From a6cf7ed5119fb22f54584a9f867b638edd3c4384 Mon Sep 17 00:00:00 2001
From: Anton Blanchard <anton@samba.org>
Date: Wed, 29 Feb 2012 21:12:16 +0000
Subject: [PATCH] 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: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
arch/powerpc/include/asm/atomic.h | 59 ++++++++++++++++++++++++++++++-
1 file changed, 58 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h
index 02e41b53488d8..14174e838ad9c 100644
--- a/arch/powerpc/include/asm/atomic.h
+++ b/arch/powerpc/include/asm/atomic.h
@@ -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__ */
--
2.30.2