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From: Sri Ram Vemulpali <>
To: Kernel-newbies <>,
	linux-kernel-mail <>
Subject: Please correct this code
Date: Mon, 31 Jan 2011 11:37:54 -0500	[thread overview]
Message-ID: <> (raw)


I have following snippet of code.

Code A

__asm__ __volatile__(
                     "   lock       ;\n"
                     "   addl %1,%0 ;\n"
                     : "=m"  (my_var)
                     : "ir"  (my_int), "m" (my_var)
                     :                                 /* no clobber-list */

Code B

 __asm__ __volatile__(  "decl %0; sete %1"
                     : "=m" (my_var), "=q" (cond)
                     : "m" (my_var)
                     : "memory"

In Code A memory contents are getting updated. And in Code B memory
contents and 'cond' var are getting updated.
In Code B in cobbler column 'memory' is used to indicate that this
code modifies memory contents. But where as in Code A it was not

Is is not that Code A is wrong, for not mentioning cobbler list
'memory' to indicate memory contents are getting updated.
Please rectify me, if I am wrong.

Also, what does '+m' constraint mean, if I use in inline assembly.

             reply	other threads:[~2011-01-31 16:37 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-31 16:37 Sri Ram Vemulpali [this message]
2011-01-31 17:58 ` Rajat Sharma
2011-01-31 20:22   ` Sri Ram Vemulpali
  -- strict thread matches above, loose matches on Subject: below --
2011-01-31 16:23 Sri Ram Vemulpali

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