fft_init.c

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/*
 * 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 "config.h"
#include "libavutil/cpu.h"
#include "libavutil/ppc/cpu.h"
#include "libavutil/ppc/util_altivec.h"
#include "libavcodec/fft.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 pairs of floats.
 */

#if HAVE_VSX
#include "fft_vsx.h"
#else
void ff_fft_calc_altivec(FFTContext *s, FFTComplex *z);
void ff_fft_calc_interleave_altivec(FFTContext *s, FFTComplex *z);
#endif

#if HAVE_GNU_AS && HAVE_ALTIVEC && (HAVE_BIGENDIAN || HAVE_VSX)
static void 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);

#if HAVE_VSX
    ff_fft_calc_vsx(s, (FFTComplex*)output);
#else
    ff_fft_calc_altivec(s, (FFTComplex*)output);
#endif

    /* 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 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);

    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 && HAVE_ALTIVEC && (HAVE_BIGENDIAN || HAVE_VSX) */

av_cold void ff_fft_init_ppc(FFTContext *s)
{
#if HAVE_GNU_AS && HAVE_ALTIVEC && (HAVE_BIGENDIAN || HAVE_VSX)
    if (!PPC_ALTIVEC(av_get_cpu_flags()))
        return;

#if HAVE_VSX
    s->fft_calc = ff_fft_calc_interleave_vsx;
#else
    s->fft_calc   = ff_fft_calc_interleave_altivec;
#endif
    if (s->mdct_bits >= 5) {
        s->imdct_calc = imdct_calc_altivec;
        s->imdct_half = imdct_half_altivec;
    }
#endif /* HAVE_GNU_AS && HAVE_ALTIVEC && HAVE_BIGENDIAN */
}