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Extend Task.FromResult default task optimization to 16 byte unmanaged types #87541

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Merged
merged 2 commits into from
Jun 15, 2023
Merged

Extend Task.FromResult default task optimization to 16 byte unmanaged types #87541

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df8dd95
Extend Task.FromResult default task optimization to 16 byte unmanaged…
stephentoub Jun 14, 2023
d80b4ca
Fix tests to accomodate additional use of default cached task
stephentoub Jun 14, 2023
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6 changes: 4 additions & 2 deletions src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -5297,13 +5297,15 @@ public static unsafe Task<TResult> FromResult<TResult>(TResult result)
}
else if (!RuntimeHelpers.IsReferenceOrContainsReferences<TResult>())
{
// For other value types, we special-case default(TResult) if we can easily compare bit patterns to default/0.
// For other value types, we special-case default(TResult) if we can efficiently compare bit patterns to default/0,
// which means any value type that's 1, 2, 4, 8, or 16 bytes in size and that doesn't contain references.
// We don't need to go through the equality operator of the TResult because we cached a task for default(TResult),
// so we only need to confirm that this TResult has the same bits as default(TResult).
if ((sizeof(TResult) == sizeof(byte) && *(byte*)&result == default(byte)) ||
(sizeof(TResult) == sizeof(ushort) && *(ushort*)&result == default(ushort)) ||
(sizeof(TResult) == sizeof(uint) && *(uint*)&result == default) ||
(sizeof(TResult) == sizeof(ulong) && *(ulong*)&result == default))
(sizeof(TResult) == sizeof(ulong) && *(ulong*)&result == default) ||
(sizeof(TResult) == sizeof(UInt128) && *(UInt128*)&result == default))
{
return Task<TResult>.s_defaultResultTask;
}
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2 changes: 1 addition & 1 deletion ...stem.Threading.Tasks/tests/System.Runtime.CompilerServices/AsyncTaskMethodBuilderTests.cs
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Expand Up @@ -377,7 +377,7 @@ public static void TaskMethodBuilderInt32_UsesCompletedCache(int result, bool sh
[Fact]
public static void TaskMethodBuilderDecimal_DoesntUseCompletedCache()
{
TaskMethodBuilderT_UsesCompletedCache(0m, shouldBeCached: false);
TaskMethodBuilderT_UsesCompletedCache(default(decimal), shouldBeCached: true);
TaskMethodBuilderT_UsesCompletedCache(0.0m, shouldBeCached: false);
TaskMethodBuilderT_UsesCompletedCache(42m, shouldBeCached: false);
}
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95 changes: 35 additions & 60 deletions src/libraries/System.Threading.Tasks/tests/Task/TaskRtTests.cs
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Expand Up @@ -470,82 +470,57 @@ public static void FromResult_KnownResults_Cached()

// Cached

foreach (bool result in new[] { false, true })
{
Assert.Same(Task.FromResult(result), Task.FromResult(result));
Assert.Equal(result, Task.FromResult(result).Result);
}
AssertCached(false);
AssertCached(true);

for (int i = -1; i <= 8; i++)
{
Assert.Same(Task.FromResult(i), Task.FromResult(i));
Assert.Equal(i, Task.FromResult(i).Result);
AssertCached(i);
}

Assert.Same(Task.FromResult('\0'), Task.FromResult('\0'));
Assert.Equal('\0', Task.FromResult('\0').Result);

Assert.Same(Task.FromResult((byte)0), Task.FromResult((byte)0));
Assert.Equal(0, Task.FromResult((byte)0).Result);

Assert.Same(Task.FromResult((ushort)0), Task.FromResult((ushort)0));
Assert.Equal(0, Task.FromResult((ushort)0).Result);

Assert.Same(Task.FromResult((uint)0), Task.FromResult((uint)0));
Assert.Equal(0u, Task.FromResult((uint)0).Result);

Assert.Same(Task.FromResult((ulong)0), Task.FromResult((ulong)0));
Assert.Equal(0ul, Task.FromResult((ulong)0).Result);

Assert.Same(Task.FromResult((sbyte)0), Task.FromResult((sbyte)0));
Assert.Equal(0, Task.FromResult((sbyte)0).Result);

Assert.Same(Task.FromResult((short)0), Task.FromResult((short)0));
Assert.Equal(0, Task.FromResult((short)0).Result);

Assert.Same(Task.FromResult((long)0), Task.FromResult((long)0));
Assert.Equal(0, Task.FromResult((long)0).Result);

Assert.Same(Task.FromResult(IntPtr.Zero), Task.FromResult(IntPtr.Zero));
Assert.Equal(IntPtr.Zero, Task.FromResult(IntPtr.Zero).Result);

Assert.Same(Task.FromResult(UIntPtr.Zero), Task.FromResult(UIntPtr.Zero));
Assert.Equal(UIntPtr.Zero, Task.FromResult(UIntPtr.Zero).Result);

Assert.Same(Task.FromResult((Half)default), Task.FromResult((Half)default));
Assert.Equal((Half)default, Task.FromResult((Half)default).Result);

Assert.Same(Task.FromResult((float)default), Task.FromResult((float)default));
Assert.Equal((float)default, Task.FromResult((float)default).Result);

Assert.Same(Task.FromResult((double)default), Task.FromResult((double)default));
Assert.Equal((double)default, Task.FromResult((double)default).Result);

Assert.Same(Task.FromResult((TimeSpan)default), Task.FromResult((TimeSpan)default));
Assert.Equal((TimeSpan)default, Task.FromResult((TimeSpan)default).Result);

Assert.Same(Task.FromResult((DateTime)default), Task.FromResult((DateTime)default));
Assert.Equal((DateTime)default, Task.FromResult((DateTime)default).Result);

Assert.Same(Task.FromResult((object)null), Task.FromResult((object)null));
Assert.Null(Task.FromResult((object)null).Result);

Assert.Same(Task.FromResult((string)null), Task.FromResult((string)null));
Assert.Null(Task.FromResult((string)null).Result);
AssertCached<byte>();
AssertCached<sbyte>();
AssertCached<char>();
AssertCached<ushort>();
AssertCached<short>();
AssertCached<uint>();
AssertCached<int>();
AssertCached<ulong>();
AssertCached<long>();
AssertCached<nuint>();
AssertCached<nint>();
AssertCached<Half>();
AssertCached<float>();
AssertCached<double>();
AssertCached<decimal>();
AssertCached<TimeSpan>();
AssertCached<DateTime>();
AssertCached<Guid>();
AssertCached<Int128>();
AssertCached<UInt128>();
AssertCached<DayOfWeek>();
AssertCached<string>();
AssertCached<object>();

static void AssertCached<T>(T value = default)
{
Assert.Same(Task.FromResult(value), Task.FromResult(value));
Assert.Equal(value, Task.FromResult(value).Result);
}

// Not cached
// Not currently cached

foreach (int i in new[] { -2, 9, int.MinValue, int.MaxValue })
{
Assert.NotSame(Task.FromResult(i), Task.FromResult(i));
Assert.Equal(i, Task.FromResult(i).Result);
}

// Should never return the same task

Assert.NotSame(Task.FromResult((double)(+0.0)), Task.FromResult((double)(-0.0)));
Assert.NotSame(Task.FromResult((float)(+0.0)), Task.FromResult((float)(-0.0)));
Assert.NotSame(Task.FromResult((Half)(+0.0)), Task.FromResult((Half)(-0.0)));

Assert.NotSame(Task.FromResult((decimal)default), Task.FromResult((decimal)default));
}

[Fact]
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