Add NEON intrinsics version for WebRtcSpl_CrossCorrelationNeon.

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

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

Change-Id: I84f9fb953448b62da452ab8dd60e2c0628293587

Review URL: https://webrtc-codereview.appspot.com/30189004

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

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7855 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/common_audio/signal_processing/cross_correlation_neon.c b/webrtc/common_audio/signal_processing/cross_correlation_neon.c
new file mode 100644
index 0000000..c358c70
--- /dev/null
+++ b/webrtc/common_audio/signal_processing/cross_correlation_neon.c
@@ -0,0 +1,92 @@
+/*
+ *  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>
+
+static inline void DotProductWithScaleNeon(int32_t* cross_correlation,
+                                           const int16_t* vector1,
+                                           const int16_t* vector2,
+                                           int length,
+                                           int scaling) {
+  int i = 0;
+  int len1 = length >> 3;
+  int len2 = length & 7;
+  int64x2_t sum0 = vdupq_n_s64(0);
+  int64x2_t sum1 = vdupq_n_s64(0);
+
+  if (length < 0) {
+    *cross_correlation = 0;
+    return;
+  }
+
+  for (i = len1; i > 0; i -= 1) {
+    int16x8_t seq1_16x8 = vld1q_s16(vector1);
+    int16x8_t seq2_16x8 = vld1q_s16(vector2);
+#if defined(WEBRTC_ARCH_ARM64)
+    int32x4_t tmp0 = vmull_s16(vget_low_s16(seq1_16x8),
+                               vget_low_s16(seq2_16x8));
+    int32x4_t tmp1 = vmull_high_s16(seq1_16x8, seq2_16x8);
+#else
+    int32x4_t tmp0 = vmull_s16(vget_low_s16(seq1_16x8),
+                               vget_low_s16(seq2_16x8));
+    int32x4_t tmp1 = vmull_s16(vget_high_s16(seq1_16x8),
+                               vget_high_s16(seq2_16x8));
+#endif
+    sum0 = vpadalq_s32(sum0, tmp0);
+    sum1 = vpadalq_s32(sum1, tmp1);
+    vector1 += 8;
+    vector2 += 8;
+  }
+
+  // Calculate the rest of the samples.
+  int64_t sum_res = 0;
+  for (i = len2; i > 0; i -= 1) {
+    sum_res += WEBRTC_SPL_MUL_16_16(*vector1, *vector2);
+    vector1++;
+    vector2++;
+  }
+
+  sum0 = vaddq_s64(sum0, sum1);
+#if defined(WEBRTC_ARCH_ARM64)
+  int64_t sum2 = vaddvq_s64(sum0);
+  *cross_correlation = (int32_t)((sum2 + sum_res) >> scaling);
+#else
+  int64x1_t shift = vdup_n_s64(-scaling);
+  int64x1_t sum2 = vadd_s64(vget_low_s64(sum0), vget_high_s64(sum0));
+  sum2 = vadd_s64(sum2, vdup_n_s64(sum_res));
+  sum2 = vshl_s64(sum2, shift);
+  vst1_lane_s32(cross_correlation, vreinterpret_s32_s64(sum2), 0);
+#endif
+}
+
+/* NEON version of WebRtcSpl_CrossCorrelation() for ARM32/64 platforms. */
+void WebRtcSpl_CrossCorrelationNeon(int32_t* cross_correlation,
+                                    const int16_t* seq1,
+                                    const int16_t* seq2,
+                                    int16_t dim_seq,
+                                    int16_t dim_cross_correlation,
+                                    int16_t right_shifts,
+                                    int16_t step_seq2) {
+  int i = 0;
+
+  for (i = 0; i < dim_cross_correlation; i++) {
+    const int16_t* seq1_ptr = seq1;
+    const int16_t* seq2_ptr = seq2 + (step_seq2 * i);
+
+    DotProductWithScaleNeon(cross_correlation,
+                            seq1_ptr,
+                            seq2_ptr,
+                            dim_seq,
+                            right_shifts);
+    cross_correlation++;
+  }
+}