signal/src/max_abs.cc

/* Copyright 2023 The TensorFlow Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#include "signal/src/max_abs.h"

#if defined(XTENSA)
#include <stdint.h>
#include <xtensa/tie/xt_misc.h>
#endif
#if XCHAL_HAVE_HIFI3
#include <xtensa/tie/xt_hifi3.h>
static inline ae_p24x2s MaxAbs16Single(ae_p24x2s max, ae_p24x2s current) {
  return AE_MAXABSSP24S(max, current);
}
#elif XCHAL_HAVE_HIFI_MINI || XCHAL_HAVE_HIFI2 || XCHAL_HAVE_HIFI_EP
#include <xtensa/tie/xt_hifi2.h>
static inline ae_p24x2s MaxAbs16Single(ae_p24x2s max, ae_p24x2s current) {
  current = AE_ABSSP24S(current);
  return AE_MAXP24S(max, current);
}
#endif

// TODO(b/286250473): remove namespace once de-duped libraries
namespace tflite {
namespace tflm_signal {

#if XCHAL_HAVE_HIFI_MINI || XCHAL_HAVE_HIFI2 || XCHAL_HAVE_HIFI_EP || \
    XCHAL_HAVE_HIFI3
int16_t XtensaMaxAbs16(const int16_t* input, int size) {
  int i;
  ae_p24x2s current_24x2;
  // AE_LP16X2F_IU() effectively pre-increments the address in input_16x2 by 4
  //  bytes before loading, so we need to initialize it accordingly.
  const ae_p16x2s* input_16x2 = (const ae_p16x2s*)(input - 2);
  ae_p24x2s max = AE_ZEROP48();
  const int num_iterations = size / 2;
  for (i = 0; i < num_iterations; i++) {
    // Advancing the pointer by 2 X 16-bits.
    AE_LP16X2F_IU(current_24x2, input_16x2, 4);
    max = MaxAbs16Single(max, current_24x2);
  }
  if (size & 1) {  // n is odd
    // Advancing the pointer by 2 X 16-bits.
    current_24x2 = AE_LP16F_I((ae_p16s*)input_16x2, 4);
    max = MaxAbs16Single(max, current_24x2);
  }
  const int max_L = AE_TRUNCA16P24S_L(max);
  const int max_H = AE_TRUNCA16P24S_H(max);
  return (max_L >= max_H) ? max_L : max_H;
}
#endif

int16_t MaxAbs16(const int16_t* input, int size) {
#if XCHAL_HAVE_HIFI_MINI || XCHAL_HAVE_HIFI2 || XCHAL_HAVE_HIFI_EP || \
    XCHAL_HAVE_HIFI3
  return XtensaMaxAbs16(input, size);
#else
  int16_t max = 0;
  for (int i = 0; i < size; i++) {
    const int16_t value = input[i];
    if (value > max) {
      max = value;
    } else if (-value > max) {
      max = -value;
    }
  }
  return max;
#endif
}

}  // namespace tflm_signal
}  // namespace tflite