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Fix ldexp for AVX512 (#2215)

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Wrong shuffle was used.  Need to interleave low/high halves with a
`permute` instruction.

Fixes #2215.
This commit is contained in:
Antonio Sanchez 2021-04-14 13:54:11 -07:00 committed by Rasmus Munk Larsen
parent 3e819d83bf
commit 1d79c68ba0
1 changed files with 3 additions and 2 deletions
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5
Eigen/src/Core/arch/AVX512/PacketMath.h
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@ -929,7 +929,8 @@ template<> EIGEN_STRONG_INLINE Packet8d pldexp<Packet8d>(const Packet8d& a, cons
Packet8i b = parithmetic_shift_right<2>(e); // floor(e/4)
// 2^b
Packet8i hi = _mm256_shuffle_epi32(padd(b, bias), _MM_SHUFFLE(3, 1, 2, 0));
const Packet8i permute_idx = _mm256_setr_epi32(0, 4, 1, 5, 2, 6, 3, 7);
Packet8i hi = _mm256_permutevar8x32_epi32(padd(b, bias), permute_idx);
Packet8i lo = _mm256_slli_epi64(hi, 52);
hi = _mm256_slli_epi64(_mm256_srli_epi64(hi, 32), 52);
Packet8d c = _mm512_castsi512_pd(_mm512_inserti64x4(_mm512_castsi256_si512(lo), hi, 1));
@ -937,7 +938,7 @@ template<> EIGEN_STRONG_INLINE Packet8d pldexp<Packet8d>(const Packet8d& a, cons
// 2^(e - 3b)
b = psub(psub(psub(e, b), b), b); // e - 3b
hi = _mm256_shuffle_epi32(padd(b, bias), _MM_SHUFFLE(3, 1, 2, 0));
hi = _mm256_permutevar8x32_epi32(padd(b, bias), permute_idx);
lo = _mm256_slli_epi64(hi, 52);
hi = _mm256_slli_epi64(_mm256_srli_epi64(hi, 32), 52);
c = _mm512_castsi512_pd(_mm512_inserti64x4(_mm512_castsi256_si512(lo), hi, 1));