linux-kernel - [PATCH RFC 2/4] include/linux/compiler.h: allow memory operands

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Message-ID: <20190102205715.14054-3-mst@redhat.com>
Date:   Wed, 2 Jan 2019 15:57:54 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Jason Wang <jasowang@...hat.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Nicholas Piggin <npiggin@...il.com>,
        David Howells <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Akira Yokosawa <akiyks@...il.com>,
        Daniel Lustig <dlustig@...dia.com>, linux-arch@...r.kernel.org,
        netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        linux-sparse@...r.kernel.org
Subject: [PATCH RFC 2/4] include/linux/compiler.h: allow memory operands

We don't really care whether the variable is in-register
or in-memory. Relax the constraint accordingly.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 include/linux/compiler.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 1ad367b4cd8d..6601d39e8c48 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -154,7 +154,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 #ifndef OPTIMIZER_HIDE_VAR
 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
 #define OPTIMIZER_HIDE_VAR(var)						\
-	__asm__ ("" : "=r" (var) : "0" (var))
+	__asm__ ("" : "=rm" (var) : "0" (var))
 #endif
 
 /* Not-quite-unique ID. */
-- 
MST