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Re: Enabling -frename-registers?
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: David Edelsohn <dje dot gcc at gmail dot com>,Bernd Schmidt <bschmidt at redhat dot com>
- Cc: Jeffrey Law <law at redhat dot com>,GCC Patches <gcc-patches at gcc dot gnu dot org>,Segher Boessenkool <segher at kernel dot crashing dot org>
- Date: Fri, 29 Apr 2016 16:21:48 +0200
- Subject: Re: Enabling -frename-registers?
- Authentication-results: sourceware.org; auth=none
- References: <CAGWvnykBEjYMgOCaR_ZGLwB3fxPg-pB3WPSwAvmUBXzmXct8gg at mail dot gmail dot com> <57236285 dot 5090908 at redhat dot com> <CAGWvnykKwAtfSin23FP4L0bNgH4bSAdV+vMRTOe+dPk15oAfGg at mail dot gmail dot com> <57236547 dot 2070707 at redhat dot com> <CAGWvnyka9pPjOmFFb8avhBWNAOWGygOeCfUzKCZbY3dxux48LQ at mail dot gmail dot com>
On April 29, 2016 3:48:37 PM GMT+02:00, David Edelsohn <dje.gcc@gmail.com> wrote:
>On Fri, Apr 29, 2016 at 9:44 AM, Bernd Schmidt <bschmidt@redhat.com>
>wrote:
>>
>>
>> On 04/29/2016 03:42 PM, David Edelsohn wrote:
>>>
>>> On Fri, Apr 29, 2016 at 9:32 AM, Bernd Schmidt <bschmidt@redhat.com>
>>> wrote:
>>>>
>>>> On 04/29/2016 03:02 PM, David Edelsohn wrote:
>>>>>
>>>>>
>>>>> How has this show general benefit for all architectures to deserve
>>>>> enabling it by default at -O2?
>>>>
>>>>
>>>>
>>>> It should improve postreload scheduling in general, and it can also
>help
>>>> clear up bad code generation left behind by register allocation.
>>>
>>>
>>> Did you test the actual performance benefit on any architectures,
>>> especially architectures other than x86?
>>
>>
>> No. If that's the standard, I'll back out the change.
>
>It seems rather strange to enable an optimization by default across
>all targets without even knowing the performance impact.
>
>I'm eager to learn the opinion of others about this.
It shows overall benefit on Itanic and ups and downs on x86.
It's stage1 and the easiest to get feedback for all archs is to enable it by default.
Richard.
>Thanks, David