3.6.1 patch nomination: r232189 - [SCEV] Fix PR22856

[Tom Stellard]

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
>