[benchmarks/ffi] Memory access with asTypedList

Adds benchmarks using `asTypedList` on Pointers to investigate from
where it pays of to do construct a TypedData to do memory access
instead of on the Pointer directly.

x64 JIT results:
- Memory access on TypedData (int8) is ~2,5 faster than on Pointer.
FfiMemory.PointerInt8(RunTime): 72.23885718413639 us.
FfiMemory.PointerInt8TypedDataReuse(RunTime): 28.239710263614928 us.

- Constructing the TypedData for 1000 reads + 1000 writes takes ~20%
  of the total runtime, 400 reads or writes on TypedData, 160 reads
  or writes on Pointer.
FfiMemory.PointerInt8TypedDataNew(RunTime): 34.345480148372026 us.
FfiMemory.PointerInt8TypedDataReuse(RunTime): 28.239710263614928 us.

x64 AOT results:
FfiMemory.PointerInt8(RunTime): 13.862134213116345 us.
FfiMemory.PointerInt8TypedDataNew(RunTime): 26.149628021913365 us.
FfiMemory.PointerInt8TypedDataReuse(RunTime): 24.73322780505299 us.
- Using asTypedList is slower. (Some optimizations fail to kick in.)

Change-Id: I401edb88baf3a3c5094ecae808f122adf258da28
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/186289
Reviewed-by: Clement Skau <cskau@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>

benchmarks/FfiMemory/dart/FfiMemory.dart

@@ -10,6 +10,7 @@
 // Dart with a specific marshalling and unmarshalling of data.
 
 import 'dart:ffi';
+import 'dart:typed_data';
 
 import 'package:ffi/ffi.dart';
 import 'package:benchmark_harness/benchmark_harness.dart';
@@ -24,6 +25,12 @@ void doStoreInt8(Pointer<Int8> pointer, int length) {
   }
 }
 
+void doStoreInt8TypedData(Int8List typedData, int length) {
+  for (int i = 0; i < length; i++) {
+    typedData[i] = 1;
+  }
+}
+
 void doStoreUint8(Pointer<Uint8> pointer, int length) {
   for (int i = 0; i < length; i++) {
     pointer[i] = 1;
@@ -103,6 +110,14 @@ int doLoadInt8(Pointer<Int8> pointer, int length) {
   return x;
 }
 
+int doLoadInt8TypedData(Int8List typedData, int length) {
+  int x = 0;
+  for (int i = 0; i < length; i++) {
+    x += typedData[i];
+  }
+  return x;
+}
+
 int doLoadUint8(Pointer<Uint8> pointer, int length) {
   int x = 0;
   for (int i = 0; i < length; i++) {
@@ -224,6 +239,62 @@ class PointerInt8 extends BenchmarkBase {
   }
 }
 
+class PointerInt8TypedDataNew extends BenchmarkBase {
+  Pointer<Int8> pointer = nullptr;
+  PointerInt8TypedDataNew() : super('FfiMemory.PointerInt8TypedDataNew');
+
+  @override
+  void setup() {
+    pointer = calloc(N);
+  }
+
+  @override
+  void teardown() {
+    calloc.free(pointer);
+    pointer = nullptr;
+  }
+
+  @override
+  void run() {
+    final typedData = pointer.asTypedList(N);
+    doStoreInt8TypedData(typedData, N);
+    final int x = doLoadInt8TypedData(typedData, N);
+    if (x != N) {
+      throw Exception('$name: Unexpected result: $x, expected $N');
+    }
+  }
+}
+
+final emptyTypedData = Int8List(0);
+
+class PointerInt8TypedDataReuse extends BenchmarkBase {
+  Pointer<Int8> pointer = nullptr;
+  Int8List typedData = emptyTypedData;
+  PointerInt8TypedDataReuse() : super('FfiMemory.PointerInt8TypedDataReuse');
+
+  @override
+  void setup() {
+    pointer = calloc(N);
+    typedData = pointer.asTypedList(N);
+  }
+
+  @override
+  void teardown() {
+    calloc.free(pointer);
+    pointer = nullptr;
+    typedData = emptyTypedData;
+  }
+
+  @override
+  void run() {
+    doStoreInt8TypedData(typedData, N);
+    final int x = doLoadInt8TypedData(typedData, N);
+    if (x != N) {
+      throw Exception('$name: Unexpected result: $x, expected $N');
+    }
+  }
+}
+
 class PointerUint8 extends BenchmarkBase {
   Pointer<Uint8> pointer = nullptr;
   PointerUint8() : super('FfiMemory.PointerUint8');
@@ -449,6 +520,8 @@ class PointerInt64Mint extends BenchmarkBase {
 void main() {
   final benchmarks = [
     () => PointerInt8(),
+    () => PointerInt8TypedDataNew(),
+    () => PointerInt8TypedDataReuse(),
     () => PointerUint8(),
     () => PointerInt16(),
     () => PointerUint16(),

benchmarks/FfiMemory/dart2/FfiMemory.dart

@@ -12,6 +12,7 @@
 // @dart=2.9
 
 import 'dart:ffi';
+import 'dart:typed_data';
 
 import 'package:ffi/ffi.dart';
 import 'package:benchmark_harness/benchmark_harness.dart';
@@ -26,6 +27,12 @@ void doStoreInt8(Pointer<Int8> pointer, int length) {
   }
 }
 
+void doStoreInt8TypedData(Int8List typedData, int length) {
+  for (int i = 0; i < length; i++) {
+    typedData[i] = 1;
+  }
+}
+
 void doStoreUint8(Pointer<Uint8> pointer, int length) {
   for (int i = 0; i < length; i++) {
     pointer[i] = 1;
@@ -105,6 +112,14 @@ int doLoadInt8(Pointer<Int8> pointer, int length) {
   return x;
 }
 
+int doLoadInt8TypedData(Int8List typedData, int length) {
+  int x = 0;
+  for (int i = 0; i < length; i++) {
+    x += typedData[i];
+  }
+  return x;
+}
+
 int doLoadUint8(Pointer<Uint8> pointer, int length) {
   int x = 0;
   for (int i = 0; i < length; i++) {
@@ -226,6 +241,60 @@ class PointerInt8 extends BenchmarkBase {
   }
 }
 
+class PointerInt8TypedDataNew extends BenchmarkBase {
+  Pointer<Int8> pointer;
+  PointerInt8TypedDataNew() : super('FfiMemory.PointerInt8TypedDataNew');
+
+  @override
+  void setup() {
+    pointer = calloc(N);
+  }
+
+  @override
+  void teardown() {
+    calloc.free(pointer);
+    pointer = null;
+  }
+
+  @override
+  void run() {
+    final typedData = pointer.asTypedList(N);
+    doStoreInt8TypedData(typedData, N);
+    final int x = doLoadInt8TypedData(typedData, N);
+    if (x != N) {
+      throw Exception('$name: Unexpected result: $x, expected $N');
+    }
+  }
+}
+
+class PointerInt8TypedDataReuse extends BenchmarkBase {
+  Pointer<Int8> pointer;
+  Int8List typedData;
+  PointerInt8TypedDataReuse() : super('FfiMemory.PointerInt8TypedDataReuse');
+
+  @override
+  void setup() {
+    pointer = calloc(N);
+    typedData = pointer.asTypedList(N);
+  }
+
+  @override
+  void teardown() {
+    calloc.free(pointer);
+    pointer = null;
+    typedData = null;
+  }
+
+  @override
+  void run() {
+    doStoreInt8TypedData(typedData, N);
+    final int x = doLoadInt8TypedData(typedData, N);
+    if (x != N) {
+      throw Exception('$name: Unexpected result: $x, expected $N');
+    }
+  }
+}
+
 class PointerUint8 extends BenchmarkBase {
   Pointer<Uint8> pointer;
   PointerUint8() : super('FfiMemory.PointerUint8');
@@ -451,6 +520,8 @@ class PointerInt64Mint extends BenchmarkBase {
 void main() {
   final benchmarks = [
     () => PointerInt8(),
+    () => PointerInt8TypedDataNew(),
+    () => PointerInt8TypedDataReuse(),
     () => PointerUint8(),
     () => PointerInt16(),
     () => PointerUint16(),