From: Momchil Velikov <velco@fadata.bg>
To: Jan-Benedict Glaw <jbglaw@microdata-pos.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: xchg and GCC's optimisation:-(
Date: 17 Dec 2001 15:18:45 +0200 [thread overview]
Message-ID: <87wuzmq91m.fsf@fadata.bg> (raw)
In-Reply-To: <20011217134526.A31801@microdata-pos.de>
In-Reply-To: <20011217134526.A31801@microdata-pos.de>
>>>>> "Jan-Benedict" == Jan-Benedict Glaw <jbglaw@microdata-pos.de> writes:
Jan-Benedict> I've looked at ./include/asm-i386/system.h which does some black
Jan-Benedict> magic with it, and I don't really understand that. However, the
Jan-Benedict> result is that the xchg gets optimized away, rendering at least
Can you try with this patch ...
--- system.h.orig.0 Mon Dec 17 15:03:38 2001
+++ system.h Mon Dec 17 15:16:58 2001
@@ -205,21 +205,15 @@ static inline unsigned long __xchg(unsig
switch (size) {
case 1:
__asm__ __volatile__("xchgb %b0,%1"
- :"=q" (x)
- :"m" (*__xg(ptr)), "0" (x)
- :"memory");
+ :"+q" (x),"=m" (*__xg(ptr)));
break;
case 2:
__asm__ __volatile__("xchgw %w0,%1"
- :"=r" (x)
- :"m" (*__xg(ptr)), "0" (x)
- :"memory");
+ :"+r" (x),"=m" (*__xg(ptr)));
break;
case 4:
__asm__ __volatile__("xchgl %0,%1"
- :"=r" (x)
- :"m" (*__xg(ptr)), "0" (x)
- :"memory");
+ :"+r" (x), "=m" (*__xg(ptr)));
break;
}
return x;
next prev parent reply other threads:[~2001-12-17 13:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-17 12:45 xchg and GCC's optimisation:-( Jan-Benedict Glaw
2001-12-17 13:18 ` Momchil Velikov [this message]
2001-12-17 13:55 ` Jan-Benedict Glaw
2001-12-17 17:33 ` vda
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