cmov.cs

// 'valueIfTrue' and 'valueIfFalse' really should be compile-time constants for maximum throughput.
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static int ConditionalSelect(bool condition, int valueIfTrue, int valueIfFalse)
{
    // From https://software.intel.com/sites/default/files/managed/9e/bc/64-ia-32-architectures-optimization-manual.pdf
    // Example 3.2. We're taking advantage of the fact that bools are passed by value as 32-bit integers,
    // so we'll blit it directly into a 1 or a 0 without a jump.
    // Codegen will emit a movzx, but on Ivy Bridge (and later) the CPU itself elides the instruction.
    return ((-Unsafe.As<bool, int>(ref condition)) & (valueIfTrue - valueIfFalse)) + valueIfFalse;
}

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