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Date:      Tue, 11 Sep 2012 06:24:10 -0700
From:      Steve Kargl <sgk@troutmask.apl.washington.edu>
To:        Roman Divacky <rdivacky@freebsd.org>
Cc:        toolchain@freebsd.org, current@freebsd.org
Subject:   Re: Clang as default compiler November 4th
Message-ID:  <20120911132410.GA87126@troutmask.apl.washington.edu>
In-Reply-To: <20120911120649.GA52235@freebsd.org>
References:  <20120910211207.GC64920@lor.one-eyed-alien.net> <20120911104518.GF37286@deviant.kiev.zoral.com.ua> <20120911120649.GA52235@freebsd.org>

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On Tue, Sep 11, 2012 at 02:06:49PM +0200, Roman Divacky wrote:
> > > tl;dr: Clang will become the default compiler for x86 architectures on 2012-11-04
> 
> > Another issue with the switch, which seems to be not only not addressed,
> > but even not talked about, is the performance impact of the change. I
> > do not remember any measurements, whatever silly they could be, of the
> > performance change by the compiler switch. We often have serious and
> > argumented push-back for kernel changes that give as low as 2-3% of
> > the speed hit. What are the numbers for clang change, any numbers ?
> 
> Agreed. We should provide numbers. At least how buildworld times change
> with clang compiled kernel/workd and gcc compiler kernel/world.

How fast clang builds world in comparison to gcc is irrelevant.
What is important is whether software built with clang functions
correctly.  See for example, 

http://math-atlas.sourceforge.net/errata.html#WhatComp

Has anyone run Spec CPU2006 on i386 and amd64 FreeBSD?

-- 
Steve



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