7-thaumaturgy-7964.md - tgtimes - The Gopher Times
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7-thaumaturgy-7964.md (585B)
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1 # This's opus C Thaumaturgy
2
3 // Returns the smaller integer of x and y but without a branch
4 // (if/else/ternary, goto etc..)
5 // Normally min is implemented something like this:
6 // return x < y ? x : y;
7 // But we have a branch there so let's do it witout. (The branch
8 // free min could be used to merge arrays for example.)
9 // If x < y, then -(x < y) => -1 => all 1's in two complement
10 // representation.
11 // So we have y ^ (x ^ y) => x
12 // If x >= y, then -(x < y) => 0 so y ^ 0 is y.
13
14 static inline uint8_t min(const uint8_t x, const uint8_t y) {
15 return y ^ ((x ^ y) & -(x < y));
16 }