[mmozeiko]

There is a simple way to get that immediate from expression you want to calculate. For example, if you want to calculate following expression:

    (NOT A) OR ((NOT B) XOR (C AND A))

then you simply write

    ~_MM_TERNLOG_A | (~_MM_TERNLOG_B ^ (_MM_TERNLOG_C & _MM_TERNLOG_A))

Literally the expression you want to calculate. It evaluates to immediate from _MM_TERNLOG_A/B/C constants defined in intrinsic headers, at least for gcc & clang:

    typedef enum {
      _MM_TERNLOG_A = 0xF0,
      _MM_TERNLOG_B = 0xCC,
      _MM_TERNLOG_C = 0xAA
    } _MM_TERNLOG_ENUM;

For MSVC you define them yourself.

[o11c]

To take the magic away, write it in binary:

  A = 0b11110000
  B = 0b11001100
  C = 0b10101010

[meow_catrix]

The Amiga manual suggests normalizing to a conjunctive normal form.

[bcoates]

The constant-math method above doesn't require that and works on denormalized expressions, too.

That said, the trick for turning four or more argument bitwise operations into a series of vpternlogd operations has yet to be posted

[LegionMammal978]

Suppose you have four boolean variables A, B, C, and D. You can calculate X as the result from A, B, C assuming that D is false, and Y as the result assuming that D is true. Then, a third ternary operation can switch between X and Y depending on D. This creates a tree of 3 operations, which I suspect is the best you can do in the worst case.

For five or more arguments, this naturally extends into a tree, though it likely isn't the most efficient encoding.