Hi,

As requested in the PR, this patch is a partial backport of r228751.

I can't claim any responsibility for it, but I did take it through the
paces on an aarch64-none-linux-gnu and x86_64-none-linux-gnu bootstrap/
test run and found no issues.

Applied as r230092 on gcc-5-branch (pre-approved in the PR) after checking
that it gives the right results for the code I derived the PR from.

I'll start a test cycle for a 4.9 backport.

Thanks,
James

---
2015-11-09  James Greenhalgh  <james.greenhalgh@arm.com>

	Partial backport from trunk r228751.
	PR tree-optimization/68238
	2015-10-13  Richard Biener  <rguenther@suse.de>

	* tree-vect-loop.c (vect_estimate_min_profitable_iters): Use
	LOOP_VINFO_COMP_ALIAS_DDRS to estimate alias versioning cost.