From: Anton Blanchard <anton@samba.org>
Date: Tue, 6 Sep 2005 03:05:58 +0000 (+1000)
Subject: [PATCH] ppc64: speedup cmpxchg
X-Git-Tag: v2.6.14-rc1~747^2~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b2c0ab17ba751abe13a28508b1ac7e9ca074cd87;p=pandora-kernel.git

[PATCH] ppc64: speedup cmpxchg

cmpxchg has the following code:

__typeof__(*(ptr)) _o_ = (o);
__typeof__(*(ptr)) _n_ = (n);

Unfortunately it makes gcc 4.0 store and load the variables to the stack.
Eg in atomic_dec_and_test we get:

  stw     r10,112(r1)
  stw     r9,116(r1)
  lwz     r9,112(r1)
  lwz     r0,116(r1)

x86 is just casting the values so do that instead. Also change __xchg*
and __cmpxchg* to take unsigned values, removing a few sign extensions.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
---

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