3.6.1 patch nomination: r232189 - [SCEV] Fix PR22856

[Sanjoy Das]

Merged r232189 into 3.6 as r232416.

On Mon, Mar 16, 2015 at 6:34 AM, Tom Stellard <tom at stellard.net> wrote:
> LGTM. Go ahead and merge this into the 3.6 branch.
>
> -Tom
>
> On Fri, Mar 13, 2015 at 02:40:52PM -0700, Andrew Trick wrote:
>> Ok for release.
>> -Andy
>>
>> > On Mar 13, 2015, at 1:36 PM, Sanjoy Das <sanjoy at playingwithpointers.com> wrote:
>> >
>> > This change fixes https://llvm.org/bugs/show_bug.cgi?id=22856.
>> >
>> > Commit message:
>> >
>> > Summary:
>> > ScalarEvolutionExpander assumes that the header block of a loop is a
>> > legal place to have a use for a phi node.  This is true only for phis
>> > that are either in the header or dominate the header block, but it is
>> > not true for phi nodes that are strictly internal to the loop body.
>> >
>> > This change teaches ScalarEvolutionExpander to place uses of PHI nodes
>> > in the basic block the PHI nodes belong to.  This is always legal, and
>> > `hoistIVInc` ensures that the said position dominates `IsomorphicInc`.
>> >
>> > Reviewers: atrick
>> >
>> > Subscribers: llvm-commits
>> >
>> > Differential Revision: http://reviews.llvm.org/D8311
>>