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use faster hash mixing algo using intrinsics 128 bit multiplication

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greg
2019-03-31 19:07:53 -04:00
parent d4937d99ab
commit d5bad0bb45
2 changed files with 47 additions and 38 deletions
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parallel_hashmap/phmap_bits.h
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+15
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@@ -467,6 +467,21 @@ PHMAP_BASE_INTERNAL_FORCEINLINE int CountTrailingZerosNonZero32(uint32_t n) {
#define PHMAP_BLOCK_TAIL_CALL_OPTIMIZATION() if (volatile int x = 0) { (void)x; }
#endif
#ifdef PHMAP_HAVE_INTRINSIC_INT128
inline uint64_t umul128(uint64_t a, uint64_t b, uint64_t* high)
{
auto result = static_cast<unsigned __int128>(a) * static_cast<unsigned __int128>(b);
*high = static_cast<uint64_t>(result >> 64);
return static_cast<uint64_t>(result);
}
#elif (defined(_MSC_VER))
#pragma intrinsic(_umul128)
inline uint64_t umul128(uint64_t a, uint64_t b, uint64_t* high)
{
return _umul128(a, b, high);
}
#endif
#if defined(__GNUC__)
// Cache line alignment
#if defined(__i386__) || defined(__x86_64__)