aarch64: NEON float FFT

Approximately as fast as the ARM NEON version on Apple's A7.

libavcodec/aarch64/Makefile

+OBJS-$(CONFIG_FFT)                      += aarch64/fft_init_aarch64.o
 OBJS-$(CONFIG_H264CHROMA)               += aarch64/h264chroma_init_aarch64.o
 OBJS-$(CONFIG_H264DSP)                  += aarch64/h264dsp_init_aarch64.o
 OBJS-$(CONFIG_H264QPEL)                 += aarch64/h264qpel_init_aarch64.o
@@ -10,6 +11,7 @@ OBJS-$(CONFIG_VC1_DECODER)              += aarch64/vc1dsp_init_aarch64.o
 
 ARMV8-OBJS-$(CONFIG_VIDEODSP)           += aarch64/videodsp.o
 
+NEON-OBJS-$(CONFIG_FFT)                 += aarch64/fft_neon.o
 NEON-OBJS-$(CONFIG_H264CHROMA)          += aarch64/h264cmc_neon.o
 NEON-OBJS-$(CONFIG_H264DSP)             += aarch64/h264dsp_neon.o              \
                                            aarch64/h264idct_neon.o

libavcodec/aarch64/fft_init_aarch64.c

+/*
+ * Copyright (c) 2009 Mans Rullgard <mans@mansr.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+
+#include "libavutil/aarch64/cpu.h"
+#include "libavcodec/fft.h"
+
+void ff_fft_permute_neon(FFTContext *s, FFTComplex *z);
+void ff_fft_calc_neon(FFTContext *s, FFTComplex *z);
+
+av_cold void ff_fft_init_aarch64(FFTContext *s)
+{
+    int cpu_flags = av_get_cpu_flags();
+
+    if (have_neon(cpu_flags)) {
+        s->fft_permute  = ff_fft_permute_neon;
+        s->fft_calc     = ff_fft_calc_neon;
+    }
+}

libavcodec/fft.h

@@ -133,6 +133,7 @@ void ff_init_ff_cos_tabs(int index);
  */
 int ff_fft_init(FFTContext *s, int nbits, int inverse);
 
+void ff_fft_init_aarch64(FFTContext *s);
 void ff_fft_init_x86(FFTContext *s);
 void ff_fft_init_arm(FFTContext *s);
 void ff_fft_init_ppc(FFTContext *s);

libavcodec/fft_template.c

@@ -158,6 +158,7 @@ av_cold int ff_fft_init(FFTContext *s, int nbits, int inverse)
 #endif
 
 #if FFT_FLOAT
+    if (ARCH_AARCH64) ff_fft_init_aarch64(s);
     if (ARCH_ARM)     ff_fft_init_arm(s);
     if (ARCH_PPC)     ff_fft_init_ppc(s);
     if (ARCH_X86)     ff_fft_init_x86(s);