Fix for left shift of potentially negative value.

webrtc/common_audio/signal_processing/levinson_durbin.c

 /*
  *  Copyright (c) 2011 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.
  */
 
@@ skipping 57 matching lines @@
     K[0] = K_hi;
 
     temp1W32 >>= 4;  // A[1] in Q27.
 
     // Put A[1] in hi and low format
     A_hi[1] = (int16_t)(temp1W32 >> 16);
     A_low[1] = (int16_t)((temp1W32 - ((int32_t)A_hi[1] * 65536)) >> 1);
 
     // Alpha = R[0] * (1-K^2)
 
-    temp1W32 = ((K_hi * K_low >> 14) + K_hi * K_hi) << 1;  // = k^2 in Q31
+    temp1W32 = ((K_hi * K_low >> 14) + K_hi * K_hi) * 2;  // = k^2 in Q31
 
     temp1W32 = WEBRTC_SPL_ABS_W32(temp1W32); // Guard against <0
     temp1W32 = (int32_t)0x7fffffffL - temp1W32; // temp1W32 = (1 - K[0]*K[0]) in Q31
 
     // Store temp1W32 = 1 - K[0]*K[0] on hi and low format
     tmp_hi = (int16_t)(temp1W32 >> 16);
     tmp_low = (int16_t)((temp1W32 - ((int32_t)tmp_hi << 16)) >> 1);
 
     // Calculate Alpha in Q31
     temp1W32 = (R_hi[0] * tmp_hi + (R_hi[0] * tmp_low >> 15) +
@@ skipping 147 matching lines @@
     for (i = 1; i <= order; i++)
     {
         // temp1W32 in Q27
         temp1W32 = (int32_t)A_hi[i] * 65536
                 + WEBRTC_SPL_LSHIFT_W32((int32_t)A_low[i], 1);
         // Round and store upper word
         A[i] = (int16_t)(((temp1W32 * 2) + 32768) >> 16);
     }
     return 1; // Stable filters
 }