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Date: Thu, 28 May 2009 20:59:00 -0000
From: Jamie Prescott <jpresss@yahoo.com>
Subject: Re: Forgetting return values
To: Adam Nemet <anemet@caviumnetworks.com>
Cc: gcc@gcc.gnu.org
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> From: Adam Nemet <anemet@caviumnetworks.com>
> To: Jamie Prescott <jpresss@yahoo.com>
> Cc: gcc@gcc.gnu.org
> Sent: Thursday, May 28, 2009 11:10:49 AM
> Subject: Re: Forgetting return values
> 
> Jamie Prescott writes:
> > static inline int set_prop(char const *path, char const *name,
> >                                           void const *data, int size)
> > {
> >         int error;
> >
> >         asm volatile ("int\t11\n\t"
> >                       : "=a0" (error): "a0" (path), "a1" (name), "a2" (data),
> >                         "a3" (size));
> >
> >         return error;
> > }
> >
> > extern int calc(int);
> >
> > int proc(int i)
> > {
> >         int j = calc(i);
> >
> >         return set_prop(0, 0, &j, sizeof(int));
> > }
> ...
> >
> > Why is the memory clobber required, and why GCC does not understand to
> > sync the value to memory when passing the address to a function?
> 
> Because you never inform GCC that you will use the value at
> address *NAME.  Try to use "m"(*name) rather than "a1"(name) in the asm.

That's 'data', not 'name'. But OK, got it. unfortunately, I cannot use "m" since
that value need to go into a specific register.
Any other solution?


- Jamie