Fix AppRTCDemo crash under iOS armv7 devices

Fix AppRTCDemo crash under iOS armv7 devices

Fix AppRTCDemo crash under iOS due to the unaligned access in vld1
instruction in iSACFix codec, which is not allowed in iOS build.

BUG=4717
R=andrew@webrtc.org, jridges@masque.com
TEST=Run the AppRTCDemo

Change-Id: Ie5fbc9b8ae88cd00b243a8e65cab95b00362a9da

Committed: https://chromium.googlesource.com/external/webrtc/+/01bbe3eb8ca29d5d1ce3b59d02532a3d9fd35e24

[jridges, 2015-06-12 15:26:05]

I was concerned the unaligned access might cause problems. Too bad it did. LGTM

[Andrew MacDonald, 2015-06-12 16:24:31]

lgtm. Zhongwei, do you suspect there may be other places in your code suffering
from the same problem?

[zhongwei, 2015-06-15 05:36:34]

On 2015/06/12 15:26:05, jridges wrote:
> I was concerned the unaligned access might cause problems. Too bad it did.
LGTM

I'm also a little surprised what unaligned access caused crash. Because ARMv7
architecture supports unaligned access in vld1 instruction. But llvm compiler on
iOS adds extra restriction on vld1_lane_s32 instrinsic (it generates vld1.32
{d1[0]}, [r2:32], not vld1.32 {d1[0]}, [r2]), while gcc not.

[zhongwei, 2015-06-15 06:56:34]

On 2015/06/12 16:24:31, andrew wrote:
> lgtm. Zhongwei, do you suspect there may be other places in your code
suffering
> from the same problem?

I have search all vld1 instruction in the source repo and find there is no such
code now. 

By the way, there is a similar code at downsample_fast_neon.c:50, but it is only
for ARM64. And the unalignment access is not a problem.

[zhongwei, 2015-06-15 06:57:10]

Committed patchset #2 (id:20001) manually as
01bbe3eb8ca29d5d1ce3b59d02532a3d9fd35e24 (presubmit successful).

[zhongwei, 2015-06-15 06:59:35]

On 2015/06/15 06:56:34, zhongwei wrote:
> On 2015/06/12 16:24:31, andrew wrote:
> > lgtm. Zhongwei, do you suspect there may be other places in your code
> suffering
> > from the same problem?
> 
> I have search all vld1 instruction in the source repo and find there is no
such
> code now. 
> 
> By the way, there is a similar code at downsample_fast_neon.c:50, but it is
only
> for ARM64. And the unalignment access is not a problem.

Sorry, I haven't made myself clear: unalignment access is not a problem on
ARM64.

[Andrew MacDonald, 2015-06-15 07:01:56]

On 2015/06/15 at 06:59:35, zhongwei.yao wrote:
> On 2015/06/15 06:56:34, zhongwei wrote:
> > On 2015/06/12 16:24:31, andrew wrote:
> > > lgtm. Zhongwei, do you suspect there may be other places in your code
> > suffering
> > > from the same problem?
> > 
> > I have search all vld1 instruction in the source repo and find there is no
such
> > code now. 
> > 
> > By the way, there is a similar code at downsample_fast_neon.c:50, but it is
only
> > for ARM64. And the unalignment access is not a problem.
> 
> Sorry, I haven't made myself clear: unalignment access is not a problem on
ARM64.

Got it. Thanks for checking.