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Re: Enabling -frename-registers?

From: Bernd Schmidt <bschmidt at redhat dot com>
To: Eric Botcazou <ebotcazou at adacore dot com>, David Edelsohn <dje dot gcc at gmail dot com>
Cc: gcc-patches at gcc dot gnu dot org, Richard Biener <richard dot guenther at gmail dot com>, Jeffrey Law <law at redhat dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>
Date: Wed, 4 May 2016 12:11:04 +0200
Subject: Re: Enabling -frename-registers?
Authentication-results: sourceware.org; auth=none
References: <CAGWvnykBEjYMgOCaR_ZGLwB3fxPg-pB3WPSwAvmUBXzmXct8gg at mail dot gmail dot com> <443D7834-6E23-4046-8DD7-F1D8F2593F2B at gmail dot com> <CAGWvny=KPTheWKc-CbKrWGsGfBXB9vWz57RfVRUY_NTOBPUKZg at mail dot gmail dot com> <2317874 dot CXT2IFrHHt at polaris>

On 05/04/2016 12:03 PM, Eric Botcazou wrote:

The IBM LTC team has tested the benefit of -frename-registers at -O2
and sees no net benefit for PowerPC -- some benchmarks improve
slightly but others degrade slightly (a few percent).  You mentioned
no overall benefit for x86.  Although you mentioned benefit for
Itanium, it is not a primary nor secondary architecture target for GCC
and continues to have limited adoption.  Andreas also reported a
bootstrap comparison failure for Itanium due to the change.


...which had nothing to do with -frename-registers but was a latent issue in
the speculation support of the scheduler, see the audit trail.

Yeah, I'd forgotten to add this to the list of issues found. Also,Alan's morestack representation issue.

Given how many latent bugs it has shown up I think that alone would makeit valuable to have enabled at -O2.



Bernd

Follow-Ups:
- Re: Enabling -frename-registers?
  - From: Eric Botcazou
- Re: Enabling -frename-registers?
  - From: David Edelsohn
- Re: Enabling -frename-registers?
  - From: Segher Boessenkool

References:
- Re: Enabling -frename-registers?
  - From: David Edelsohn
- Re: Enabling -frename-registers?
  - From: Eric Botcazou

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