| /* This is the function for which it is desired to find more efficient |
| code. It must have either one or two arguments, both int, and must |
| return a 32-bit int quantity. It is declared in aha.h. */ |
| |
| int userfun(int x) { |
| // if (x > 0) return 1; // x > 0 predicate. |
| // else return 0; // Turn off div & divu. |
| // Found a new formula for HD. |
| |
| // if (x >= 32) return 0; |
| // return 1 << (unsigned)x; |
| |
| // return 3*x + 1; |
| |
| // if (x >= 0) return x; // Absolute value. |
| // else return -x; |
| |
| return (x & 0xfffffffc) | ((x & 1) << 1) | ((x & 2) >> 1); |
| // Swap rightmost 2 bits. |
| } |
