34 lines
1.0 KiB
C
34 lines
1.0 KiB
C
#include "nif_target.h"
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#if NIF_IS_ARCH(NIF_ARCH_X86_64)
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#include "nif_internal.h"
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#include "nif_intrinsic.h"
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static __m128i facIncrement;
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static __m128i facBase;
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INTERNAL uint64_t NIF_DECL factorial_simd_sse(int n)
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{
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facIncrement = _mm_set1_epi32(4);
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facBase = _mm_setr_epi32(1, 2, 3, 4);
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__m128i baseResult = facBase;
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__m128i facBaseLocal = facBase;
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const int cycle = (n - 3) >> 2;
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const uint32_t rest = (cycle << 2) + 1;
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for (size_t i = 0; i < cycle; i++) {
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facBaseLocal = _mm_add_epi32(facBaseLocal, facIncrement);
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baseResult = _mm_mullo_epi32(baseResult, facBaseLocal);
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}
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NIF_ALIGNAS(16) int32_t lanes[4];
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_mm_store_si128((__m128i *)lanes, baseResult);
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uint64_t result = (uint64_t)lanes[0] * (uint64_t)lanes[1] * (uint64_t)lanes[2] *
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(uint64_t)lanes[3];
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for (uint64_t i = rest; i < n; i++) {
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result *= i;
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}
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return result;
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}
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#endif
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