[llvm] r237539 - Reapply r237520 with another fix for infinite looping

[Hans Wennborg]

On Sun, May 17, 2015 at 1:27 AM, James Molloy <james.molloy at arm.com> wrote:
> Author: jamesm
> Date: Sun May 17 03:27:27 2015
> New Revision: 237539
>
> URL: http://llvm.org/viewvc/llvm-project?rev=237539&view=rev
> Log:
> Reapply r237520 with another fix for infinite looping
>
> SimplifyDemandedBits was "simplifying" a constant by removing just sign bits.
> This caused a canonicalization race between different parts of instcombine.
>
> Fix and regression test added - third time lucky?

Sorry, but it seems this broke some tests in Chromium. I reduced it to
PR23583. Reverted in r237739.

 - Hans