[llvm-commits] [llvm] r136435 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineShifts.cpp test/Transforms/InstCombine/shift.ll

[Eli Friedman]

On Thu, Jul 28, 2011 at 11:55 PM, Nick Lewycky <nicholas at mxc.ca> wrote:
> Eli Friedman wrote:
>>
>> Author: efriedma
>> Date: Thu Jul 28 19:18:19 2011
>> New Revision: 136435
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=136435&view=rev
>> Log:
>> Make sure to correctly clear the exact/nuw/nsw flags off of shifts when
>> they are combined together.<rdar://problem/9859829>
>
> Maybe I'm missing something, but isn't it safe to preserve the intersection
> of the flags on a chain of same-directional shifts? I'm pretty sure it's
> safe.

Yes, it's safe.  But it's not what the code was doing, and it's not
trivial to implement given the current structure of the code.

-Eli