From: "H. Peter Anvin" <hpa@zytor.com>
To: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: 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: Wed, 19 May 2010 17:42:17 -0700 [thread overview]
Message-ID: <4BF48569.7080203@zytor.com> (raw)
In-Reply-To: <4BF46FFE.1080903@redhat.com>
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.
-hpa
next prev parent reply other threads:[~2010-05-20 0:42 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 [this message]
2010-05-20 12:44 ` Ingo Molnar
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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