Use Unsafe.ReadUnaligned for vector creation in SpanHelpers.Fill
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MihaZupan
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Jan 4, 2025
src/libraries/System.Private.CoreLib/src/System/SpanHelpers.T.cs
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This reverts commit 93e46f0.
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Unsafe.BitCast to avoid taking addressUnsafe.BitCast in SpanHelprs.Fill
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Unsafe.BitCast in SpanHelprs.FillUnsafe.BitCast in SpanHelpers.Fill
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Unsafe.BitCast in SpanHelpers.FillSpanHelpers.Fill
This was referenced Feb 6, 2025
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SpanHelpers.FillUnsafe.ReadUnaligned for vector creation in SpanHelpers.Fill
| @@ -34,29 +34,29 @@ public static unsafe void Fill<T>(ref T refData, nuint numElements, T value) | |||
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| if (sizeof(T) == 1) | |||
| { | |||
| vector = new Vector<byte>(Unsafe.As<T, byte>(ref tmp)); | |||
| vector = Vector.Create(Unsafe.As<T, byte>(ref tmp)); | |||
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these should rather use Vector.LoadUnsafe(ref tmp).AsByte() or similar.
We should be explicit that its a load API and not do extra or other things that the JIT has to elide or reason about
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Ah nevermind, I see the issue here. This is doing a broadcast and is reinterpreting the ref to a supported T
This pattern in general is not great and something that we probably should have a centralized helper or some other API around...
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This was referenced Feb 12, 2025
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We should use
Unsafe.ReadUnalignedinstead ofUnsafe.As<T, ushort>(ref tmp)as the alignment of a typeTmay be less than its size.Zero code generation diffs.