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Re: Live on Exit renaming.


On Mon, Jul 6, 2015 at 12:02 PM, Ajit Kumar Agarwal
<ajit.kumar.agarwal@xilinx.com> wrote:
>
>
> -----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
As far as I understand, fsplit-ivs-in-unroller is a transformation in
RTL unroller.

Thanks,
bin
> 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


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