text: ﻿/*
   * FFT/IFFT transforms
   * AltiVec-enabled
   * Copyright (c) 2009 Loren Merritt
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  #include "libavcodec/fft.h"
  #include "util_altivec.h"
  #include "types_altivec.h"
  
  /**
   * Do a complex FFT with the parameters defined in ff_fft_init(). The
   * input data must be permuted before with s->revtab table. No
   * 1.0/sqrt(n) normalization is done.
   * AltiVec-enabled
   * This code assumes that the 'z' pointer is 16 bytes-aligned
   * It also assumes all FFTComplex are 8 bytes-aligned pair of float
   */
  
  void ff_fft_calc_altivec(FFTContext *s, FFTComplex *z);
  void ff_fft_calc_interleave_altivec(FFTContext *s, FFTComplex *z);
  
  #if HAVE_GNU_AS
  static void ff_imdct_half_altivec(FFTContext *s, FFTSample *output, const FFTSample *input)
  {
      int j, k;
      int n = 1 << s->mdct_bits;
      int n4 = n >> 2;
      int n8 = n >> 3;
      int n32 = n >> 5;
      const uint16_t *revtabj = s->revtab;
      const uint16_t *revtabk = s->revtab+n4;
      const vec_f *tcos = (const vec_f*)(s->tcos+n8);
      const vec_f *tsin = (const vec_f*)(s->tsin+n8);
      const vec_f *pin = (const vec_f*)(input+n4);
      vec_f *pout = (vec_f*)(output+n4);
  
      /* pre rotation */
      k = n32-1;
      do {
          vec_f cos,sin,cos0,sin0,cos1,sin1,re,im,r0,i0,r1,i1,a,b,c,d;
  #define CMULA(p,o0,o1,o2,o3)\
          a = pin[ k*2+p];                       /* { z[k].re,    z[k].im,    z[k+1].re,  z[k+1].im  } */\
          b = pin[-k*2-p-1];                     /* { z[-k-2].re, z[-k-2].im, z[-k-1].re, z[-k-1].im } */\
          re = vec_perm(a, b, vcprm(0,2,s0,s2)); /* { z[k].re,    z[k+1].re,  z[-k-2].re, z[-k-1].re } */\
          im = vec_perm(a, b, vcprm(s3,s1,3,1)); /* { z[-k-1].im, z[-k-2].im, z[k+1].im,  z[k].im    } */\
          cos = vec_perm(cos0, cos1, vcprm(o0,o1,s##o2,s##o3)); /* { cos[k], cos[k+1], cos[-k-2], cos[-k-1] } */\
          sin = vec_perm(sin0, sin1, vcprm(o0,o1,s##o2,s##o3));\
          r##p = im*cos - re*sin;\
          i##p = re*cos + im*sin;
  #define STORE2(v,dst)\
          j = dst;\
          vec_ste(v, 0, output+j*2);\
          vec_ste(v, 4, output+j*2);
  #define STORE8(p)\
          a = vec_perm(r##p, i##p, vcprm(0,s0,0,s0));\
          b = vec_perm(r##p, i##p, vcprm(1,s1,1,s1));\
          c = vec_perm(r##p, i##p, vcprm(2,s2,2,s2));\
          d = vec_perm(r##p, i##p, vcprm(3,s3,3,s3));\
          STORE2(a, revtabk[ p*2-4]);\
          STORE2(b, revtabk[ p*2-3]);\
          STORE2(c, revtabj[-p*2+2]);\
          STORE2(d, revtabj[-p*2+3]);
  
          cos0 = tcos[k];
          sin0 = tsin[k];
          cos1 = tcos[-k-1];
          sin1 = tsin[-k-1];
          CMULA(0, 0,1,2,3);
          CMULA(1, 2,3,0,1);
          STORE8(0);
          STORE8(1);
          revtabj += 4;
          revtabk -= 4;
          k--;
      } while(k >= 0);
  
      ff_fft_calc_altivec(s, (FFTComplex*)output);
  
      /* post rotation + reordering */
      j = -n32;
      k = n32-1;
      do {
          vec_f cos,sin,re,im,a,b,c,d;
  #define CMULB(d0,d1,o)\
          re = pout[o*2];\
          im = pout[o*2+1];\
          cos = tcos[o];\
          sin = tsin[o];\
          d0 = im*sin - re*cos;\
          d1 = re*sin + im*cos;
  
          CMULB(a,b,j);
          CMULB(c,d,k);
          pout[2*j]   = vec_perm(a, d, vcprm(0,s3,1,s2));
          pout[2*j+1] = vec_perm(a, d, vcprm(2,s1,3,s0));
          pout[2*k]   = vec_perm(c, b, vcprm(0,s3,1,s2));
          pout[2*k+1] = vec_perm(c, b, vcprm(2,s1,3,s0));
          j++;
          k--;
      } while(k >= 0);
  }
  
  static void ff_imdct_calc_altivec(FFTContext *s, FFTSample *output, const FFTSample *input)
  {
      int k;
      int n = 1 << s->mdct_bits;
      int n4 = n >> 2;
      int n16 = n >> 4;
      vec_u32 sign = {1U<<31,1U<<31,1U<<31,1U<<31};
      vec_u32 *p0 = (vec_u32*)(output+n4);
      vec_u32 *p1 = (vec_u32*)(output+n4*3);
  
      ff_imdct_half_altivec(s, output+n4, input);
  
      for (k = 0; k < n16; k++) {
          vec_u32 a = p0[k] ^ sign;
          vec_u32 b = p1[-k-1];
          p0[-k-1] = vec_perm(a, a, vcprm(3,2,1,0));
          p1[k]    = vec_perm(b, b, vcprm(3,2,1,0));
      }
  }
  #endif /* HAVE_GNU_AS */
  
  av_cold void ff_fft_init_altivec(FFTContext *s)
  {
  #if HAVE_GNU_AS
      s->fft_calc   = ff_fft_calc_interleave_altivec;
      if (s->mdct_bits >= 5) {
          s->imdct_calc = ff_imdct_calc_altivec;
          s->imdct_half = ff_imdct_half_altivec;
      }
  #endif
  }
  