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Editorial Team
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Asked: 2026-05-29T06:21:06+00:00

I am translating a program written in C++ to C#, and I have come

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I am translating a program written in C++ to C#, and I have come across an intrinsic function that I cannot work around. In C++ this is known as: 

unsigned char _BitScanForward(unsigned long * Index, unsigned long Mask);

If I only knew what DLL, if any, the intrinsic functions were in, I could use P/Invoke. Since I do not know, I looked for alternatives in the .NET framework, but I have come up empty handed.

Does anyone know how use P/Invoke on _BitScanForward, or an .NET method that does the same thing?

Any help is appreciated, thank you.

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1 Answer

  1. Editorial Team

    Intrinsic functions aren’t in any library, they’re implemented inside the CPU, the compiler emits the machine code which the CPU recognizes as evoking this particular behavior.

    They’re a way of getting access to instructions that don’t have a simple C equivalent.

    Until the .NET optimizer becomes smart enough to recognize them (for example, the Mono JIT recognizes some SIMD instructions, encoded in MSIL as calls to functions of a particular class, similarly the .NET JIT replaces calls to System.Math methods with floating-point operations), your C# code is doomed to run an order of magnitude slower than the original C++.

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