Re-enable UBsan on AGC.

webrtc/modules/audio_processing/agc/legacy/digital_agc.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 171 matching lines @@
       if (tmpU32no2 < tmpU32no1) {
         logApprox = (tmpU32no1 - tmpU32no2) >> (8 - zerosScale);  // Q14
       }
     }
     numFIX = (maxGain * constMaxGain) * (1 << 6);  // Q14
     numFIX -= (int32_t)logApprox * diffGain;       // Q14
 
     // Calculate ratio
     // Shift |numFIX| as much as possible.
     // Ensure we avoid wrap-around in |den| as well.
-    if (numFIX > (den >> 8))  // |den| is Q8.
+    if (numFIX > (den >> 8) || -numFIX > (den >> 8))  // |den| is Q8.
     {
       zeros = WebRtcSpl_NormW32(numFIX);
     } else {
       zeros = WebRtcSpl_NormW32(den) + 8;
     }
     numFIX *= 1 << zeros;  // Q(14+zeros)
 
     // Shift den so we end up in Qy1
-    tmp32no1 = WEBRTC_SPL_SHIFT_W32(den, zeros - 8);  // Q(zeros)
-    if (numFIX < 0) {
-      numFIX -= tmp32no1 / 2;
-    } else {
-      numFIX += tmp32no1 / 2;
-    }
-    y32 = numFIX / tmp32no1;  // in Q14
+    tmp32no1 = WEBRTC_SPL_SHIFT_W32(den, zeros - 9);  // Q(zeros - 1)
+    y32 = numFIX / tmp32no1;  // in Q15
+    y32 = (y32 + (y32 >= 0 ? 1 : -1)) / 2;  // This is to do rounding in Q14.

[peah-webrtc, 2016/06/03 08:00:56]

Why not use:
if (y32 < 0)
  y32 = -(((-y32) + 1) >> 1);
else
  y32 = (y32 + 1) >> 1);

The above statement is not more complex than the above, as that also contains a
short-hand if statement.

I doubt that the compiler will optimize the division by two into a shift, as it
too need to make the assumption on the sign to achieve that.

+
     if (limiterEnable && (i < limiterIdx)) {
       tmp32 = WEBRTC_SPL_MUL_16_U16(i - 1, kLog10_2);  // Q14
       tmp32 -= limiterLvl * (1 << 14);                 // Q14
       y32 = WebRtcSpl_DivW32W16(tmp32 + 10, 20);
     }
     if (y32 > 39000) {
       tmp32 = (y32 >> 1) * kLog10 + 4096;  // in Q27
       tmp32 >>= 13;                        // In Q14.
     } else {
       tmp32 = y32 * kLog10 + 8192;  // in Q28
@@ skipping 463 matching lines @@
   // limit
   if (state->logRatio > 2048) {
     state->logRatio = 2048;
   }
   if (state->logRatio < -2048) {
     state->logRatio = -2048;
   }
 
   return state->logRatio;  // Q10
 }