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KawPow: fixed crash on old CPUs

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- Use `popcnt` instruction only when it's supported
This commit is contained in:
SChernykh 2020-06-10 21:49:43 +02:00
parent e4c8714daa
commit dc0aee1432
3 changed files with 27 additions and 3 deletions
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27
src/crypto/kawpow/KPHash.cpp
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@ -25,6 +25,7 @@
*/
#include "backend/cpu/Cpu.h"
#include "crypto/kawpow/KPHash.h"
#include "crypto/kawpow/KPCache.h"
#include "3rdparty/libethash/ethash.h"
@ -156,7 +157,22 @@ static inline uint32_t popcount(uint32_t a)
}
static inline uint32_t random_math(uint32_t a, uint32_t b, uint32_t selector)
// Taken from https://en.wikipedia.org/wiki/Hamming_weight
static inline uint32_t popcount_soft(uint64_t x)
{
constexpr uint64_t m1 = 0x5555555555555555ull;
constexpr uint64_t m2 = 0x3333333333333333ull;
constexpr uint64_t m4 = 0x0f0f0f0f0f0f0f0full;
constexpr uint64_t h01 = 0x0101010101010101ull;
x -= (x >> 1) & m1; //put count of each 2 bits into those 2 bits
x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits
x = (x + (x >> 4)) & m4; //put count of each 8 bits into those 8 bits
return (x * h01) >> 56; //returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24) + ...
}
static inline uint32_t random_math(uint32_t a, uint32_t b, uint32_t selector, bool has_popcnt)
{
switch (selector % 11)
{
@ -181,7 +197,10 @@ static inline uint32_t random_math(uint32_t a, uint32_t b, uint32_t selector)
case 9:
return clz(a) + clz(b);
case 10:
return popcount(a) + popcount(b);
if (has_popcnt)
return popcount(a) + popcount(b);
else
return popcount_soft(a) + popcount_soft(b);
default:
#ifdef _MSC_VER
__assume(false);
@ -260,6 +279,8 @@ void KPHash::calculate(const KPCache& light_cache, uint32_t block_height, const
uint32_t jsr0 = jsr;
uint32_t jcong0 = jcong;
const bool has_popcnt = Cpu::info()->has(ICpuInfo::FLAG_POPCNT);
for (uint32_t r = 0; r < ETHASH_ACCESSES; ++r) {
uint32_t item_index = (mix[r % LANES][0] % num_items) * 4;
@ -302,7 +323,7 @@ void KPHash::calculate(const KPCache& light_cache, uint32_t block_height, const
for (size_t l = 0; l < LANES; ++l)
{
const uint32_t data = random_math(mix[l][src1], mix[l][src2], sel1);
const uint32_t data = random_math(mix[l][src1], mix[l][src2], sel1, has_popcnt);
random_merge(mix[l][dst], data, sel2);
}
}