RandomWOW/src/squareHash.h

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/*
Copyright (c) 2019 tevador
This file is part of RandomX.
RandomX is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
RandomX is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with RandomX. If not, see<http://www.gnu.org/licenses/>.
*/
/*
Based on the original idea by SChernykh:
https://github.com/SChernykh/xmr-stak-cpu/issues/1#issuecomment-414336613
*/
#include <stdint.h>
#if !defined(_M_X64) && !defined(__x86_64__)
typedef struct {
uint64_t lo;
uint64_t hi;
} uint128_t;
#define LO(x) ((x)&0xffffffff)
#define HI(x) ((x)>>32)
static inline uint128_t square128(uint64_t x) {
uint64_t xh = HI(x), xl = LO(x);
uint64_t xll = xl * xl;
uint64_t xlh = xl * xh;
uint64_t xhh = xh * xh;
uint64_t m1 = 2 * LO(xlh) + HI(xll);
uint64_t m2 = 2 * HI(xlh) + LO(xhh) + HI(m1);
uint64_t m3 = HI(xhh) + HI(m2);
uint128_t x2;
x2.lo = (m1 << 32) + LO(xll);
x2.hi = (m3 << 32) + LO(m2);
return x2;
}
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#undef LO
#undef HI
inline uint64_t squareHash(uint64_t x) {
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x += 9507361525245169745ULL;
for (int i = 0; i < 42; ++i) {
uint128_t x2 = square128(x);
x = x2.lo - x2.hi;
}
return x;
}
#else
#if defined(__cplusplus)
extern "C" {
#endif
uint64_t squareHash(uint64_t);
#if defined(__cplusplus)
}
#endif
#endif