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* Please correct this code
@ 2011-01-31 16:23 Sri Ram Vemulpali
  0 siblings, 0 replies; 4+ messages in thread
From: Sri Ram Vemulpali @ 2011-01-31 16:23 UTC (permalink / raw)
  To: Kernel-newbies, linux-kernel-mail

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
mentioned

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.
-- 
Regards,
Sri.

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Please correct this code
@ 2011-01-31 16:37 Sri Ram Vemulpali
  2011-01-31 17:58 ` Rajat Sharma
  0 siblings, 1 reply; 4+ messages in thread
From: Sri Ram Vemulpali @ 2011-01-31 16:37 UTC (permalink / raw)
  To: Kernel-newbies, linux-kernel-mail

Hi,

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
mentioned

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.
--
Regards,
Sri.

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2011-01-31 20:22 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-01-31 16:23 Please correct this code Sri Ram Vemulpali
2011-01-31 16:37 Sri Ram Vemulpali
2011-01-31 17:58 ` Rajat Sharma
2011-01-31 20:22   ` Sri Ram Vemulpali

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