pcm/PcmFormat: ARM NEON optimizations for float->s16

This is nearly 4 times faster than the "portable" algorithm.
2014-03-14 23:45:27 +01:00
parent 3932e62fc7
commit 5696f91a1e
4 changed files with 137 additions and 1 deletions
--- a/src/pcm/Neon.hxx
+++ 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