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| typedef struct { uint64_t b[4]; } uint4x64_t; | |
| // Bitsliced 4-bit adder | |
| uint4x64_t add_sliced(uint4x64_t x, uint4x64_t y) { | |
| uint4x64_t s; | |
| uint64_t c = 0; | |
| for (int i = 0; i < 4; i++) { | |
| uint64_t p = x.b[i] ^ y.b[i] | |
| s.b[i] = p ^ c; | |
| c = (x.b[i] & y.b[i]) | (p & c); | |
| } | |
| return s; | |
| } | |
| // Packed 4-bit adder with even/odd parallelism | |
| uint4x64_t add_packed(uint4x64_t x, uint4x64_t y) { | |
| enum { E = 0x0F0F0F0F0F0F0F0Full, O = ~E }; | |
| uint4x64_t s; | |
| for (int i = 0; i < 4; i++) { | |
| uint64_t se = (x.b[i] & E) + (y.b[i] & E); | |
| uint64_t so = (x.b[i] & O) + (y.b[i] & O); | |
| s.b[i] = (se & E) | (so & O); | |
| } | |
| return s; | |
| } |
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