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Commit a6cf7ed5 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
Browse files

powerpc/atomic: Implement atomic*_inc_not_zero 



Implement atomic_inc_not_zero and atomic64_inc_not_zero. At the
moment we use atomic*_add_unless which requires us to put 0 and
1 constants into registers. We can also avoid a subtract by
saving the original value in a second temporary.

This removes 3 instructions from fget:

- c0000000001b63c0:       39 00 00 00     li      r8,0
- c0000000001b63c4:       39 40 00 01     li      r10,1
...
- c0000000001b63e8:       7c 0a 00 50     subf    r0,r10,r0

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent b1ada601

arch/powerpc/include/asm/atomic.h

+58 −1
Original line number Diff line number Diff line
@@ -212,6 +212,36 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u) 
	return t;

}



/**

 * atomic_inc_not_zero - increment unless the number is zero

 * @v: pointer of type atomic_t

 *

 * Atomically increments @v by 1, so long as @v is non-zero.

 * Returns non-zero if @v was non-zero, and zero otherwise.

 */

static __inline__ int atomic_inc_not_zero(atomic_t *v)

{

	int t1, t2;



	__asm__ __volatile__ (

	PPC_ATOMIC_ENTRY_BARRIER

"1:	lwarx	%0,0,%2		# atomic_inc_not_zero\n\

	cmpwi	0,%0,0\n\

	beq-	2f\n\

	addic	%1,%0,1\n"

	PPC405_ERR77(0,%2)

"	stwcx.	%1,0,%2\n\

	bne-	1b\n"

	PPC_ATOMIC_EXIT_BARRIER

	"\n\

2:"

	: "=&r" (t1), "=&r" (t2)

	: "r" (&v->counter)

	: "cc", "xer", "memory");



	return t1;

}

#define atomic_inc_not_zero(v) atomic_inc_not_zero((v))



#define atomic_sub_and_test(a, v)	(atomic_sub_return((a), (v)) == 0)

#define atomic_dec_and_test(v)		(atomic_dec_return((v)) == 0)
@@ -467,7 +497,34 @@ static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u) 
	return t != u;

}



#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)

/**

 * atomic_inc64_not_zero - increment unless the number is zero

 * @v: pointer of type atomic64_t

 *

 * Atomically increments @v by 1, so long as @v is non-zero.

 * Returns non-zero if @v was non-zero, and zero otherwise.

 */

static __inline__ long atomic64_inc_not_zero(atomic64_t *v)

{

	long t1, t2;



	__asm__ __volatile__ (

	PPC_ATOMIC_ENTRY_BARRIER

"1:	ldarx	%0,0,%2		# atomic64_inc_not_zero\n\

	cmpdi	0,%0,0\n\

	beq-	2f\n\

	addic	%1,%0,1\n\

	stdcx.	%1,0,%2\n\

	bne-	1b\n"

	PPC_ATOMIC_EXIT_BARRIER

	"\n\

2:"

	: "=&r" (t1), "=&r" (t2)

	: "r" (&v->counter)

	: "cc", "xer", "memory");



	return t1;

}



#endif /* __powerpc64__ */