+    if (x != N) {
+      throw Exception('$name: Unexpected result: $x');
+    }
+  }
+}
+
 class PointerInt64 extends BenchmarkBase {
   Pointer<Int64> pointer = nullptr;
   PointerInt64() : super('FfiMemory.PointerInt64');
@@ -527,6 +551,7 @@ void main() {
     () => PointerUint16(),
     () => PointerInt32(),
     () => PointerUint32(),
+    () => PointerUint32Unaligned(),
     () => PointerInt64(),
     () => PointerInt64Mint(),
     () => PointerUint64(),

benchmarks/FfiMemory/dart2/FfiMemory.dart

@@ -390,6 +390,30 @@ class PointerUint32 extends BenchmarkBase {
   }
 }
 
+class PointerUint32Unaligned extends BenchmarkBase {
+  Pointer<Float> pointer;
+  Pointer<Uint32> unalignedPointer;
+  PointerUint32Unaligned() : super('FfiMemory.PointerUint32Unaligned');
+
+  @override
+  void setup() {
+    pointer = calloc(N + 1);
+    unalignedPointer = Pointer.fromAddress(pointer.address + 1);
+  }
+
+  @override
+  void teardown() => calloc.free(pointer);
+
+  @override
+  void run() {
+    doStoreUint32(unalignedPointer, N);
+    final int x = doLoadUint32(unalignedPointer, N);
+    if (x != N) {
+      throw Exception('$name: Unexpected result: $x');
+    }
+  }
+}
+
 class PointerInt64 extends BenchmarkBase {
   Pointer<Int64> pointer;
   PointerInt64() : super('FfiMemory.PointerInt64');
@@ -527,6 +551,7 @@ void main() {
     () => PointerUint16(),
     () => PointerInt32(),
     () => PointerUint32(),
+    () => PointerUint32Unaligned(),
     () => PointerInt64(),
     () => PointerInt64Mint(),
     () => PointerUint64(),

tests/ffi/unaligned_test.dart

@@ -0,0 +1,74 @@
+// Copyright (c) 2021, 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.
+
+// This tests exercises misaligned reads/writes on memory.
+//
+// The only architecture on which this is known to fail is arm32 on Android.
+
+import 'dart:ffi';
+import 'dart:io';
+
+import 'package:expect/expect.dart';
+import 'package:ffi/ffi.dart';
+
+void main() {
+  print("hello");
+  testUnalignedInt16(); //# 01: ok
+  testUnalignedInt32(); //# 02: ok
+  testUnalignedInt64(); //# 03: ok
+  if (!Platform.isAndroid || sizeOf<Pointer>() == 8) {
+    // TODO(http://dartbug.com/45009): Support unaligned reads/writes on
+    // Android arm32.
+    testUnalignedFloat(); //# 04: ok
+    testUnalignedDouble(); //# 05: ok
+  }
+  _freeAll();
+}
+
+void testUnalignedInt16() {
+  final pointer = _allocateUnaligned<Int16>();
+  pointer.value = 20;
+  Expect.equals(20, pointer.value);
+}
+
+void testUnalignedInt32() {
+  final pointer = _allocateUnaligned<Int32>();
+  pointer.value = 20;
+  Expect.equals(20, pointer.value);
+}
+
+void testUnalignedInt64() {
+  final pointer = _allocateUnaligned<Int64>();
+  pointer.value = 20;
+  Expect.equals(20, pointer.value);
+}
+
+void testUnalignedFloat() {
+  final pointer = _allocateUnaligned<Float>();
+  pointer.value = 20.0;
+  Expect.approxEquals(20.0, pointer.value);
+}
+
+void testUnalignedDouble() {
+  final pointer = _allocateUnaligned<Double>();
+  pointer.value = 20.0;
+  Expect.equals(20.0, pointer.value);
+}
+
+final Set<Pointer> _pool = {};
+
+void _freeAll() {
+  for (final pointer in _pool) {
+    calloc.free(pointer);
+  }
+}
+
+/// Up to `size<T>() == 8`.
+Pointer<T> _allocateUnaligned<T extends NativeType>() {
+  final pointer = calloc<Int8>(16);
+  _pool.add(pointer);
+  final misaligned = pointer.elementAt(1).cast<T>();
+  Expect.equals(1, misaligned.address % 2);
+  return misaligned;
+}

tests/ffi_2/unaligned_test.dart

@@ -0,0 +1,74 @@
+// Copyright (c) 2021, 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.
+
+// This tests exercises misaligned reads/writes on memory.
+//
+// The only architecture on which this is known to fail is arm32 on Android.
+
+import 'dart:ffi';
+import 'dart:io';
+
+import 'package:expect/expect.dart';
+import 'package:ffi/ffi.dart';
+
+void main() {
+  print("hello");
+  testUnalignedInt16(); //# 01: ok
+  testUnalignedInt32(); //# 02: ok
+  testUnalignedInt64(); //# 03: ok
+  if (!Platform.isAndroid || sizeOf<Pointer>() == 8) {
+    // TODO(http://dartbug.com/45009): Support unaligned reads/writes on
+    // Android arm32.
+    testUnalignedFloat(); //# 04: ok
+    testUnalignedDouble(); //# 05: ok
+  }
+  _freeAll();
+}
+
+void testUnalignedInt16() {
+  final pointer = _allocateUnaligned<Int16>();
+  pointer.value = 20;
+  Expect.equals(20, pointer.value);
+}
+
+void testUnalignedInt32() {
+  final pointer = _allocateUnaligned<Int32>();
+  pointer.value = 20;
+  Expect.equals(20, pointer.value);
+}
+
+void testUnalignedInt64() {
+  final pointer = _allocateUnaligned<Int64>();
+  pointer.value = 20;
+  Expect.equals(20, pointer.value);
+}
+
+void testUnalignedFloat() {
+  final pointer = _allocateUnaligned<Float>();
+  pointer.value = 20.0;
+  Expect.approxEquals(20.0, pointer.value);
+}
+
+void testUnalignedDouble() {
+  final pointer = _allocateUnaligned<Double>();
+  pointer.value = 20.0;
+  Expect.equals(20.0, pointer.value);
+}
+
+final Set<Pointer> _pool = {};
+
+void _freeAll() {
+  for (final pointer in _pool) {
+    calloc.free(pointer);
+  }
+}
+
+/// Up to `size<T>() == 8`.
+Pointer<T> _allocateUnaligned<T extends NativeType>() {
+  final pointer = calloc<Int8>(16);
+  _pool.add(pointer);
+  final misaligned = pointer.elementAt(1).cast<T>();
+  Expect.equals(1, misaligned.address % 2);
+  return misaligned;
+}