ARM assembler: fix undefined behaviour in fits_shifter

ARM assembler: fix undefined behaviour in fits_shifter

Bit-shifts have undefined behaviour if the shift amount is greater
or equal to the width of the type.

In this case the code would do imm32 >> 32 when rot == 0.

A newer version of Clang unrolled the loop, optimized the first
iteration away, causing the test suite to fail with:

  #
  # Fatal error in ../src/arm/assembler-arm.cc, line 1212
  # Check failed: !rn.is(ip).
  #

as well as crashing when running Chromium tests on Android (at least
we think this was the cause, see the bug).

BUG=463436, 444089
LOG=Y

Committed: https://crrev.com/721fdb56e0fc92c662c7d8b42be8a1d689c3b535
Cr-Commit-Position: refs/heads/master@{#26974}

[hans, 2015-03-04 00:46:07]

hans@chromium.org changed reviewers:
+ jochen@chromium.org, thakis@chromium.org, ulan@chromium.org

[hans, 2015-03-04 00:46:08]

This is blocking the Clang roll. It would be great if someone could review this,
and ideally help getting it rolled into Chromium too.

[Erik Corry, 2015-03-04 01:21:09]

erik.corry@gmail.com changed reviewers:
+ erik.corry@gmail.com

[Erik Corry, 2015-03-04 01:21:09]

LGTM

[jochen (gone - plz use gerrit), 2015-03-04 01:21:41]

lgtm

[Nico, 2015-03-04 01:31:24]

On 2015/03/04 01:21:41, jochen (traveling) wrote:
> lgtm

Can someone land?

[jochen (gone - plz use gerrit), 2015-03-04 01:31:53]

The CQ bit was checked by jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-03-04 01:32:28]

On 2015/03/04 at 01:31:24, thakis wrote:
> On 2015/03/04 01:21:41, jochen (traveling) wrote:
> > lgtm
> 
> Can someone land?

Let me press the button for you...

[commit-bot: I haz the power, 2015-03-04 01:32:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/979633002/1

[commit-bot: I haz the power, 2015-03-04 03:13:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-04 03:13:47]

Patchset 1 (id:??) landed as
https://crrev.com/721fdb56e0fc92c662c7d8b42be8a1d689c3b535
Cr-Commit-Position: refs/heads/master@{#26974}

[hans, 2015-03-04 03:25:19]

Thanks!

Who can help getting this merged to and rolled into Chromium?

[jochen (gone - plz use gerrit), 2015-03-04 03:39:11]

On 2015/03/04 at 03:25:19, hans wrote:
> Thanks!
> 
> Who can help getting this merged to and rolled into Chromium?

It should auto-roll