Thanks! Changing the order of the operands worked, the destination was the second operand. On Thu, Sep 27, 2012 at 2:25 PM, Ian Lance Taylor-3 [via gcc] < ml-node+s1065356n873142h84@xxxxxxxxxxxxx> wrote: > On Thu, Sep 27, 2012 at 6:44 AM, jonnyjack <[hidden email]<http://user/SendEmail.jtp?type=node&node=873142&i=0>> > wrote: > > > For a school project, I have to implement a simple atomic_sub() function > in > > c. The implementation must use the asm() function. > > > > Right now, my code looks like this > > > > void atomic_sub( int * value, int dec_val) { > > asm ("LOCK SUB (%0), %1;\n" > > : > > : "r" (value), "r" (dec_val) > > : "memory"); > > } > > > > The intention is for "value" to decrement by "dec_val" atomically, but > when > > I try to compile I get the following error. > > > > "locking.c:28: Error: expecting lockable instruction after 'lock'" > > > > This asm() call is on line 28, so this is the instruction the error is > > referring to. Does anyone know why this isn't a lockable instruction? > > According to the documentation from Intel I've read, a sub with a > > destination of a memory address is lockable. Any ideas? > > You are running into syntax issues. You are using Intel syntax and > the assembler is probably expecting AT&T syntax. You could try the > -masm=intel option. Or reverse the operands. > > Ian > > > ------------------------------ > If you reply to this email, your message will be added to the discussion > below: > > http://gcc.1065356.n5.nabble.com/using-asm-to-execute-an-atomic-subtraction-instruction-tp873076p873142.html > To unsubscribe from using asm() to execute an atomic subtraction > instruction, click here<http://gcc.1065356.n5.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=873076&code=am9ubnlqYWNrN0BnbWFpbC5jb218ODczMDc2fDQ4ODAyMjI3OQ==> > . > NAML<http://gcc.1065356.n5.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> > -- View this message in context: http://gcc.1065356.n5.nabble.com/using-asm-to-execute-an-atomic-subtraction-instruction-tp873076p873158.html Sent from the gcc - Help mailing list archive at Nabble.com.
