dl/sp/src/arm/arm64/omxSP_FFTInv_CToC_FC32.c

/*
 *  Copyright (c) 2014 The WebRTC 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 in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include <arm_neon.h>

#include "dl/api/omxtypes.h"
#include "dl/sp/api/armSP.h"
#include "dl/sp/api/omxSP.h"

extern void armSP_FFTInv_CToC_FC32_Radix2_fs_OutOfPlace(
    const OMX_FC32* pSrc,
    OMX_FC32* pDst,
    OMX_FC32* pTwiddle,
    long* subFFTNum,
    long* subFFTSize);

extern void armSP_FFTInv_CToC_FC32_Radix2_ls_OutOfPlace(
    const OMX_FC32* pSrc,
    OMX_FC32* pDst,
    OMX_FC32* pTwiddle,
    long* subFFTNum,
    long* subFFTSize);

extern void armSP_FFTInv_CToC_FC32_Radix2_OutOfPlace(
    const OMX_FC32* pSrc,
    OMX_FC32* pDst,
    OMX_FC32* pTwiddle,
    long* subFFTNum,
    long* subFFTSize);

extern void armSP_FFTInv_CToC_FC32_Radix4_fs_OutOfPlace(
    const OMX_FC32* pSrc,
    OMX_FC32* pDst,
    OMX_FC32* pTwiddle,
    long* subFFTNum,
    long* subFFTSize);

extern void armSP_FFTInv_CToC_FC32_Radix4_OutOfPlace(
    const OMX_FC32* pSrc,
    OMX_FC32* pDst,
    OMX_FC32* pTwiddle,
    long* subFFTNum,
    long* subFFTSize);

extern void armSP_FFTInv_CToC_FC32_Radix4_ls_OutOfPlace(
    const OMX_FC32* pSrc,
    OMX_FC32* pDst,
    OMX_FC32* pTwiddle,
    long* subFFTNum,
    long* subFFTSize);

extern void armSP_FFTInv_CToC_FC32_Radix8_fs_OutOfPlace(
    const OMX_FC32* pSrc,
    OMX_FC32* pDst,
    OMX_FC32* pTwiddle,
    long* subFFTNum,
    long* subFFTSize);

/*
 * Scale FFT data by 1/|length|. |length| must be a power of two
 */
static inline ScaleFFTData(OMX_FC32* fftData, unsigned length) {
  float32_t* data = (float32_t*)fftData;
  float32_t scale = 1.0f / length;

  /*
   * Do two complex elements at a time because |length| is always
   * greater than or equal to 2 (order >= 1)
   */
  do {
    float32x4_t x = vld1q_f32(data);

    length -= 2;
    x = vmulq_n_f32(x, scale);
    vst1q_f32(data, x);
    data += 4;
  } while (length > 0);
}

/**
 * Function:  omxSP_FFTInv_CToC_FC32
 *
 * Description:
 * These functions compute an inverse FFT for a complex signal of
 * length of 2^order, where 0 <= order <= 15. Transform length is
 * determined by the specification structure, which must be
 * initialized prior to calling the FFT function using the appropriate
 * helper, i.e., <FFTInit_C_FC32>. The relationship between the input
 * and output sequences can be expressed in terms of the IDFT, i.e.:
 *
 *     x[n] = SUM[k=0,...,N-1] X[k].e^(jnk.2.pi/N)
 *     n=0,1,2,...N-1
 *     N=2^order.
 *
 * Input Arguments:
 *   pSrc - pointer to the complex-valued input signal, of length 2^order ;
 *          must be aligned on a 32-byte boundary.
 *   pFFTSpec - pointer to the preallocated and initialized specification
 *            structure
 *
 * Output Arguments:
 *   order
 *   pDst - pointer to the complex-valued output signal, of length 2^order;
 *          must be aligned on a 32-byte boundary.
 *
 * Return Value:
 *
 *    OMX_Sts_NoErr - no error
 *    OMX_Sts_BadArgErr - returned if one or more of the following conditions
 *              is true:
 *    -   one or more of the following pointers is NULL: pSrc, pDst, or
 *              pFFTSpec.
 *    -   pSrc or pDst is not 32-byte aligned
 *
 */

OMXResult omxSP_FFTInv_CToC_FC32_Sfs(const OMX_FC32* pSrc,
                                     OMX_FC32* pDst,
                                     const OMXFFTSpec_C_FC32* pFFTSpec) {
  ARMsFFTSpec_FC32* spec = (ARMsFFTSpec_FC32*)pFFTSpec;
  int order;
  long subFFTSize;
  long subFFTNum;
  OMX_FC32* pTwiddle;
  OMX_FC32* pOut;

  /*
   * Check args are not NULL and the source and destination pointers
   * are properly aligned.
   */
  if (!validateParametersFC32(pSrc, pDst, spec))
    return OMX_Sts_BadArgErr;

  order = fastlog2(spec->N);

  subFFTSize = 1;
  subFFTNum = spec->N;
  pTwiddle = spec->pTwiddle;
  pOut = spec->pBuf;

  if (order > 3) {
    OMX_FC32* argDst;

    /*
     * Set up argDst and pOut appropriately so that pOut = pDst for
     * the very last FFT stage.
     */
    if ((order & 2) == 0) {
      argDst = pOut;
      pOut = pDst;
    } else {
      argDst = pDst;
    }

    /*
     * Odd order uses a radix 8 first stage; even order, a radix 4
     * first stage.
     */
    if (order & 1) {
      armSP_FFTInv_CToC_FC32_Radix8_fs_OutOfPlace(
          pSrc, argDst, pTwiddle, &subFFTNum, &subFFTSize);
    } else {
      armSP_FFTInv_CToC_FC32_Radix4_fs_OutOfPlace(
          pSrc, argDst, pTwiddle, &subFFTNum, &subFFTSize);
    }

    /*
     * Now use radix 4 stages to finish rest of the FFT
     */
    if (subFFTNum >= 4) {
      while (subFFTNum > 4) {
        OMX_FC32* tmp;

        armSP_FFTInv_CToC_FC32_Radix4_OutOfPlace(
            argDst, pOut, pTwiddle, &subFFTNum, &subFFTSize);
        /*
         * Swap argDst and pOut
         */
        tmp = pOut;
        pOut = argDst;
        argDst = tmp;
      }

      armSP_FFTInv_CToC_FC32_Radix4_ls_OutOfPlace(
          argDst, pOut, pTwiddle, &subFFTNum, &subFFTSize);
    }
  } else if (order == 3) {
    armSP_FFTInv_CToC_FC32_Radix2_fs_OutOfPlace(
        pSrc, pDst, pTwiddle, &subFFTNum, &subFFTSize);
    armSP_FFTInv_CToC_FC32_Radix2_OutOfPlace(
        pDst, pOut, pTwiddle, &subFFTNum, &subFFTSize);
    armSP_FFTInv_CToC_FC32_Radix2_ls_OutOfPlace(
        pOut, pDst, pTwiddle, &subFFTNum, &subFFTSize);
  } else if (order == 2) {
    armSP_FFTInv_CToC_FC32_Radix2_fs_OutOfPlace(
        pSrc, pOut, pTwiddle, &subFFTNum, &subFFTSize);
    armSP_FFTInv_CToC_FC32_Radix2_ls_OutOfPlace(
        pOut, pDst, pTwiddle, &subFFTNum, &subFFTSize);
  } else {
    /* Order = 1 */
    armSP_FFTInv_CToC_FC32_Radix2_fs_OutOfPlace(
        pSrc, pDst, pTwiddle, &subFFTNum, &subFFTSize);
  }

  ScaleFFTData(pDst, spec->N);
  return OMX_Sts_NoErr;
}