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Remove unsafe code from Log2SoftwareFallback #118560

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Remove unsafe code from Log2SoftwareFallback #118560

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8 changes: 2 additions & 6 deletions src/libraries/System.Private.CoreLib/src/System/Numerics/BitOperations.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -389,12 +389,8 @@ private static int Log2SoftwareFallback(uint value)
value |= value >> 08;
value |= value >> 16;

// uint.MaxValue >> 27 is always in range [0 - 31] so we use Unsafe.AddByteOffset to avoid bounds check
return Unsafe.AddByteOffset(
// Using deBruijn sequence, k=2, n=5 (2^5=32) : 0b_0000_0111_1100_0100_1010_1100_1101_1101u
ref MemoryMarshal.GetReference(Log2DeBruijn),
// uint|long -> IntPtr cast on 32-bit platforms does expensive overflow checks not needed here
(IntPtr)(int)((value * 0x07C4ACDDu) >> 27));
// Using deBruijn sequence, k=2, n=5 (2^5=32) : 0b_0000_0111_1100_0100_1010_1100_1101_1101u
return Log2DeBruijn[(int)((value * 0x07C4ACDDu) >> 27)];
}

/// <summary>Returns the integer (ceiling) log of the specified value, base 2.</summary>
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