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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#if defined(LIB_JXL_QUANTIZER_INL_H_) == defined(HWY_TARGET_TOGGLE)
#ifdef LIB_JXL_QUANTIZER_INL_H_
#undef LIB_JXL_QUANTIZER_INL_H_
#else
#define LIB_JXL_QUANTIZER_INL_H_
#endif
#include <stddef.h>
#include <hwy/highway.h>
HWY_BEFORE_NAMESPACE();
namespace jxl {
namespace HWY_NAMESPACE {
namespace {
// These templates are not found via ADL.
using hwy::HWY_NAMESPACE::Rebind;
using hwy::HWY_NAMESPACE::Vec;
template <class DI>
HWY_INLINE HWY_MAYBE_UNUSED Vec<Rebind<float, DI>> AdjustQuantBias(
DI di, const size_t c, const Vec<DI> quant_i,
const float* HWY_RESTRICT biases) {
const Rebind<float, DI> df;
const auto quant = ConvertTo(df, quant_i);
// Compare |quant|, keep sign bit for negating result.
const auto kSign = BitCast(df, Set(di, INT32_MIN));
const auto sign = And(quant, kSign); // TODO(janwas): = abs ^ orig
const auto abs_quant = AndNot(kSign, quant);
// If |x| is 1, kZeroBias creates a different bias for each channel.
// We're implementing the following:
// if (quant == 0) return 0;
// if (quant == 1) return biases[c];
// if (quant == -1) return -biases[c];
// return quant - biases[3] / quant;
// Integer comparison is not helpful because Clang incurs bypass penalties
// from unnecessarily mixing integer and float.
const auto is_01 = abs_quant < Set(df, 1.125f);
const auto not_0 = abs_quant > Zero(df);
// Bitwise logic is faster than quant * biases[c].
const auto one_bias = IfThenElseZero(not_0, Xor(Set(df, biases[c]), sign));
// About 2E-5 worse than ReciprocalNR or division.
const auto bias =
NegMulAdd(Set(df, biases[3]), ApproximateReciprocal(quant), quant);
return IfThenElse(is_01, one_bias, bias);
}
} // namespace
// NOLINTNEXTLINE(google-readability-namespace-comments)
} // namespace HWY_NAMESPACE
} // namespace jxl
HWY_AFTER_NAMESPACE();
#endif // LIB_JXL_QUANTIZER_INL_H_
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