arch/tile: use better definitions of xchg() and cmpxchg()

These definitions use a ({}) construct to avoid some cases where
we were getting warnings about unused return values.  We also
promote the definition to the common <asm/atomic.h>, since it applies
to both the 32- and 64-bit atomics.

In addition, define __HAVE_ARCH_CMPXCHG for TILE-Gx since it has
efficient direct atomic instructions.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

3 files changed, 44 insertions, 32 deletions

diff --git a/arch/tile/include/asm/atomic.h b/arch/tile/include/asm/atomic.h
index 75a16028a95..739cfe0499d 100644
--- a/arch/tile/include/asm/atomic.h
+++ b/arch/tile/include/asm/atomic.h
@@ -130,17 +130,52 @@ static inline int atomic_read(const atomic_t *v)
  */
 #define atomic_inc_not_zero(v)          atomic_add_unless((v), 1, 0)
 
-
-/*
- * We define xchg() and cmpxchg() in the included headers.
- * Note that we do not define __HAVE_ARCH_CMPXCHG, since that would imply
- * that cmpxchg() is an efficient operation, which is not particularly true.
- */
-
 /* Nonexistent functions intended to cause link errors. */
 extern unsigned long __xchg_called_with_bad_pointer(void);
 extern unsigned long __cmpxchg_called_with_bad_pointer(void);
 
+#define xchg(ptr, x)                                                    \
+        ({                                                              \
+                typeof(*(ptr)) __x;                                     \
+                switch (sizeof(*(ptr))) {                               \
+                case 4:                                                 \
+                        __x = (typeof(__x))(typeof(__x-__x))atomic_xchg( \
+                                (atomic_t *)(ptr),                      \
+                                (u32)(typeof((x)-(x)))(x));             \
+                        break;                                          \
+                case 8:                                                 \
+                        __x = (typeof(__x))(typeof(__x-__x))atomic64_xchg( \
+                                (atomic64_t *)(ptr),                    \
+                                (u64)(typeof((x)-(x)))(x));             \
+                        break;                                          \
+                default:                                                \
+                        __xchg_called_with_bad_pointer();               \
+                }                                                       \
+                __x;                                                    \
+        })
+
+#define cmpxchg(ptr, o, n)                                              \
+        ({                                                              \
+                typeof(*(ptr)) __x;                                     \
+                switch (sizeof(*(ptr))) {                               \
+                case 4:                                                 \
+                        __x = (typeof(__x))(typeof(__x-__x))atomic_cmpxchg( \
+                                (atomic_t *)(ptr),                      \
+                                (u32)(typeof((o)-(o)))(o),              \
+                                (u32)(typeof((n)-(n)))(n));             \
+                        break;                                          \
+                case 8:                                                 \
+                        __x = (typeof(__x))(typeof(__x-__x))atomic64_cmpxchg( \
+                                (atomic64_t *)(ptr),                    \
+                                (u64)(typeof((o)-(o)))(o),              \
+                                (u64)(typeof((n)-(n)))(n));             \
+                        break;                                          \
+                default:                                                \
+                        __cmpxchg_called_with_bad_pointer();            \
+                }                                                       \
+                __x;                                                    \
+        })
+
 #define tas(ptr) (xchg((ptr), 1))
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/tile/include/asm/atomic_32.h b/arch/tile/include/asm/atomic_32.h
index ed359aee883..92a8bee3231 100644
--- a/arch/tile/include/asm/atomic_32.h
+++ b/arch/tile/include/asm/atomic_32.h
@@ -110,16 +110,6 @@ static inline void atomic_set(atomic_t *v, int n)
         _atomic_xchg(v, n);
 }
 
-#define xchg(ptr, x) ((typeof(*(ptr))) \
-  ((sizeof(*(ptr)) == sizeof(atomic_t)) ? \
-   atomic_xchg((atomic_t *)(ptr), (long)(x)) : \
-   __xchg_called_with_bad_pointer()))
-
-#define cmpxchg(ptr, o, n) ((typeof(*(ptr))) \
-  ((sizeof(*(ptr)) == sizeof(atomic_t)) ? \
-   atomic_cmpxchg((atomic_t *)(ptr), (long)(o), (long)(n)) : \
-   __cmpxchg_called_with_bad_pointer()))
-
 /* A 64bit atomic type */
 
 typedef struct {
diff --git a/arch/tile/include/asm/atomic_64.h b/arch/tile/include/asm/atomic_64.h
index 32170529480..1c1e60d8ccb 100644
--- a/arch/tile/include/asm/atomic_64.h
+++ b/arch/tile/include/asm/atomic_64.h
@@ -148,21 +148,8 @@ static inline long atomic64_add_unless(atomic64_t *v, long a, long u)
 #define smp_mb__before_atomic_inc()     smp_mb()
 #define smp_mb__after_atomic_inc()      smp_mb()
 
-#define xchg(ptr, x)                                                    \
-        ((typeof(*(ptr)))                                               \
-         ((sizeof(*(ptr)) == sizeof(atomic_t)) ?                        \
-          atomic_xchg((atomic_t *)(ptr), (long)(x)) :                   \
-          (sizeof(*(ptr)) == sizeof(atomic_long_t)) ?                   \
-          atomic_long_xchg((atomic_long_t *)(ptr), (long)(x)) :         \
-          __xchg_called_with_bad_pointer()))
-
-#define cmpxchg(ptr, o, n)                                              \
-        ((typeof(*(ptr)))                                               \
-         ((sizeof(*(ptr)) == sizeof(atomic_t)) ?                        \
-          atomic_cmpxchg((atomic_t *)(ptr), (long)(o), (long)(n)) :     \
-          (sizeof(*(ptr)) == sizeof(atomic_long_t)) ?                   \
-          atomic_long_cmpxchg((atomic_long_t *)(ptr), (long)(o), (long)(n)) : \
-          __cmpxchg_called_with_bad_pointer()))
+/* Define this to indicate that cmpxchg is an efficient operation. */
+#define __HAVE_ARCH_CMPXCHG
 
 #endif /* !__ASSEMBLY__ */