Re: [Bugme-new] [Bug 7602] New: Failure on compilation: include/asm/bitops.h:122: error: inconsistent operand constraints in an `asm' in nfs_access_add_cache()

[Andi Kleen]

On Thursday 30 November 2006 23:32, Andrew Morton wrote:
> On Thu, 30 Nov 2006 23:22:00 +0100
> Andi Kleen <ak@xxxxxxx> wrote:
> 
> > > 
> > > static __inline__ int __test_and_set_bit(int nr, volatile void * addr)
> > > {
> > > 	int oldbit;
> > > 
> > > 	__asm__(
> > > 		"btsl %2,%1\n\tsbbl %0,%0"
> > > 		:"=r" (oldbit),"+m" (ADDR)
> > > 		:"dIr" (nr));
> > > 	return oldbit;
> > > }
> > > 
> > > explodes with gcc-3.4.4.
> > 
> > Known issue.  The new form is correct and needed, but the old gcc doesn't accept
> > it. I haven't gotten a form that is both and correct and works on the old compiler
> > out of the gcc hackers I asked.
> 
> Oh, thanks.
> 
> What does "d" do, btw?  My gcc info page only covers "x86" and says only "`d' register"

Hmm, normally edx (aka Extended D register eXtended :) or rdx 

But you're right it doesn't make sense here because 'd' is already included in 'r'.
Probably should be dropped.

> 
> (And, more importantly, where is the best description of gcc asm constraints?)

Either info pages or gcc source. There was also a web page somewhere with a tutorial,
but i don't think it was a full reference.

-Andi
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