To: linux-kernel@vger.kernel.org
Cc: gcc@gcc.gnu.org
Subject: i386 flags register clober in inline assembly
From: Momchil Velikov <velco@fadata.bg>
Date: 17 Nov 2001 16:06:22 +0200
Message-ID: <87y9l58pb5.fsf@fadata.bg>
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Sender: linux-kernel-owner@vger.kernel.org


There are several inline assembly routines in the i386 port, which
clobber the flags register, nevertheless fail to declare that.
E.g. atomic_inc

	__asm__ __volatile__(
		LOCK "incl %0"
		:"=m" (v->counter)
		:"m" (v->counter));

should be

	__asm__ __volatile__(
		LOCK "incl %0"
		:"=m" (v->counter)
		:"m" (v->counter)
                : "cc");

since "incl" clobbers flags.

Any ideas if these functions should be corrected ?

Although gcc documentation says "cc" has no effect on some machines,
it seems this is not the case with i386, judging from the "(set (reg:CC 17) ..."
and "(clobber (reg:CC 17))" in i386.md.

Regards,
-velco


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