[FFmpeg-devel] [PATCH] avcodec/ac3: Implement float_to_fixed24 for aarch64 neon

[Geoff Hill]

Tested on AWS Graviton2 (t4g.medium), NixOS 23.11, GCC 12.3:

float_to_fixed24_c: 2462.7
float_to_fixed24_neon: 513.5

Signed-off-by: Geoff Hill <geoff at geoffhill.org>
---
 libavcodec/aarch64/Makefile              |  2 ++
 libavcodec/aarch64/ac3dsp_init_aarch64.c | 36 +++++++++++++++++++++++
 libavcodec/aarch64/ac3dsp_neon.S         | 37 ++++++++++++++++++++++++
 libavcodec/ac3dsp.c                      |  4 ++-
 libavcodec/ac3dsp.h                      |  3 +-
 5 files changed, 80 insertions(+), 2 deletions(-)
 create mode 100644 libavcodec/aarch64/ac3dsp_init_aarch64.c
 create mode 100644 libavcodec/aarch64/ac3dsp_neon.S

diff --git a/libavcodec/aarch64/Makefile b/libavcodec/aarch64/Makefile
index beb6a02f5f..5151b7510e 100644
--- a/libavcodec/aarch64/Makefile
+++ b/libavcodec/aarch64/Makefile
@@ -35,6 +35,8 @@ ARMV8-OBJS-$(CONFIG_VIDEODSP)           += aarch64/videodsp.o
 
 # subsystems
 NEON-OBJS-$(CONFIG_AAC_DECODER)         += aarch64/sbrdsp_neon.o
+NEON-OBJS-$(CONFIG_AC3DSP)              += aarch64/ac3dsp_init_aarch64.o       \
+                                           aarch64/ac3dsp_neon.o
 NEON-OBJS-$(CONFIG_FMTCONVERT)          += aarch64/fmtconvert_neon.o
 NEON-OBJS-$(CONFIG_H264CHROMA)          += aarch64/h264cmc_neon.o
 NEON-OBJS-$(CONFIG_H264DSP)             += aarch64/h264dsp_neon.o              \
diff --git a/libavcodec/aarch64/ac3dsp_init_aarch64.c b/libavcodec/aarch64/ac3dsp_init_aarch64.c
new file mode 100644
index 0000000000..e3320de0f5
--- /dev/null
+++ b/libavcodec/aarch64/ac3dsp_init_aarch64.c
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2024 Geoff Hill <geoff at geoffhill.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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 <stdint.h>
+
+#include "libavutil/arm/cpu.h"
+#include "libavutil/attributes.h"
+#include "libavcodec/ac3dsp.h"
+#include "config.h"
+
+void ff_float_to_fixed24_neon(int32_t *dst, const float *src, size_t len);
+
+av_cold void ff_ac3dsp_init_aarch64(AC3DSPContext *c)
+{
+    int cpu_flags = av_get_cpu_flags();
+    if (!have_neon(cpu_flags)) return;
+
+    c->float_to_fixed24 = ff_float_to_fixed24_neon;
+}
diff --git a/libavcodec/aarch64/ac3dsp_neon.S b/libavcodec/aarch64/ac3dsp_neon.S
new file mode 100644
index 0000000000..77106ea586
--- /dev/null
+++ b/libavcodec/aarch64/ac3dsp_neon.S
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2024 Geoff Hill <geoff at geoffhill.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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 "libavutil/aarch64/asm.S"
+
+// void ff_float_to_fixed24_neon(int32_t *dst, const float *src, unsigned int len)
+
+function ff_float_to_fixed24_neon, export=1
+0:      ld1         {v0.4s, v1.4s}, [x1], #32
+        fcvtzs      v0.4s, v0.4s, #24
+        ld1         {v2.4s, v3.4s}, [x1], #32
+        fcvtzs      v1.4s, v1.4s, #24
+        fcvtzs      v2.4s, v2.4s, #24
+        st1         {v0.4s, v1.4s}, [x0], #32
+        fcvtzs      v3.4s, v3.4s, #24
+        st1         {v2.4s, v3.4s}, [x0], #32
+        subs        w2, w2, #16
+        b.ne        0b
+        ret
+endfunc
diff --git a/libavcodec/ac3dsp.c b/libavcodec/ac3dsp.c
index 8397e03d32..730fa70fff 100644
--- a/libavcodec/ac3dsp.c
+++ b/libavcodec/ac3dsp.c
@@ -389,7 +389,9 @@ av_cold void ff_ac3dsp_init(AC3DSPContext *c)
     c->downmix               = NULL;
     c->downmix_fixed         = NULL;
 
-#if ARCH_ARM
+#if ARCH_AARCH64
+    ff_ac3dsp_init_aarch64(c);
+#elif ARCH_ARM
     ff_ac3dsp_init_arm(c);
 #elif ARCH_X86
     ff_ac3dsp_init_x86(c);
diff --git a/libavcodec/ac3dsp.h b/libavcodec/ac3dsp.h
index ae33b361a9..b1b2bced8f 100644
--- a/libavcodec/ac3dsp.h
+++ b/libavcodec/ac3dsp.h
@@ -106,7 +106,8 @@ typedef struct AC3DSPContext {
     void (*downmix_fixed)(int32_t **samples, int16_t **matrix, int len);
 } AC3DSPContext;
 
-void ff_ac3dsp_init    (AC3DSPContext *c);
+void ff_ac3dsp_init(AC3DSPContext *c);
+void ff_ac3dsp_init_aarch64(AC3DSPContext *c);
 void ff_ac3dsp_init_arm(AC3DSPContext *c);
 void ff_ac3dsp_init_x86(AC3DSPContext *c);
 void ff_ac3dsp_init_mips(AC3DSPContext *c);
-- 
2.42.0