Re-enable UBsan on AGC.

webrtc/modules/audio_processing/agc/legacy/digital_agc.c

Index: webrtc/modules/audio_processing/agc/legacy/digital_agc.c
diff --git a/webrtc/modules/audio_processing/agc/legacy/digital_agc.c b/webrtc/modules/audio_processing/agc/legacy/digital_agc.c
index 2ca967a4aae1a0d0a00758b4861a4838b1d11d46..ea5a0ca1fef362bb317cbc2f405c8e63d838fbb4 100644
--- a/webrtc/modules/audio_processing/agc/legacy/digital_agc.c
+++ b/webrtc/modules/audio_processing/agc/legacy/digital_agc.c
@@ -189,7 +189,7 @@ int32_t WebRtcAgc_CalculateGainTable(int32_t* gainTable,       // Q16
     // 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.

[peah-webrtc, 2016/06/03 05:10:35]

The if-condition will compute den >> 8 twice. Please pre-compute it outside the
if-statement.

     {
       zeros = WebRtcSpl_NormW32(numFIX);
     } else {
@@ -198,13 +198,10 @@ int32_t WebRtcAgc_CalculateGainTable(int32_t* gainTable,       // Q16
     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 + 1) / 2;  // in Q14 rounded

[peah-webrtc, 2016/06/03 05:10:35]

Nice! 
This should work apart from that the rounding is wrong if y32<0.

Furthermore, I think you can do the division by 2 as a left shift, but please
take care to ensure that a negative sign does not get into the way.

[peah-webrtc, 2016/06/03 05:11:05]

Sorry, meant right shift.

[minyue-webrtc, 2016/06/03 06:40:05]

Nice catch! I was careless there. To round negative value (a), is it either (a -
1) / 2, or a >> 1, no "-1" if using shift. See my new patch.

+
     if (limiterEnable && (i < limiterIdx)) {
       tmp32 = WEBRTC_SPL_MUL_16_U16(i - 1, kLog10_2);  // Q14
       tmp32 -= limiterLvl * (1 << 14);                 // Q14