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Unify Altivec/VSX pexp(double) with default implementation

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This commit is contained in:
Gael Guennebaud
2018-11-27 13:53:05 +01:00
parent 7655a8af6e
commit b5695a6008
2 changed files with 54 additions and 117 deletions
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53
Eigen/src/Core/arch/AltiVec/PacketMath.h
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@@ -1024,6 +1024,59 @@ template<> EIGEN_STRONG_INLINE Packet2d preverse(const Packet2d& a)
}
template<> EIGEN_STRONG_INLINE Packet2d pabs(const Packet2d& a) { return vec_abs(a); }
// VSX support varies between different compilers and even different
// versions of the same compiler. For gcc version >= 4.9.3, we can use
// vec_cts to efficiently convert Packet2d to Packet2l. Otherwise, use
// a slow version that works with older compilers.
// Update: apparently vec_cts/vec_ctf intrinsics for 64-bit doubles
// are buggy, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70963
static inline Packet2l ConvertToPacket2l(const Packet2d& x) {
#if EIGEN_GNUC_AT_LEAST(5, 4) || \
(EIGEN_GNUC_AT(6, 1) && __GNUC_PATCHLEVEL__ >= 1)
return vec_cts(x, 0); // TODO: check clang version.
#else
double tmp[2];
memcpy(tmp, &x, sizeof(tmp));
Packet2l l = { static_cast<long long>(tmp[0]),
static_cast<long long>(tmp[1]) };
return l;
#endif
}
template<> EIGEN_STRONG_INLINE Packet2d pldexp<Packet2d>(const Packet2d& a, const Packet2d& exponent) {
// build 2^n
Packet2l emm0 = ConvertToPacket2l(exponent);
#ifdef __POWER8_VECTOR__
const Packet2l p2l_1023 = { 1023, 1023 };
const Packet2ul p2ul_52 = { 52, 52 };
emm0 = vec_add(emm0, p2l_1023);
emm0 = vec_sl(emm0, p2ul_52);
#else
// Code is a bit complex for POWER7. There is actually a
// vec_xxsldi intrinsic but it is not supported by some gcc versions.
// So we shift (52-32) bits and do a word swap with zeros.
const Packet4i p4i_1023 = pset1<Packet4i>(1023);
const Packet4i p4i_20 = pset1<Packet4i>(20); // 52 - 32
Packet4i emm04i = reinterpret_cast<Packet4i>(emm0);
emm04i = vec_add(emm04i, p4i_1023);
emm04i = vec_sl(emm04i, reinterpret_cast<Packet4ui>(p4i_20));
static const Packet16uc perm = {
0x14, 0x15, 0x16, 0x17, 0x00, 0x01, 0x02, 0x03,
0x1c, 0x1d, 0x1e, 0x1f, 0x08, 0x09, 0x0a, 0x0b };
#ifdef _BIG_ENDIAN
emm0 = reinterpret_cast<Packet2l>(vec_perm(p4i_ZERO, emm04i, perm));
#else
emm0 = reinterpret_cast<Packet2l>(vec_perm(emm04i, p4i_ZERO, perm));
#endif
#endif
return pmul(a, reinterpret_cast<Packet2d>(emm0));
}
template<> EIGEN_STRONG_INLINE double predux<Packet2d>(const Packet2d& a)
{
Packet2d b, sum;