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From: Ingo Molnar <mingo@elte.hu>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	mingo@redhat.com, linux-kernel@vger.kernel.org,
	suresh.b.siddha@intel.com, tglx@linutronix.de, avi@redhat.com,
	linux-tip-commits@vger.kernel.org
Subject: Re: Does anyone care about gcc 3.x support for x86 anymore?
Date: Thu, 20 May 2010 14:44:53 +0200	[thread overview]
Message-ID: <20100520124453.GC2734@elte.hu> (raw)
In-Reply-To: <4BF48569.7080203@zytor.com>


* H. Peter Anvin <hpa@zytor.com> wrote:

> On 05/19/2010 04:10 PM, Mauro Carvalho Chehab wrote:
> > 
> > However, if the problems are just performance/dead 
> > code removal, I would just add a big warning if 
> > someone tries to compile x86 with it. I don't like 
> > very much the idea of having different minimum gcc 
> > requirements for each architecture, except if gcc is 
> > producing a broken code.
> > 
> 
> I should clarify the problem.  The problems we have seen 
> are related to constant propagation, which causes gcc3 
> to die when there is an assembly constraint like:
> 
> 	asm("..." : : "i" (foo));
> 
> ... since "foo" isn't constant as far as it is 
> concerned.  We can put in workarounds, but it's real 
> effort to keep it alive that probably isn't well spent.
> 
> Similarly, lack of constant propagation can cause code 
> that should have been compile-time removed to still be 
> there, causing link failures.

Put in a deprecation warning first perhaps?

	Ingo

  reply	other threads:[~2010-05-20 12:45 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-06  8:45 [PATCH v3 0/2] x86 FPU API Avi Kivity
2010-05-06  8:45 ` [PATCH v3 1/2] x86: eliminate TS_XSAVE Avi Kivity
2010-05-10 20:39   ` [tip:x86/fpu] x86: Eliminate TS_XSAVE tip-bot for Avi Kivity
2010-05-12  0:18   ` [tip:x86/fpu] x86, fpu: Use the proper asm constraint in use_xsave() tip-bot for H. Peter Anvin
2010-05-12  1:06   ` [tip:x86/fpu] x86: Add new static_cpu_has() function using alternatives tip-bot for H. Peter Anvin
2010-05-18 20:10     ` Eric Dumazet
2010-05-18 20:43       ` H. Peter Anvin
2010-05-18 20:57       ` H. Peter Anvin
2010-05-18 21:11         ` Eric Dumazet
2010-05-18 21:31           ` H. Peter Anvin
2010-05-18 21:38           ` Does anyone care about gcc 3.x support for x86 anymore? H. Peter Anvin
2010-05-19 23:10             ` Mauro Carvalho Chehab
2010-05-20  0:39               ` H. Peter Anvin
2010-05-20  0:42               ` H. Peter Anvin
2010-05-20 12:44                 ` Ingo Molnar [this message]
2010-05-18 20:58       ` [tip:x86/fpu] x86: Add new static_cpu_has() function using alternatives H. Peter Anvin
2010-05-18 21:31         ` Eric Dumazet
2010-05-27 20:12         ` [tip:x86/urgent] x86, cpufeature: Unbreak compile with gcc 3.x tip-bot for H. Peter Anvin
2010-05-12  1:06   ` [tip:x86/fpu] x86, fpu: Use static_cpu_has() to implement use_xsave() tip-bot for H. Peter Anvin
2010-05-06  8:45 ` [PATCH v3 2/2] x86: Introduce 'struct fpu' and related API Avi Kivity
2010-05-10 20:39   ` [tip:x86/fpu] " tip-bot for Avi Kivity
2010-05-10 20:40   ` [tip:x86/fpu] x86, fpu: Unbreak FPU emulation tip-bot for H. Peter Anvin
2010-05-10  8:48 ` [PATCH v3 0/2] x86 FPU API Avi Kivity
2010-05-10 15:24   ` H. Peter Anvin
  -- strict thread matches above, loose matches on Subject: below --
2010-05-19  1:19 Does anyone care about gcc 3.x support for *x86* anymore? H. Peter Anvin
2010-05-19  7:13 ` Ingo Molnar
2010-05-19 13:38 ` Andi Kleen
2010-05-19 14:08   ` H. Peter Anvin
2010-05-19 22:45     ` Justin P. Mattock
2010-05-20 18:37   ` Martin Michlmayr
2010-05-20 19:56     ` Miguel Ojeda

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