supression of 'matching constraint does not allow a register' warning

[Peter Barada <peter at the-baradas dot com>]

In the Linux-2.4.x kernel for m68k, the atomic operations use the
addql/subql instructions for incrementing/decrementing atomic
variables, and force the variables to memory to make the operation
truly atomic.  The definition from linux-2.4.x/include/asm-m68k/atomic.h:

static __inline__ void atomic_inc(volatile atomic_t *v)
{
	__asm__ __volatile__("addql #1,%0" : "=m" (*v): "0" (*v));
}

static __inline__ void atomic_dec(volatile atomic_t *v)
{
	__asm__ __volatile__("subql #1,%0" : "=m" (*v): "0" (*v));
}

Unfortunately when used they generate the following warning from
parse_input_contstraint in gcc/stmt.c:

  if (saw_match && !*allows_reg)
    warning ("matching constraint does not allow a register");


Since atomic_inc/atomic_dec are defined that way to enforce an
atomic operation to memory, when building the kernel, *lots* of
warnings are generated making it hard to wade through the log looking
for other warnings/errors.

I'd like to add a flag to suppress this warning, and was wondering if
a patch for this would be accepted, and what best to call the flag.

Any comments are appreciated.

-- 
Peter Barada
peter@the-baradas.com