Add clz functions (Count number of Leading Zero bits), 32-and 64-bit variants

webrtc/common_audio/signal_processing/spl_inl.c

Index: webrtc/common_audio/signal_processing/spl_inl.c
diff --git a/webrtc/common_audio/signal_processing/spl_inl.c b/webrtc/common_audio/signal_processing/spl_inl.c
new file mode 100644
index 0000000000000000000000000000000000000000..efa6a65f0e4551f5c8b0a35a508e7964266518dd
--- /dev/null
+++ b/webrtc/common_audio/signal_processing/spl_inl.c
@@ -0,0 +1,24 @@
+/*
+ *  Copyright (c) 2016 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 <stdint.h>
+
+#include "webrtc/common_audio/signal_processing/include/spl_inl.h"
+
+// Table used by WebRtcSpl_CountLeadingZeros32_NotBuiltin. For each uint32_t n
+// that's a sequence of 0 bits followed by a sequence of 1 bits, the entry at
+// index (n * 0x8c0b2891) >> 26 in this table gives the number of zero bits in
+// n.
+const int8_t kWebRtcSpl_CountLeadingZeros32_Table[64] = {
+    32, 8,  17, -1, -1, 14, -1, -1, -1, 20, -1, -1, -1, 28, -1, 18,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  26, 25, 24,
+    4,  11, 23, 31, 3,  7,  10, 16, 22, 30, -1, -1, 2,  6,  13, 9,
+    -1, 15, -1, 21, -1, 29, 19, -1, -1, -1, -1, -1, 1,  27, 5,  12,
+};