iSAC fix: Ignore overflow in signed left shift

iSAC fix: Ignore overflow in signed left shift

A left shift by 10 was assumed to never overflow, since "[s]imulation
of the 25 files shows that maximum value in the vector gain_lo_hiQ17[]
is 441344, which means that it is log2((2^31)/441344) = 12.2 shifting
bits from saturation." However, a fuzzer test succeeded in provoking
an overflow, which we ignore in this CL on the theory that only
"abnormal" inputs cause overflow.

Also had to replace a "foo << 1" with "foo * (1 << 1)" in
WEBRTC_SPL_MUL_16_32_RSFT15 because foo could be negative; this
problem showed up as soon as I'd asked UBSan to ignore the overflow
discussed above.

BUG=chromium:615819
Committed: https://crrev.com/2b1b7a83ad377b8540096d96c472f12bceed8172
Cr-Commit-Position: refs/heads/master@{#14162}

[kwiberg-webrtc, 2016-09-07 12:12:51]

kwiberg@webrtc.org changed reviewers:
+ henrik.lundin@webrtc.org, tina.legrand@webrtc.org

[hlundin-webrtc, 2016-09-07 20:51:35]

lgtm

[kwiberg-webrtc, 2016-09-08 08:20:06]

The CQ bit was checked by kwiberg@webrtc.org

[commit-bot: I haz the power, 2016-09-08 08:20:11]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2016-09-08 08:24:21]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-09-08 08:24:21]

Try jobs failed on following builders:
  ios_api_framework on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/ios_api_framework/build...)

[kwiberg-webrtc, 2016-09-09 12:00:12]

The CQ bit was checked by kwiberg@webrtc.org

[kwiberg-webrtc, 2016-09-09 12:00:13]

The patchset sent to the CQ was uploaded after l-g-t-m from
henrik.lundin@webrtc.org
Link to the patchset: https://codereview.webrtc.org/2314413002/#ps20001 (title:
"rebase")

[commit-bot: I haz the power, 2016-09-09 12:00:18]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2016-09-09 12:51:36]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-09-09 12:51:46]

Description was changed from

==========
iSAC fix: Ignore overflow in signed left shift

A left shift by 10 was assumed to never overflow, since "[s]imulation
of the 25 files shows that maximum value in the vector gain_lo_hiQ17[]
is 441344, which means that it is log2((2^31)/441344) = 12.2 shifting
bits from saturation." However, a fuzzer test succeeded in provoking
an overflow, which we ignore in this CL on the theory that only
"abnormal" inputs cause overflow.

Also had to replace a "foo << 1" with "foo * (1 << 1)" in
WEBRTC_SPL_MUL_16_32_RSFT15 because foo could be negative; this
problem showed up as soon as I'd asked UBSan to ignore the overflow
discussed above.

BUG=chromium:615819
==========

to

==========
iSAC fix: Ignore overflow in signed left shift

A left shift by 10 was assumed to never overflow, since "[s]imulation
of the 25 files shows that maximum value in the vector gain_lo_hiQ17[]
is 441344, which means that it is log2((2^31)/441344) = 12.2 shifting
bits from saturation." However, a fuzzer test succeeded in provoking
an overflow, which we ignore in this CL on the theory that only
"abnormal" inputs cause overflow.

Also had to replace a "foo << 1" with "foo * (1 << 1)" in
WEBRTC_SPL_MUL_16_32_RSFT15 because foo could be negative; this
problem showed up as soon as I'd asked UBSan to ignore the overflow
discussed above.

BUG=chromium:615819

Committed: https://crrev.com/2b1b7a83ad377b8540096d96c472f12bceed8172
Cr-Commit-Position: refs/heads/master@{#14162}
==========

[commit-bot: I haz the power, 2016-09-09 12:51:48]

Patchset 2 (id:??) landed as
https://crrev.com/2b1b7a83ad377b8540096d96c472f12bceed8172
Cr-Commit-Position: refs/heads/master@{#14162}