From 5696f91a1e5e0cd1022c60737465c29b429ea599 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Fri, 14 Mar 2014 23:45:27 +0100
Subject: [PATCH] pcm/PcmFormat: ARM NEON optimizations for float->s16
This is nearly 4 times faster than the "portable" algorithm.
---
Makefile.am | 1 +
NEWS | 1 +
src/pcm/Neon.hxx | 97 +++++++++++++++++++++++++++++++++++++++++++
src/pcm/PcmFormat.cxx | 39 ++++++++++++++++-
4 files changed, 137 insertions(+), 1 deletion(-)
create mode 100644 src/pcm/Neon.hxx
diff --git a/Makefile.am b/Makefile.am
index e1a5415d8..700511338 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -452,6 +452,7 @@ libpcm_a_SOURCES = \
src/pcm/PcmFormat.cxx src/pcm/PcmFormat.hxx \
src/pcm/FloatConvert.hxx \
src/pcm/ShiftConvert.hxx \
+ src/pcm/Neon.hxx \
src/pcm/FormatConverter.cxx src/pcm/FormatConverter.hxx \
src/pcm/ChannelsConverter.cxx src/pcm/ChannelsConverter.hxx \
src/pcm/Resampler.hxx \
diff --git a/NEWS b/NEWS
index fa5c49298..79bb27b5f 100644
--- a/NEWS
+++ b/NEWS
@@ -36,6 +36,7 @@ ver 0.19 (not yet released)
- allow playlist directory without music directory
- use XDG to auto-detect "music_directory" and "db_file"
* new resampler option using libsoxr
+* ARM NEON optimizations
* install systemd unit for socket activation
* Android port
diff --git a/src/pcm/Neon.hxx b/src/pcm/Neon.hxx
new file mode 100644
index 000000000..a6f52db42
--- /dev/null
+++ b/src/pcm/Neon.hxx
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_PCM_NEON_HXX
+#define MPD_PCM_NEON_HXX
+
+#include "Traits.hxx"
+
+#include <arm_neon.h>
+
+/**
+ * Call a NEON intrinsic for each element in the vector.
+ *
+ * @param func the NEON intrinsic
+ * @param result the vector variable that gets assigned the result
+ * @param vector the input vector
+ */
+#define neon_x4_u(func, result, vector) do { \
+ result.val[0] = func(vector.val[0]); \
+ result.val[1] = func(vector.val[1]); \
+ result.val[2] = func(vector.val[2]); \
+ result.val[3] = func(vector.val[3]); \
+} while (0)
+
+/**
+ * Call a NEON intrinsic for each element in the vector.
+ *
+ * @param func the NEON intrinsic
+ * @param result the vector variable that gets assigned the result
+ * @param vector the input vector
+ * @param arg an additional argument that gets passed to each call
+ */
+#define neon_x4_b(func, result, vector, arg) do { \
+ result.val[0] = func(vector.val[0], arg); \
+ result.val[1] = func(vector.val[1], arg); \
+ result.val[2] = func(vector.val[2], arg); \
+ result.val[3] = func(vector.val[3], arg); \
+} while (0)
+
+/**
+ * Convert floating point samples to 16 bit signed integer using ARM NEON.
+ */
+struct NeonFloatTo16 {
+ static constexpr SampleFormat src_format = SampleFormat::FLOAT;
+ static constexpr SampleFormat dst_format = SampleFormat::S16;
+ typedef SampleTraits<src_format> SrcTraits;
+ typedef SampleTraits<dst_format> DstTraits;
+
+ typedef typename SrcTraits::value_type SV;
+ typedef typename DstTraits::value_type DV;
+
+ static constexpr size_t BLOCK_SIZE = 16;
+
+ void Convert(int16_t *dst, const float *src, const size_t n) const {
+ const float32x4_t factor =
+ vdupq_n_f32(1 << (DstTraits::BITS - 1));
+
+ for (unsigned i = 0; i < n / BLOCK_SIZE;
+ ++i, src += BLOCK_SIZE, dst += BLOCK_SIZE) {
+ /* load 16 float samples into 4 quad
+ registers */
+ float32x4x4_t value = vld4q_f32(src);
+
+ /* apply factor */
+ neon_x4_b(vmulq_f32, value, value, factor);
+
+ /* convert to 32 bit integer */
+ int32x4x4_t ivalue;
+ neon_x4_u(vcvtq_s32_f32, ivalue, value);
+
+ /* convert to 16 bit integer with saturation */
+ int16x4x4_t nvalue;
+ neon_x4_u(vqmovn_s32, nvalue, ivalue);
+
+ /* store result */
+ vst4_s16(dst, nvalue);
+ }
+ }
+};
+
+#endif
diff --git a/src/pcm/PcmFormat.cxx b/src/pcm/PcmFormat.cxx
index f2d71a6fb..4cabc05a0 100644
--- a/src/pcm/PcmFormat.cxx
+++ b/src/pcm/PcmFormat.cxx
@@ -76,9 +76,46 @@ struct Convert32To16 {
};
template<SampleFormat F, class Traits=SampleTraits<F>>
-struct FloatToInteger
+struct PortableFloatToInteger
: PerSampleConvert<FloatToIntegerSampleConvert<F, Traits>> {};
+template<SampleFormat F, class Traits=SampleTraits<F>>
+struct FloatToInteger : PortableFloatToInteger<F, Traits> {};
+
+/**
+ * A template class that attempts to use the "optimized" algorithm for
+ * large portions of the buffer, and calls the "portable" algorithm"
+ * for the rest when the last block is not full.
+ */
+template<typename Optimized, typename Portable>
+class GlueOptimizedConvert : Optimized, Portable {
+public:
+ typedef typename Portable::SrcTraits SrcTraits;
+ typedef typename Portable::DstTraits DstTraits;
+
+ void Convert(typename DstTraits::pointer_type out,
+ typename SrcTraits::const_pointer_type in,
+ size_t n) const {
+ Optimized::Convert(out, in, n);
+
+ /* use the "portable" algorithm for the trailing
+ samples */
+ size_t remaining = n % Optimized::BLOCK_SIZE;
+ size_t done = n - remaining;
+ Portable::Convert(out + done, in + done, remaining);
+ }
+};
+
+#ifdef __ARM_NEON__
+#include "Neon.hxx"
+
+template<>
+struct FloatToInteger<SampleFormat::S16, SampleTraits<SampleFormat::S16>>
+ : GlueOptimizedConvert<NeonFloatTo16,
+ PortableFloatToInteger<SampleFormat::S16>> {};
+
+#endif
+
template<class C>
static ConstBuffer<typename C::DstTraits::value_type>
AllocateConvert(PcmBuffer &buffer, C convert,