x86: consolidate xchg and xadd macros

They both have a basic "put new value in location, return old value"
pattern, so they can use the same macro easily.
Signed-off-by: NJeremy Fitzhardinge <jeremy@goop.org>

arch/x86/include/asm/cmpxchg.h

@@ -34,59 +34,46 @@ extern void __add_wrong_size(void)
 #endif
 
 /* 
- * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.
- * Since this is generally used to protect other memory information, we
- * use "asm volatile" and "memory" clobbers to prevent gcc from moving
- * information around.
+ * An exchange-type operation, which takes a value and a pointer, and
+ * returns a the old value.
  */
-#define __xchg(x, ptr, size)						\
-({									\
-	__typeof(*(ptr)) __x = (x);					\
-	switch (size) {							\
+#define __xchg_op(ptr, arg, op, lock)					\
+	({								\
+	        __typeof__ (*(ptr)) __ret = (arg);			\
+		switch (sizeof(*(ptr))) {				\
 		case __X86_CASE_B:					\
-	{								\
-		volatile u8 *__ptr = (volatile u8 *)(ptr);		\
-		asm volatile("xchgb %0,%1"				\
-			     : "=q" (__x), "+m" (*__ptr)		\
-			     : "0" (__x)				\
-			     : "memory");				\
+			asm volatile (lock #op "b %b0, %1\n"		\
+				      : "+r" (__ret), "+m" (*(ptr))	\
+				      : : "memory", "cc");		\
 			break;						\
-	}								\
 		case __X86_CASE_W:					\
-	{								\
-		volatile u16 *__ptr = (volatile u16 *)(ptr);		\
-		asm volatile("xchgw %0,%1"				\
-			     : "=r" (__x), "+m" (*__ptr)		\
-			     : "0" (__x)				\
-			     : "memory");				\
+			asm volatile (lock #op "w %w0, %1\n"		\
+				      : "+r" (__ret), "+m" (*(ptr))	\
+				      : : "memory", "cc");		\
 			break;						\
-	}								\
 		case __X86_CASE_L:					\
-	{								\
-		volatile u32 *__ptr = (volatile u32 *)(ptr);		\
-		asm volatile("xchgl %0,%1"				\
-			     : "=r" (__x), "+m" (*__ptr)		\
-			     : "0" (__x)				\
-			     : "memory");				\
+			asm volatile (lock #op "l %0, %1\n"		\
+				      : "+r" (__ret), "+m" (*(ptr))	\
+				      : : "memory", "cc");		\
 			break;						\
-	}								\
 		case __X86_CASE_Q:					\
-	{								\
-		volatile u64 *__ptr = (volatile u64 *)(ptr);		\
-		asm volatile("xchgq %0,%1"				\
-			     : "=r" (__x), "+m" (*__ptr)		\
-			     : "0" (__x)				\
-			     : "memory");				\
+			asm volatile (lock #op "q %q0, %1\n"		\
+				      : "+r" (__ret), "+m" (*(ptr))	\
+				      : : "memory", "cc");		\
 			break;						\
-	}								\
 		default:						\
-		__xchg_wrong_size();					\
+			__ ## op ## _wrong_size();			\
 		}							\
-	__x;								\
-})
+		__ret;							\
+	})
 
-#define xchg(ptr, v)							\
-	__xchg((v), (ptr), sizeof(*ptr))
+/*
+ * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.
+ * Since this is generally used to protect other memory information, we
+ * use "asm volatile" and "memory" clobbers to prevent gcc from moving
+ * information around.
+ */
+#define xchg(ptr, v)	__xchg_op((ptr), (v), xchg, "")
 
 /*
  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
@@ -167,36 +154,6 @@ extern void __add_wrong_size(void)
 	__cmpxchg_local((ptr), (old), (new), sizeof(*ptr))
 #endif
 
-#define __xadd(ptr, inc, lock)						\
-	({								\
-	        __typeof__ (*(ptr)) __ret = (inc);			\
-		switch (sizeof(*(ptr))) {				\
-		case __X86_CASE_B:					\
-			asm volatile (lock "xaddb %b0, %1\n"		\
-				      : "+r" (__ret), "+m" (*(ptr))	\
-				      : : "memory", "cc");		\
-			break;						\
-		case __X86_CASE_W:					\
-			asm volatile (lock "xaddw %w0, %1\n"		\
-				      : "+r" (__ret), "+m" (*(ptr))	\
-				      : : "memory", "cc");		\
-			break;						\
-		case __X86_CASE_L:					\
-			asm volatile (lock "xaddl %0, %1\n"		\
-				      : "+r" (__ret), "+m" (*(ptr))	\
-				      : : "memory", "cc");		\
-			break;						\
-		case __X86_CASE_Q:					\
-			asm volatile (lock "xaddq %q0, %1\n"		\
-				      : "+r" (__ret), "+m" (*(ptr))	\
-				      : : "memory", "cc");		\
-			break;						\
-		default:						\
-			__xadd_wrong_size();				\
-		}							\
-		__ret;							\
-	})
-
 /*
  * xadd() adds "inc" to "*ptr" and atomically returns the previous
  * value of "*ptr".
@@ -205,6 +162,7 @@ extern void __add_wrong_size(void)
  * xadd_sync() is always locked
  * xadd_local() is never locked
  */
+#define __xadd(ptr, inc, lock)	__xchg_op((ptr), (inc), xadd, lock)
 #define xadd(ptr, inc)		__xadd((ptr), (inc), LOCK_PREFIX)
 #define xadd_sync(ptr, inc)	__xadd((ptr), (inc), "lock; ")
 #define xadd_local(ptr, inc)	__xadd((ptr), (inc), "")