Live on Exit renaming.

[Ajit Kumar Agarwal]

-----Original Message-----
From: Bin.Cheng [mailto:amker.cheng@gmail.com] 
Sent: Monday, July 06, 2015 7:04 AM
To: Steven Bosscher
Cc: Ajit Kumar Agarwal; law@redhat.com; Richard Biener; gcc@gcc.gnu.org; Vinod Kathail; Shail Aditya Gupta; Vidhumouli Hunsigida; Nagaraju Mekala
Subject: Re: Live on Exit renaming.

On Mon, Jul 6, 2015 at 6:02 AM, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
> On Sat, Jul 4, 2015 at 3:45 PM, Ajit Kumar Agarwal wrote:
>> I am not sure why the above optimization is not implemented in GCC.
>
> -fsplit-ivs-in-unroller

>>And thing might have changed.  Given the condition GCC does IVO on gimple, unrolling on RTL, there is inconsistency between the two optimizer since IVO >>takes register pressure of IVs into consideration and assumes IVs will take single registers.  At least for some cases, splitting live range of IVs results in bad >>code.  See PR29256 for more information.  As described in the comment, actually I am going to do some experiments disabling such transformation to see >>what happens.

The above optimization is implemented as a part of unroller in gimple. There is an unroller pass in rtl which does not have support for this 
optimization.  Shouldn't be the fsplit-ivs-in-unroller optimization implemented in the unroller pass of rtl. I am looking at the implementation
perspective for implementing the fsplit-ivs-in-unroller optimizations in the unroller rtl pass.

Thanks & Regards
Ajit

Thanks,
bin
>
> Ciao!
> Steven