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Fix rint SSE/NEON again, using optimization barrier.

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This is a new version of !423, which failed for MSVC.

Defined `EIGEN_OPTIMIZATION_BARRIER(X)` that uses inline assembly to
prevent operations involving `X` from crossing that barrier. Should
work on most `GNUC` compatible compilers (MSVC doesn't seem to need
this). This is a modified version adapted from what was used in
`psincos_float` and tested on more platforms
(see #1674, https://godbolt.org/z/73ezTG).

Modified `rint` to use the barrier to prevent the add/subtract rounding
trick from being optimized away.

Also fixed an edge case for large inputs that get bumped up a power of two
and ends up rounding away more than just the fractional part.  If we are
over `2^digits` then just return the input.  This edge case was missed in
the test since the test was comparing approximate equality, which was still
satisfied.  Adding a strict equality option catches it.
This commit is contained in:
Antonio Sanchez
2021-03-03 19:22:15 -08:00
parent 5f0b4a4010
commit 82d61af3a4
6 changed files with 172 additions and 50 deletions
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45
test/packetmath.cpp
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@@ -299,6 +299,29 @@ void packetmath_minus_zero_add() {
CHECK_CWISE2_IF(internal::packet_traits<Scalar>::HasAdd, REF_ADD, internal::padd);
}
// Ensure optimization barrier compiles and doesn't modify contents.
// Only applies to raw types, so will not work for std::complex, Eigen::half
// or Eigen::bfloat16. For those you would need to refer to an underlying
// storage element.
template<typename Packet, typename EnableIf = void>
struct eigen_optimization_barrier_test {
static void run() {}
};
template<typename Packet>
struct eigen_optimization_barrier_test<Packet, typename internal::enable_if<
!NumTraits<Packet>::IsComplex &&
!internal::is_same<Packet, Eigen::half>::value &&
!internal::is_same<Packet, Eigen::bfloat16>::value
>::type> {
static void run() {
typedef typename internal::unpacket_traits<Packet>::type Scalar;
Scalar s = internal::random<Scalar>();
Packet barrier = internal::pset1<Packet>(s);
EIGEN_OPTIMIZATION_BARRIER(barrier);
eigen_assert(s == internal::pfirst(barrier) && "EIGEN_OPTIMIZATION_BARRIER");
}
};
template <typename Scalar, typename Packet>
void packetmath() {
@@ -317,6 +340,10 @@ void packetmath() {
EIGEN_ALIGN_MAX Scalar data3[size];
EIGEN_ALIGN_MAX Scalar ref[size];
RealScalar refvalue = RealScalar(0);
eigen_optimization_barrier_test<Packet>::run();
eigen_optimization_barrier_test<Scalar>::run();
for (int i = 0; i < size; ++i) {
data1[i] = internal::random<Scalar>() / RealScalar(PacketSize);
data2[i] = internal::random<Scalar>() / RealScalar(PacketSize);
@@ -543,10 +570,10 @@ void packetmath_real() {
CHECK_CWISE1_IF(PacketTraits::HasCos, std::cos, internal::pcos);
CHECK_CWISE1_IF(PacketTraits::HasTan, std::tan, internal::ptan);
CHECK_CWISE1_IF(PacketTraits::HasRound, numext::round, internal::pround);
CHECK_CWISE1_IF(PacketTraits::HasCeil, numext::ceil, internal::pceil);
CHECK_CWISE1_IF(PacketTraits::HasFloor, numext::floor, internal::pfloor);
CHECK_CWISE1_IF(PacketTraits::HasRint, numext::rint, internal::print);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasRound, numext::round, internal::pround);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasCeil, numext::ceil, internal::pceil);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasFloor, numext::floor, internal::pfloor);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasRint, numext::rint, internal::print);
// Rounding edge cases.
if (PacketTraits::HasRound || PacketTraits::HasCeil || PacketTraits::HasFloor || PacketTraits::HasRint) {
@@ -583,10 +610,10 @@ void packetmath_real() {
for (size_t k=0; k<values.size(); ++k) {
data1[0] = values[k];
CHECK_CWISE1_IF(PacketTraits::HasRound, numext::round, internal::pround);
CHECK_CWISE1_IF(PacketTraits::HasCeil, numext::ceil, internal::pceil);
CHECK_CWISE1_IF(PacketTraits::HasFloor, numext::floor, internal::pfloor);
CHECK_CWISE1_IF(PacketTraits::HasRint, numext::rint, internal::print);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasRound, numext::round, internal::pround);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasCeil, numext::ceil, internal::pceil);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasFloor, numext::floor, internal::pfloor);
CHECK_CWISE1_EXACT_IF(PacketTraits::HasRint, numext::rint, internal::print);
}
}
@@ -644,7 +671,7 @@ void packetmath_real() {
if (PacketTraits::HasExp) {
data1[0] = Scalar(-1);
// underflow to zero
data1[PacketSize] = Scalar(std::numeric_limits<Scalar>::min_exponent-10);
data1[PacketSize] = Scalar(std::numeric_limits<Scalar>::min_exponent-55);
CHECK_CWISE2_IF(PacketTraits::HasExp, REF_LDEXP, internal::pldexp);
// overflow to inf
data1[PacketSize] = Scalar(std::numeric_limits<Scalar>::max_exponent+10);