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Message-ID: <20071229095253.GC27360@does.not.exist>
Date: Sat, 29 Dec 2007 11:52:53 +0200
From: Adrian Bunk <bunk@...nel.org>
To: Sam Ravnborg <sam@...nborg.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...e.de>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: unify x86 Makefile(s)
On Sat, Dec 29, 2007 at 10:39:04AM +0100, Sam Ravnborg wrote:
> On Sat, Dec 29, 2007 at 12:13:24AM +0200, Adrian Bunk wrote:
> > On Fri, Dec 28, 2007 at 10:23:41PM +0100, Sam Ravnborg wrote:
> > >...
> > > Noteworthy remarks on the unification:
> > >...
> > > - -funit-at-a-time should be easy to unify but it looks like we have a bug
> > > in 32 bit. We only enable -funit-at-a-time for gcc less than 0400 if they
> > > support it
> >
> > No, we _dis_able it on 32bit if a gcc < 4.0 supports it.
> I have:
> $ gcc --version
> gcc (GCC) 4.1.2 20070925 (Red Hat 4.1.2-33)
>
> And with the current code in arch/x86/Makefile_32 I do not
> have -funit-at-a-time.
>...
You do not have this option, but you do not need it since it's enabled
with -O in all gcc versions that support it except for some vendor
backports to gcc 3.3.
>...
> This is the relevant snippet from the Makefile:
> KBUILD_CFLAGS += $(shell if [ $(call cc-version) -lt 0400 ] ; then echo $(call cc-option,-fno-unit-at-a-time); fi ;)
>
> It reads:
> If gcc version is less than 4.00 then enable -funit-at-a-time only for gcc that supports it.
> -funit-at-a-time is NOT enabled for gcc >= 4.00
It is not _explicitely_ enabled for gcc >= 4.0 since it's anyway enabled.
> So it will enable -funit-at-a-time for gcc 3.4 as it is now.
> Which was what we wanted to avoid..
> So I see no reason not to enable it uncondintionally (if gcc supports it) as we have
> used it for 3.4 for as long as we have introduced -funit-at-a-time.
We have never used it with gcc 3.4 on i386.
> Sam
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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