[llvm] r259236 - [InstCombine] avoid an insertelement transformation that induces the opposite extractelement fold (PR26354)

[Hans Wennborg via llvm-commits]

Merged in r259245.

On Fri, Jan 29, 2016 at 1:33 PM, David Majnemer <majnemer at google.com> wrote:
> LGTM
>
> On Fri, Jan 29, 2016 at 1:03 PM, Hans Wennborg <hans at chromium.org> wrote:
>>
>> (actually cc'ing David this time)
>>
>> On Fri, Jan 29, 2016 at 1:02 PM, Hans Wennborg <hans at chromium.org> wrote:
>> > David, OK to merge to 3.8?
>>
>> ^^
>>
>> >
>> > On Fri, Jan 29, 2016 at 12:21 PM, Sanjay Patel via llvm-commits
>> > <llvm-commits at lists.llvm.org> wrote:
>> >> Author: spatel
>> >> Date: Fri Jan 29 14:21:02 2016
>> >> New Revision: 259236
>> >>
>> >> URL: http://llvm.org/viewvc/llvm-project?rev=259236&view=rev
>> >> Log:
>> >> [InstCombine] avoid an insertelement transformation that induces the
>> >> opposite extractelement fold (PR26354)
>> >>
>> >> We would infinite loop because we created a shufflevector that was
>> >> wider than
>> >> needed and then failed to combine that with the insertelement. When
>> >> subsequently
>> >> visiting the extractelement from that shuffle, we see that it's
>> >> unnecessary,
>> >> delete it, and trigger another visit to the insertelement.
>
>