Add NEON intrinsics version for WebRtcSpl_DownsampleFastNeon.

WebRtcSpl_DownsampleFastNeon is added. SplTest in common_audio_unittests
is passed on ARM32/ARM64 platform.

BUG=4002
R=andrew@webrtc.org, jridges@masque.com

Change-Id: Ic43f5452eb7e555b998b1d1e79a9e1530be5c948

Review URL: https://webrtc-codereview.appspot.com/24359004

Patch from Yang Zhang <yang.zhang@arm.com>.

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@7856 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/common_audio/signal_processing/downsample_fast_neon.c b/common_audio/signal_processing/downsample_fast_neon.c
new file mode 100644
index 0000000..f775e69
--- /dev/null
+++ b/common_audio/signal_processing/downsample_fast_neon.c
@@ -0,0 +1,217 @@
+/*
+ *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
+
+#include <arm_neon.h>
+
+// NEON intrinsics version of WebRtcSpl_DownsampleFast()
+// for ARM 32-bit/64-bit platforms.
+int WebRtcSpl_DownsampleFastNeon(const int16_t* data_in,
+                                 int data_in_length,
+                                 int16_t* data_out,
+                                 int data_out_length,
+                                 const int16_t* __restrict coefficients,
+                                 int coefficients_length,
+                                 int factor,
+                                 int delay) {
+  int i = 0;
+  int j = 0;
+  int32_t out_s32 = 0;
+  int endpos = delay + factor * (data_out_length - 1) + 1;
+  int res = data_out_length & 0x7;
+  int endpos1 = endpos - factor * res;
+
+  // Return error if any of the running conditions doesn't meet.
+  if (data_out_length <= 0 || coefficients_length <= 0
+                           || data_in_length < endpos) {
+    return -1;
+  }
+
+  // First part, unroll the loop 8 times, with 3 subcases
+  // (factor == 2, 4, others).
+  switch (factor) {
+    case 2: {
+      for (i = delay; i < endpos1; i += 16) {
+        // Round value, 0.5 in Q12.
+        int32x4_t out32x4_0 = vdupq_n_s32(2048);
+        int32x4_t out32x4_1 = vdupq_n_s32(2048);
+
+#if defined(WEBRTC_ARCH_ARM64)
+        // Unroll the loop 2 times.
+        for (j = 0; j < coefficients_length - 1; j += 2) {
+          int32x2_t coeff32 = vld1_dup_s32((int32_t*)&coefficients[j]);
+          int16x4_t coeff16x4 = vreinterpret_s16_s32(coeff32);
+          int16x8x2_t in16x8x2 = vld2q_s16(&data_in[i - j - 1]);
+
+          // Mul and accumulate low 64-bit data.
+          int16x4_t in16x4_0 = vget_low_s16(in16x8x2.val[0]);
+          int16x4_t in16x4_1 = vget_low_s16(in16x8x2.val[1]);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_0, coeff16x4, 1);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_1, coeff16x4, 0);
+
+          // Mul and accumulate high 64-bit data.
+          // TODO: vget_high_s16 need extra cost on ARM64. This could be
+          // replaced by vmlal_high_lane_s16. But for the interface of
+          // vmlal_high_lane_s16, there is a bug in gcc 4.9.
+          // This issue need to be tracked in the future.
+          int16x4_t in16x4_2 = vget_high_s16(in16x8x2.val[0]);
+          int16x4_t in16x4_3 = vget_high_s16(in16x8x2.val[1]);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_2, coeff16x4, 1);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_3, coeff16x4, 0);
+        }
+
+        for (; j < coefficients_length; j++) {
+          int16x4_t coeff16x4 = vld1_dup_s16(&coefficients[j]);
+          int16x8x2_t in16x8x2 = vld2q_s16(&data_in[i - j]);
+
+          // Mul and accumulate low 64-bit data.
+          int16x4_t in16x4_0 = vget_low_s16(in16x8x2.val[0]);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_0, coeff16x4, 0);
+
+          // Mul and accumulate high 64-bit data.
+          // TODO: vget_high_s16 need extra cost on ARM64. This could be
+          // replaced by vmlal_high_lane_s16. But for the interface of
+          // vmlal_high_lane_s16, there is a bug in gcc 4.9.
+          // This issue need to be tracked in the future.
+          int16x4_t in16x4_1 = vget_high_s16(in16x8x2.val[0]);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_1, coeff16x4, 0);
+        }
+#else
+        // On ARMv7, the loop unrolling 2 times results in performance
+        // regression.
+        for (j = 0; j < coefficients_length; j++) {
+          int16x4_t coeff16x4 = vld1_dup_s16(&coefficients[j]);
+          int16x8x2_t in16x8x2 = vld2q_s16(&data_in[i - j]);
+
+          // Mul and accumulate.
+          int16x4_t in16x4_0 = vget_low_s16(in16x8x2.val[0]);
+          int16x4_t in16x4_1 = vget_high_s16(in16x8x2.val[0]);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_0, coeff16x4, 0);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_1, coeff16x4, 0);
+        }
+#endif
+
+        // Saturate and store the output.
+        int16x4_t out16x4_0 = vqshrn_n_s32(out32x4_0, 12);
+        int16x4_t out16x4_1 = vqshrn_n_s32(out32x4_1, 12);
+        vst1q_s16(data_out, vcombine_s16(out16x4_0, out16x4_1));
+        data_out += 8;
+      }
+      break;
+    }
+    case 4: {
+      for (i = delay; i < endpos1; i += 32) {
+        // Round value, 0.5 in Q12.
+        int32x4_t out32x4_0 = vdupq_n_s32(2048);
+        int32x4_t out32x4_1 = vdupq_n_s32(2048);
+
+        // Unroll the loop 4 times.
+        for (j = 0; j < coefficients_length - 3; j += 4) {
+          int16x4_t coeff16x4 = vld1_s16(&coefficients[j]);
+          int16x8x4_t in16x8x4 = vld4q_s16(&data_in[i - j - 3]);
+
+          // Mul and accumulate low 64-bit data.
+          int16x4_t in16x4_0 = vget_low_s16(in16x8x4.val[0]);
+          int16x4_t in16x4_2 = vget_low_s16(in16x8x4.val[1]);
+          int16x4_t in16x4_4 = vget_low_s16(in16x8x4.val[2]);
+          int16x4_t in16x4_6 = vget_low_s16(in16x8x4.val[3]);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_0, coeff16x4, 3);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_2, coeff16x4, 2);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_4, coeff16x4, 1);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_6, coeff16x4, 0);
+
+          // Mul and accumulate high 64-bit data.
+          // TODO: vget_high_s16 need extra cost on ARM64. This could be
+          // replaced by vmlal_high_lane_s16. But for the interface of
+          // vmlal_high_lane_s16, there is a bug in gcc 4.9.
+          // This issue need to be tracked in the future.
+          int16x4_t in16x4_1 = vget_high_s16(in16x8x4.val[0]);
+          int16x4_t in16x4_3 = vget_high_s16(in16x8x4.val[1]);
+          int16x4_t in16x4_5 = vget_high_s16(in16x8x4.val[2]);
+          int16x4_t in16x4_7 = vget_high_s16(in16x8x4.val[3]);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_1, coeff16x4, 3);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_3, coeff16x4, 2);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_5, coeff16x4, 1);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_7, coeff16x4, 0);
+        }
+
+        for (; j < coefficients_length; j++) {
+          int16x4_t coeff16x4 = vld1_dup_s16(&coefficients[j]);
+          int16x8x4_t in16x8x4 = vld4q_s16(&data_in[i - j]);
+
+          // Mul and accumulate low 64-bit data.
+          int16x4_t in16x4_0 = vget_low_s16(in16x8x4.val[0]);
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_0, coeff16x4, 0);
+
+          // Mul and accumulate high 64-bit data.
+          // TODO: vget_high_s16 need extra cost on ARM64. This could be
+          // replaced by vmlal_high_lane_s16. But for the interface of
+          // vmlal_high_lane_s16, there is a bug in gcc 4.9.
+          // This issue need to be tracked in the future.
+          int16x4_t in16x4_1 = vget_high_s16(in16x8x4.val[0]);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_1, coeff16x4, 0);
+        }
+
+        // Saturate and store the output.
+        int16x4_t out16x4_0 = vqshrn_n_s32(out32x4_0, 12);
+        int16x4_t out16x4_1 = vqshrn_n_s32(out32x4_1, 12);
+        vst1q_s16(data_out, vcombine_s16(out16x4_0, out16x4_1));
+        data_out += 8;
+      }
+      break;
+    }
+    default: {
+      for (i = delay; i < endpos1; i += factor * 8) {
+        // Round value, 0.5 in Q12.
+        int32x4_t out32x4_0 = vdupq_n_s32(2048);
+        int32x4_t out32x4_1 = vdupq_n_s32(2048);
+
+        for (j = 0; j < coefficients_length; j++) {
+          int16x4_t coeff16x4 = vld1_dup_s16(&coefficients[j]);
+          int16x4_t in16x4_0 = vld1_dup_s16(&data_in[i - j]);
+          in16x4_0 = vld1_lane_s16(&data_in[i + factor - j], in16x4_0, 1);
+          in16x4_0 = vld1_lane_s16(&data_in[i + factor * 2 - j], in16x4_0, 2);
+          in16x4_0 = vld1_lane_s16(&data_in[i + factor * 3 - j], in16x4_0, 3);
+          int16x4_t in16x4_1 = vld1_dup_s16(&data_in[i + factor * 4 - j]);
+          in16x4_1 = vld1_lane_s16(&data_in[i + factor * 5 - j], in16x4_1, 1);
+          in16x4_1 = vld1_lane_s16(&data_in[i + factor * 6 - j], in16x4_1, 2);
+          in16x4_1 = vld1_lane_s16(&data_in[i + factor * 7 - j], in16x4_1, 3);
+
+          // Mul and accumulate.
+          out32x4_0 = vmlal_lane_s16(out32x4_0, in16x4_0, coeff16x4, 0);
+          out32x4_1 = vmlal_lane_s16(out32x4_1, in16x4_1, coeff16x4, 0);
+        }
+
+        // Saturate and store the output.
+        int16x4_t out16x4_0 = vqshrn_n_s32(out32x4_0, 12);
+        int16x4_t out16x4_1 = vqshrn_n_s32(out32x4_1, 12);
+        vst1q_s16(data_out, vcombine_s16(out16x4_0, out16x4_1));
+        data_out += 8;
+      }
+      break;
+    }
+  }
+
+  // Second part, do the rest iterations (if any).
+  for (; i < endpos; i += factor) {
+    out_s32 = 2048;  // Round value, 0.5 in Q12.
+
+    for (j = 0; j < coefficients_length; j++) {
+      out_s32 = WebRtc_MulAccumW16(coefficients[j], data_in[i - j], out_s32);
+    }
+
+    // Saturate and store the output.
+    out_s32 >>= 12;
+    *data_out++ = WebRtcSpl_SatW32ToW16(out_s32);
+  }
+
+  return 0;
+}